Comprehensive Watershed Management Plan November 2000

COMPREHENSIVE WATERSHED

MANAGEMENT PLAN

Prepared by:

Southwest Florida Water Management District

The District does not discriminate upon the basis of any individual’s disability status. Anyone requiring

reasonable accommodation under the ADA should contact Gwen Brown, Resource Management

Department at 352-796-7211 or 1-800-423-1476 (Florida only), extension 4226;

TDD ONLY 1-800-231-6103 (Florida only); FAX 352-754-6885/SUNCOM 663-6885.
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TABLE OF CONTENTS

CHAPTER 1 - EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

CHAPTER 2 - INTRODUCTION ........................................... 4

CHAPTER 3 - SOUTHERN COASTAL WATERSHED DESCRIPTION . . . . . . . . . . . .10

CHAPTER 4 - WATER SUPPLY. . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

CHAPTER 5- FLOOD PROTECTION. .. . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

CHAPTER 6 - WATER QUALITY. . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

CHAPTER 7 - NATURAL SYSTEMS. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
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CHAPTER I

EXECUTIVE SUMMARY

The Southwest Florida Water Management District (District) recently developed the

Comprehensive Watershed Management (CWM) Program for water resource assessment

and planning on a watershed-wide basis. The CWM Program was designed to allow for

careful evaluation of the status of water resources on a regional basis, with special attention

paid to the District’s primary Areas of Responsibility (AOR’s): 1) water supply, 2) flood

protection, 3) water quality, and 4) natural systems. This document represents the first draft

of the CWM Program effort focusing on the Southern Coastal Watershed.

The Southern Coastal Watershed contains the watersheds of Sarasota Bay, Dona and

Roberts Bays, Lemon Bay, and Gasparilla Sound. These watersheds are south and west

of the watersheds of the Manatee and Myakka Rivers, and north and west of the watershed

of the coastal basin of the Charlotte Harbor estuary. The Southern Coastal watershed is

highly developed, particularly in the northern portions in Manatee and Sarasota County.

Fortunately, many resource assessments have been completed in the Southern Coastal

Watershed, and much information already exists to aid in the evaluation of potential issues

associated with the above-mentioned AOR’s.

After reviewing available information gathered from completed and ongoing efforts, the

following issues have emerged as priorities.

For Water Supply, there is a need to: 1) seek inclusion of water resource/land use planning

as a consistency requirement for Local Government Comprehensive Plans, 2) improve

compliance with water shortage restrictions and year-round conservation measures, 3)

develop alternative water sources, 4) adopt minimum aquifer levels for the Intermediate

Aquifer, 5) improve coordination between land and water planners, and 5) promote

conservation and reuse.

For Flood Protection, there is a need to: 1) enhance flood protection data collection and

management efforts, 2) acquire additional floodplain information, 3) effectively manage

and/or regulate for increased runoff associated with urbanization of the watershed, 4)

coordinate water resource planning and land use planning, 5) determine ownership,

operation and maintenance responsibilities for flood management systems, 6) seek

consistent sources of funding for flood management systems, and, 7) educate the public

on the role that floodplains play in flood protection and the probability of flood events in lowlying areas.

For Water Quality, there is a need to: 1) continue ongoing monitoring and data management

activities in Sarasota and Manatee Counties, 2) expand ongoing monitoring and data

management activities into Charlotte County, 3) determine the potential ecological
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consequences of increased nutrient loads into Lemon Bay, 4) develop a detailed hydrologic

model to better understand the ecological impacts associated with flood control practices

in the Cow Pen Slough sub-basin, 5) continue ongoing efforts to reduce wastewater-related

point and non-point source pollutant loads throughout the watershed, and 6) continue

ongoing efforts to reduce stormwater-related non-point source loads throughout the

watershed.

For Natural Systems, there is a need to: 1) continue ongoing efforts focused on enhancing,

restoring and creating wetlands in the watershed, and 2) protect existing natural systems

within the watershed through purchase and the use of conservation easements.

Background information that led to the prioritization of these needs is found in chapters

relating to the District’s AOR’s - water supply, flood protection, water quality, and natural

systems. The desire of the individuals who helped to develop the Southern Coastal

Watershed Management Plan is that this document would be modified and updated

regularly, as required. It is hoped that most of the projects outlined within this text will be

funded and completed through the combined efforts of the appropriate federal, state,

regional and local governments.

Many thanks are due to the members of the Southern Coastal CWM Team for their long

hours spent on this project. 

Name Affiliation

Mark Alderson Sarasota Bay National Estuary Program

Rob Brown Manatee County

Pat Collins City of Venice

Gary Comp Sarasota County

Barry Hill Southwest Florida Water Management District

John Knowles Sarasota County

Doug Leeper1 Southwest Florida Water Management District

Tiffany Lutterman Charlotte Harbor National Estuary Program

Dianne McCommons-Beck Florida Department of Environmental Protection

Ian McDonald2 Southwest Florida Water Management District

Scott McGookey Southwest Florida Water Management District

Steve Minnis Southwest Florida Water Management District

Joe Quinn3 Southwest Florida Water Management District

John Rickerson4 Southwest Florida Water Management District

Rich Schultz Southwest Florida Water Management District

Dave Tomasko5 Southwest Florida Water Management District

Chuck Walter Charlotte County

1 Primary author of Chapter III

2 Primary author of Chapter II

3 Primary author of Chapters IV and V

4 Generated GIS-based maps in Appendix

5 Primary author of Chapters VI and VII and Team Leader
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CHAPTER II

INTRODUCTION

COMPREHENSIVE WATERSHED MANAGEMENT

The District's Comprehensive Watershed Management (CWM) Program is a watershed

approach to water management. This approach is the most effective way to integrate a

variety of resource activities. This program is the District's response to the recent federal

and state ecosystem management focus. From a hydrologic standpoint, watersheds are

a logical unit within which to apply the ecosystem concept. In fact, the District Governing

Board made CWM an FY-94 Strategic Initiative that directed staff and funding resources

to this project. Additionally, a majority of the District Basin Boards have also made

watershed assessments a priority for future cooperative funding proposals and projects.

A staff workgroup was convened to develop and implement the CWM Program. The

workgroup consists of members from several District departments including resource-based

and management support representatives. This group developed three primary goals for

the CWM Program:

1. To identify and prioritize existing and potential water resource issues within the

District relating to Water Quality, Flooding, Water Supply, and Natural Systems.

2. To develop strategies for remedial or protective action(s) to address the water

resource issues identified in Goal #1.

3. To implement the strategies in Goal #2 and monitor their effectiveness.

The District is applying this CWM Program approach to 13 watersheds to protect and/or

restore their water resource assets. These 13 watersheds are an aggregate of the 16 that

comprise the 16-county region as recognized by the Resource Regulation Department.

The CWM Program, similar to the development of Surface Water Improvement and

Management (SWIM) Plans and Comprehensive Conservation and Management Plans

through the federally-initiated National Estuary Program (NEP), will also produce several

additional benefits. First, by focusing on more defined areas within the District, problems

and solutions can be addressed within the constraints of limited funds. Secondly, the

interconnective aspects of the watershed approach are more compatible with basic

ecological principles. Evaluating the relationships between activities and natural systems

will provide more effective surface water assessments and management plans. The links

between terrestrial activities and habitats and their interactions with surface waterbodies

can thus be accounted for. Thirdly, by clearly defining long-term goals the CWM Program

plans will promote greater consistency in management planning and implementation and

thus lead to more equitable management decisions.
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The CWM Program approach to watersheds is very similar in concept to the Ecosystems

Management philosophy now being employed by the Florida Department of Environmental

Protection. The southern parts of the Southern Coastal Watershed around the Cape Haze

peninsula lie within the Charlotte Harbor Ecosystem Management Area (EMA) and the

Charlotte Harbor NEP study area and CWM Program efforts within the coastal basins will

complement and reinforce the programs within the general Charlotte Harbor watershed,

which also include the Myakka River, the Peace River and coastal basin areas. The

northern portions of the watershed surround Sarasota Bay, which is also a NEP waterbody

and a SWIM program waterbody. The Southern Coastal CWM Program team will help

coordinate and complement efforts by various local governments, state and federal

agencies, and non-governmental organizations throughout the watershed.

DISTRICT DIRECTIVES

Mission Statement

The CWM Program, as with all District activities, must be consistent with the District's

mission. The Governing Board of the Southwest Florida Water Management District has

adopted a formal Mission Statement, as follows:

The mission of the Southwest Florida Water Management District (the District) is to manage

the water and water-related resources for the people through regulatory and other

programs. Central to the mission is maintaining the balance between the water needs of

current and future users while protecting and maintaining the natural systems which provide

the District with its existing and future water supply.

The Governing Board of the Southwest Florida Water Management District assumes its

responsibilities as authorized in Chapter 373 and other chapters of the Florida Statutes by

directing a wide-range of programs, initiatives, and actions. These programs include, but

are not limited to, flood control, regulatory programs, water conservation, education, and

supportive data collection and analysis efforts.

Primary Areas of Responsibility and Goal Statements

The District's mission has been subdivided into four primary Areas of Responsibility (AORs).

Goals have been developed to establish the long-term direction of programs and activities

that address water resource issues. The four areas of responsibility and their respective

goals are as follows:

WATER QUALITY: To protect water quality by preventing further degradation of the

water resource and enhancing water quality where appropriate.

FLOOD PROTECTION: To minimize the potential for damage from floods by protecting

and restoring the natural water storage and conveyance

functions of flood prone areas. The District shall give
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preference wherever possible to nonstructural surface water

management methods.

NATURAL SYSTEMS: To protect, preserve and restore natural Florida ecosystems

and to establish minimum water levels and flows necessary to

maintain these natural systems.

WATER SUPPLY: To ensure an adequate supply of the water resource for all

reasonable and beneficial uses, now and in the future, while

protecting and maintaining the water and related resources of

the District.

These regional water management goals build a bridge between the divergent functions of

the District, local, other regional, state and federal agencies. This bridge creates common

ground for consistent, coordinated action in the best interest of Florida citizens. The

predominant theme of this Watershed Management Plan is the effective integration of land

and water planning to achieve sound resource management and protection.

The AORs have been agreed upon by all five water management districts and the Florida

Department of Environmental Protection as representative of our collective water

management agenda. This coordinated decision was a development step of the

comprehensive, 20-year District Water Management Plans (DWMP). The District’s DWMP

(1995a, b) identified the issues that led to the creation of the Comprehensive Watershed

Management Initiative. It is that initiative that has resulted in the development of watershed

management plans.

Additionally, the DWMP has adopted specific goals regarding the Southern Coastal

Watershed:

 

WATER QUALITY: Historically, the major point source of pollution in the basin was the City

of Sarasota wastewater treatment plant which discharges into Whitaker Bayou. The plant

has been upgraded, with substantial reductions in discharged pollutant loads. The City

continues to explore options to further improve its reuse programs, to further reduce

pollutant loads. Agricultural and urban stormwater runoff is also a problem in this basin.

