Thesis (M.A.)--University of South Florida, 2006. An
exploratory study of the geomorphology of Florida's springs
was conducted using morphometric analysis. Spatial datasets
for spring locations, elevation data, physiography, geology
and hydrography were acquired for incorporation and analysis
with GIS technology. ArcGIS 9 was used to measure certain
morphometric parameters from the spatial data for Florida's
springs. Other Parameters representing physical and
dimensional characteristics of the springs were acquired from
FGS Bulletin 66, Springs of Florida. All measured and
collected data was compiled into a usable morphometric
database. The data is described statistically and summarized
according to the spatial distribution of Florida's springs
with respect to geology and landforms. This examination is
carried out at two different scales; 1) the entire population
of Florida's 754 springs is examined with emphasis placed
upon geology, physiography, and elevation, 2) a subset of 102
springs that is deemed to be a representative sample is
examined according to all morphometric parameters. It was
concluded that the presence of karst terrain at the majority
of the spring sites that were examined in this study is the
prevailing factor that has influenced where springs have
resurged in Florida. This was observed at both scales in the
study. It is also concluded that spring sites in Florida are
strongly linked to lower elevations, and therefore that
elevation also influences their distribution. Suggestions for
future research are posed, including specific ways in which
the current methodology can be expanded upon and
A Morphometric Analysis of the Geomorphology of Floridas Springs by Andrew Curtis Walker A thesis submitted in partial fulfillment of the requirements for the degree of Master of Arts Department of Geography College of Arts and Sciences University of South Florida Major Professor: Philip Reeder, Ph.D. Robert Brinkmann, Ph.D. Paul Zandbergen, Ph.D. Date of Approval: June 23, 2006 Keywords: magnitude, discharge, run, orientation, physiography Copyright 2006, Andrew C. Walker
Acknowledgements Many thanks to my thesis committee: Philip Reeder, Ph.D. RobertBrinkmann, Ph.D. Paul Zandbergen, Ph.D. Special thanks to: David Dewitt Greg Johnson Mike Bascom
i Table of Contents List of Figures List of Tables Abstract Chapter One: Introduction Research Design Chapter Two: Literature Review Chapter Three: Study Area Chapter Four: Methodology Compiling Morphometric Data Spatial Data Preparation Measuring Morphometric Data Chapter Five: Results & Discussion Exploration of the springs database Physiography & Geology Elevation & Distance to Coastline Comparison of noticeable spring clusters Evaluation of GIS as an asset to morphometric analysis Chapter Six: Summary & Conclusions Cited References Bibliography i iii iv 1 3 6 19 28 29 31 32 35 53 56 78 81 88 89 93 96
ii List of Figures Figure 1: The locations of Floridas k nown springs with first, second, and third magnitude springs differentiated Figure 2: Florida Spring s Classification System Figure 3: Precipitation Map of Florida Figure 4: Physiographic Regions of Florida Figure 5: Soil Orders in Florida Figure 6: Environmental Geology of Florida Figure 7: Floridas Karst Terrain Figure 8: Geologic Formations of Florida Figure 9: The Aquifers of Florida Figure 10: Landuse in Florida Figure 11: Spring locations overlaid w ith 30m DEM and hillshade raster Figure 12: Bar graph of 20-foot elevation ranges & corresponding spring totals Figure 13: Bar graph of geologic forma tions and corresponding spring totals Figure 14: Entire spring populat ion overlaid with geology Figure 15: Spring locations overlaid with geology Figure 16: Legend of geologic formations Figure 17: Bar graph of physiographic regions & corresponding spring totals Figure 18: Spring locations overlaid with physiography Figure 19: Legend of Physiographic Regions Figure 20: Physiography overlaid with spring locations Figure 21: Geologic formations overlaid with spring locations Figure 22: Locations of springs corres ponding to the Gulf Coastal Lowlands and the Ocala Limestone Figure 23: USGS 30m DEM overl aid with spring locations Figure 24: Euclidian distance to coastline overlaid with spring locations Figure 25: Locations of spring clusters Figure 26: Spring locations symbolized by run length and overlaid with geologic formations Figure 27: Spring locations symbolized by run length and overlaid with Euclidian distance to coastline 2 4 20 21 22 23 24 25 26 27 36 38 41 43 44 45 49 51 52 65 74 75 79 80 82 86 87
iii List of Tables Table 1: Morphometric parameters and data sources Table 2: % of spring population corresponding to 20-foot elevation ranges Table 3: % of spring population corresponding to geologic formations Table 4: Formation names of the Quaternary and Tertiary/Quaternary Periods Table 5: Formation names of the Tertiary period Table 6: % of spring population corresponding to physiographic regions Table 7: Descriptive Statisti cs of the Springs Database Table 8: Magnitude and run ge neration by physiographic region Table 9: Elevation descriptives by physiographic region Table 10: Discharge descriptives by physiographic region Table 11: Depth descriptives by physiographic region Table 12: Pool area descrip tives by physiographic region Table 13: Distance to coastline de scriptives by physiographic region Table 14: Run length descrip tives by physiographic region Table 15: Magnitude and run generati on descriptives by geologic formation Table 16: Elevation descriptives by geologic formation Table 17: Depth descriptives by geologic formation Table 18: Discharge descriptives by geologic formation Table 19: Pool area descri ptives by geologic formation Table 20: Distance to coastline de scriptives by geologic formation Table 21: Run length descriptives by geologic formation Table 22: Cluster 1 descriptives Table 23: Cluster 2 descriptives Table 24: Cluster 3 descriptives Table 25: Descriptives for non-clustere d springs in northern peninsular Florida 29 38 40 46 47 48 54 57 58 59 60 61 62 63 66 67 68 69 70 71 72 81 83 84 85
iv A Morphometric Analysis of the Geomorphology of Floridas Springs Andrew Curtis Walker ABSTRACT An exploratory study of the geomorphology of Floridas springs was conducted using morphometric analysis. Spatial datasets for spring locations, elevation data, physiography, geology and hydrography were ac quired for incorpora tion and analysis with GIS technology. ArcGIS 9 was used to measure certain morphometric parameters from the spatial data for Floridas springs. Other Parameters re presenting physical and dimensional characteristics of the spri ngs were acquired from FGS Bulletin 66, Springs of Florida. All measured and collected data was compiled into a usable morphometric database. The data is described statistically and summarized according to the spatial distribution of Floridas springs with respect to geology and landforms. This examination is carried out at two different scales; 1) the entire population of Floridas 754 springs is examined with emphasi s placed upon geology, physiography, and elevation, 2) a subset of 102 sp rings that is deemed to be a representative sample is examined according to all morphometric parameters. It was concluded that the presence of karst terrain at the majority of the spring sites that were examined in this study is the
v prevailing factor that has in fluenced where springs have resurged in Florida. This was observed at both scales in the study. It is also concluded th at spring sites in Florida are strongly linked to lower elevations, and theref ore that elevation al so influences their distribution. Suggestions for future research are posed, including specific ways in which the current methodology can be expanded upon and improved.
This research gives attention to both the spatial distribution and frequency of spring locations with respect to the physiographic and geologic regions of Florida, and it is also concerned with observing any trends that exist with respect to the orientation of all generated spring runs, as well as spring elevation, discharge, run length, pool length, pool width, pool area, depth, and distance to coast. The research objectives are carried out in an effort to provide information about the geographical and geomorphological characteristics of Floridas springs that will readily compliment the Florida Springs Classification System (Copeland, 2003). This research will also help to evaluate the usefulness of GIS as a research tool in a morphometric study. 1 This research is an exploratory study of several aspects of Floridas springs. Location data for 754 springs within the state has been acquired and this population will be examined relative to their elevation, physiography, and geology. Additionally, a subset of 102 first, second and third magnitude springs will be studied in more detail. By using an abstract application of morphometric analysis, dimensional and spatial attributes of both data sets will be explored. Figure 1 shows the location of all 754 springs for which location data was obtained, and the first, second and third magnitude springs that are part of the 102 spring data subset are differentiated. Chapter One Introduction
2 Figure 1: The locations of Floridas known springs with first, second, and third magnitude springs differentiated.
3 Research Design Problem Statement Contemporary research on Floridas springs ha s yet to compile a comprehensive database of each springs geographical and geomorphological attributes. An abstract application of morphometric analysis will aid in forming such a compilation of data into a format that is both usable with current studi es and applicable to future research of Floridas springs. It will also allow a preliminary analysis or the spatial aspects of the geographical and geomorphological components of the spring database. Research Questions Do springs that exist in different geogra phic regions of Florida exhibit distinct morphometric patterns re lative to these regions? Does physiography and geology influence th e spatial distribu tion of Floridas springs? Sample Design There are currently over 700 known spring resurgences in Florida. The vast majority of Floridas springs, including all thos e that are of the first magnitude, are karst springs (Bulletin 66, 2004). There are severa l seeps and karst windows as well. Figure 2 displays how these features are categorized by the Florida Springs Classification System. Using this system, the vast majority of Fl oridas springs fall into the onshore vent category. Out of the entire population, 462 have been visited and surveyed by Florida Geologic Survey (FGS) field teams. While the locations of all of the springs in Florida are important in this study, morphometric data is not comprehensive for the entire
4 population. This research is therefore conducte d at two scales. Locations for 754 springs have been acquired. The entire populati on will be examined re lative to elevation, physiography, and geology. A sample consisti ng of 102 first, second and third magnitude SPRING ONSHORE OFFSHORE Onshore Vent Offshore Vent Examples: Examples: Karst spring Offshore karst spring Resurgence (River Rise) Unnamed offshore vent Estavelle (intermittent resurgence or exsurgence) Offshore estavelle vent Subaqueous riverine vent Subaqueous lacustrine vent Sand boil VENT Onshore Seep Offshore Seep Examples: Examples: Subaerial riverine seep Unnamed offshore seep SEEP Subaqueous lacustrine seep Offshore estavelle seep Figure 2: Florida Springs Classi fication System (Copeland, 2003) springs will be examined in greater detail based on the greater amount of morphometric data that exists for these features. These 102 springs represent the most well known springs in Florida for which the most hist orical data is avai lable (Dewitt, 2006). Consequently, FGS Bulletin 66 contains c onsiderably more flow data on these 102 springs than the others that have been surveyed and included in the publication. This subset comprises a good representative sample of the entire population (Dewitt, 2006). Several of the first magnitude springs are actu ally groups of multiple resurgences or vents that have been studied as a single feature for the purposes of measuring their combined flow value. Flow data is not available fo r the individual springs in each spring group and
5 therefore the groups will be traditionally represented by si ngle features for analysis purposes. Significance and Rationale This study is significant to current research being conduc ted on Floridas springs in its capacity to consolidate many important physical parameters of the springs into a single database. This morphometry has yet to be pursued for Florida natural springs and will serve as an informative tool for future studies, as well as the foundation for a more comprehensive morphometric analysis.