The watershed contains numerous drainage ditches and residential canals which discharge

to estuaries and the Gulf. Many of these manmade waterways do not have adequate

circulation, allowing the build up of contaminants from stormwater runoff. Tributaries and

direct runoff also supply the bay systems with heavy nutrient loading. High densities of

septic systems constructed in areas of poor drainage and inappropriate soils pose a threat

to surface water quality as well.

 GOAL: Protect water quality in near shore coastal areas by working with federal and

State agencies, local governments, and the public and by enforcing existing

District regulations to prevent further degradation. 
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FLOOD PROTECTION: Tidal flooding and inland flooding are both problems in this

watershed. Flood damage occurs where there is development in coastal and interior floodprone areas. Since some of the most extensive flood damage can occur as a result of tidal

surges associated with tropical storms, coastal development should be planned with this in

mind. Local governments authorize land uses, and must be the first line of defense in flood

prevention. Where development has already occurred in low lying coastal and inland areas,

there must be an effort to reduce the potential for damage.

 GOAL: Minimize potential for damage from floods by protecting and restoring the natural

water storage and conveyance functions of flood prone areas. 

NATURAL SYSTEMS: This watershed contains valuable upland and wetland areas which

provide habitats for numerous listed species and provide recharge, runoff attenuation and

water quality treatment benefits. Both Sarasota Bay and Charlotte Harbor have been

designated as Estuaries of National Significance under the National Estuary Program

(NEP). In addition, two Outstanding Florida Waters (OFW) water bodies (Sarasota Bay

Estuarine System, and Lemon Bay Estuarine System are present. All, however, are

threatened by increased boat traffic, shoreline hardening and the trimming of mangroves

and other intertidal habitats and their replacement by lawns, landscaping and drainage

canals. 

 GOAL: Protect, preserve and restore important upland and wetland systems.

WATER SUPPLY: Surface water from this watershed will not be a source of future potable

supply due to the small size of streams. This area is in the Southern Water Use Caution

Area (SWUCA) indicating a strain on existing ground water supply sources. Emphasis in

this watershed will be on conservation and alternative supply sources.

 GOAL: Maximize use of alternative supplies, including conservation, and protect surface

water features from adverse impacts associated with water supply development

and withdrawal.

The four resource-based primary areas of responsibility cover all aspects of water

management and are strongly linked. For example, it is difficult and undesirable to separate

the role of natural systems in assuring adequate water supplies for humans, or to sever the

effects of flood protection actions on water quality downstream. As a result, some

duplication is inevitable in dealing with complex water management programs that span

more than a single area of responsibility. This plan will address all four areas of

responsibility in a comprehensive and integrated manner for the Southern Coastal

Watershed.

METHODS AND APPROACH

The general approach taken to develop the CWM Plan for the Southern Coastal Watershed

was to evaluate existing data and analyses, examine existing and potential future activities
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within the watershed, to develop a list of identified issues which need to be addressed, and

to develop a two-part program, one part to implement District efforts and activities and one

part toward guiding local government and private sector activities and land use practices

within the watershed.

After initial data and literature search efforts within the District, state agencies, local

governments were pulled in to provide their input and guidance to the development of the

plan. 

Further discussion under this section will outline more specifically the various efforts,

processes, meetings, workshops, etc. that will help develop the adopted plan for the

watershed. The plan will include a process for periodic revision and update and will

eventually have a “five-year plan” component outlining projects, data collection, rule

revisions, etc. which will be undertaken within specific time frames and for which adequate

budgets are identified. The five-year plan will eventually be coordinated with the Manasota

and Peace River Basin Boards’ Five-Year Plans for the purposes of Basin Board Initiatives

and the cooperative funding of appropriate projects.
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LITERATURE CITED

SWFWMD (Southwest Florida Water Management District). 1995a. District water

management plan, volume 1. Brooksville, Florida.

SWFWMD (Southwest Florida Water Management District). 1995b. District water

management plan, volume 2. Brooksville, Florida.
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CHAPTER III

WATERSHED DESCRIPTION

Section 3.1 Location

The Southern Coastal Watershed (Watershed) extends along the southwestern shore of

Florida from the mouth of Tampa Bay to the mouth of Charlotte Harbor (Map 1 in Appendix).

It is bounded to the north by the Tampa Bay/Anclote Drainage and the Manatee River

Watershed, and to the east by the Myakka River watershed. More than 60 miles of barrier

islands and the estuaries they protect are included in the Watershed. Most of the

Watershed falls within the Manasota Basin of the Southwest Florida Water Management

District, although the southernmost section lies within the Peace River Basin. The

Watershed includes portions of Manatee, Sarasota and Charlotte Counties. Major urban

centers include portions of Bradenton, as well as all of Sarasota and Venice.

Section 3.2 Climate

The climate of the Southern Coastal Watershed is humid subtropical, characterized by

warm, wet summers and mild, dry winters. The annual average temperature at two closely

spaced weather stations near Bradenton, at the northern end of the Watershed, is 72F

(period of record 1954-1993, NOAA 1993). At a Fort Myers station, about 25 miles south

of the Watershed, the annual average temperature is 74 F (period of record 1961-1990,

Southeast Regional Climate Center 1998). Monthly average temperatures range from the

low to mid-eighties in July and August to the low sixties in January. 

Annual rainfall averages about 56 inches per year at Bradenton and 53 inches per year at

Fort Myers. Monthly rainfall is highest from June through September, when over half the

annual rainfall occurs. Convective thunderstorms typically account for the bulk of

precipitation during summer and early fall, often producing extremely intense localized

rainfall events.

The evapotranspiration rate for the region including the Southern Coastal Watershed has

been estimated at 39 inches per year (Dohrenwend 1977). Nearly 60% of the

evapotranspiration occurs during the six-month period from May through October.

Section 3.3 Physiography and Soils

The Southern Coastal Watershed lies within the Gulf Coastal Lowlands and DeSoto Plain

subdivisions of the central or mid-peninsular physiographic zone of Florida (White 1970).

Most of the Watershed is within the Gulf Coastal Lowlands, which are nearly level plains

extending the length of Florida’s Gulf coast. A small segment of the Watershed drained by

the upper reach of Cow Pen Slough lies within the DeSoto Plain, a broad, gently sloping

plain extending from central Manatee County into the northwest corner of Glades County.
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Elevations in the Southern Coastal Watershed are generally between 5 and 35 feet above

the National Geodetic Vertical Datum.

The soils of the Southern Coastal Watershed may be classified into four groups: very

poorly drained; poorly drained; somewhat poorly drained to moderately well drained; and

poorly to moderately well drained (United States Department of Agriculture Soil

Conservation Service 1983, 1984, 1991). Very poorly drained soils, including the Estero,

Wulfert and Kesson groups are common in the tidal mangrove swamps. Poorly drained

soils, including the Eau Gallie, Floridana, Wabasso, and Bradenton series are the dominant

soils in the northern portion of the Watershed. To the south, in Sarasota and Charlotte

Counties, the dominant soils are the Eau Gallie, Myakka, Holopaw, Pineda, and Imokalee

series. Myakka, Waveland and Cassia soils, which are somewhat poorly drained to

moderately well drained, occur in the northeastern section of the Watershed on the DeSoto

Plain. The barrier islands along the western edge of the Watershed consist of poorly

drained to well drained sandy soils of the Canaveral, Beaches, Kesson, Wulfurt, and

Myakka groups.

Section 3.4 Hydrogeology

The Southern Coastal Watershed is underlain by numerous layers of sedimentary deposits

which store, confine or provide conveyance for ground water. The principal hydrogeologic

units of the Watershed include the surficial, intermediate and Floridan aquifer systems. 

The surficial aquifer system in the Southern Coastal Watershed consists of unconsolidated

sands, marl and shell originating from the Holocene and Pleistocene ages. These deposits

are generally less than 50 ft thick throughout the Watershed (Barr 1996). Poor

transmissivity and the shallow nature of the surficial aquifer in the area limit use of this

system as a water supply.

The intermediate aquifer system includes permeable and impermeable sedimentary

deposits lying between the surficial and Floridan aquifer systems (Southeastern Geological

Society 1986). These deposits consist of undifferentiated sediments from the Pleistocene

and Pliocene ages, and the Hawthorn Group of the Miocene age. Thickness of the

intermediate aquifer systems varies from about 300-650 ft in the Southern Coastal

Watershed (Barr 1996). The intermediate aquifer is the primary source of ground water for

irrigation and domestic supply in the Watershed. 

The Floridan aquifer system consists of limestones and dolomites that formed prior to the

Miocene age (Miller 1986). In the region of the Southern Coastal Watershed, the aquifer

consists of two hydrologic units, the Upper and Lower Floridan aquifers, which are

separated by a middle confining unit. The Upper Floridan aquifer is the most productive

aquifer of the region, although the high mineral content of ground water from the aquifer

limits use of this resource in much of the Southern Coastal Watershed. The top of the

Upper Floridan aquifer ranges from about 300-700 feet below the surface in the Watershed

and thickness of the aquifer varies from about 1300-1800 feet (SWFWMD 1988c, after

Wolansky and Garbade 1981). The Lower Floridan aquifer contains highly mineralized
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water.

The potential for contamination of groundwater in aquifers of the Southern Coastal

Watershed has been evaluated using physical information on the hydrogeologic setting of

the region and chemical/isotopic information on water in the aquifers. Both approaches

indicate that the potential for contamination of the Upper Floridan aquifer is very low

(SWFWMD 1988a, b, c, Swancar and Hutchinson 1992). The thickness of the intermediate

aquifer system in the region, and its relatively low permeability, function as a barrier to

downward movement of contaminants. Analyses based on the hydrogeologic setting

indicate that the susceptibility of the intermediate aquifer system to contamination from

surface sources is also very low (SWFWMD 1988a, b, c). However, the potential for

contamination of the intermediate aquifer with ground water from the Upper Floridan aquifer

exists as a result of the high potentiometric surface of the Upper Floridan aquifer and from

improperly cased wells (Metz and Brendle 1996). Lateral intrusion of salt water into the

intermediate aquifer system is also a problem in the Watershed. The surficial aquifer of the

region is highly susceptible to ground-water contamination, due to the lack of confinement

and non-artesian properties of the aquifer (Map 2 in Appendix). 

Section 3.5 Surface Water Hydrology

The Southern Coastal Watershed includes numerous estuaries, wetlands, and small coastal

streams that are tidally influenced over much of their length, and also a few longer

stream/canal systems with predominantly freshwater habitats. Based on information

collected by the United States Geological Survey’s Hydrologic Division, the Watershed can

be divided into 23 sub-basins (Map 1 in Appendix). 

At the northern end of the Watershed, a small area drains into Palma Sola Bay (sub-basin

2) and several sub-basins drain to the Sarasota Bay estuary. Freshwater runoff enters

Sarasota Bay from the Bowlees Creek system (sub-basin 3), Whitaker Bayou (sub-basin

5), Hudson Bayou (sub-basin 7), other mainland coastal areas and the barrier islands of

Longboat Key, Lido Key and Anna Maria Island (sub-basin 1). Portions of Anna Maria

Island also drain to Anna Maria Sound.

To the south, Phillippi Creek (sub-basin 6), a highly channelized drainage system, empties

into Roberts Bay and Little Sarasota Bay. Catfish Creek (sub-basin 10) also drains into

Little Sarasota Bay. Downshore, South Creek (sub-basin 9) empties into a region known

as Dryman Bay. Runoff from other coastal regions of the mainland, Siesta Key, and Casey

Key (sub-basin 8) also contributes to the freshwater flow entering Little Sarasota Bay.

The estuaries of Anna Maria Sound, Palma Sola Bay, Sarasota Bay, Roberts Bay and Little

Sarasota Bay have been included in State and Federal habitat conservation and restoration

programs. The United States Environmental Protection Agency designated these waters,

which total about 52 square miles in area collectively, as an Estuary of National Significance

in 1988, and established the Sarasota Bay National Estuary Program. The Sarasota Bay

National Estuary Program (1995) subsequently developed a conservation and management

plan for restoring and maintaining the ecological integrity of the bay. The estuaries have
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also been designated as Outstanding Florida Waters by the Florida Department of

Environmental Regulation (now the Florida Department of Environmental Protection). In

1995, the Southwest Florida Water Management District included Sarasota Bay on its list

of priority water bodies for protection or restoration in accordance with the Surface Water

Improvement and Management (SWIM) Act passed by the Florida Legislature. The

SWFWMD (1997) has developed a management plan which identifies actions in the

Sarasota Bay National Estuary Program comprehensive plan which may be funded with

monies from the SWIM Trust Fund.

Dona Bay and Roberts Bay (the second “Roberts Bay” in the Watershed), which become

contiguous at their western ends, are small estuaries near the City of Venice. Dona Bay

receives some discharge from coastal regions included in sub-basin 8, but most flow into

the estuary is from Shakett Creek/Cow Pen Slough (sub-basin 4), a network of canals and

natural stream segments which drain an area of approximately 90 square miles. Increased

seasonal freshwater flow and sediment loads transported by this highly-modified drainage

system have contributed to the degradation of water quality and habitat in Dona Bay (Mote

Marine Laboratory 1975). Roberts Bay is the terminus for Curry Creek (sub-basin 11).

Hatchett Creek (sub-basin 12) is a highly channelized system that drains into the

Intercoastal Waterway near the southern end of Roberts Bay.

Lemon Bay extends from the vicinity of South Venice to the Gasparilla Island Causeway.

This estuary is within the boundaries of the Charlotte Harbor NEP, and has been designated

as an aquatic preserve by the Florida Legislature and an Outstanding Florida Water by the

Department of Natural Resources. These designations should promote the preservation

of the exceptional biological, aesthetic and scientific qualities of the bay (see Florida

Department of Natural Resources 1991 for a review of the natural and cultural history of

Lemon Bay). Alligator Creek (sub-basin 13) flows through the city of South Venice into the

bay. Forked Creek (sub-basin 14) drains a sizable area south of the city. Rock and Oyster

Buck Creeks (sub-basins 16 and 18) flow into the bay through less populated regions of the

Watershed. Runoff from coastal regions of the mainland, and the barrier islands of

Manasota Key, Don Pedro Island and Little Gasparilla Island (sub-basin 8) also enters

Lemon Bay.

Gasparilla Sound receives runoff through Buck Creek (sub-basin 19), Coral Creek (subbasin 20), Catfish Creek Bayou (sub-basin 21), Boggess Hole outflow (sub-basin 23),

Whidden Creek (sub-basin 22), and other mainland coastal areas (sub-basin 8). Portions

of Gasparilla Sound, Charlotte Harbor and much of the land along the eastern shore of

Charlotte Harbor below the mouth of the Myakka River is included in sub-basin 17.

In Chapters VI and VII of this Comprehensive Watershed Management Plan, sub-basins

of the Southern Coastal Watershed are grouped into larger basin units (Map 3 in Appendix).

The reader is referred to Chapter VI - Water Quality, for further details. 

Section 3.6 Population Growth and Economy

The population of Florida has increased greatly during recent years and Florida’s coastal
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communities have experienced a large portion of the growth. The vast majority of the

residents of Manatee, Sarasota and Charlotte Counties, and most of the seasonal visitors

to the area live within a relatively narrow corridor extending roughly ten miles inland from

the Gulf. Most of the future growth in the region is expected to occur in this corridor as

there is ample land available for development and local governments are encouraging

concentrated development where adequate infrastructure exists or is expected to be

developed. This means that the entire Southern Coastal Watershed, except public lands,

conservation areas and possibly some of the easternmost sections of the Watershed will

eventually become urbanized. 

The region experienced tremendous growth during the decade between the 1980 and the

1990 Census of Population and Housing (Table III-1). Manatee County’s population grew

nearly 43%, Sarasota County grew nearly 37%, and Charlotte County grew by 90%. Nearly

all of the recent population growth in the region can be attributed to net immigration. This

is not surprising given that 30% of the population is over the age of 65 (Bureau of Economic

and Business Research 1994). The population of the region is expected to grow

considerably during the next thirty years, although at a rate less than that which occurred

in the 1980's. By 2010, the number of people living in Manatee, Sarasota and Charlotte

counties is expected to be 65% greater than in 1990.

Table III-1. Permanent resident population estimates and projections for Manatee,

Sarasota and Charlotte Counties, and major urban areas of the Southern Coastal

Watershed for the period 1980-2020 (N/A indicates data are not available).

County or Urban Area 1980 1990 1995 2000 2010 2020

Manatee County 1 148,400 211,707 223,508 258,418 302,674 344,000

Sarasota County 2 202,300 277,776 301,528 326,800 375,100 423,200

Charlotte County 3 58,460 110,975 127,646 147,400 185,800 225,500

City of Bradenton 4 30,288 43,769 44,200 46,900 52,100 N/A 

City of Sarasota 5 48,868 50,897 51,143 51,967 53,526 N/A 

City of Venice 6 12,153 17,052 18,450 21,246 22,556 22,556

Barrier Island Towns 7 11,998 14,148 16,037 17,021 N/A 18,4558

Sources: 1. Manatee County Board of Commissioners (1996); seasonal population multiplier is about 16%.

2. Sarasota County Board of Commissioners (1997); functional population increase estimated at 26%. 

3. Charlotte County Board of Commissioners (1997); seasonal population increase estimated at 30%.

4. Bradenton, City of, City Council (1996) and Bureau of Economic and Business Research (1997); seasonal population

increase estimated at 13%.

5. Sarasota, City of, City Commission (1998) and Bureau of Economic and Business Research (1997); seasonal population

increase of 20% , daily functional population increase of 46%.

6. Venice, City of, City Council (1996); functional population increase of 37%.

7. Anna Maria ( ), Holmes Beach, City of, City Commission (1997), Bradenton Beach, ( ), Longboat Key, Town of, Town

Council (1997), and Bureau of Economic and Business Research (1997); seasonal population increase on entire barrier

islands estimated at more than 90%.

8. Estimated build out population of barrier island communities assuming current densities and no annexations.
Comprehensive Watershed Management Plan November 2000

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Employment in Manatee, Sarasota and Charlotte Counties (Table III-2) is dominated by the

service and retail industry sectors, which account for about 60% of the total number of jobs

in the region. This is typical of counties with resort communities and large populations of

retirees, seasonal visitors, tourists and other immigrants. The public sector constitutes the

next largest employment category, accounting for 12% of the regional job base.

Manufacturing is also a significant employment category of the region. In Manatee County,

this sector accounts for 14% of the total number of jobs, well above the state average of 8

percent.

Table III-2. Employment (numbers of jobs and percentages of totals) by major

category for Manatee, Sarasota and Charlotte Counties in 1995. 

Employment Category Manatee % Sarasota % Charlotte % Total %

Agriculture 5,445 6.5 1,461 1.2 582 1.9 7,488 3.2

Construction 3,326 4.0 6,616 5.6 2,042 6.7 11,984 5.1

Manufacturing 11,568 13.8 8,246 6.9 892 2.9 20,706 8.9

Transportation & Public 1,502 1.8 3,572 3.0 997 3.3 6,071 2.6

Wholesale Trade 2,272 2.7 3,999 3.4 537 1.8 6,808 2.9

Retail Trade 17,266 20.6 29,722 25.0 8,840 28.9 55,828 23.9

Finance, Insurance & Real 2,872 3.4 7,666 6.4 1,486 4.9 12,024 5.1

Services 29,289 34.9 43,460 36.5 10,506 34.3 83,255 35.6

Government 10,082 12.0 13,864 11.6 4,639 15.2 28,585 12.2

Other 331 0.4 531 0.45 83 0.3 945 0.4

Total 83,953 119,137 30,604 233,69

Source: Bureau of Economic and Business Research (1997).

Section 3.7 Land Use and Transportation

Using categories derived from Florida Department of Transportation (1985) land use/cover

in the Southern Coastal watershed is an amalgam of urban, agricultural and wetland or

open water habitats (Map 4 in Appendix, Table III-3). Based on aerial photographs from

1995, urbanized areas account for over one-third of the total area of the Watershed

(including open water areas). Coastal areas, including the barrier islands are almost entirely

urbanized. Eastern portions of the watershed contain substantial areas of agricultural lands,

which account for 10% of the total acreage of the Watershed. Agriculture in the Watershed

is dominated by range and pastureland and row-crop farming. Upland forests are patchily

distributed in the watershed, although a sizable intact forested area remains inland from
Comprehensive Watershed Management Plan November 2000

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Lower Sarasota Bay. Significant wetland acreage remains in the southern region of the

watershed, along the shores of Gasparilla Sound and Charlotte Harbor.

Table III-3.Land use/cover (acreage and percentage of total acreage) for the Southern

Coastal Watershed and receiving water bodies in 1995.

Land Use / Land Cover Acreage % of Total Acreage

Urban and Built-Up 108,945 35

Transportation, Communication and Utilities 5,829 2

Agriculture 31,014 10

Rangeland 15,643 5

Barren Land 330 <1

Upland Forest 32,603 11

Wetlands 41,578 14

Mining 498 <1

Water 71,804 23

Total 308,244 100

Much of the Watershed is within the 100-year flood zone designated by the Federal

Emergency Management Administration (Map 5 in Appendix). Additional acreage in areas

of the Watershed away from the coast and stream channels is also prone to flooding. Much

of the urban development in the Watershed has occurred in these flood prone areas.

Improper development of these areas has, and may result in significant threats to life,

property, and the quality of aquatic and shoreline habitats.