6 Chapter Two Literature Review Ritter (1978) in his book entitled Process Geomorphology provides a very useful understanding of general geomorphologic proces ses. The chapter on karst processes and landforms was the most directly related to this research on Floridas springs. Gaining an understanding of this is essential for studying Floridas landfor ms and springs as part of the natural and physical landscape. Ritter ( 1978) provides a detailed explanation of terms related to Florida such as exsurgence a nd resurgence, which are distinguished one apart from the other. Resurgences are noted to be more unpredictable due to the variety of discharge and chemistry characteristics than exsurgences. This research will focus on spring resurgences as per their abundance and ch aracteristics. Ritter also discusses some of the specifics of karst drainage systems and he outlines some of the aspects of morphology as well. White (1988) in his book Geomorphology and Hydrology of Karst Terrains provides a comprehensive text on both subjects, and how they are related in geographic studies. This research of Floridas springs requires, and even assumes, some basic knowledge of geomorphology and specifically karst hydrology due to the carbonate geology of most of Florida. Whites book has been an excellent source regarding understanding the fundamental principals of karst hydrology and geomorphology. White begins by distinguishing between the nature of each of the two scienc es. He states that while geomorphology has been regarded as qualitative in nature, hydrology is decidedly
7 quantitative. This difference is further elucidated through specific examples. White makes specific mention of karst springs with respect to their formation, development, and classification. Karst springs are categorized in to several groups: grav ity springs, alluvial springs, vauclusian springs and offshore springs. Each category is explained with a full description, which was very helpful in facili tating a better basic understanding of the characteristics of Floridas springs in this study. In an article entitled Karst Lands, Mylroie (1995) gives a comprehensive overview of karst features and processes. Ca rbonate rocks and their importance to karst development are explained. My lroie describes the fine balance that must exist between mechanically sound rocks and the rapid chemi cal weathering of th em. These processes are further explained and elaborated upon. Karst lands are placed in a geographical perspective with the information on world-wide total land-cover that corresponds to karst features. Mylroie also discusses drainage basins in karst areas, giving information on underground drainage systems and interaction between them and surface hydrology. Springs are mentioned as one of the key features to most conduit systems. Of particular interest to the research on Floridas springs is the explanation of discharge from karst aquifers. The Floridan aquife r underlies the study area, and is characterized as being a conduit system. Mylroie draws attention to springs as being the typical outlet for discharge in conduit systems. He also mentions that these points of discharge are usually found at lower elevations. The research on Fl oridas springs has yielded the same trend, and will discuss this observation further. Blackith and Reyments (1971) book Multivariate Morphometrics is one of the earliest textbooks on morphometrics. Morphome trics, a branch of mathematical and
8 scientific study, is widely a pplicable to geographic study. Sp ecific topics contained in this book related to this research include the role of significance te sting in morphometrics and the use of quadratic discriminants. Bl ackith and Reyment also discuss geographys influence over the amount of environmental variation obser ved in occurrences of the study subject, as well as trendsurface analysis. A difference is also stated between the morphometry of biological subjects, compar ed to geographic features. While it is generally understood that morphometry of anim als is a product of adaptation, the reasons for geographic morphometry are causal in nature. Blackith and Re yment establish that morphometrics began as a tool for studying plants and anim als. By 1971, the publication date of this book, morphometrics was just begi nning to be abstractly applied to studies and analyses in other fields such as geology and/or geography. More recently morphometry has been utilized as an analytic al tool, similar to how it is used in this research on Floridas springs. An article entitled The Marine Resources of the Parker River Plum Island Sound Estuary: An Update After 30 Years (2003) is a biological resour ce survey conducted by the Massachusetts Audubon Soci ety. This study was a follow up to a previous study of the marine biological resources, and it sought to compare data from both studies in order to discover and understand any changes that occurred in the Parker River Plum Island Sound ecosystem between the two study periods. As part of this assessment it was necessary to include information about the mo rphometry of the rivers and estuaries that comprise the study area. Several physical char acteristics of the study area are outlined in detail to serve as an informative quantitative description of the region. Specific attributes that comprised the morphometry include both maximum and mean values for length,
9 width and depth, shoreline length, total surface ar ea and volume. It is clear that within the scope of the Plum Island study, the morpho metric portion of the analysis that was conducted to better understand the general nature of the study area prior to the study of its marine biological resources. All of the at tributes studied are phys ical characteristics relating to its size and shape. This is in keeping with the traditional uses of morphometrics. This study contributes to the building of a morphometry of Floridas springs by providing another example of how morphometrics can further the understanding and examination of a ge ographic region based on its physical characteristics. Furthermore, the methodology for this research has also included several morphometric parameters that represent th e physical attributes of the springs being studied. This approach is influenced by the success of the Parker River study. Chalkias and Karymbalis (2003) in their study entitled Prototype GIS Application in Delta Morphometry seek to develop a reliable m eans of morphometric analysis on deltas using a customized GIS. It is stated in the problem statement that morphometrics can benefit delta research by providing a sy stematic means of quantifying the physical characteristics and processes that shape the feat ures over time. This relationship is better explained later in the public ation where morphometry is de scribed as a quantitative method that can relate processes to morphology. The morphometric analysis is focused is the deltaic protrusion portion of the study area. All of the morphometric parameters that are used are indices or ratios, and are similar to those collected in previously reviewed studies: length and width of delta protrusion, length of shoreline, etc. although this morphometric analysis contai ns significantly more calculated parameters. The measured parameters were used to derive several othe r values crucial to th e study: sediment volume
10 of delta segments, ratio of the seaward portion of the deltaic protrusion, protrusion distribution indexes and a vulnera bility ratio. This research c ontributes to the building of a morphometry of Floridas springs by providing an example of how calculated morphometric parameters can be custom-tailo red to the specific needs of the study. It also shows how morphometrics can be abstract ly applied to studying parameters that are not in the strictest sense shape or size related. Sauchyn, Cruden and Hu (1997) in their paper entitled Structural control of the morphometry of open rock basins, Kananaskis region, Canadian Rocky Mountains, examine variations in morphometry as they relate to geographi c changes in dominant structural formation in the Canadian Rocky Mountains. This research seeks to add to previous geomorphologic knowledge of st eep rock slope development by using morphometric analysis to relate open rock ba sins to rock fall mass wasting events. Rock formations that were examined include f unnels, cirques and chutes located across 56 basin sites. Morphometric data was acqui red from DEMs with custom coordinate system. Measured morphometric parameters for the basins include length, width, relief, area, perimeter compactness, length-width rati o, length-relief ratio, wi dth-relief ratio, and area-relief ratio, although the resolution of the DEMs was unmentioned in the paper. A Wilcoxon rank sum test was performed on the morphometric data to allow for statistical analysis. This paper is helpful to the task of building a morphometry of Floridas springs by providing a good example of a substantial lis t of parameters that could and indeed should be included when studying a phenomen on based on its morphometry. Many of the same physical characteristics that are measur ed from rock basins and analyzed in this paper will also be measured for Floridas springs.
11 Ganas, Pavlides and Karastathis (2004) in their paper entitled DEM-based morphometry of range-front escarpments in Attica, central Greece, and its relation to fault slip rates use DEM data as a method to identif y active fault locations. This paper builds on previous research, which used shaded relief imagery created from DEM data to display the known location of the Fili fault segment in Parnitha Mountain, Greece. DEM analysis is combined with measured morpho metric data to identify and describe four additional faults in Attica. The study area is a region of Greece in the Aegean Sea where normal faulting is constantly occurring. Two DEM mosaics, 20m and 60m, were used to map the fault segments. The DEMs were derived from contour maps produced by the Hellenic Army Geographical Service. Active fault characteristics were identified by searching for sharp tonal changes between pi xels on the shaded relief imagery. Slope angles were computed for pixe ls corresponding to areas of sharp tonal changes. Abrupt slope changes were interpreted as possible loca tions of active faults. Slope profiles were also generated. One significant way in which this study utilized slope profiles was to compute mean slope angels for several range-fr onts in the study area. These values were used to estimate ages and slip-rates for the four potentially active faults. The paper is concluded with confirmed identification of five active faults, and a magnitude prediction for the next major earthquake that occurs along a ny of them. This research is relevant to the Florida spring research conducted for this thesis because it gives a clear example of how morphometry can be measured and used to identify spatial phenomena Dong, Wang and Wang (2004) in their article Geomorphology of the megadunes in the Badain Jaran Desert give an example of how effec tive morphometric analysis can be for studying and understanding the physical characteristics of a spatial phenomenon.
12 The study area is one of the few places on the earth where megadunes form. Several parameters representing the physical attri butes of the megadunes are measured and analyzed morphometrically. This analysis contributes new knowledge of how and why megadunes form where they form in the Badain Jaran Desert. The springs research is also attempting to add to the knowledge base on what f actors most influence where springs form in Florida, and similarly, will do so through an analysis of their morphometric parameters. Frumkin and Fischhindler (2005) in their article entitled Morphometry and distribution of isolated caves as a guide for phreatic and con fined paleohydrological conditions, conduct a study that serves as an excellent example of the utility of morphometric analyses of geomorphological la ndforms. Isolated caves are defined and explained in terms of their physical and de velopmental characteristics. Morphometric parameters for several known isolated cav es in the region surrounding Jerusalem were measured and analyzed. A set of criteria consisting of acceptable value ranges for these morphometric parameters was established. Th e study is concluded with a presentation of these criteria as good and effective for determ ining if any cave should be classified as isolated. This article was the first of several to be referen ced in this study of Floridas springs. Although the springs research is not aimed at using morpho metrics to classify them, this source was very informative in showing how morphometry can be abstractly applied to a geographic study. Randazzo and Jones (1997) in their book entitled The Geology of Florida provide a very comprehensive overview of Floridas geology, and of pa rticular interest to this thesis, its geomorphology, hydrogeology, fossil record, and coastal and environmental
13 geology. More specifically it provides a good overview on ho w Floridas springs are an integral part of Floridas groundwater systems. The ch apter on the hydrogeology of Florida differentiates the five aquifers that make up Floridas freshwater resources. First magnitude springs are quantitatively defined as those di scharging at least 100 cubic feet per second, and all of the known springs of this magnitude issue from the Floridan aquifer. A small-scale map from 1970 is included, that shows all of the known first magnitude springs in Florida at that time (six more have been discovered since then, bringing the current total to 33) This book was also among the first to be referenced for the springs research. While it covers a broad topic in a sense, it was particularly helpful in its capacity to explain the previously referenced topics of karst terrain and hydrology in terms of their role in the geography of Florida. In an article entitled Use of chemical and isotopic tracers to characterize the interactions between ground water and surface water in mantled karst, Davis (1997) conducted a study aimed at determining if the interaction between surface and groundwater affects water quality in the Upper Floridan Aquifer. The study area consisted of two areas in Leon County, Lake Bradford and a large sinkhole. Davis identifies the Upper Floridan aquifer as provi ding northern Florida with most of its water supply. He also states that the knowledge base concerning water quality in this aquifer is currently very small. Lake Bradford and th e sinkhole were chosen because they represent sites where the intermingling of surface a nd groundwater could result in a negative impact upon water quality. Water samples we re taken over the course of about one month for each site, and then tested for specific elements and pollutants. He discusses
14 the relationship between surface water and ground water interaction and the closeness to karst terrain. Davis concludes that the degree to which the water quality of the Upper Floridan aquifer is influenced by its interaction with surface water is determined by the level of interconnectivity between the two. This influence, as stated in the article, is related to the abundance of karst terrain in the study area. The article specifically mentions the important role that proximity to karst features plays in determining the level of interaction between surface and ground water. Daviss article has been beneficial to the research on Floridas springs by providing an explanation of one of the ways in which groundwater in Florida is influe nced by karst lands. The springs research has also made some conclusions regarding the relationship between karst terrain and springs. These conclusions are later discussed in greater de tail, and center on how springs locations are tied to the distribution of karst lands. In an article entitled Conduit properties and karsti fication in the unconfined Floridan Aquifer, Smith (2004) continues with an existing study of the hydraulics of a portion of the Floridan Aquife r. His study is concerned with determining the overall loss or gain of fluids across the portion of the Santa Fe River that fl ows underground. It is stated in the article that younger aquifers, such as the Floridan, exhibit much higher hydraulic conductivity rates outside of conduits th an do older aquifers. This fact suggests an increased risk for contaminants to leech into groundwater from the surrounding matrix. It also suggests a relationship betw een the rate of flow through conduits and the intensity of karstification in the surrounding matrix. Data wa s collected at several karst windows in the study area, as well as at the two sites marking the beginning and end of
15 the underground portion of the Santa Fe River. Data was gathered over twelve months, from August of 2001 to August of 2002. This collection phase was affected by drought conditions. The information that is presented on fl uid transfer between conduits and the surrounding matrix, and the conditions that must be present for the transfer to occur, facilitates a broader knowledge base for this thesis on the to pics of karst processes. Smith concludes that fluid only passes from the conduits into the surrounding matrix during peak discharge events. This article contributes spec ifically to the research on Floridas springs by providing information on another way in which groundwater and karst lands in Florida are related. In an article entitled A ground-water sapping landscape in the Florida Panhandle, Schumm, Boyd, Wolff and Spitz (1994) study spring steepheads in Okaloosa and Walton Counties. The authors begin by explaining the relationship between surface runoff and the capacity for infiltration in the surrounding land. The term steephead is defined as a linear-forming valley with a steep semicircul ar feature at the springhead, somewhat resembling a natural amphitheatre. These feat ures are acknowledged to be the result of spring-sapping. In this study, the authors e ndeavor to measure and quantify Florida steephead topography. This article has aided the research on Floridas springs by serving as another source in which the karst terrain in Florida is identified and described in terms of its role in the geomorphology of the states landforms. The authors describe Fl orida as a land of plentiful ground-water and home to very permeab le soils. Of specifi c interest to this thesis is the physiographic desc ription of Floridas Panhandle that the authors offer. The
16 Eglin Air Force Base, a region spanning the sout hern part of Okaloosa County, is said to be made up of Western Highlands and Gulf Coastal Lowlands. These physiographic designations were surmised to be representa tive of most of the panhandle. The support that is given in this article is important to the research on Floridas springs, as it encourages an understanding of the parts of the panhandle that are not included in some physiographic datasets. Reese and Zarikian (2004) in their report entitled Review of Aquifer Storage and Recovery in the Floridan Aquife r system of southern Florida give a synopsis of aquifer storage and recovery research as it is being conducted in southern Florida. A brief description of aquifer stor age and recovery (ASR) pract ices is given by way of summarizing the means by which excess freshwat er runoff is stored in local groundwater systems for later on-demand use during dry seasons. A survey of 30 ASR wells in southern Florida and the data th at was yielded from them is included. This report initially served the research on Floridas springs as a reference for aquifer depths and also as a comparable method of monitoring groundwater conditions to that of the recording of discharge measurements in Floridas springs. A report by the Southwest Florida Water Ma nagement District entitled (2001) The Hydrology and Water Quality of Springs in West-Central Florida is a compilation of data and information on several of the larger spri ngs in the district. All of the springs mentioned in the report are included as part of this thesis. Much of the hydrologic data presented in the SWFWMD report is typical of many of Floridas karst springs, and is therefore applicable to this re search. Reasons for the lack of springs in the north-central section of the district are given, as well as speculations on the scarcity of rivers and
17 streams. Major rivers in the springs regi on are listed and described, as are the overall geologic characteristics of SWFWMD. Open file report #85 by the FSG, First Magnitude Springs of Florida (2002) was equally, if not more informative than the pr eviously mentioned SWFMWD report. This publication contains a wealth of information on the classification of Floridas springs. This information served as an introduction to first magnitude springs of Florida and each of the eight magnitude classes are defined acco rding to their range of quantitative flow values, and several accepted units of flow measurement are listed. The information contained in this report provided a reference fo r some of the characte ristics of Floridas springs that could and indeed should be incl uded in the morphometry. This report was also informative in its descri ption of the geography of Floridas first magnitude springs and how the panhandles geology diff ers from peninsular Florida. Open file report #66 by the FSG, Springs of Florida (2004) served as a foundation for the data gathering portion of this thesis. This publication contains detailed quantitative data of the physic al attributes of over 450 spri ngs in Florida, and names a total of over 700 that are known in the state. These attributes include pool length, pool width, depth, presence of spring run, spring run length, and discharge. This data collectively represented a small scale versi on of spring morphometry that was built upon with the addition of other attr ibutes that had to be measured for the study. Having the data that is available in FGS Bulletin 66 in a single concise source greatly expedited the initial data gathering phase of this thesis. Based on this review of literature it was determined that a wealth of literature exists on the hydrologic aspects of springs, but the brea th of the literature is more limited
18 when assessing springs as part of the physic al landscape. Regarding the springs of Florida, various detailed technical reports produced mostly by government agencies, provide both an overview of Florida's springs as well as technical details. But none of these sources really considers the geomorphol ogic aspect of springs and views springs and related morphologic characteri stics as part of the physical landscape of Florida. This thesis takes this geographic approach to st udying Florida's springs, and will thus add an important new perspective to the ex isting literature on Florida springs.