The communities of the Southern Coastal Watershed are served by a highly-developed

transportation infrastructure. Two major roads, U.S. 41 and Interstate 75 roughly parallel

the coast, providing north-south transit in the upper two-thirds of the watershed, and eastwest transit around Charlotte Harbor to Punta Gorda in the lower third. Other major roads

include State Road 64, which connects the City of Bradenton to Zolfo Springs in central

Hardee County, and State Roads 70 and 72, which begin in Bradenton and Sarasota,

respectively, and converge on the City of Arcadia in DeSoto County. A major rail line enters

the Watershed at Bradenton and runs south past the City of Venice. Another connects

Gasparilla Island with the City of Arcadia. In addition to these highway and rail systems, the

region is served by the Sarasota-Bradenton International Airport which overlaps the

Sarasota-Manatee County line at U.S. 41. 
Comprehensive Watershed Management Plan November 2000

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LITERATURE CITED 

Barr, G. L. 1996. Hydrogeology of the surficial and intermediate aquifer systems in

Sarasota and adjacent counties, Florida. United States Geological Survey Water

Resources Investigations Report 96-4063. Tallahassee, Florida.

Bradenton, City of, City Council. 1996. City of Bradenton adopted comprehensive plan

evaluation and approval report. Bradenton, Florida.

Bureau of Economic Business and Research. 1994. 1994 Florida statistical abstract.

University Press of Florida, Gainesville, Florida.

Bureau of Economic Business and Research. 1997. 1997 Florida statistical abstract.

University Press of Florida, Gainesville, Florida.

Charlotte County Board of Commissioners. 1997. Charlotte County comprehensive plan

1997-2010. 

Dohrenwend, R. E. 1977. Evapotranspiration patterns in Florida. Florida Scientist 40: xxxx.

Florida Department of Natural Resources. 1991. Lemon Bay Aquatic Preserve

management plan. Bureau of Submerged Lands and Preserves, Tallahassee, Florida. 

Florida Department of Transportation. 1985. Florida land use, cover, and forms

classification system, second edition. State Topographic Bureau, Tallahassee, Florida.

Holmes Beach, City of, City Commission. 1997. Comprehensive plan (revised EAR-based

comprehensive plan amendments). Holmes Beach, Florida.

Longboat Key, Town of, Town Council. 1997. Town of Longboat Key comprehensive plan.

Longboat Key, Florida.

Manatee County Board of Commissioners. 1996. Manatee County evaluation and

appraisal report. Bradenton, Florida.

Metz, P. A. and Brendle, D. L. 1996. Potential for water-quality degradation of

interconnected aquifers in west-central Florida. United State Geological Survey Water

Resources Investigations, Report 96-4030. Tallahassee, Florida.

Miller, J. A. 1986. Hydrogeologic framework of the Floridan aquifer system in Florida and

parts of Georgia, Alabama, and South Carolina. United States Geological Survey

Professional Paper 1403-B.

Mote Marine Laboratory. 1975. The ecological status of Dona and Robert’s Bays and its
Comprehensive Watershed Management Plan November 2000

18

relationship to Cow Pen Slough and other possible perturbations. Prepared for the

Sarasota County Board of Commissioners, Sarasota, Florida. 

NOAA (National Oceanographic and Atmospheric Administration). 1993. Climatological

data - annual summary, Florida.

Sarasota Bay National Estuary Program. 1995. Sarasota Bay: the voyage to paradise

reclaimed.

Sarasota, Florida.

Sarasota Board of County Commissioners. 1997. Apoxsee: the revised and updated

Sarasota County comprehensive plan. Sarasota, Florida.

Sarasota, City of, City Commission. 1998. Sarasota city plan. Sarasota, Florida.

Southeast Regional Climate Center. 1998. Climatological normals 1961-1990 (Internet

Site).

Southeastern Geological Society. 1986. Hydrogeological units of Florida. Florida

Geological Survey Special Publication Number 28.

Swancar, A. and Hutchinson, C. B. 1992. Chemical and isotopic composition and potential

for contamination of water in the Upper Floridan Aquifer, west-central Florida, 1986-1989.

United States Geological Survey Open Filer Report 92-47.

SWFWMD (Southwest Florida Water Management District). 1988a. Ground-water

resource availability inventory: Charlotte County, Florida. Brooksville, Florida.

SWFWMD (Southwest Florida Water Management District). 1988b. Ground-water

resource availability inventory: Manatee County, Florida. Brooksville, Florida.

SWFWMD (Southwest Florida Water Management District). 1988c. Ground-water

resource availability inventory: Sarasota County, Florida. Brooksville, Florida.

SWFWMD (Southwest Florida Water Management District). 1997. Sarasota Bay surface

water improvement and management (SWIM) plan. Brooksville, Florida.

United States Department of Agriculture Soil Conservation Service. 1983. Soil survey of

Manatee County, Florida.

 

United States Department of Agriculture Soil Conservation Service. 1984. Soil survey of

Charlotte County, Florida. 

United States Department of Agriculture Soil Conservation Service. 1991. Soil survey of

Sarasota County, Florida. 
Comprehensive Watershed Management Plan November 2000

19

Venice, City of, City Council. 1996. 1996 Comprehensive plan evaluation and approval

report. Venice, Florida.

White, W. A. 1970. The geomorphology of the Florida peninsula. Florida Bureau of

Geology Bulletin No. 51. Tallahassee, Florida.

Wolanske, R.M. and Garbade, J.M. 1981. Generalized thickness of the Floridan Aquifer,

Southwest Florida Water Management District. U.S.G.S., OFR 80-1288.
Comprehensive Watershed Management Plan November 2000

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CHAPTER IV

WATER SUPPLY

4.1 Overview of Watershed

The Southern Coastal Watershed is located within the Southern West-Central Florida

Ground-Water Basin (SWCFGWB or the Basin), one of three distinct ground water basins

within west-central Florida. No significant ground water flow crosses the basin boundaries;

therefore, nearly all ground water is derived from recharge by rainfall within the Basin.

Upper Floridan aquifer flow in the SWCFGWB is derived primarily from rainfall recharge that

occurs in the Lake Wales Ridge area, and also in the Green Swamp, which are located

along the northern and eastern edges of the Basin, respectively. Down gradient of these

areas, ground water flows west and southwest toward and into the Gulf of Mexico, except

in southern Hillsborough and western Manatee Counties, where flows are limited due to

ground water pumpage.

Within the SWCFGWB, the ground water system is divided into three main aquifers: the

surficial, intermediate and Upper Floridan. Each aquifer is separated by a confining layer

of variable thickness and areal extent. The uppermost aquifer, the surficial, is largely

undeveloped due to its limited thickness and low permeability, except near the coast and

in Charlotte County where ground water from deeper aquifers is too mineralized for potable

use. Underlying the surficial aquifer is the intermediate or secondary artesian aquifer

system. The intermediate aquifer system is a moderately productive, highly developed

source of water which is used for domestic and public supplies south of Polk County. The

lowermost and most productive aquifer is the Upper Floridan aquifer system. The Upper

Floridan is a major source of water for agriculture, industry and public supply, except in

Charlotte County and the coastal area of Sarasota County. 

Surface waters within the Southern Coastal Watershed include numerous fresh and salt

water wetlands and several coastal streams and sloughs. The creeks and sloughs found

in the Southern Coastal Watershed primarily serve as drainage features for the coastal

region, however, and do not currently represent significant water supplies for industrial,

agricultural or domestic use, with the possible exception of Cow Pen Slough (see Chapters

VI and VII).

Water Use

Public supply represents the most significant water use within the watershed. Each

community within the watershed meets its potable water demands through either ground

or surface water resources. Nine public supply wellfields/withdrawal sites with average

permitted quantities greater than one million gallons per day are located within the Southern

Coastal watershed. Fourteen public supply water facilities with withdrawal quantities greater
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than 100,000 gallons per day (gpd) are also located throughout the watershed. 

Agriculture has historically been a significant activity within the Southern Coastal watershed

and continues to play a significant role in water supply demands. As development

pressures continue to consume increasingly valuable coastal agricultural lands, water

demands from agricultural activities within the watershed are likely to decrease. Continued

urbanization of the Southern Coastal watershed may, however, lead to expanded

agricultural and/or ranching operations further inland, thereby increasing water demands

within those watersheds.

Recreational water use represents another significant water use demand category within

the Southern Coastal watershed. The majority of withdrawals within this category are used

to meet golf course irrigation demands. In recent years, many golf courses have sought to

offset all or a portion of their potable water use with reclaimed wastewater reuse. District

rules require water use permit holders to use reclaimed wastewater reuse to offset potable

water use, if available. Reuse of reclaimed wastewater has proven to be a significant water

conservation measure in reducing ground and surface water withdrawals. However, Utilities

must develop additional wet weather storage in order to make reuse available year round.

Significant surface water public supply sources play an important role in meeting potable

water demands for populations within the Southern Coastal watershed. These sources

include Lake Manatee and the Evers Reservoir, which are impoundments of the Manatee

and Braden Rivers, respectively, in Manatee County. The Peace River/Manasota Regional

Water Supply Authority’s (PRMRWSA’s) water treatment facility is located on the Peace

River in DeSoto County. Lake Manatee serves as a potable water supply source for

Manatee County Utilities, while the Evers Reservoir provides potable water resources to the

City of Bradenton. While none of these facilities are located within the Southern Coastal

watershed, they do supply significant quantities of potable water to communities within the

watershed. Lake Manatee is permitted for average and maximum daily withdrawal

quantities of 34.9 mgd and 50.2 mgd, respectively. The Evers Reservoir is permitted for

average and maximum daily withdrawal quantities of 5.6 mgd and 8.2 mgd, respectively.

The PRMRWSA facility is permitted to withdraw up to 17.6 mgd. Table IV-1 shows reported

water withdrawals within the Southern Coastal watershed, by source and type. 

(rest of page left blank intentionally)
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Table IV-1. Reported water withdrawals within the Southern Coastal Watershed

(data from J. Quinn, SWFWMD, 1997).

Use Sector Ground Water (mgd) Surface Water (mgd) Total Withdrawals

Agriculture 4.49 0.16 4.64

Commercial/Ind. 0.14 0.01 0.14

Mining/Dewatering 0.00 0.84 0.84

Public Supply 17.27 0.02 17.29

Recreation 3.76 3.39 7.14

Total 25.66 4.42 30.05

In addition to meeting demands for public supply, agricultural, recreational, commercial,

industrial, and other activities, the water resources of the Southern Coastal watershed

support a variety of wetland and upland ecosystems. Many water dependent ecosystems

rely on the seasonal freshwater flows from the watershed’s surface water features to

maintain their health and viability. Increased demand on the watershed’s once abundant

water resources must now be closely managed to ensure that adequate supplies are

available for human needs and the natural environment.

Membrane Technology

Ground water characteristics within the Southern Coastal watershed generally mirror those

of the District; that is, mineralization increases with depth with movement to the south and

toward the coast. Many ground water withdrawals within the Southern Coastal watershed

are from brackish ground water sources. Brackish water is generally defined as water with

a total dissolved solids concentration greater than 1,000 parts per million. The high mineral

content of brackish water is not suitable for potable use with conventional treatment

methods. Brackish water can, however, be made potable by various membrane

technologies. While these methods have historically been expensive for water supply

development, recent improvements in technology involving low pressure reverse osmosis

and ultra-filtration membranes have reduced operating costs for newer systems.