19 Chapter Three The Study Area The study area for this research is define d by the portions of the state of Florida within which natural springs occur. More ge nerally this includes all of the panhandle and most of peninsular Florida down to just south of Hillsborough C ounty (see Figure 1). The highest density of spring resurgences is centered on the big bend area where peninsular Florida and the panhandle meet. This distribution is mostly due to the shallow depth of the Floridan aquifer and the pe rvading carbonate limestone underlying the region (Randazzo, 1997). Southern Florida has a mo re tropical climate while ce ntral and northern Florida are sub-tropical. Average maximum summer and temperatures range between 88 F and 92F. Average minimum winter temperatures range between 42 F and 64 F. Average annual rainfall varies across the study area, as shown in Figure 3. The northern portion of peninsular Florida is at the low end of th e range, receiving between 54 and just under 50 inches of precipitation annually. The bi g bend region receives 50-60 inches, and the western panhandle receives as much as 68 inches (SCAS, OSU, 2006). The geographic center of Florida is a bout 12 miles north of the town of Brooksville. The state is made up of over 53,000 square miles of land and has over 8,700 miles of coastline. Topography is characteri zed by very little re lief, ranging from sea level to about 345 feet at the highest point. Most elevations are in the range of 50 to 100 feet (SCAS, OSU, 2006). Physi ography is varied, but mostly consists of coastal lowlands
Figure 3 Precipitation map of Florida (From: http://www.ocs.orst.edu/pub/maps/Precipitation/Total/States/FL/fl.gif) and interior uplands. There are several ridges constituting regions of slightly greater relief than most of the state, the most prominent of which is the Brooksville Ridge. Of particular interest to this thesis are the lowland regions, as they are the location where the majority of springs resurge. Approximately three quarters of Florida is classified as coastal lowland. These regions range from being only 10 miles wide to penetrating up to 100 miles inland. Figure 4 displays the physiographic regions of Florida as delineated by Randazzo and Jones (1997). 20
Figure 4: Physiographic Regions of Florida (Randazzo & Jones, 1997) As seen is this figure, the physiography of peninsular Florida has been determined, but the physiography of the panhandle region has yet to be determined. 21 For the most part, most of Floridas soil is very sandy with little silt or clay composition. Soils gradually become more silty and clayey further inland. The northern panhandle is characterized by some red clay. There are seven soil orders in Florida: 1) Histosols, 2) Spodosols, 3) Ultisols, 4) Mollisols, 5) Alfisols, 6) Inceptisols, 7) Entisols. The first three orders occur most extensively in Florida (UFL, 2006). Histosols are present throughout the state, with the largest coverage spreading from the southern shores
of Lake Okeechobee south to the Everglades. Spodosols, though also present throughout, are more abundant in peninsular Florida than in the panhandle. Ultisols are heavily distributed across the northern panhandle and the big bend area. Figure 5 shows the distribution of Floridas seven soil orders. Figure 5: Soil Orders in Florida (UFL, 2005) (From http://grunwald.ifas.ufl.edu/Projects/NRC_2001/STATSGO.gif ) The general nature of the geology of the state can be summarized by the environmental geology map of Florida shown in Figure 6. Sand and silt are present throughout the state, with the highest concentrations centered on central peninsular Florida. Peat and clay are somewhat confined to the southern peninsula and the far northwestern portion of the panhandle. Of particular interest to this thesis are the regions 22
predominated by limestone. These areas are centered on the big bend region and underlie the highest density of springs in the state. Figure 6: Environmental Geology of Florida (USGS) (From http://www.luddist.com/karst2.GIF ) Florida is dominated by karst terrain as seen in Figure 7. Limestone is present throughout the state, although not always exposed at the surface. The big bend area, in terms of karst, is characterized by well-established karst terrain and limestone that is exposed or just under the surface. This region is of particular interest to this thesis as it corresponds to the previously mentioned high density of springs. Around and amongst this area are other areas characterized by limestone that lies beneath a moderate or thick layer of sediment. Both categories of karst are also present in parts of the western 23
panhandle. Further elaboration upon the geology of Florida can be summarized by Figure 8 which displays the geologic formations that underlie the state. Florida is an ongoing recipient of deposition, as can be seen by the far-reaching coverage of the Pleistocene and recent formation. The Oligocene formation has the most discrete distribution, and the Eocene can be seen to correspond to the big bend area around which the high density of karst springs is centered. Figure 7: Floridas Karst Terrain (From http://www.caves.com/fss/pages/misc/images/karst_map.gif) 24
Figure 8: Geologic Formations of Florida (FGS, 2000) (From http://www.dep.state.fl.us/geology/gisdatamaps/geo_map_florida.jpg) As previously mentioned, Florida's geology is dominated by sandy units, most of which are associated with the Pleistocene, and carbonate units that form karst landforms, including springs. Considering the carbonate units, the Ocala, Suwannee and St. Marks Formations are most important. The geologic periods corresponding to them, specifically the Eocene, Miocene, and Oligocene, are displayed in Figure 8. The Ocala Limestone is the most widely distributed carbonate unit in Florida, covering nearly 4000 square miles. The Suwannee limestone is second to the Ocala, covering just under 1000 square miles, and the St. Marks formation occupies about 300 square miles. 25
In terms of Floridas groundwater system, the Principal Artesian Aquifer extends beneath the entire state and covers parts of southern Alabama and Georgia. The Floridan Aquifer also underlies the study area and is the source for most of the springs in this study (FGS Bulletin 66). The Floridan aquifer ranges in depth from about 200 feet to as deep as 2700 feet (ISWD, 2004). Karst topography is present throughout Florida, and accounts for the porous limestone that makes possible the expansive groundwater system of the state (Randazzo, 1997). Figure 9 displays the aquifers of Florida and their extents. All of the springs in this study are part of the Floridan Aquifer system. Figure 9: The Aquifers of Florida 26
Landuse in the state of Florida is classified according to eight distinct categories, including several levels for urban, forest, agricultural, wetlands, and transportation. Between 1936 and 1995, the state saw a decline in forested lands by 22% and also in wetlands by 51%. Total agricultural lands grew by 60% and developed lands by over 600% (Kautz, 1998). As seen in Figure 10, much of the land that makes up the study area is occupied by agriculture and preserved lands. Some localized and sparsely distributed commercial and residential lands are also present. Most of the major water bodies that are located within the study area are found in northern peninsular Florida. Figure 10 Land Use in Florida (From: http://archone.tamu.edu/epsru/images/Maps/FLU.jpg ) 27
28 Chapter Four Methodology It should be noted that morphometry in its conceptual sense is infinite to some degree and is defined not only by the quantity of parameters examined, but also by the nature of these parameters. This study cons idered a mixture of phys ical and geographical characteristics in its examination of the spa tial distribution of Floridas springs. These characteristics are presented as the mor phometry of the springs. However, the morphometry of Floridas spri ngs should not be assumed to be restricted to just the parameters that are considered in this study. For the sake of methodological explanation, the data that is used in this study can be separated into two cate gories: (1) preexisting data and (2) measured data. Many of the parameters for which data was needed had already been measured by the FGS. The re maining parameters for which data did not already exist essentially had to be created for use in this research. Table 1 lists each parameter and its data source. Compiling Morphometric Data FGS Bulletin 66 played an integral role is this study because it contains data for many of the parameters that collectively make up the morphometry of Floridas springs. These data were measured in the field by vari ous researchers associated with the FGS. Since the main interest in studying the morphome try of these features is to explore their spatial distributions, it is first necessary to establish the location of each spring. Latitude
29 and longitude coordinates are given in FGS Bulletin 66 for every known spring in Florida. This information was used to create a table of spri ng names with their coordinates. This same table served as the foundation upon which all other compiled parameter values were appended. The first se t of parameters that were compiled for the database are dimensional in nature. As previous ly stated, this approach is in keeping with that of The Marine Resources of the Parker River(2003). Parameter Source elevation USGS NED discharge FGS Bulletin 66 magnitude FGS Bulletin 66 generates run FGS Bulletin 66 run length FGS Bulletin 69, USGS NHD run orientation derived from USGS NED pool length FGS Bulletin 66 pool width FGS Bulletin 66 pool area derived from Bulletin 66 depth FGS Bulletin 66 geologic region USGS physiographic region FDEP distance to coastline created with ArcGIS 9.1 Table 1: Morphometric Parameters and Data Sources With the exception of noting which county each spring is located in, and giving a brief set of directions for navigating to the si tes, all of the data contained in FGS Bulletin 66 corresponds to the physical characteristic s of the springs. The data is given in paragraph form describing each individual spring or spring group. All of this information was parsed out of the public ation and put into a databa se. The parameters spring location, elevation, geologic regi on and physiographic region were utilized for analysis of the entire 754-spring database. The para meters length of spring run, pool length, pool width, pool depth, and discharge we re utilized for analysis of the 102 spring data subset.
30 Two more dimensional parameters, magnitude and pool area were also applied to the data subset. The resulting table was then joined to a spatial datase t of point data for Floridas springs. Every point in the springs dataset ha s a unique name attribut e that is shared by a single record of parameter en tries in the morphometric database. The join was based on this relationship. It should be noted that ma gnitude values were derived from the median discharge measurement that is available for each spring. This is done according to the convention set forth in the Florida Spri ngs Classification system (Copeland, 2003). Spatial Data Preparation ArcGIS 9.1 was used for spatially expl oring the morphometry of Floridas springs. Locations for all 754 springs in the study had to be established in a known coordinate system before they could be inco rporated using the software. Once prepared for use in a GIS, the parameters listed in the original table would serve as attribute fields for the 754-spring database and/or the 102 sp ring subset data base. The previously created table containing all parameters f ound in FGS Bulletin 66 was used to create a new spatial dataset of Floridas springs. The latitude and longitude values contained therein served as x/y inputs fo r the location of each feature. All of the remaining parameters could then be added as additional attribute fields. Values for these remaining geographical para meters were collected from several other spatial datasets. Elevation, hydrography, phys iography and geology, were acquired from various sources. The spatial datasets were not all digitized in the sa me coordinate system or projection at the time of their creation. E ach one had to be prepared for incorporation with each other in ArcGIS 9.1. It was not onl y necessary to have all data in the same projection and coordinate system, but also to choose a projection that maximized
31 accuracy and conformality for the study area. The Albers Equal Area Conic projection is customized specifically for the state of Flor ida and has been used because it meets both of these needs. Measuring Morphometric Data All of the data that was created for this study corresponds to the geographical parameters of Floridas springs. That is, the spatial characteristics that help to define each spring based on the details of where they are located. ArcGIS 9.1 was utilized as the analysis tool for measuring the geogra phical parameters and then populating the database with values for each one. Thes e parameters are: elevation, physiographic region, geologic region (for the entire data ba se), distance to coas tline and spring run orientation (for the 102 data subset). Elevation data was provided by several US GS NED 30m DEMs. They were used to create a mosaic covering the entire state of Florida. This mosaic was overlaid with the springs dataset and the extract values to points tool was used to generate elevation values for each spring point. This tool assi gns a value to each point that is equal to the value of the raster cell that it falls within. The elevati on field is then populated with these values. A hillshade raster layer was generate d using the DEM, and serves as a visual aid to interpreting all figures which display elevation data. A spatial join was used to observe wh ich physiographic and geologic region each spring is located in. The two fields for listing these designations were then populated with the names of the physiographic or geol ogic region that corresponds to each spring respectively. Both datasets have statewide coverage.