One of the more significant problems facing this industry, however, is the disposal of waste

brine. Reject water from membrane treatment plants is classified as industrial waste. The

Florida Department of Environmental Protection (FDEP) regulates the treatment and

disposal of industrial wastewater through Chapters 62-3, 62-4, 62-6 and 62-8, Florida

Administrative Code (F.A.C.). Since most plants are located near the coast, discharge to

tidal or brackish surface waters is one method of disposal. Location of disposal sites with

adequate dilution, flushing and marine characteristics can, however, be problematic. Other

methods of disposal include percolation ponds, spray irrigation or deep well injection. Table

IV-2 lists water supply plants in the Southern Coastal watershed that are employing

membrane treatment technology and have permitted treatment capacities greater than
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100,000 gpd. Given the continued growth in Florida’s coastal areas, unpredictable rainfall

and increasing trends of salt water intrusion, the use of membrane technology for potable

water supply development is anticipated to increase in the future. (SWFWMD, 1992).

Table IV-2. Water supply plants using membrane treatment technology in the

Southern Coastal Watershed (>100,000 gpd treatment capacity;

SWFWMD, 1992).

Name of Plant City Treatment Capacity (mgd)

City of Sarasota Sarasota 4.5

City of Sarasota Sarasota 12.0

Camelot Lakes Sarasota 0.1

Sun N’ Fun Resort, Inc. Sarasota 0.127

Southbay Utilities Sarasota 0.25

Spanish Lakes MHP Nokomis 0.10

City of Venice Venice 4.0

Venice Gardens Utility Corp. Venice 1.0

The Plantation Venice 0.5

Charlotte Harbor Water Assoc. Harbour Heights 0.45

Englewood Water District Englewood 3.0

Rotonda West Utilities Rotonda West 0.5

Gasparilla Island Englewood 0.2

Wastewater Reuse

The reuse of domestic wastewater, or wastewater reuse, can significantly reduce demands

on ground and surface water withdrawals. Rules of the Florida Department of

Environmental Protection (FDEP), Chapter 62-610, Florida Administrative Code (F.A.C.),

govern wastewater reuse. Specific provisions of the rule regulate public access to reuse,

including use of treated wastewater for residential, commercial and public landscape

irrigation, golf course irrigation, and agricultural irrigation of edible crops. Also covered are

slow- and rapid-rate land application systems for ground water recharge.

Section 403.064, Florida Statutes (F.S.), requires a wastewater reuse cost/benefit

evaluation be conducted by all applicants seeking permits to construct and/or operate a

wastewater treatment facility within a critical water supply problem area. The District has

declared two critical water supply problem areas within the Southern Coastal watershed:

the Eastern Tampa Bay and Southern Water Use Caution Areas. District rule, Chapter
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40D-2, F.A.C., requires wastewater generators with Water Use Permits to provide a map

indicating areas where reclaimed water facilities are located and their available quantities

of reuse water. Further, Water Use Permit holders are required to investigate the feasibility

of using reclaimed wastewater to offset potable water demands.

There are a number of wastewater treatment facilities that supply reclaimed wastewater to

users within the Southern Coastal Watershed. A variety of projects have been, or are

scheduled to be completed to expand wastewater reuse availability within the watershed.

The District, through its Basin Cooperative Funding Program, has been involved in partially

funding these projects in conjunction with local government cooperators. To date, the

District has budgeted approximately $13,500,000 for wastewater reuse projects with

Manatee, Sarasota and Charlotte Counties. These projects will result in a reduction in

potable water use demands of approximately 30 million gallons per day (SWFWMD, 1996).

Population and Growth

Counties within the Southern Coastal Watershed continue to grow at a rapid pace. Areas

of the watershed nearest the coast tend to be older developments, with some newer infill

development and redevelopment. Recently, eastward growth has occurred toward the

Interstate 75 corridor. This trend will likely continue for the foreseeable future. Obviously,

as population increases, so will the water supply needs. Table IV-3 illustrates current and

projected population for Manatee, Sarasota and Charlotte Counties (see citations listed for

Table III-1).

Table IV-3. Estimated population and projections for Southern Coastal Watershed

Counties 

County 1995 2000 2010 2020

Manatee 223,508 258,418 302,674 344,100

Sarasota 301,528 326,800 375,100 423,200

Charlotte 127,646 147,400 185,800 225,500

4.2 Previous Studies

A number of studies and technical reports concerning water supply have been generated

for portions of the Southern Coastal Watershed. The following is a brief summary of the

selected studies.

Water Supply Studies and Reports

The District Water Management Plan (SWFWMD, 1995a) is a broad-based planning

document that addresses activities related to water supply, flood protection, water quality,

and natural systems (SWFWMD, 1995a). The plan identifies current programs, issues, and
Comprehensive Watershed Management Plan November 2000

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strategies for regional water management. The water supply element of the DWMP

comprises two sub-elements: (1) needs and sources and (2) source protection.

To address the first element, the District developed a Needs and Sources Plan. The initial

Needs and Sources Plan was adopted in 1992 and was incorporated in the DWMP. The

objective of the plan was to examine water demands and sources for the period 1990-2020

to provide a framework for water supply management (SWFWMD, 1992). The 1992 Needs

and Sources Plan recognized that groundwater resources are stressed in the west-central

and southern portions of the District (including all of the Southern Coastal Watershed).

Reuse, conservation, desalination, surface water, and limited groundwater development

were identified as potential sources to meet future needs in this area.

Continued viability of existing water supply sources is addressed through Water Resource

Assessment Projects (WRAPs) and the delineation of Water Use Caution Areas (WUCAs).

To date, four studies have been undertaken within the District including the Highlands

Ridge, Eastern Tampa Bay, Northern Tampa Bay, and Southern WRAPs. Due to staff

limitations, however, only the Eastern Tampa Bay and Northern Tampa Bay WRAPs have

been completed. The WRAP reports contain hydrologic analyses and provide the technical

basis for the establishment of safe yields in each area. Water Use Caution Areas have

been declared by the District to prevent existing problems from becoming worse in areas

where water resources are stressed (SWFWMD, 1992). The four designated Water Use

Caution Areas correspond to the WRAP study areas. A more advanced discussion of these

topics follows in the Ground Water Studies subsection. Other District programs which

address long-term water supply source protection and viability are discussed in the DWMP,

including District water use permitting, water shortage management, and land acquisition.

Water supply issues identified in the DWMP include: (1) water allocation strategies, (2)

linkage of water use planning to local government comprehensive planning, (3) compliance

and enforcement, (4) alternative supplies, (5) additional data collection, (6) watershed water

budget approach to water management, and (7) water use fees. Options to address each

issue have been evaluated and are outlined in the DWMP. 

Surface Water Studies

The District’s Needs and Sources study determined that the Peace River could be

considered for additional water supply development to meet projected demands in Charlotte

County, southern Sarasota County and the City of North Port, based on flow characteristics

and available storage at the Peace River/Manasota Regional Water Supply Authority’s

(PRMRWSA’s) Peace River Regional Water Treatment Facility in DeSoto County

(SWFWMD, 1992). The PRMRWSA owns and operates the facilities and provides

wholesale water to local governments in Charlotte and Sarasota counties.

While not located within the Southern Coastal Watershed, potable water is supplied from

the Authority’s facility to areas within the watershed through surface water withdrawals from

the Peace River. The Authority’s Peace River Water Treatment Facility consists of a river
Comprehensive Watershed Management Plan November 2000

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intake, an off-stream storage reservoir, water treatment plant and an aquifer storage and

recovery (ASR) system. The PRMRWSA is presently permitted to withdraw an average

quantity of 32.4 million gallons per day (mgd) and a maximum quantity of 90.0 mgd from the

Peace River, based on a phased approach to be reviewed by a peer-review committee

required by the permit. The Authority’s ASR system enables surface waters withdrawn

during the wet season to be stored in the Upper Floridan aquifer. These stored waters are

later withdrawn for use during the dry spring season when surface water withdrawals from

the Peace River are limited by low flows.

The Manasota and Peace River Basin Boards’ Peace River Option, a New Water Source

Initiative (NWSI) project, has studied the feasibility of increasing withdrawals from the Peace

River to offset potable ground water withdrawals for Charlotte and Sarasota counties.

These studies, and ongoing monitoring programs, are focused on the impacts, if any, of

these withdrawals on the River and Upper Charlotte Harbor. Proposed additional

withdrawals must meet strict environmental standards and demonstrate no adverse effects

on the River or Charlotte Harbor. Increased use of surface water sources could offset or

reduce ground water withdrawals, which in turn would benefit the Floridan Aquifer

throughout the region.

Ground Water Studies

Potentiometric levels of the Upper Floridan aquifer, the principal aquifer in the Southwest

Florida Water Management District (SWFWMD), have been declining in the coastal areas

of southern Hillsborough, Manatee and northern Sarasota Counties since the 1930's

(SWFWMD, 1993, 1995). The rate of these declines greatly accelerated beginning in the

early 1960s, and declines are now observed throughout the entire Southern West-Central

Florida Ground-Water Basin (SWCFGWB). The SWCFGWB includes all of DeSoto,

Hardee, Manatee, and Sarasota Counties, and portions of Charlotte, Highlands,

Hillsborough, and Polk Counties. These declines are primarily caused by ground water

withdrawals within the affected areas. Public supply wellfields and water use permit points

are depicted earlier in Figure IV-1. Regional impacts caused by these lowered levels include

water quality deterioration in coastal areas due to lateral salt water intrusion and local water

quality deterioration due to upward movement of mineralized water from lower portions of

the aquifer. Additional impacts include reduced well efficiency due to greater pumping

depths, lowered lake levels, and reductions in spring and stream flows.

In response to these declines and associated impacts, the Governing Board of the

SWFWMD directed staff to conduct detailed Water Resource Assessment Projects

(WRAPs) to address the issue of safe yields in the areas of greatest concern. Safe yield,

as addressed in the WRAPs, is the quantity of water available for man’s use without

causing unacceptable impacts to the water resources, associated natural systems, and

existing legal users of water. Safe yield is established by the SWFWMD Governing Board

based on determination of acceptable levels of impacts. The WRAP projects provide the

District’s Governing Board with the necessary water resource based technical information

and tools necessary to establish safe yields for the project areas. The Southern Coastal
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watershed is located within two of the District’s four identified WRAP areas, the Eastern

Tampa Bay and Southern District WRAPs. The WRAP areas were identified based on a

number of factors including hydrologic regime, types of impacts observed, the profile of

water use and future growth.

In 1989, the District’s Governing Board declared the Eastern Tampa Bay WRAP area to be

a Water Use Caution Area (WUCA). In conjunction with declaring the WUCA, the

Governing Board implemented a strategy to address concerns within this area including the

development and implementation of short-, mid- and long-term solutions. Short-term and

mid-term solutions were comprehensive in nature and were designed to limit further impacts

to the area, based on best available information at the time. Long-term solutions would be

a refinement of the existing measures based on the results of the WRAP. 

The Eastern Tampa Bay WRAP report (SWFWMD, 1993) concluded that saltwater intrusion

was a currently active process and that saltwater would continue to replace freshwater in

the Upper Floridan Aquifer if 1989 water use levels persisted. The report further noted that

the Upper Floridan Aquifer is a highly transmissive, well-confined aquifer where ground

water withdrawals several tens of miles inland have a significant effect on coastal ground

water levels. Previous work showed water levels along the Highlands Ridge were similarly

affected by equally distant withdrawals. Overall, ground water levels at any location in the

SWCFGWB are affected by cumulative ground water withdrawals occurring tens of miles

away. These findings were the basis for declaration of the Southern Water Use Caution

Area (SWUCA) in 1994.

4.2.2 Available Data

A variety of local, regional, and state agencies compile data regarding the health of ground

and surface water resources in the Southern Coastal Watershed. The District has a

comprehensive hydrologic conditions monitoring program. Conditions that are monitored

include rainfall, evaporation, lake levels, groundwater levels, springflow, various water

quality parameters, and river discharge and stage elevation. 

Hydrologic data are also collected by the District through regulatory programs. Public

supply permittees and all permittees located in water use caution areas must report ground

and surface water withdrawals where permitted withdrawals exceed 0.1 mgd. Other water

use permittees are required to report pumpage if permitted withdrawals are greater than 0.5

mgd. Selected water use permittees are also required to report water levels and waterquality data. The United States Geological Survey also maintains a data base of stage,

flow, and water-quality measurements which includes monitoring sites within the Southern

Coastal Watershed.

4.2.3 Regulatory Authority and Special Rules

Water supply development throughout the Southern Coastal Watershed is subject to the

District’s Water Use Permit rule, Chapter 40D-2, Florida Administrative Code (F.A.C.).
Comprehensive Watershed Management Plan November 2000

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Water supply withdrawals within the northern portion of the Southern Coastal Watershed,

part of the existing Eastern Tampa Bay WUCA, are subject to additional permitting criteria.

These criteria include the imposition of conservation and efficiency requirements for all

water users and the setting of per capita water use standards and planning goals for public

supply.

The District’s well construction permitting program ensures both the protection of ground

and surface water resources and the protection of water quality for potable uses. District

rule, Chapter 40D-3, F.A.C., regulates well construction practices and water well contractor

licensing. In addition, selected Florida Department of Environmental Protection rules

incorporated into Chapter 40D-3, F.A.C., by reference, are intended to ensure that all water

wells and test or foundation holes within the District are located, constructed, maintained,

used and abandoned in a manner that protects water resources. 

4.2.4 Regulatory Issues

As of Summer 1998, there were several outstanding permitting issues which have water

supply implications for the Southern Coastal Watershed. The most notable of involves the

evaluation of proposed additional water supply withdrawals from the Peace River. These

additional quantities would be used, at least in part, by residents, businesses and industries

located within the Southern Coastal watershed. 

A key component to identifying acceptable withdrawal quantities for the Peace River and

other water bodies within the District is the establishment of minimum flows and levels

(MFLs). The term "minimum flow" refers to the limit in a watercourse at which further

withdrawals would be significantly harmful to the water resources or ecology of an area.

Similarly, "minimum water level" is statutorily defined as the level of ground water in an

aquifer or surface water, such as a lake, at which further withdrawals would be significantly

harmful to the water resources of an area.

Once established, MFLs are implemented through a variety of means, including the

application of these flows and levels to the District’s water use permitting program. As

directed by Chapter 373.042, Florida Statutes (F.S.), the District may restrict withdrawals

of water which would cause flows or levels to drop below their established minimums and

which would be significantly harmful to the water resources or ecology of an area. The

District’s water use permitting rules, which include criteria to prevent adverse impacts from

occurring as a result of withdrawals, effectively establish MFLs for specific sources

throughout the District. Implementation of the pending Southern WUCA rules would expand

the area affected to include the entire Southern Coastal watershed.

4.2.5 Other Governmental Activities and Watershed Initiatives

The following section briefly describes other governmental activities in the Southern Coastal

Watershed that relate to water supply.
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Peace River-Manasota Regional Water Supply Authority

The Peace River/Manasota Regional Water Supply Authority (PRMRWSA) completed its

Water Supply Master Plan in 1990 (Boyle Engineering, 1990). The Plan identified three

potential sources of water supply within the region that may be available for future

development by the Authority. The Peace River, currently used as a withdrawal source by

the Authority, was identified as having sufficient capacity to safely yield additional quantities

of water. In addition, the Plan identified the northwest DeSoto County/southeast Manatee

County and north-central DeSoto County areas as having favorable characteristics for

additional ground water development from the Upper Floridan aquifer.

The Peace River was identified as the primary source of additional water supply quantities,

pending public acquisition of the General Development Utilities Peace River Water

Treatment Facility, which occurred in 1991. A renewed water use permit, issued by the

District in 1995, provides for an incremental increase in allowable withdrawal rates up to a

maximum daily average of 32.7 mgd. Permit provisions require independent scientific

review and analysis prior to each phased increase. Withdrawals from the Peace River are

restricted from exceeding 10 percent of river flow, as measured at the Arcadia gaging

station, and are prohibited when river flow falls below 130 cubic feet per second (cfs).

(SWFWMD, 1996).

4.3 Water Supply Issues

An overview of current water supply issues within the Southern Coastal Watershed is given

below. Also included are strategies and actions to address these issues.

Enhance Coordination for Effective Water Resource and Land Use Planning

Strategy: Seek inclusion of water resource/land use planning as a consistency requirement

for Local Government Comprehensive Plans.

To date, no clear linkages have been developed between District water resource planning

activities and the land use planning activities of local governments (SWFWMD, 1995). The

District is the agency charged with primary responsibility for water management decisions

within its region and is a centralized source for water related research and information.

Local governments exercise primary authority over land use through long-range (20-year)

comprehensive plans. Existing statutes relating to land and water planning and

management create two separate tracks with minimal connection and no requirements for

consistency between them. Integration between land and water resource planning and

management is essential for either to be effective. This issue was the subject of the

Governor’s Task Force on Land and Water Planning.

Actions:

1) Use the District’s Needs and Sources report as the source document for water supply
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availability.

2) Include land use and water resource planning consistency as part of the District’s 1999

legislative agenda.

3) Seek opportunities to enhance linkages between the District and local governments as

they relate to water resources and land use planning.

Strategy: Improve coordination between land and water planners

Enhanced coordination between District planning staff and local government planning staffs

will further the linkage between land use and water resource planning.

Actions:

1) Increase District involvement with the Tampa Bay and Southwest Florida Regional

Planning Councils and local government planning departments.

2) Develop an annual report summarizing the status of water supply, water resources, and

new regulations for distribution to local land use planners and others.

3) Develop procedures with local governments so that District input becomes part of

government decisions on land use planning.

4) Coordinate five-year planning documents, such as Comprehensive Plan Updates and

Basin Plans, on the same time frame.

Continuation and Expansion of Conservation and Water Shortage Initiatives

Strategy: Promote conservation and reuse

In order to reduce demands on existing potable water resources within the Southern

Coastal watershed, existing water conservation programs and initiatives should be

continued and additional opportunities for water conservation should be sought.

Actions:

1) Continue existing conservation programs and reuse system expansion.

2) Continue interconnection and regionalization of reuse systems, where cost-effective, to

improve efficiency and increase reclaimed water utilization.

3) Investigate opportunities to develop reuse systems in new areas.

4) Continue current funding levels and the associated programs and regulatory

requirements for conservation and reuse.

5) Investigate financial incentives to offset the costs of industrial and commercial reuse and

conservation programs.

6) Recognize and reward industries and other entities who have strong conservation and/or

reuse programs.

7) Develop pilot projects for stormwater reuse.

8) Increase public awareness of the environmental costs of water use.

9) Investigate increasing funding levels for conservation and reuse programs.
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Strategy: Improve compliance with water shortage restrictions and year-round conservation

measures

Coordination with local governments is necessary to achieve effective enforcement of the

District’s year-round water conservation measures and water shortage restrictions,

implemented during periods of District-declared water shortages.

Actions:

1) Educate the public on how year-round water conservation measures and water shortage

restrictions affect them.

2) When noticing adjacent property owners regarding Water Use Permits, mention any

water shortage restrictions included in the permit. For example, in noticing nearby

homeowners when golf courses are issued water use permits, homeowners could be

informed regarding the allowable golf course irrigation schedules and could assist in

ensuring their compliance with water shortage restrictions.

3) Coordinate with local governments to identify means of enforcing watering restrictions.

Strategy: Develop alternative water sources.

Recognizing the limited availability of groundwater resources, the SWFWMD has developed

a water supply policy which states that the SWFWMD will “encourage, assist in, and where

appropriate require, the development and efficient use of alternative sources of water”

(SWFWMD, 1995). Alternative water sources are sources other than traditional

groundwater such as surface water, reclaimed water, stormwater reuse, aquifer storage and

recovery, and brackish water or seawater desalination. To promote the development of

alternative water sources, the SWFWMD established the New Water Source Initiative

(NWSI) in 1993. The NWSI is a financial assistance and water supply planning program

which assists local and regional agencies in developing alternative water supplies.

Actions:

1) Continue New Water Sources Initiative and Cooperative Funding Program to assist local

governments in developing alternative supplies. Include alternative sources as a

primary component of water supply plans.

2) Continue regulatory requirements/incentives for alternative water sources.

3) Optimize use of aquifer storage and recovery for reclaimed and surface water sources.

Minimum Aquifer Levels for the Intermediate Aquifer

Strategy: Adopt aquifer levels for the Intermediate aquifer to establish limits on withdrawals

that will not cause significant harm to the water resources or the ecology of the

area.
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The District has scheduled to establish minimum aquifer levels for the Intermediate aquifer

by 2011. Minimum flows and levels are defined in the Florida Administrative Code as “the

limit at which further withdrawals would be significantly harmful to the water resources or

ecology of the area.” In establishing minimum ground water levels, the District will evaluate

the demands on, and existing impacts to, the Intermediate aquifer to ensure the long-term

viability of the resource. 

Actions:

1) Collect and evaluate hydrologic and ecological information necessary to establish

minimum levels ground water for the Intermediate aquifer.

2) Adopt minimum ground water levels for the Intermediate aquifer.
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LITERATURE CITED

Boyle Engineering Corporation. July 1990. Peace River/Manasota Regional Water Supply

Authority Water Supply Master Plan.

Southwest Florida Water Management District (SWFWMD). March 1988. Ground-Water

Resource Availability Inventory: Charlotte County, Florida.

SWFWMD. March 1988. Ground-Water Resource Availability Inventory: Manatee County,

Florida.

SWFWMD. March 1988. Ground-Water Resource Availability Inventory: Sarasota County,

Florida.