32 The distance from each spring to the near est coastline was computed with aid of raster analysis. ArcGIS 9.1 was used to genera te a raster layer with the same extents as the DEM mosaic given it statewide coverage. This raster consisted of cells that existed everywhere within the extents, but not ove r any portion of the state of Florida. A Euclidian distance function was then applied to the raster layer. This resulted in a new raster layer for which every cell had a value eq ual to its distance to the nearest cell of the first raster layer. That is each cell in the raster produced with the Euclidian distance function had a value equal to its distance to th e nearest coastline (102 spring data subset). The same extract values to points tool that was used to generate elevation values for each spring was used again here in the same fashion. The field for distance to coastline was then populated with values corresponding each individual spring. Because each of the spatial datasets came from a diffe rent source and were not digitized together, the features contained with in them are not coincident. Spring points do not coincide with endpoints of river and stream polylines from the National Hydrography Dataset (NHD). These same pol ylines do not perfectly coincide with county boundaries that are draw n according to major rivers either. This presents a challenge when trying to identify the polylines that represent the r uns for springs in the 102 spring data subset that are known to generate one according to the information provided in FGS Bulletin 66. Each polyline representing a spring run needed to be identified in order to determine its orientat ion. To accomplish this, the characteristics of all polylines believed to be sp ring runs were meticulously comp ared with the descriptions given in FGS Bulletin 66. In addition to facilitating the determ ination of spring run orientation this procedure produced more accura te values for the run length field. The
33 run lengths given in FGS Bulletin 66 are some what generalized. They are reported in either whole feet for the shorter runs and whole miles for the longer ones. The NHD was used to locate the runs mentioned in Bulletin 66 and then more exact values were measured for each run. These values have been reported in feet rather than miles. To be confirmed as spring run using the NHD, a polyl ine corresponding to th e run of a specific spring had to originate in the vicinity of that spring and its length had to match the generalized length given in FGS Bulletin 66. It should be noted that th is procedure brought to atte ntion one of the weaknesses of the NHD. Only the longer spring runs with lengths of at least a mile were included when the data was digitized. Shorter spring runs of less than a mile were not included and therefore an orientation value was not dete rmined for them in this study. It should also be noted that this peculiarity gave rise to a reliable means to verify the total number of spring runs that were recognized using the NHD The database of morphometric parameters for the 102 springs in the data subs et shows that 13 of the springs generate a run exceeding one mile in length. This me thodology recognized exactly 13 polylines as representing spring runs using the NHD. A comparison of the NAME attributes between the polylines and the spring poi nts confirmed all 13 matches. An orientation value was then calculated for each of these polylines using a VB script in ArcMap 9.1. The azimuth of each polyline is measured at its midpoint and then values are reported in degrees. It should be noted that this method is less desirable than having an azimuth value that represents the mean all azimuths taken at multiple points along the polyline, for example. Howe ver, no such VB script was found for implementation in this study. Another VB scri pt was used to calcula te lengths for all 13
34 of the spring run polylines so that the reported values could be compared with the more generalized lengths give in FGS Bulletin 66.
35 Chapter Five Results & Discussion Compiling and measuring of morphometric parameters using ArcGIS 9.1 resulted in a spatial dataset for 754 Florida springs, as well as a 102 spring data subset for a sampling of first, second and third magnitude springs. Because this dataset represents a compilation of descriptive a nd geographic information about Floridas springs, the features can be symbolized according to their parameters in such a way as to display any nonrandom spatial distributions of the spring features with similar parameters. The assumption is that there are geographic fact ors influencing where springs with certain parameters occur. As previously mentioned, this research has evaluated Floridas springs on two scales. The data that was av ailable for this study for the 102-spring data subset was more extensive and detailed because these springs te nd to be the most well-known, or the most frequently visited. This level of data was not available for the entire 754spring database, and as a result, data that describes some of the physic al attributes of the springs wasnt available for the entire population. Alth ough the data is incomplete for all of the springs, the geographic parameters (locati on, elevation, physiogra phy and geology) that were derived through this studys methodology ar e examined for the entire population of 754 springs. Figure 11 displays Floridas sp rings overlaid with the 30m DEM mosaic and a hillshade raster layer.
36 Figure 11: Spring locations overlaid with 30m DEM and hillshade raster
37 A visual inspection of Figure 11 provides information related to the spatial distribution of Florida's springs. First of all, the areas of higher el evation, as indicated by the brown hillshade grading toward yellow, contain very few spring resurgences. The spatial distribution of the spring resurgences seems to be more aligned with lower elevation areas. Also, the spring resurgences in the north-central part of the state and the panhandle appear to be related to surf ace hydrologic/geomorphic features. Surface dendritic drainage patterns are easily dis cernable on the 30 meter DEM, and many of the spring resurgences in these areas correspond to the surface drainage pattern. This observation seems to indicate a link be tween surface stream hydrology area geomorphology related to these stream (va lley incision, headward erosion), and the spatial location of the spring re surgences. In the coastal sec tions of the western extension of the Big Bend area of the state, the relati onships mentioned above are not as clear, but can still be observed. Moving around the Big Bend and along the west coast toward Tampa Bay, numerous springs are located in the lower elevation areas between the Gulf of Mexico and the Brooksville Ridge section of Florida (see Figure 4). This relationship may result from the groundwater associated with the karst topogra phy of the Brooksville Ridge flowing down gradient toward the Gulf of Mexico. When this water meets the sediments of the Gulf Lowland areas it co me to the surface as the various spring resurgences found in the is ar ea. This may also be the case with the springs located essentially at the same latitude, but on the east side of the state. These springs are seaward of upland area, and re surge at lower elevations. The springs were classified according to th eir elevation values. Thirteen classes were established, each one representing a 20-f oot elevation range. These classes and the
number of springs each one represents are shown in Table 2. A graph illustrating this data is shown in Figure 12. Class # Elevation Class (feet) # of springs % of Population 1 0-20.00 271 35.94 2 20.01-40.00 241 31.96 3 40.01-60.00 134 17.77 4 60.01-80.00 59 7.82 5 80.01-100.00 28 3.71 6 100.01-120.00 9 1.19 7 120.01-140.00 2 0.27 8 140.01-160.00 4 0.53 9 160.01-180.00 0 0.00 10 180.01-200.00 2 0.27 11 200.01-220.00 2 0.27 12 220.01-240.00 0 0.00 13 240.01-260.00 2 0.27 Table 2: % of spring population corresponding to 20-foot elevation ranges 05010015020025030012345678910111213Class ## of Springs Figure 12: Bar graph of 20-foot elevation ranges & corresponding spring totals 38
39 The first class, ranging from zero to 20.00 feet above sea level, contains the largest percentage of springs. About 36% of the population corresponds to this elevation range. About 32% of the population has elevations ranging from 20.01 to 40.00 feet above sea level. Nearly 18% of the population has elevations ranging from 40.01 to 60.00 feet above sea level. Together, these three classes represent 646 of Floridas 754 springs, or about 86%. The fact that 86% of the springs in the data set are found at lower elevations (<60 feet) reconfirms the previ ously discussed observations from Figure 11. At the other end of the sc ale, there are very few springs found in the higher elevation classes. The seven classes that correspond to elevations ranging from 120.01 to 260.00 feet above sea level represent only 12 springs, or about 1.6% of the population, which again reconfirms the observation that Fl orida springs are more directly associated more with lower elevation areas of the state. Floridas springs are only found at eleva tions ranging from sea level to about 260 feet. Regarding this range of values, 86% of the springs correspond to the lower 25% of the range. This fact suggests that elevation has considerable influe nce over where springs are located in Florida. Not only are ther e a number of high-discharge first-magnitude springs in Florida, but most of the entire population are located at elevations that range in the lower 25% of all elevations at which springs are found. Mylroie (1995), also observed the tendency for springs to be lo cated at generally lo w elevations. The examination of spring elevations values in this thesis support My lroies observation. The entire population of Floridas spri ngs was examined with regard to the underlying geologic formations. It should be noted that the geology dataset that was acquired from the USGS, was created to repr esent surface or near-surface geology. In
Formation Name # of springs % of pop. Qal Alluvium 66 8.75 Qbd Beach ridge and dune 8 1.06 Qh Holo cene sediments 22 2.92 Qtr Trail Ridge sands 4 0.53 Qu Undifferentiated sediments 45 5.97 TQsu Shelly sediments of Plio-Pleistocene age 1 0.13 TQu Undifferentiated sediments 1 0.13 Tab Alum Bluff Group 35 4.64 Tap Avon Park Formation 2 0.27 Tc Cypre sshead Formation 38 5.04 Tch Chata hoochee Formation 17 2.25 Tci Citron elle Formation 13 1.72 Th Ha wthorn Group 2 0.27 Tha Hawthorn Group, Arcadia Formation 1 0.13 That Hawthorn Group, Arcadia Formation, Tampa Member 13 1.72 Thc Hawthorn Group, Coosawhatchie Formation 14 1.86 Thp Hawthorn Group, Peace River Formation 4 0.53 Ths Hawthorn Group, Statenville Formation 4 0.53 Tht Hawthorn Group, Torreya Formation 1 0.13 Tmc Miccosukee Formation 1 0.13 To Ocal a Limestone 273 36.21 Tre Residuum on Eocene sediments 5 0.66 Tro Residuum on Oligocene sediments 11 1.46 Ts Suwan nee Limestone 107 14.19 Tsm Suwannee Limestone Marianna Limestone undifferentiated 13 1.72 Tsmk St. Marks Formation 53 7.03 40 digitizing this spatial data, FGS geologists mapped the first recognizable lithostratigraphic unit occurring within 20 feet of the land surface. Table 3 displays the number of springs located within each geologic formation, and Figure 13 displays a graph of this data. Please note that two formations, the Ocala Limestone and the Suwannee Limestone, have been omitted from this graph because they are outliers and skew the display of the rest of the data. The data corresponding to these two formations is subsequently discussed in further detail. Table 3: % of spring population corresponding to geologic formations
010203040506070TsmTsmkTreTroQalQbdQhQtrQuTQsuTQuTabTapTcTchTciThThaThatThcThpThsThtTmc# of springsGeologic Regions 41 Figure 13: Bar graph of geologic formations and corresponding spring totals
42 Figure 14 displays the entire population of Floridas springs overlaid with geologic data for the entire state. Figure 15 depicts only the three previously mentioned formations (Ocala Limestone, Suwannee Limestone, St. Marks Formation). The observed correspondence between these formations and the bulk of the entire springs population is readily noticeable when Figures 14 and 15 are visually compared and viewed spatially. The importance of these formations to the representative sample of 102 springs will be discussed later in the study. This breakdown of Floridas springs into the individual geologic formations from which they issue helps provide a better understanding of the relationship between geology and the distribution of the springs. As depicted in the preceding data, three of the 37 geologic formations found in Florida represent over half of the entire population of springs. All three of these formations are representative of karst terrain, and together correspond to the largest percentage of Floridas springs that are geologically related. In all, approximately 60% of Floridas springs correspond to carbonate geologic units. This fact indicates that karst terrain is a factor that strongly influences the location of the largest percentage of Floridas springs. Several formations stand out as representing significantly more springs than others. The Ocala Limestone corresponds to 273 springs, roughly one third of the entire population. The Suwannee Limestone corresponds to 107 springs, or about 14%. Alluvium corresponds to 66 springs (about 9%) and the St. Marks Formation corresponds to 53 springs (about 7%). As previously mentioned, all of this information is displayed in the preceding figure and table with the exception of the Ocala Limestone and the Suwannee Limestone.
Figure 14: Entire spring population overlaid with geology 43
44 Figure 15: Spring locations overlaid with geology
Figure 16: Legend of geologic formations 45
46 The geologic dataset includes an attribut e identifying each geologic formation. This terminology is explained in Tables 4 and 5. Each formation is identified here by its common name. Quaternary Holocene Qh Holocene sediments Pleistocene/Holocene Qal Alluvium Qbd Beach ridge and dune Qu Undifferentiated sediments Pleistocene Qa Anastasia Formation Qk Key Largo Limestone Qm Miami Limestone Qtr Trail Ridge sands Tertiary/Quaternary Pliocene/Pleistocene TQsu Shelly sediments of Plio-Pleistocene age TQu Undifferentiated sediments TQd Dunes TQuc Reworked Cypresshead sediments Table 4: Formation names of the Quat ernary and Tertiary/Quaternary Periods
47 Tertiary Pliocene Tc Cypresshead Formation Tci Citronelle Formation Tmc Miccosukee Formation Tic Intracoastal Formation Tt Tamiami Formation Tjb Jackson Bluff Formation Miocene/Pliocene Thcc Hawthorn Group, Co osawhatchie Formation, Charlton Member Thp Hawthorn Group, P eace River Formation Thpb Hawthorn Group, Peace River Formation, Bone Valley Member Miocene Trm Residuum on Miocene sediments Tab Alum Bluff Group Th Hawthorn Group Thc Hawthorn Group, Coos awhatchie Formation Ths Hawthorn Group, St atenville Formation Tht Hawthorn Group, Torreya Formation Tch Chatahoochee Formation Tsmk St. Marks Formation Oligocene/Miocene Tha Hawthorn Group, Arcadia Formation That Hawthorn Group, Arcadia Formation, Tampa Member Oligocene Tro Residuum on Oligocene sediments Ts Suwannee Limestone Tsm Suwannee Limestone Marianna Limestone undifferentiated Eocene Tre Residuum on Eocene sediments To Ocala Limestone Tap Avon Park Formation Table 5: Formation names of the Tertiary period The entire population of Floridas springs was also examined with regard to physiographic regions. Table 6 shows the number of springs that are located within each physiographic region, and Figure 16 displays a graph of these values. Please note that two regions, the Gulf Coastal Lowland and the Marriana Lowland, have been omitted
48 from this graph because they are outliers and sk ew the display of the re st of the data. The data corresponding to these two regions is subsequently disc ussed in greater detail. Physiographic Region # of springs % of pop. Central Valley 29 3.85 Coastal Swamps 37 4.91 Crescent City Ridge 1 0.13 Deland Ridge 1 0.13 Duval Upland 1 0.13 Eastern Valley 12 1.59 Fountain Slope 6 0.80 Geneva Hill 1 0.13 Grand Ridge 2 0.27 Greenhead Slope 9 1.19 Gulf Coastal Lowlands 337 44.69 High Springs Gap 28 3.71 Kenwood Gap 1 0.13 Lake Harris Cross Valley 1 0.13 Lake Wales Ridge 1 0.13 Marianna Lowlands 130 17.24 Marion Upland 30 3.98 Mount Dora Ridge 3 0.40 New Hope Ridge 1 0.13 Northern Highlands 22 2.92 Osceola Plain 12 1.59 Palatka Hill 1 0.13 Polk Upland 4 0.53 St. Johns River Offset 8 1.06 Sumter Upland 1 0.13 Tallahassee Hills 1 0.13 Trail Ridge 4 0.53 Tsala Apopka Plain 17 2.25 Wakulla Sand Hills 1 0.13 Western Highlands 5 0.66 Western Valley 32 4.24 Zephyrhills Gap 15 1.99 Table 6: % of spring population co rresponding to physiographic regions
010203040Marion UplandMount Dora RidgeNew Hope RidgeNorthern HighlandsOsceola PlainPalatka HillPolk UplandSt. Johns River OffsetSumter UplandTallahassee HillsTrail RidgeTsala Apopka PlainWakulla Sand HillsWestern HighlandsWestern ValleyZephyrhills GapHigh Springs GapKenwood GapLake Harris Cross ValleyLake Wales RidgeCentral ValleyCoastal SwampsCrescent City RidgeDeland RidgeDuval UplandEastern ValleyFountain SlopeGeneva HillGrand RidgeGreenhead SlopePhysiographic Regions# of springs Figure 17: Bar graph of physiographic regions & corresponding spring totals 49
50 The largest percentage of springs is located within the Gulf Coastal Lowlands. This region contains 337 springs, or about 45%. Other regions of note are the Marianna Lowlands, which contains 130 springs (about 17%), the Coastal Swamps, containing 37 springs (about 5%), and the Western Valley, containing 32 springs (about 4%). The distribution of springs within these regions is closely related to the distribution of the carbonate geologic units that underlay them. The relationship between spring locations and carbonate geology will be illustrated in greater detail at the second scale of examination, as this fact again implicates karst terrain as being an influencing factor in the locations of Floridas springs. Also, the fact that a majority of the spring resurgences in the data set correspond to lowland and valley physiographic regions further validates the similar observations derived from the visual inspection of the 30-meter DEM (Figure 11). The high concentration of springs in the Gulf Coastal Lowland can be observed in Figure 17, which displays the entire population of Floridas springs overlaid with physiographic data. The Gulf Coastal Lowland is represented by the light green region that covers much of the big bend area. The large quantity of springs that this region encompasses is clearly notable. Figure 18 serves as a legend of names for each physiographic region.