SWFWMD. 1992. Water Supply Needs and Sources 1990-2020.

SWFWMD. March 1993. Eastern Tampa Bay Water Resource Assessment Project.

SWFWMD. October 1994. Supplemental Investigations and Other Reports Prepared for

the Eastern Tampa Bay and Southern Water Use Caution Areas Since March 1993.

SWFWMD. February 1995a. District Water Management Plan.

SWFWMD. February 1995b. Water Use Permit Information Manual.

SWFWMD. November 1996. A Plan for the Use and Management of the RV Griffin

Reserve.

University of Florida, Bureau of Economic and Business Research. Volume 29, Number

2, Bulletin No. 114, February 1996. Florida Population Studies: Projections of Florida

Population by County, 1995-2020.
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CHAPTER V

FLOOD PROTECTION

5.1 Introduction

One of the most important aspects of flood protection is the recognition that flooding is a

natural part of the hydrologic cycle. Flood prone lands provide a number of valuable

functions. With respect to flood protection, Flood prone lands help regulate the timing,

velocities and levels of flood discharges by providing temporary storage for stormwater

runoff and overflow from water bodies. These lands also help maintain water quality and

provide habitat for fish and wildlife. Flood prone lands include not only wetlands but also

the less frequently flooded lands which make up the floodplain. Both are important in

providing necessary storage for periodic inundations.

A primary concern of watershed management is the understanding of floodplain functions

and the provision of safeguards within such areas, not only from damages when flooding

occurs, but also for the natural systems and habitats. Effective floodplain management

recognizes the importance of maintaining and/or restoring floodplain functions and related

natural systems as a way of reducing flood related damages. The District recognizes the

importance of maintaining floodplain functions as an effective component of watershed

management.

The District has adopted a non-structural approach to flood control and has developed a

variety of flood protection information and data resources for use by local governments

identifying and managing Flood prone areas within their jurisdictions. District flood

protection efforts include: funding and development of watershed management studies,

including aerial mapping; maintenance and dissemination of geographic information system

data, Federal Emergency Management Agency (FEMA) floodplain maps and other mapping

resources; hydrologic monitoring and data collection; operation and maintenance of existing

regional flood control structures; land acquisition; aquatic plant management; and,

integration of the District’s water resources planning with local government land use

planning.

5.1.1 Overview of Watershed

Surface water features within the Southern Coastal Watershed include a variety of fresh

and salt water wetlands and a number of coastal streams and sloughs. These streams and

sloughs are typically intersected by manmade drainage canals which provide varying levels

of stormwater conveyance during storm events. The extent and type of development,

however, strongly influences the quantity and quality of stormwater runoff within each of the

watershed sub-basins.
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Regulation of land uses within flood prone areas is necessary in order to reduce potential

flood damages and maintain the natural conveyance functions of floodplains. Local

governments regulate development within the 100-year floodplain in order to participate in

the National Flood Insurance Program (NFIP). The NFIP, administered by the Federal

Emergency Management Agency, allows residents of participating local governments to

purchase federally subsidized flood insurance. Areas of 100-year floodplain within the

Southern Coastal Watershed are depicted in Map 5 in the Appendix.

The most significant area of 100-year floodplain is found on the Cape Haze Peninsula, a

broad, relatively flat land mass located between Charlotte Harbor and the Gulf of Mexico.

Significant flood events on the Peninsula generally occur from tidal inundation in association

with land falling tropical storm or hurricane events. Land development activities have

altered the natural drainage patterns on the Peninsula. Today, lands that historically

drained south and southwest to Lemon Bay, Placida Harbor and Gasparilla Sound, now

drain east into the northwestern portion of Charlotte Harbor.

Agricultural drainage within the Southern Coastal Watershed occurs primarily from citrus

groves located west of Interstate 75 and rangeland situated at the headwaters of Phillippi

Creek and Cow Pen Slough. One of the more significant agricultural drainage sub-basins

within the watershed is Cow Pen Slough, which begins in southeastern Manatee County

and traverses south-southwestward before terminating at the coast just north of the City of

Venice. A number of smaller streams and sloughs provide drainage for other parts of the

watershed. One of these systems, Oyster Creek, functions within its historic flow regime

with the exception of peak events, when it discharges through the Newgate Waterway

System (Chuck Walter, Charlotte County, pers. commun.).

Developed urban areas of the Southern Coastal watershed include the cities of Sarasota,

Venice and Bradenton, and the barrier island communities of Longboat Key, Bradenton

Beach, Holmes Beach and Anna Maria. Older urban development within the watershed has

increased stormwater runoff resulting in increased non-point source pollution. Due to a

variety of factors, identification of non-point sources of pollution is far more difficult than

determining point source discharges. Stormwater runoff amounts, rainfall intervals, types

and patterns of land uses, and the types of street debris and level of street cleaning are just

a few of the factors that influence the quality of stormwater runoff.

Many water dependent ecosystems rely on the seasonal freshwater flows from the

watershed’s surface water features to maintain their health and viability. Modification of

these features, either for water supply development, or more commonly for urban

development, has the potential to reduce or change the hydrologic characteristics of these

features.

Population and Growth

The population of the Southern Coastal Watershed is growing at a rapid pace (see Table

III-1). Recent development trends are directing significant new growth to the areas around
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the Interstate 75 corridor with this trend likely continuing into the foreseeable future. The

coastal areas of the watershed, on the other hand, tend to be older development, much of

it built prior to the implementation of current surface water management regulations.

Limited infill development and redevelopment is occurring in these areas, however, with

current stormwater management requirements generally applicable.

Historic Flood Events

Flood events within the Southern Coastal watershed typically result from tropical storm

events and hurricanes which cause intense rainfall, excessive runoff and tidal surge

influences. Previous years have recorded several storm events that have produced flood

conditions within the Southern Coastal watershed. Two of the most significant storm events

occurred, however, relatively recently in 1992 and 1995, causing severe flood impacts

throughout the watershed.

The June 1992 storm event produced significant rainfall within the Southern Coastal

watershed. A tropical disturbance in the Gulf of Mexico during June 24-30 produced 16-24

inches of rainfall. The July 1995 storm event also produced significant rainfall within the

watershed. A tropical disturbance during the July 14-20 period produced 3-11 inches of

rainfall in one 15 hour period. Rainfall and streamflow data for these events was collected

from a variety of sites, both within and outside the watershed. During both events, local

government staffs also attempted to document the extent of flooding within their jurisdictions

by surveying high water marks.

As a result of these two events, significant watershed analysis and management activities

were either initiated or their completion expedited by Sarasota County and other local

governments within the watershed. The results and recommendations of these studies are

outlined in following sections of this chapter.

5.2 Previous Studies

A number of planning documents, technical reports and studies related to flood protection

issues in the Southern Coastal Watershed are available. These documents are

summarized briefly below:

5.2.1 Flood Protection Studies and Reports

District Water Management Plan

The District Water Management Plan (SWFWMD, 1995) is a broad-based planning

document that addresses activities related to water supply, flood protection, water quality,

and natural systems. The plan identifies current programs, issues, and strategies for

regional water management. The flood protection element of the DWMP addresses two

subcategories of responsibility: (1) flood protection facilities and (2) flood-prone areas.
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The Facilities subsection of the DWMP discusses the District’s structural approach in

providing flood protection, including its regulatory activities in the management and storage

of surface waters. Although a non-structural approach to flood control is generally

advocated today, the District is still responsible for the maintenance and operation of those

existing facilities. Further, structural flood control will likely continue to serve a role in

solving flood problems associated with previous development and in accommodating future

growth and development in the region.

The Flood-prone Areas subsection of the DWMP describes District efforts aimed at

identifying, evaluating, protecting and restoring the natural functions of flood-prone areas.

Identified programs and initiatives include the current CWM Program, floodplain analysis,

stormwater management master planning, aerial mapping, land acquisition, Environmental

Resources Permitting, local government planning and technical assistance and the

establishment of management levels for lakes. 

Master Stormwater Management Plans 

In recognition of the need to be more proactive in flood protection and watershed planning,

Sarasota County initiated the development of drainage basin master plans in 1991 with the

preparation of detailed master plans for the Phillippi Creek and Hudson Bayou watersheds.

Each basin master plan includes a detailed study of existing and potential water resource

problems within the watershed and identifies facility improvements necessary to provide an

acceptable level of resource protection. Since then, development of master plans for a

number of other watersheds have been completed or initiated (e.g., Briley, Wild and

Associates, 1992; Kimley-Horn and Associates, Inc., 1994a, 1994b; Parsons Engineering

Science, 1996, 1997; Gee and Jenson, 1997, 1998, etc.). As noted previously, significant

flood events in 1992 and 1995 accelerated the process for completion of these plans by

local governments within the watershed.

Cow Pen Slough Basin Master Plan

Cow Pen Slough’s watershed extends from southern Manatee County south and west to

its outfall into Dona Bay in Sarasota County. The watershed is characterized by flat

topography and undefined drainageways, with primary drainage conveyed through

approximately 14 miles of improved channel. Given the watershed’s relatively rural nature,

the Cow Pen Slough Master Plan (USDA, 1997) focuses on the conversion of land uses

from agricultural to residential. Hydrologic studies were conducted to determine floodplain

boundaries and level of service (LOS) deficiencies for both current and future land use

scenarios. The Plan also analyzed the potential for wetlands restoration and enhancement.

The Cow Pen Slough watershed was significantly altered and expanded (68 square miles

to 90 square miles) in the 1960s. As part of this watershed-wide assessment, it was noted

that Cow Pen Slough is a large contributor of freshwater inflow to the Dona and Roberts

Bay (DARB) system. These large influxes of fresh water disrupt the normal circulation and

salinity distribution patterns within the DARB system, resulting in poor water quality. The
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Southern Coastal Watershed Team has adopted a goal of determining the feasibility of

using the excessive wet season flows from the Cow Pen Slough watershed to offset potable

and/or non-potable water supply demands within the Southern Coastal Watershed, thereby

reducing impacts to the DARB system. 

5.2.2 Available Data

The following is a brief list of flood protection data resources available from the Southwest

Florida Water Management District. Many of these reports, maps and electronic data sets

can be accessed through the District’s web site, http://swfwmd.state.fl.us. All the belowmentioned data can be accessed by calling the District’s Brooksville headquarters at (352)

796-7211 or 1-800-423-1476 (Florida only).

Data Collection - The District maintains a comprehensive hydrologic conditions monitoring

program. Conditions that are monitored include rainfall, evaporation, lake levels,

groundwater levels, springflow, various water quality parameters, and river discharge and

stage elevation. This data can be very useful for flood protection and flood forecasting

activities, including development of watershed management plans.

Aerial Mapping and Floodplain Delineations - The District’s aerial mapping program,

initiated in the early 1970's, maintains an extensive inventory of aerial photography and

aerial contour maps for use by local governments. These projects are funded by the Basin

Boards on a cost-share basis with the local governments. Aerial contour mapping has been

completed for the majority of the District. In addition, floodplain delineations have been

completed for selected areas of the District since the early 1970s. This information is

beneficial to local governments in regulating development in Flood prone areas.