Figure 18: Spring locations overlaid with physiography 51
52 Figure 19: Legend of Physiographic Region
53 Exploration of the springs database Ths studys examination of the entire population of Floridas springs has indicated that there is a re lationship between elevation a nd geology, and the location of spring resurgences. A subset of the 754 springs was created to allow a more detailed analysis of the relationship between spring location and various morphometric characteristics to be completed. A represen tative sample of 102 springs is hereafter discussed, with the analysis focusing on examin ing the springs with respect to the spatial datasets representing elevation, physiogra phy and geology. These examinations do not differ in method from those that were conducted at the first scale. The difference is the fact that the second data set is smaller a nd only represents the higher magnitude springs (magnitudes 1, 2, and 3). Visual appraisal of maps created for the 102 spring data base yields three observed clusters of springs, as well as a s eemingly high number of springs located within certain physi ographic and geologic regions. These supposed trends are hereafter explored and discussed. A database comprised of values for all of the morphometric parameters in this portion of the study was compiled. Descriptive statistics were calculated for the entirety of the morphometric database, and are shown in Table 7. It has been noted within Table 4 that statistics for run length represent 79 springs, from the sample of 102, due to this being the number of springs that generate a spring run. The other 23 springs do not generate a spring run and therefore have a va lue of zero for their r un length attribute.
54 PARAMETER MIN MAX MEAN ELEVATION (ft) 0.330 86.346 32.127 DISCHARGE (cfs) 0.36 1153.5 110.781 RUN LENGTH (79 SPRINGS) (ft) 7 89760 6907.658 POOL LENGTH (ft) 6 396 117.054 POOL WIDTH (ft) 6 372 122.075 POOL AREA (sq. ft) 36 147312 19390.452 DEPTH (ft) 2 185 29.334 DISTANCE TO COAST (mi) 0.028 15.822 6.914 Table 7: Descriptive Statistics of the Springs Database Existing literature on Floridas springs stat es that most of th em are karst springs (FGS Bulletin 66, Randazzo, 1997). The following discussion will seek to demonstrate how the presence of karst landscapes is related to the regions of Florida where springs are found. Karst springs are points of groundwater resurgence in the landscape. The groundwater travels below the surface as an underground stre am in discrete continuous diffuse flow through naturall y enlarged micro-openings. Its direction and point of resurgence are controlled partia lly by local geologic conditions including: 1) strike and dip of area rocks, 2) degree of karstification, 3) presence or absence of geologic structure such as faults, joints and bedding planes, and 4) the physical and chemical nature of area bedrock. In northern peninsul ar Florida and parts of th e panhandle where springs are found, limestone formations are generally shallow or exposed at the surface. Jackson Blue spring has the highest elevat ion in the database, at 86.35 feet above sea level. It is located in the panhandle and is therefore outside the coverage of the physiography dataset. However, its dist ance of 12.22 miles from the coastline would most likely place it outside of the coasta l lowlands physiographic region in the panhandle, which contains numerous spring resurgences. The spring issues from Suwannee Limestone Marianna Limestone Un differentiated which probably indicates
55 that this spring is a karst so lution spring. The nature of th e karst landscape contributes to the ability of the groundwater at the spring s ite to make its way through the system of voids found in the karst aquifers, to eventually emerge on the land. The Spring Creek springs group has the highest maximum discharge of 1153.5 cubic feet per second. It is located in the panhandle and very near the coastline. The group lies outside of the extents of the physiography dataset, and it issues from the St. Marks formation. The St. Marks formation is a sandy marine limestone from the Lower Miocene that is often exposed in streambeds and sinkholes in northern Florida (FGS, 2006). It should be noted that there are 14 different spri ngs that make up the Spring Creek springs group, a fact that undoubtedly influences the extremely high amount of discharge. The low elevation and close pr oximity to the coastline are not necessarily causal factors for high discharge. Wekiwa spring generates the longest spri ng run at about 89,760 feet, or about 17 miles. It is located in nort hern peninsular Florida in the Osceola Plain, and it resurges from the Cypresshead formation. This fo rmation is a shallow marine sandstone indigenous to peninsular Flor ida and parts of Georgia (U SGS, 2004). Other maximums in the data set include the fact that Apopka spring is the furthest from the coastline at 51.91 miles. It is located in northern peninsular Florida in the Central Valley, and issues from the Cypresshead formation. Wakulla spri ng has the deepest pool at about 185 feet. The spring issues from the St. Marks formation.
56 Physiography & Geology The distribution of the springs in the repr esentative sample relative to Floridas physiographic regions and geologic formations was also examined. Attention has been given to which regions and fo rmations contain the highest concentrations of springs. Because this research has generated a large vol ume of data related to numerous aspects of Floridas springs, it will not be practical to di scuss the entire database Instead, only the portions of the database deemed as most pert inent after visual inspection of figures and tables will be discussed in detail. In tables 5-11 the gray-shaded rows of data fit this description and are therefor e discussed in detail. Tables 8-14 show descriptive statistics for each of the physiographic regions that contain springs. Since the springs are con centrated within 21 physiographic regions, 64 regions do not contain any first, second, or th ird magnitude springs that are examined in this study. Please note that some physiograp hic regions only cont ain one spring group. Descriptives for these regions were not calculated. Although springs groups are considered to be a single feature, morpmometric data is rarely available for each individual vent in the group. Some general observations we re made concerning the Gulf Coastal Lowland region. This region is excep tionally notable in Tables 5-18 as follows.
57 Magnitude Run PHYIOGRAPHIC REGION N 1 2 3 Yes No Central Valley 2 1 0 1 2 0 Coastal Swamps 5 2 1 2 4 1 Crescent City Ridge 1 0 1 0 1 0 Eastern Valley 1 0 0 1 1 0 Fountain Slope 2 1 1 0 2 0 Greenhead Slope 1 0 1 0 1 0 Gulf Coastal Lowlands 47 19 23 5 39 8 High Springs Gap 7 4 3 0 4 3 Lake Harris Cross Valley 1 0 1 0 1 0 Lake Wales Ridge 1 0 1 0 0 1 Marianna Lowlands 13 1 11 1 12 1 Marion Upland 5 2 3 0 5 0 Mount Dora Ridge 1 0 1 0 1 0 Northern Highlands 2 0 2 0 2 0 Osceola Plain 3 0 3 0 3 0 Polk Upland 1 0 1 0 1 0 St. Johns River Offset 2 1 1 0 2 0 Tsala Apopka Plain 2 0 2 0 2 0 Wakulla Sand Hills 1 0 1 0 1 0 Western Valley 3 2 1 0 2 1 Zephyrhills Gap 1 0 1 0 0 1 Table 8: Magnitude and run generation by physiographic region The Gulf Coastal Lowlands stands out for its higher percentage of springs that do not generate a spring run. Out of the 47 springs located within this region, eight (or about 17%) do not generate a spring run. The high perc entage of springs that do not generate a spring run can also be attributed to the nature of the karst landscape. Higher secondary porosity and permeability values in some areas of the Ocala Limestone probably inhibit surface flow in these areas.
58 ELEVATION (FT.) PHYIOGRAPHIC REGION N MIN MAX MEAN Central Valley 2 24.693 45.061 34.877 Coastal Swamps 5 3.491 27.396 10.693 Crescent City Ridge 1 18.226 18.226 18.226 Eastern Valley 1 16.139 16.139 16.139 Fountain Slope 2 18.790 27.688 23.239 Greenhead Slope 1 30.123 30.123 30.123 Gulf Coastal Lowlands 47 0.330 80.798 27.056 High Springs Gap 7 24.365 49.582 32.651 Lake Harris Cross Valley 1 62.227 62.227 62.227 Lake Wales Ridge 1 68.120 68.120 68.120 Marianna Lowlands 13 26.688 86.346 58.269 Marion Upland 5 4.068 32.052 18.617 Mount Dora Ridge 1 50.892 50.892 50.892 Northern Highlands 2 39.769 48.966 44.367 Osceola Plain 3 27.006 39.014 34.076 Polk Upland 1 6.585 6.585 6.585 St. Johns River Offset 2 0.502 14.423 7.463 Tsala Apopka Plain 2 37.144 44.080 40.612 Wakulla Sand Hills 1 15.759 15.759 15.759 Western Valley 3 33.617 53.710 40.880 Zephyrhills Gap 1 51.643 51.643 51.643 Table 9: Elevation descriptives by physiographic region The Marianna Lowlands contains Jack son Blue Spring, the highest elevation spring in the sample at 86.346 feet above sea level, and also contains Blue Hole Spring at 84.480 feet of elevation. Springs in the Gulf Coastal Lowland represent the secondhighest maximum elevation value, occurr ing at Owens Spring, 80.879 feet above sea level. It interesting to note the these regi ons contain springs with some of the highest elevation values in the sample, and yet they are classified as lowlands. This further illustrates the marginal range of elevation values at which Floridas springs are typically found.
59 DISCHARGE (CFS) PHYIOGRAPHIC REGION N MIN MAX MEAN Central Valley 2 5.270 556.000 280.635 Coastal Swamps 5 0.360 360.000 118.084 Crescent City Ridge 1 10.710 10.710 10.710 Eastern Valley 1 3.590 3.590 3.590 Fountain Slope 2 11.530 160.800 86.165 Greenhead Slope 1 26.480 26.480 26.480 Gulf Coastal Lowlands 47 7.650 1153.500 138.591 High Springs Gap 7 39.500 222.930 104.930 Lake Harris Cross Valley 1 10.930 10.930 10.930 Lake Wales Ridge 1 30.090 30.090 30.090 Marianna Lowlands 13 5.700 165.600 48.458 Marion Upland 5 10.630 118.000 67.044 Mount Dora Ridge 1 57.310 57.310 57.310 Northern Highlands 2 27.830 98.950 63.390 Osceola Plain 3 15.300 70.050 34.700 Polk Upland 1 33.540 33.540 33.540 St. Johns River Offset 2 26.350 121.000 73.675 Tsala Apopka Plain 2 15.960 35.170 25.565 Wakulla Sand Hills 1 15.000 15.000 15.000 Western Valley 3 33.920 783.600 310.297 Zephyrhills Gap 1 75.670 75.670 75.670 Table 10: Discharge descriptives by physiographic region The Gulf Coastal Lowland shows a relative ly high mean discharge, and contains three of the highest dischargi ng springs in the sample: the Spring Creek Springs Group at over 1000 cfs, the Kings Bay Springs Group at 97 5 cfs, and the Alaphia River Rise at 605 cfs (Table 7). This is attributed to the welldeveloped karst landscape in the region that is characterized by the Ocala Limestone. Hence, this indicates that the springs are karst solution springs.
60 DEPTH (FT.) PHYIOGRAPHIC REGION N MIN MAX MEAN Central Valley 2 12.000 12.000 12.000 Coastal Swamps 5 4.000 53.000 22.100 Crescent City Ridge 1 18.000 18.000 18.000 Eastern Valley 1 28.000 28.000 28.000 Fountain Slope 2 2.000 2.000 2.000 Greenhead Slope 1 10.100 10.100 10.100 Gulf Coastal Lowlands 47 5.900 185.000 29.550 High Springs Gap 7 12.200 49.000 26.971 Lake Harris Cross Valley 1 170.000 170.000 170.000 Lake Wales Ridge 1 45.000 45.000 45.000 Marianna Lowlands 13 14.000 49.100 27.169 Marion Upland 5 5.000 25.000 15.940 Mount Dora Ridge 1 5.000 0.000 0.000 Northern Highlands 2 7.800 83.000 45.400 Osceola Plain 3 7.200 14.800 11.900 Polk Upland 1 8.200 8.200 8.200 St. Johns River Offset 2 20.000 28.000 24.000 Tsala Apopka Plain 2 9.800 22.000 15.900 Wakulla Sand Hills 1 12.000 12.000 12.000 Western Valley 3 21.400 34.500 27.950 Zephyrhills Gap 1 10.000 10.000 10.000 Table 11: Depth descriptives by physiographic region The Gulf Coastal Lowland contains Wakulla spring, the deepest spring in the sample at 185 feet. Springs in the Marria nna Lowlands also exhibit a relatively high mean depth, considering the higher number of springs contained within the region. It is difficult to speculate upon the significance of regions like the Lake Harris Cross Valley or the Lake Wales Ridge. Although these regi ons also stand out fo r their depth values, they only contain a single spring.
61 POOL AREA (SQ. FT.) PHYIOGRAPHIC REGION N MIN MAX MEAN Central Valley 2 10989.000 10989.000 10989.000 Coastal Swamps 5 2430.000 62040.000 18060.000 Crescent City Ridge 1 18963.000 18963.000 18963.000 Eastern Valley 1 225.000 225.000 225.000 Fountain Slope 2 5985.000 5985.000 5985.000 Greenhead Slope 1 3249.000 3249.000 3249.000 Gulf Coastal Lowlands 47 36.000 99225.000 14721.917 High Springs Gap 7 6300.000 28875.000 15460.571 Lake Harris Cross Valley 1 147312.000 147312.000 147312.000 Lake Wales Ridge 1 32400.000 32400.000 32400.000 Marianna Lowlands 13 900.000 90000.000 23060.308 Marion Upland 5 10800.000 77400.000 31856.200 Mount Dora Ridge 1 NA NA NA Northern Highlands 2 425.000 41280.000 20852.500 Osceola Plain 3 900.000 11025.000 5427.000 Polk Upland 1 30240.000 30240.000 30240.000 St. Johns River Offset 2 14175.000 31752.000 22963.500 Tsala Apopka Plain 2 5589.000 14400.000 9994.500 Wakulla Sand Hills 1 1225.000 1225.000 1225.000 Western Valley 3 4536.000 22785.000 9107.000 Zephyrhills Gap 1 37260.000 37260.000 37260.000 Table 12: Pool area descriptives by physiographic region It is interesting to note that the lowest minimum pool area value as well as one of the highest maximum pool area values both correspond to springs that are located within the Gulf Coastal Lowlands. This could be a result of that region containing the highest number of springs in the dataset, and th e fact that any given spring has a higher probability of being located within the Gulf Coastal Lowland than in any other region.
62 RUN LENGTH (FT.) PHYIOGRAPHIC REGION N MIN MAX MEAN Central Valley 2 500.000 26400.000 13450.000 Coastal Swamps 4 75.000 29040.000 6949.000 Crescent City Ridge 1 2500.000 2500.000 2500.000 Eastern Valley 1 450.000 450.000 450.000 Fountain Slope 2 500.000 820.000 660.000 Greenhead Slope 1 443.000 443.000 443.000 Gulf Coastal Lowlands 47 7.000 39600.000 2846.438 High Springs Gap 7 500.000 1100.000 819.000 Lake Harris Cross Valley 1 4224.000 4224.000 4224.000 Lake Wales Ridge 1 0.000 0.000 0.000 Marianna Lowlands 13 150.000 8448.000 1441.846 Marion Upland 5 600.000 52800.000 24144.000 Mount Dora Ridge 1 45408.000 45408.000 45408.000 Northern Highlands 2 90.000 90.000 90.000 Osceola Plain 3 500.000 89760.000 30086.667 Polk Upland 1 950.000 950.000 950.000 St. Johns River Offset 2 1050.000 1320.000 1185.000 Tsala Apopka Plain 2 2112.000 4224.000 3168.000 Wakulla Sand Hills 1 50.000 50.000 50.000 Western Valley 3 21270.000 30096.000 25683.000 Zephyrhills Gap 1 0.000 0.000 0.000 Table 13: Distance to coastline de scriptives by physiographic region The Coastal Swamps region contains the lowe st minimum, maximum, and mean values for distance to coastline in the entire sample dataset. This is not surprising, due to the region being a very narrow strip of Floridas land that skirts the gulf coast in the big bend area. No clear trend in the data could be found for this variable.
63 RUN LENGTH (FT.) PHYIOGRAPHIC REGION N MIN MAX MEAN Central Valley 2 500.000 26400.000 13450.000 Coastal Swamps 5 75.000 29040.000 6949.000 Crescent City Ridge 1 2500.000 2500.000 2500.000 Eastern Valley 1 450.000 450.000 450.000 Fountain Slope 2 500.000 820.000 660.000 Greenhead Slope 1 443.000 443.000 443.000 Gulf Coastal Lowlands 47 7.000 39600.000 2846.438 High Springs Gap 7 500.000 1100.000 819.000 Lake Harris Cross Valley 1 4224.000 4224.000 4224.000 Lake Wales Ridge 1 NA NA NA Marianna Lowlands 13 150.000 8448.000 1441.846 Marion Upland 5 600.000 52800.000 24144.000 Mount Dora Ridge 1 45408.000 45408.000 45408.000 Northern Highlands 2 90.000 90.000 90.000 Osceola Plain 3 500.000 89760.000 30086.667 Polk Upland 1 950.000 950.000 950.000 St. Johns River Offset 2 1050.000 1320.000 1185.000 Tsala Apopka Plain 2 2112.000 4224.000 3168.000 Wakulla Sand Hills 1 50.000 50.000 50.000 Western Valley 3 21270.000 30096.000 25683.000 Zephyrhills Gap 1 NA NA NA Table 14: Run length descript ives by physiographic region Spring runs in the Gulf Coastal Lowland represent the lowest mean length of the entire sample, due to the springs dischargi ng over a short distance into the three major rivers in the region. Regarding the distribution of springs am ong the physiographic regions, there is a relatively large difference between the region w ith the highest number of springs and the region with the second-highest number of spri ngs (Table 5). The Gulf Coastal Lowlands region contains a total of 47 springs (19 first magnitude, 23 second magnitude, and 5 third magnitude), which is nearly four tim es as many springs as the next-closest
64 hysiographic region (Marianna Lowlands with 13 springs). Figures 19 displays this concentration of springs within the Gulf Coastal Lowland.
65 Figure 20: Physiography overlaid with spring locations
66 There are 37 different geologic formations in Florida. All of the springs in the sample are distributed within 15 of those fo rmations, leaving 22 formations that do not contain any springs. Tables 15-21 show descri ptive statistics for each of the 15 geologic formations that contain springs. Table 16 c ontains a topology which indicates the general nature of the geologic formation contained in the database used in this research. 69 springs issue from carbonate (karst forming) units, 22 from unconsolidated sediments, and 10 from a quartz sandstone unit. Magnitude Run Geologic Formation N 1 2 3 Yes No Alluvium 5 0 4 1 5 0 Alum bluff group 5 0 5 0 5 0 Beach ridge and dune 1 1 0 0 1 0 Cypresshead formation 6 2 4 0 5 1 Hawthorn Group, Arcadi a Formation, Tampa Member 3 0 2 1 3 0 Hawthorn Group, Co osawhatchie Formation 4 0 4 0 4 0 Hawthorn Group, Peace Ri ver Formation 1 0 1 0 1 0 Holocene Sediments 3 1 2 0 3 0 Ocala Limestone 39 16 23 2 30 9 Residuum on Oligocene sediments 4 0 4 0 4 0 St. Marks Formation 9 4 4 2 8 1 Suwannee Limestone 11 4 5 2 7 4 Suwannee Limestone Marianna Limestone undifferentiated 2 1 0 1 1 1 Undifferentiated sediments 9 4 1 4 9 0 Table 15: Magnitude and run generation descriptives by geologic formation The vast majority of Floridas firs t magnitude springs correspond to karst geologic units (all 33 first magnitude springs ar e included in the representative sample). Of these 33 springs 28, or 84.8% correspond to the carbonate geologi c units highlighted in the table above.
67 ELEVATION (FT.) GEOLOGIC FORMATION N TYP. MIN MAX MEAN ALLUVIUM 5 US 26.688 195.922 59.714 ALUM BLUFF GROUP 5 C 22.252 163.401 49.802 BEACH RIDGE AND DUNE 1 US 17.645 57.894 17.645 CYPRESSHEAD FORMATION 6 S 13.718 223.502 68.120 HAWTHORN GROUP, ARCADIA FORMATION, TAMPA MEMBER 3 C 6.585 25.168 7.671 HAWTHORN GROUP, COOSAWHATCHIE FORMATION 4 S 27.006 128.006 39.014 HAWTHORNE GROUP, PEACE RIVER FORMATION 1 M 9.121 29.927 9.121 HOLOCENE SEDIMENTS 3 US 0.502 50.219 15.306 OCALA LIMESTONE 39 C 1.083 277.176 84.479 RESIDUUM ON OLIGOCENE SEDIMENTS 4 US 68.514 260.534 79.407 ST. MARKS FORMATION 9 C 3.461 60.122 18.324 SUWANNEE LIMESTONE 11 C 3.491 194.867 59.393 SUWANNEE LIMESTONE-MARIANNA LIMESTONE UNDIFF. 2 C 86.346 283.301 86.346 UNDIFFERENTIATED SEDIMEN TS 9 US 16.139 199.787 60.892 Table 16: Elevation descriptives by geologic formation. Also included is a typology for each of the geologic form ations that expresses the general nature of the geology. US=unconsolidated sediment, S=sandsto ne, C=carbonate rock, and M=mixed geology It is interesting to note the range of mean elevation values among the listed physiographic regions. Most re gions contain springs with m ean elevation less than 60 feet. It was previously observ ed that about 86% of Floridas springs fall into this range. Even those regions with mean elevation valu es higher than 60 feet, such as the Ocala Limestone, Residuum on Oligocene Sediments, the Hawthorne Group, Arcadia Formation, Tampa Member, and the Suwannee Limestone-Marianna Limestone Undifferentiated, all have mean elevation valu es that are, relatively speaking, not much higher than the most populous range.
68 DEPTH (FT.) GEOLOGIC FORMATION N MIN MAX MEAN ALLUVIUM 5 15 46 29.05 ALUM BLUFF GROUP 5 2 36 17.22 BEACH RIDGE AND DUNE 1 45 45 45 CYPRESSHEAD FORMATION 6 13.7 170 54.74 HAWTHORN GROUP, ARCADIA FORMATION, TAMPA MEMBER 3 8.2 30 19.1 HAWTHORN GROUP, COOSAWHATCHIE FORMATION 4 5 14.8 9.675 HAWTHORNE GROUP, PEACE RIVER FORMATION 1 8.3 8.3 8.3 HOLOCENE SEDIMENTS 3 18 28 22 OCALA LIMESTONE 39 5.9 84 24.8 RESIDUUM ON OLIGOCENE SEDIMENTS 4 18 49.1 32.125 ST. MARKS FORMATION 9 6 185 41.867 SUWANNEE LIMESTONE 11 4 150 43.936 SUWANNEE LIMESTONE-MARIANNA LIMESTONE UNDIFF. 2 16.5 16.5 16.5 UNDIFFERENTIATED SEDIMENTS 9 9 39 19.833 Table 17: Depth descriptiv es by geologic formation The three formations with highest mean depth values, the Cypresshead Formation, the St Marks Formation, and th e Suwannee Limestone, all contai n a very deep spring that skews this statistic. Wakulla spring, the deepest in the entire dataset, corresponds to the St Marks Formation. There is no clear trend in the data for this variable.
69 DISCHARGE (CFS) GEOLOGIC FORMATION N MIN MAX MEAN ALLUVIUM 5 5.7 89.47 46.708 ALUM BLUFF GROUP 5 11.53 40.52 25.048 BEACH RIDGE AND DUNE 1 176 176 176 CYPRESSHEAD FORMATION 6 10.93 121 70.014 HAWTHORN GROUP, ARCADIA FORMATION, TAMPA MEMBER 3 33.54 62.43 47.985 HAWTHORN GROUP, COOSAWHATCHIE FORMATION 4 10.63 18.75 14.64 HAWTHORNE GROUP, PEACE RIVER FORMATION 1 13.23 13.23 13.23 HOLOCENE SEDIMENTS 3 26.35 112 73.02 OCALA LIMESTONE 39 9.98 350 74.377 RESIDUUM ON OLIGOCENE SEDIMENTS 4 15.4 62.4 35.245 ST. MARKS FORMATION 9 7.65 452 113.93 SUWANNEE LIMESTONE 11 0.36 605.4 134.753 SUWANNEE LIMESTONE-MARIANNA LIMESTONE UNDIFF. 2 165.6 165.6 165.6 UNDIFFERENTIATED SEDIMENTS 9 3.59 184 37.013 Table 18: Discharge descript ives by geologic formation The highest mean discharge values are all associated with karst geologic formations. The Suwannee Limestone correspon ds to the Alaphia River Rise, the highest discharging spring in the sample at 605.4 cfs, and also corresponds to the Nutall River Rise which discharges 360 cfs. The s econd highest maximum discharge is found among the spring of the St. Marks Formation, due to the St. Marks River Rise at 452 cfs. This formation also corresponds to Wakulla Spri ng, another very high discharging spring at 390 cfs.
70 POOL AREA (SQ. FT.) GEOLOGIC FORMATION N MIN MAX MEAN ALLUVIUM 5 900 90000 26712 ALUM BLUFF GROUP 5 3249 28620 12366 BEACH RIDGE AND DUNE 1 34650 34650 34650 CYPRESSHEAD FORMATION 6 11025 147312 56462.4 HAWTHORN GROUP, ARCADIA FORMATION, TAMPA MEMBER 3 8100 30240 19170 HAWTHORN GROUP, COOSAWHATCHIE FORMATION 4 900 11700 6939 HAWTHORNE GROUP, PEACE RIVER FORMATION 1 2025 2025 2025 HOLOCENE SEDIMENTS 3 24381 35000 30377.667 OCALA LIMESTONE 39 1190 53865 14740.111 RESIDUUM ON OLIGOCENE SEDIMENTS 4 4680 22500 12917.25 ST. MARKS FORMATION 9 1225 99225 22102.778 SUWANNEE LIMESTONE 11 36 62040 16552.273 SUWANNEE LIMESTONE-MARIANNA LIMESTONE UNDIFF. 2 55920 55920 55920 UNDIFFERENTIATED SEDIMENTS 9 225 24336 10710 Table 19: Pool area descript ives by geologic formation The Suwannee Limestone-Marianna Limestone Undifferentiated formation corresponds to the lowest minimum pool area. The highest maximu m pool area is found issuing from the Cypresshead Formation, and many of the highest maximum and mean pool area values correspond to car bonate geologic units. Howeve r, there is no clear trend in the data for this variable.
71 DISTANCE TO COASTLINE (MI.) GEOLOGIC FORMATION N MIN MAX MEAN ALLUVIUM 5 9.563 23.079 17.598 ALUM BLUFF GROUP 5 7.994 22.785 14.459 BEACH RIDGE AND DUNE 1 4.6 4.6 4.6 CYPRESSHEAD FORMATION 6 23.949 51.914 38.324 HAWTHORN GROUP, ARCADIA FORMATION, TAMPA MEMBER 3 5.219 9.423 7.321 HAWTHORN GROUP, COOSAWHATCHIE FORMATION 4 33.033 38.873 35.987 HAWTHORNE GROUP, PEACE RIVER FORMATION 1 5.663 5.663 5.663 HOLOCENE SEDIMENTS 3 21.134 36.096 30.272 OCALA LIMESTONE 39 2.768 43.735 30.307 RESIDUUM ON OLIGOCENE SEDIMENTS 4 19.948 20.544 20.227 ST. MARKS FORMATION 9 1.582 14.213 9.8 SUWANNEE LIMESTONE 11 0.876 20.895 10.116 SUWANNEE LIMESTONE-MARIANNA LIMESTONE UNDIFF. 2 12.219 12.219 12.219 UNDIFFERENTIATED SEDIM ENTS 9 4.216 43.145 22.034 Table 20: Distance to coastline de scriptives by ge ologic formation The lowest minimum distance to the coastline corresponds to the St. Marks formation, which also represents one of the lowest mean values. The highest maximum distance from the coastline for any spring is found issuing from the Cypresshead formation. The Gulf Coastal Lowland also corresponds to a high maximum and mean value for this variable, probably due to its wi despread coverage. No clear trend in the data could be found for this variable.
72 RUN LENGTH (FT.) GEOLOGIC FORMATION N MIN MAX MEAN ALLUVIUM 5 1800 29040 15420 ALUM BLUFF GROUP 5 150 3696 1399 BEACH RIDGE AND DUNE 1 350 4752 1389 CYPRESSHEAD FORMATION 6 26400 26400 26400 HAWTHORN GROUP, ARCADIA FORMATION, TAMPA MEMBER 3 1050 89760 36536.4 HAWTHORN GROUP, COOSAWHATCHIE FORMATION 4 650 950 800 HAWTHORNE GROUP, PEACE RIVER FORMATION 1 500 52800 17966.667 HOLOCENE SEDIMENTS 3 15 15 15 OCALA LIMESTONE 39 1320 21120 8800 RESIDUUM ON OLIGOCENE SEDIMENTS 4 25 31680 4019.379 ST. MARKS FORMATION 9 275 1025 662.5 SUWANNEE LIMESTONE 11 50 39600 6095 SUWANNEE LIMESTONE-MARIANNA LIMESTONE UNDIFF. 2 75 5280 2377 UNDIFFERENTIATED SEDIMENTS 9 350 26400 5108.333 Table 21: Run length descript ives by geologic formation While the Holocene Sediments formation corresponds to the lowest minimum run length value, it interesting to not ice that some of the lowest mean values for this variable (relatively speaking) correspond to carbonate units such as the Suwannee Limestone and the St. Marks formation. With this said, other carbonate units, such as the Ocala Limestone, correspond to a much higher mean r un length value. No clear trend in the data could be found for this variable. Several geologic formations stand out as having substantially more springs located within them than the others. Th ese include the Ocala Limestone, the Suwannee Limestone, the St. Marks Formation (a marine limestone), and the designation undifferentiated sediments. Because 70 of the 102 first, second, and third magnitude springs used in this study re surge from carbonate units, it ap pears that many of Floridas springs can be specifically classified as karst solution springs Areas where the limestone
73 Figure 21 displays spring locations overlaid with the Gulf Coastal Lowland and carbonate geologic formations. The Ocala Limestone, the Suwannee Limestone, the St. Marks formation, and Undifferentiated Sediments are shown. Figure 20 displays the representative sample of Floridas springs overlaid with geologic data. The four previously mentioned formations (Ocala Limestone, Suwannee Limestone, St. Marks Formation, and Undifferentiated sediments) are shown. These formations are singled out because they exhibit high concentrations of springs. As was the case with the previous examination of the entire population of springs relative to area geology, the observed correspondence between these formations and the bulk of the entire springs population is hereby observed. is exposed at or near to the surface will therefore be the most likely locations where springs will form. The Ocala Limestone contains nearly four times as many spring resurgences as the Suwannee Limestone, which contains the second highest number of resurgences. 37.2% of the springs in the study issue from the Ocala Limestone, while 10.9% resurge from the Suwannee Limestone. In total 59 springs (or 57.8%) issue from geologic units that contain limestone or are formed in some type of carbonate material, and are thus directly associated with Floridas karst landscape.
Figure 21: Geologic formations overlaid with spring locations 74
75 Figure 22: Locations of springs corresponding to the Gulf Coastal Lowlands and the Ocala Limestone
76 Figure 21 displays data that serve to aid in the examination of how the distribution of the sample of Floridas spri ngs compares with the distribution of karst lands. Out of the total of 47 springs in the Gulf Coastal Lowland, 25 (or about 53%) correspond to the Ocala Limestone, 8 (or about 17%) correspond to the St. Marks Formation, and 5 (or 10.7%) correspond to the Suwannee Limestone. The overlap that is seen between springs in this region and thos e that correspond to the Ocala Limestone and the other carbonate units is al so recognizable. As previous ly noted, 72.2% of the springs in the Gulf Coastal Lowland region resurge from the Ocala Limestone and about 28% issue directly from other carbonate units. Th e influence that karst terrain has on spring locations can be observed through visual appraisal of the spatial di stribution of springs relative to the Gulf Coastal Lowland and the three geologic formations mentioned. This again is an indication of the importance of the karst landscape influence on spring development. Several additional observations were also made with respect to the relationship between the geologic formations and the springs that resurge from these formations. The most noteworthy of these obs ervations all corr espond to limestone formations, thus further illuminating the relationship between area geology and th e influence it exerts upon spring formation in Florida. As previous ly noted, the Ocala Limestone is associated with 39 springs, more than any other geologic formation, the Suwannee Limestone contains 11 spring resurgences (the second highest number in the database), and the St. Marks Formation and Undifferentiated Sediments each possess nine spring resurgences (Table 15). The Ocala Limestone contains the highest number of springs that do not generate a spring run (Table 15). The Ocala and Suwannee/Marianna Limestone
77 formations correspond to the two springs with the highest mean discharge values (Table 18). The undifferentiated sediments geologic formation also has one of the highest mean discharge values, as well as the second hi ghest number of springs. The high mean discharge value, as well as th e high number of springs, can be attributed to the fact that the sediment buries adjacent to carbonate geologic units. Groundwater resurging from the associated limestone units is possibly seeping through the undiffe rentiated sediments to eventually resurge on the land surface. The data accumulated and discussed thus far seems to indicat e that the springs studied as part of this research are for th e most part associated with the limestone formations and karst terrain of the study area. This point is further illuminated by the point that the geologic formations that ar e characterized by car bonate units or are somehow associated with the carbonates, lik e the undifferentiated sediments, are most commonly associated with physiographic regions that contain the highest number of springs. Hence, this examination of Floridas springs in terms of geology and physiography supports the conclusion that majo rity of Floridas springs are located in regions characterized by karst te rrain. More specifically, th is phenomenon in fact imparts the prevailing influence on the spatia l distribution of Floridas springs. This is further illustrated by the fact that 69 of the 102 (about 68%) springs utilized in this study issue from carbonate geologic units (see table 16). Twenty-two springs (21%) resurge from unconsolidated se diments, which as previously noted, are probably related to the carbonate units in that groundwater discharges from the carbonates, and seeps through the sediments to eventually resurge on the land surface. Of the 102 springs utilized in this study, only eleven (10.7%) resurge from sandstone, or
Elevation & Distance to Coastline Figure 23 displays the Euclidian distance raster layer overlaid with locations of Floridas springs. Initial visual appraisal of the spatial distribution of springs across the Euclidian distance raster does not indicate a relationship between the two. Figure 22 shows the DEM mosaic and hillshade raster overlaid with springs data points. The hillshade/DEM combination offers a perspective that makes the elevation data easier to interpret visually. It has been noted in this figure that most of the springs points correspond to areas with low elevations. As was to be expected, the pattern of springs in the representative sample being distributed mostly across areas with low elevations reflects that of the entire population. This observation is also in keeping with those of Mylroie (1995), who, as previously stated, observed the trend of springs being located and generally low elevations. 78 geologically mixed units, and these springs may also have some relation to area carbonate units. The connection that has been observed between spring distribution and karst lands is related to observations made by Smith (2004) and Davis (1997). Smith (2004) discusses the influence of karst lands upon the degree to which the water quality of the Upper Floridan aquifer is influenced by its interaction with surface water, and states its dependency proximity to karst features. Davis (1997) discusses the role that karst plays in the effectiveness of fluid transfer between conduits and the surrounding matrix. Both discussions point to karst terrain as a strong influencing factor upon specific attributes and processes of the Floridan Aquifer. The research on Floridas springs also names karst terrain as the prevailing influence upon the distribution of Floridas springs, a collection of karst features that are part of the Floridan Aquifer.
Figure 23: USGS 30m DEM overlaid with spring locations 79
80 Figure 24: Euclidian distance to coastline overlaid with spring locations
81 Comparison of Noticeable Spring Clusters There are several noticeable cl usters of springs. Springs within each cluster are in such close proximity to each other and in such distant proximity to those in other clusters that these clusters can be obs erved and recognized visually. Attention has been given to noting how springs in each cluster are similar to each other but differ from those in other clusters. Attention has also been given to noting the similarities and differences as expressed through notable morphometric tr ends or patterns between the clusters themselves. For the sake of discussion, the clusters have been assigned numbers 1, 2 and 3. Figure 24 shows these clusters as they have been visually noted. Cluster 1 is made up of 17 springs (16.6% of the springs used in this study) and is located near the western end of the panhandle. All of the springs in this cluster drain to either the Apalachicola or the Choctawhatchee Rivers. Of the 16 springs in this cluster that generate a run, 12 of them, or 75% are less than 1000 feet long. The close proximity of spring in this cluster to major rivers ma y be influencing the shorter spring run lengths as is the case with cluster 3 as well. Table 22 shows descriptive stat istics for cluster 1. PARAMETER MIN MAX MEAN DEPTH (FT.) 2.000 49.100 22.782 DISCHARGE (CFM) 5.700 165.600 51.134 ELEVATION (M) 5.727 26.317 15.353 POOL AREA (SQ. FT.) 900.000 90000.000 18902.294 DISTANCE TO COAST (MI.) 7.071 23.079 15.679 RUN LENGTH (FT.) 150.000 8448.000 1485.824 Table 22: Cluster 1 descriptives
82 Figure 25: Locations of spring clusters
83 Cluster 2 is made up of 13 springs (12.7% of the springs used in this study) and is located in the panhandle just we st of the big bend area. Th is cluster is characterized by most of its springs being very close to the gul f coast. They range from being less than a tenth of a mile to the coastline to 15.257 miles distant. Furthermore, springs in cluster 2 establish a shorter range of distances to the coastline than clusters 1 and 3. This constitutes the lowest mean distance to coas tline out of the three clusters. Springs in cluster 2 also establish the lowest mean el evation, with values ranging from about three quarters of a meter up to 9.263 meters high. This is also a manifestation of the fact that they are close to the Gulfs coas tline. It is also noted that cluster 2 has the longest mean run length of 39,600 feet, or a bout 7.5 miles. Table 23 show s descriptive statistics for cluster 2. PARAMETER MIN MAX MEAN DEPTH (FT.) 6.000 185.000 36.062 DISCHARGE (CFM) 7.650 1153.500 221.796 ELEVATION (M) 0.725 9.263 3.394 POOL AREA (SQ. FT.) 1225.000 99225.000 25837.692 DISTANCE TO COAST (MI.) 0.093 15.257 8.235 RUN LENGTH (FT.) 50.000 39600.000 3889.231 Table 23: Cluster 2 descriptives Examining cluster 2 based on its morphometry helps to explain some preliminary observations made on the springs it contains. All of the spring s in cluster 2 either drain directly to the gulf via a small stream or drai n to a lesser river such as the Wakulla or the Saint Marks Rivers, which ultimately flow into th e gulf. This trend is very different from the other two clusters, especially cluster 3 in which all of the springs flow directly into a major river. As a result, it could be expect ed that run lengths of springs that drain
84 directly to the gulf will be longer than thos e which can drain to a nearby major river. Springs in cluster 2 are also located in a coastal lowland region, accounting for their low elevation values. The morphometry of cl uster 2 supports these expectations, and furthermore may be typical of springs that are in such close proximity to the coastline. Cluster 3 is made up of 38 springs (37% of the springs used in this study) and is located at the big bend area. All of the 29 sp rings in this cluster which generate a run drain into one of three major rivers: the Suwannee, the Withlacoochee, or the Santa Fe River. Consequently, the longe st spring run found in cluster 3 is only a mile long. Of the 29 spring runs corresponding to th is cluster, 23 of them, or 79.3% are less than 1000 feet long. This trend is unique to cluster 3, as is the large percentage of springs within the cluster that all correspond to the same phys iographic region. The Gulf Coastal Lowland underlies 36 of the 38 springs in cluster 3, or 94.7%. Table 24 shows descriptive statistics for cluster 3. PARAMETER MIN MAX MEAN DEPTH (FT.) 5.900 150.000 30.090 DISCHARGE (CFM) 9.270 605.400 94.678 ELEVATION (M) 1.081 24.626 11.592 POOL AREA (SQ. FT.) 36.000 42750.000 12975.790 DISTANCE TO COAST (MI.) 8.388 43.735 29.093 RUN LENGTH (FT.) 25.000 5280.000 646.368 Table 24: Cluster 3 descriptives These results are supported by the initial observations of the springs in cluster 3. They are all in very close proximity (one mile distant or less) to either the Suwannee, the Withlacoochee, or the Santa Fe River. Spri ng runs in this cluster discharge into these hydrographic features rather than draining all the way to the gulf coast. As a result,
85 springs in this area generate the shortest distance runs overall of any region in Florida. This trend places cluster 3 in very sharp contrast to cluster 2. These two clusters also differ significantly with regard to the range of elevations at which springs are located. Cluster 3 represents a wider range of elevation values because the springs contained within it are spread out across an area that also represents a wider range of distances to the coastline. This cluster reaches further inland and therefore also reaches areas of higher elevations than those found in the lower coastal lowlands that underlie cluster 2. Figures 25 and 26 display spring locations symbolized according to their run length attribute values, overlaid with geology and Euclidian distance to coastline. The trends in run length can be viewed here, particularly with regard to those discussed in cluster 3. The remaining 33 springs spread across northern peninsular Florida are not grouped into any visually recognizable clusters. Examination of the morphometry of these springs does not yield any noticeable trends or patterns. Descriptive statistics for these springs are displayed in Table 25. Table 25: Descriptives for non-clustered springs in northern peninsular Florida PARAMETER MIN MAX MEAN DEPTH (FT.) 4.000 170.000 21.230 DISCHARGE (CFM) 0.360 975.000 119.566 ELEVATION (M) 0.153 20.762 7.523 POOL AREA (SQ. FT.) 900.000 147312.000 19781.152 DISTANCE TO COAST (MI.) 0.876 51.914 22.471 RUN LENGTH (FT.) 15.000 89760.000 13481.030
Figure 26: Spring locations symbolized by run length and overlaid with geologic formations 86
87 Figure 27: Spring locations symbolized by run length and overlaid with Euclidian distance to coastline
88 Evaluation of GIS as an asset to morphometric analysis The overall usefulness of GIS as a research tool in this study has been evaluated. This evaluation considers how well ArcGIS 9.1 aided the user in exploring the descriptive elements of Florida s springs and how they relate to their locations. In order for any tool to be considered a valuable asset to a study whose main purpose is to conduct research on the morphometry of a spatial phenom enon, that tool must give the user some perspective of how the description of that phenomenon varies according to the location of each occurrence. The spatial da taset of Floridas springs that was created in this study represents a union of these two things. Im plementing GIS in this study increased the overall efficiency of the tasks associated with compiling, creating and consolidating the final morphometric database. Acquiring valu es for the geographical parameters was expedited due to the automated functions of ArcMap 9.1. More generally speaking, this study finds that the fundamental capability of processing location and attribute information about a single dataset that is found with almost all GIS technologies is naturally suited to a morphometric study.
89 Chapter 6 Summary & Conclusions This study has sought to examine a subs et of Floridas springs based on their geographic locations and morphometric at tributes. Research was conducted on two different scales to better facilitate this objective. Regarding the question of whether springs that exist in different geographic regions of Florida exhibit distinct morphometric patterns, those that have been examined in this study can be di stinguished by observed trends among the attributes that have been used to classify them. On the broadest scale, the distribution of springs in Florida can be separated into two larg e areas: 1) those found across the panhandle or centered on the big bend area and 2) those found in the northern peninsula. The distribution of springs in bot h broad regions is most clearly seen when viewing the entire population of 754 springs, and is less appa rent when only considering the representative sample of 102 springs. The latter region does not seem to contain any noticeable patterns or clusters. The distribution of springs in northern peninsular Florida was thereby excluded from the closer examina tion of spring clusters, and the three visual clusters noted in the Panhandl e were discussed in detail. Regarding the question of whether phys iography and geology influence the locations of Floridas springs, it is concluded that the presence of karst terrain at the majority of the spring sites that were examined in this study is the prevailing factor that has influenced where springs have resurged in Florida. Even in physiographic regions that do not contain a great deal of limestone ge ologic formations, such as is the case with
90 the Western Valley, the springs that are locate d in the region are all associated with the limestone. The springs that are located within the Gulf Coastal Lowland have been demonstrated to be closely linked to the presence of carbonate geol ogic units within the region. The high percentage of sp rings that issue from karst te rrain further te stifies to the influence that such geology has upon the locatio ns of Floridas springs. These trends have been observed at both scales in the study, with the observations of the representative sample of 102 springs essentially echoing t hose that were made regarding the entire population of 754 springs. The geography of Floridas springs is therefore heavily influenced by where karst geology is located. Elevation also influences the distribution of springs in Florida. Spring sites are strongly linked to lower elevations, a fact that is supported by the vast majority of Floridas springs being located in the lowest quarter of the full range of elevations at which they occur. This trend is striking enough that it can be identified visually by viewing an appropriately symbo lized terrain map of Florida th at contains spring locations (see figures 11 and 23). To further facilitate this examinati on and answer the question of whether physiography and geology influence the locatio ns of Floridas springs, the springs were separated into spatially occurring clusters. There are factors influencing the existence of two smaller clusters of springs in the panhandl e, and one larger cluster located at the big bend. All three clusters that were examined share a common geographic characteristic. Each cluster is comprised of springs that are e ither mostly or in part located in a coastal lowland region. In the case of cluster 2, the close proximity of these springs to the gulf coast accounts for the lower elevation values corresponding to them, and furthermore has
91 influenced the direction and distance over which their generated runs drain. This conclusion is in keeping with the observed tre nd of longer spring runs that flow directly to the gulf rather than into major rivers. This trend stands in sharp contrast to that which has been noted of cluster 3. Higher elevati on values correspond to these springs, and the Ocala Limestone is very common in this regi on. A relationship exists between the Ocala Limestone and spring locations in the big bend area. This area is also characterized by the Gulf Coastal Lowland. The Ocala Limestone has influenced the higher number of springs found in the Gulf Coastal Lowlands, most of which discharge directly into the Suwannnee, Santa Fe, and Withlacoochee Rivers. The close proximity of these rivers to the springs in the big bend area has influen ced the high percentage of relatively short runs. Being a representative sample of Fl orida springs in general, the subset of 102 springs that was examined in this study was presumed to include mostly karst solution springs. The presumption is supported by the high number (about 66%) of the springs in the subset issuing from limestone formations. Future research should seek to improve upon this study in several ways. First and foremost the sample size should be increase d. The FGS currently has published data on all of the morphometric parameters tested in this study for an addi tional 450 springs in Florida. This data can be appended to the mo rphometric database th at has resulted from this study using its methodology. Perhaps incr easing the sample size will unearth and define the noticed patterns of the morphomet ric parameters of Fl oridas springs even further. Future research should also a ttempt to increase the utility of the NHD by appending as many of the missing spring runs as possible. It is reco mmended that aerials consisting of 2004 or newer DOQQs be used as a base layer for the digitizing of these
92 spring runs. The addition of this data would allow for additional methodology for determining and examination spring run orie ntation on a statewide scale. This study would also have benefited from a complete physiography dataset wi th coverage for the entire state of Florida. Conclusions regarding the influence that geology and physiography have had upon the location of spri ng clusters being in such close proximity to the gulf coast, could be further substantia ted by having an official confirmation of the coastal lowland areas actually extendi ng around the big bend and along the panhandle coastline as this study has conjectured.
93 Cited References Blackith, R. E. and R. A. Reyment. Multivariate Morphometrics London & New York: Academic Press, 1971. Buchsbaum, Robert, Tim Purinton and Britta Magnuson. The Marine Resources Of the Parker River Plum Island S ound Estuary: An Update After 30 Years Massachusetts Office of Coastal Zo ne Management. Massachusetts: 2003. Chalkias, Cristos, and Efthimios Karymba lis. Prototype GIS Application in Delta Morphometry. Diss. Harokopio University, 2003. Champion, Kyle M. and Roberta Starks. Th e Hydrology and Water Quality of Springs in West-Central Florida Southwest Florida Water Ma nagement District. N.p.p.: May 2001. Copeland, Rick, comp. Florida Springs Cl assification System and Spring Glossary Florida Geological Survey, Special P ublication No. 52. Tallahassee, Florida: 2003. Davis, Hal J. Use of chemical and isotopi c tracers to characterize the interactions between ground water and surface water in mantled karst. Ground Water (1997). Dewitt, David. Interview with Curt Walker. Southwest Florida Water Management District. 26 Jan. 2006. Dong, Zhibao, Tao Wang and Xunming Wang. G eomorphology of the megadunes in the Badain Jaran Desert. Geomorphology 60 (2004): 191-203
94 Frumkin, Amos and Itay Fischhendler. Morph ometry and distributi on of isolated caves as a guide for phreatic and confined paleohydrol ogical conditions. Geomorphology 67 (2005): 457-471 Ganas, Athanassios, Spyros Pavlides a nd Vassilios Karastathis. DEM-based morphometry of range-front escarpments in Attica, central Gr eece, and its relation to fault slip rates. Geomorphology 65 (2005): 301-319. Mylroie, John E. Karst Lands. American Scientist (1995). Precipitation Analysis. Spatial Climate Analysis Service, Oregon State University 1 March 2006. Keywords: Florida, precipitation Randazzo, Anthony F. and Douglas S. Jones. The Geology of Florida Florida: University Press of Florida, 1997. Reese, Ronald S. and Carlos A. Alvarez Zarikian. Review of Aquifer Storage and Recovery in the Floridan Aquifer System of Southern Florida. USGS Fact Sheet #2004-3128. Miami, Florida: 2004. Ritter, Dale F. Process Geomorphology Dubuque, Iowa: Wm. C. Brown Publishers, 1978. Sauchyn, D.J., D.M. Cruden and X.Q. Hu. Str uctural control of the morphometry of open rock basins, Kananaskis re gion, Canadian Rocky Mountains. Geomorphology 22 (1998): 313-324 Schumm S.A.; Boyd K.F. ; Wolff C.G.; Spitz W.J. A gr ound-water sapping landscape in the Florida Panhandle. Geomorphology 12 (1995): 281-297
95 Scott, Thomas M., Guy H. Means, Ryan C. Means and Rebecca P. Meegan. First Magnitude Springs of Florida Florida Geological Survey, Open File Report No. 85. Tallahassee, Florida: 2002. Scott, Thomas M., Guy H. Means, Rebecca P. Meegan, Ryan C. Means, Sam. B. Upchurch, R. E. Copeland, James Jones, Tina Roberts and Alan Willet. Springs of Florida Florida Geological Survery, Open File Report No. 66. Tallahassee, Florida: 2004. Smith, Lauren. Conduit properties and karsti fication in the unconfined Floridan Aquifer. Ground Water (2004). White, William B. Geomorphology a nd Hydrology of Karst Terrains New York, Oxford: Oxford University Press, 1988.
96 Bibliography Aquifer Storage Recovery. Inte rnational School of Well Drilling 2004. 1 March 2006. Keywords: Floridan, aquifer Barcelo, Mark D. Stimulation of Regional Gr ound Water Flow and Salt Water Intrusion In Hernando County, Florida. Ground Water (2000). Grunwald, S. and W.F. deBusk. Inventory of Physico-Chemical Soil Properties and Spatial Pattern Analyses in the Everglades Ecosystem University of Florida Soil and Water Science Department, University of Houston Soil and Water Science Department. 2002. < http://grunwald.ifas.ufl.e du/Projects/NRC_2001/NRC.htm > Kautz, Randy S. Land use and land cover tre nds in Florida 1936-1995. Florida Scientist Vol. 61, No. 3 (1998): 171-187