GIS Data - Since the mid-1980's, the District’s Mapping and Geographic Information

Systems (MGIS) Section has developed a significant database of ARC/INFO data layers

for use by District staff and local governments. Many of the District’s data layers are useful

for local government flood protection activities and have been provided to a number of local

governments for use on their GIS. Such layers include drainage basin boundaries, land

use/land cover, topography and soils.

Model Flood Protection Ordinance - The District’s Model Flood Management Ordinance was

produced in 1982 and distributed to all local governments within the District. The document

contains valuable floodplain management information for local government planners,

engineers and administrators (SWFWMD, 1982).

Technical and Financial Flood Protection Assistance - The District’s Basin Boards have

provided financial and technical assistance for the development and implementation of

watershed management plans within the watershed. These management plans identify

existing and potential flood problem areas, recommend preventive and remedial actions and

provide detailed floodplain delineations suitable for use by local governments in regulating

development within these areas.
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5.2.3 Regulatory Authority and Special Rules

The following discussion briefly identifies the major laws and rules governing Florida’s

surface water resources. Since water quantity and quality issues are interrelated, the list

does not attempt to segregate these two areas.

United States Environmental Protection Agency

The Federal Clean Water Act was amended in 1987 to require the establishment of the

National Pollutant Discharge Elimination System (NPDES) and Municipal Separate Storm

Sewer System (MS4) permitting programs. These programs require local governments to

comply with certain conditions in order to obtain permits for existing and future stormwater

management systems.

Southwest Florida Water Management District

Chapter 40D-2, Florida Administrative Code (FAC), “Basis of Review,” includes stormwater

system design criteria as well as technical and administrative information for applicants and

permits.

Chapter 40D-4 and Chapter 40D-40 FAC, “Management and Storage of Surface Waters”

(MSSW) states that the SWFWMD governs surface water permitting and stormwater runoff.

Chapter 40D-4's Basis of Review specifies that post-development peak discharge rates for

new development not exceed pre-development peak discharge rates for the 25-year, 24

hour event. In closed watersheds, i.e., those that do not have a surface outfall up to and

including the 100-year, 24 hour event, post-development discharge volumes must not

exceed pre-development discharge volumes for the 100-year, 24 hour event. In addition

to regulating discharge, the District also restricts floodplain encroachment. District

regulations require compensating storage be provided for fill placed within the 100-year

floodplain. Rules also stipulate that activities affecting floodplains and floodways will not

cause adverse impacts, i.e., increase flooding. Technical guidelines further clarify how to

analyze and minimize impacts from activities in the floodplain.

Chapter 40D-6 FAC, “Works of the District,” requires a permit to be obtained prior to

connecting with, placing construction across, discharging into, or otherwise making use of

works of the District. The rule protects existing works and works for which planning is

underway (e.g., canals, water control structures, rights-of-way, lakes and streams) from

actions which would impair their ability to function as intended.

Chapter 40D-8 FAC, “Lake levels Program,” establishes guidelines (primarily in floodplains)

for development bordering lakes, conservation water storage and recharge capabilities to

lakes. It also provides for operation of lake control structures and a means for providing

information on District consumptive use permitting activities.
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Florida Department of Environmental Protection

Chapter 62-16 FAC, “Prohibition of Pollutant Discharges,” covers the powers and duties of

the FDEP as they relate to prohibition of pollutant discharges, as defined in Florida Statutes

403.803(13), and the removal of prohibited discharges.

Chapter 62-25 FAC, “Regulation of Stormwater Discharge,” provides minimum criteria for

discharge into surface waters and groundwater of the state. The rule’s basic objective is

to achieve 80 to 90 percent removal of stormwater pollutants before discharging into

receiving waters. This is generally achieved through treatment of runoff from the first inch

of rainfall, although specific developments may be required to do more or less depending

upon size and other criteria such as proximity to an Outstanding Florida Water (OFW).

Chapter 62-3 FAC, “Water Quality Standards,” provides minimum criteria which govern

stormwater drainage necessary to protect the designated uses of State waters. The

legislation provides detailed criteria for both surface water and ground water protection.

Chapter 62-302 FAC, “State Surface Water Quality Standards,” classifies surface waters

into one of five different categories based upon the expected uses of each waterbody. It

establishes minimum criteria for each surface water classification in order to protect public

health and to enhance the quality of the waters of the State.

Chapter 62-312 FAC, “Dredge and Fill Activities,” requires permits for dredging and filling

in, on, or over navigable waters and provides for mitigation criteria and exemptions.

Chapter 62-340 FAC, “Delineation of Wetlands and Surface Waters,” provides the

methodology for delineating wetlands and surface waters. 

Chapter 62-4 FAC, “Permits,” provides FDEP/SWFWMD rules regarding permit standards

for issuing dredge and fill, stormwater, and water quality permits. It provides for the

classification and exemption of certain waterbodies for permitting purposes and includes

water quality standards. It also provides that permits cannot be issued for sewage facilities

that directly discharge into OFWs which would lower ambient water quality, or for

discharges that would degrade a downstream OFW.

Chapter 62-40 FAC, “State Water Policy,” addresses many different aspects of water

resource management and protection. Stormwater and surface water management

components are critical to addressing local government stormwater management systems

and required levels of service.

The above regulations were developed as a result of historic legislation passed during the

early and mid-1970s. This legislation includes: Chapter 373 Florida Statutes (FS), Florida

Water Resources Act; Chapter 380 F.S., the Florida Environmental Land and Water Act of

1972; and, Chapter 403 F.S., “Water Resources Act.”
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Local Government Regulations

The Southern Coastal watershed is primarily within the jurisdictions of Manatee, Sarasota

and Charlotte Counties. Several municipalities also are located within the watershed,

including the mainland cities of Bradenton, Sarasota, and Venice and the barrier island

communities of Anna Maria, Holmes Beach, Bradenton Beach and Longboat Key. The

following is a brief synopsis of their regulations as they relate to flood protection within the

watershed.

Manatee

Existing County regulations require stormwater management systems to be designed to

retain and treat the first inch of rainfall for the 25-year/24-hour design storm event. For

systems that discharge within the Evers or Manatee Reservoir Watershed Overlay Districts,

or to Outstanding Florida Waters or Aquatic Preserves, systems must be designed to

provide 50 percent greater water quality treatment by retaining and treating the first one and

one-half inch of rainfall. 

Manatee County Ordinance 89-10, "Manatee County Floodplain Management Code,"

provides for the regulation of development within Federal Emergency Management Agency

identified 100-year floodplain areas.

Sarasota County

Sarasota County Ordinance 89-117 establishes a Stormwater Environmental Utility (SEU)

which is responsible for the funding, planning, development and maintenance of the

County’s storm and surface water management facilities. The SEU is also responsible for

the permitting of stormwater facilities in private developments. 

Sarasota County Ordinance No. 81-12, as amended, “Land Development Regulations,”

provides regulations which guide development as it pertains to the attenuation and drainage

of surface water runoff. The ordinance stipulates facility design standards; provides for the

attenuation and retention of stormwater with the rate of runoff to be equal to or less than

pre-development conditions; and requires treatment of the runoff from the first inch of

rainfall. Additionally, the ordinance regulates subdivision activities within the 25-year

floodplain by withholding development approval “unless the developer submits substantial

and competent evidence that all lands intended for use as building sites can be used safely

for building purposes, without undue danger from flood or adverse soil or foundation

conditions.” Compensation is required on an equivalent basis for any loss of flood storage

due to the filling of an area within a floodplain (Sarasota County, 1997).

Charlotte County

The Charlotte County Stormwater Management Ordinance #89-37 was enacted to protect,

maintain and enhance both the immediate and long term health, safety and general welfare
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of citizens. The ordinance sets requirements for the content, performance standards, and

design standards of a Stormwater Management and Conservation Flood Plan which must

receive county approval prior to the commencement of any development activity. The

County’s requirements for a stormwater permit are based upon determined predevelopment runoff rates from a 25-year, 24-hour storm event and post-development runoff

rates are not allowed to exceed these except for discharge going to tidally influenced water

bodies. Additionally, the County is developing a Master Stormwater Management Plan to

better understand its drainage basins and how they are affected by rainfall, especially the

greater Port Charlotte area between the Myakka and Peace Rivers and areas south of the

Peace River.

Municipalities

Similar to the counties, municipalities within the Southern Coastal watershed incorporate

standards governing the release of runoff within the land development regulations. Most

of the municipalities mimic the District’s surface water management regulations. These

regulations require stormwater management systems be designed to accommodate a storm

event of 25-year return frequency, 24-hour duration. However, these regulations only

address new development and selected redevelopment that meet District permitting

thresholds. They do not address the construction of single family homes in existing platted

subdivisions. In many cases, existing areas developed prior to District regulations also

correspond to areas of identified flood problems. To address additional development within

these areas, many local governments must undertake watershed studies to identify and

correct existing and anticipated future stormwater management problems. 

5.2.4 Other Government Activities

In addition to administering water quantity and floodplain regulations, governmental entities

also impact flood protection through other activities. Some of these activities involve

information collection, such as cataloging flood complaints by residents. Other government

programs that affect flood protection include land acquisition and restoration programs, land

use regulation, emergency management, and road and highway construction and

maintenance.

Flood Complaints/Records

The District tracks and records flood complaints by section, township and range.

Complaints are assessed to determine if there is a violation of District rules, and if so,

actions are taken to correct the situation. Cities and local residents are also good sources

of information. The Florida Department of Transportation keeps records of high water

marks related to road design.

Land Acquisition Programs

Several agencies have land-buying programs that operate or may operate within the
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watershed. These programs include the Department of Environmental Protection's

Conservation and Recreational Lands (CARL) program, the District's Save Our Rivers

(SOR) program, Sarasota County's Environmentally Sensitive Lands Acquisition Committee

(ESLAC) and Manatee County’s Environmental Lands Management and Acquisition

Committee (ELMAC).

These programs typically emphasize the preservation of natural systems and enhancement/

preservation of water quality. Since the lands purchased often include flood-prone wetland

areas, acquisition also serves to prevent development in these natural flood storage areas.

Land Use Regulation

Each of the counties and municipalities in the watershed regulates land use within their

boundaries in accordance with a State-approved Comprehensive Plan. These plans specify

the type and amount of development allowed in any given area. As a result, the plans

influence where and to what extent development will be allowed in floodplains. To

participate in the National Flood Insurance Program, FEMA requires the local governments

to adopt floodplain management ordinances meeting their specifications. All Counties and

municipalities within the watershed participate in the program.

Emergency Management

Many agencies and organizations are involved in emergency management, such as Federal

agencies (including FEMA), State agencies, Regional Planning Councils, County and City

government, and the Red Cross. Flooding requires actions such as evacuation planning

and implementation (including operation of evacuation shelters and delivery of food and

water), rescue operations, medical mobilization, flood control system operations, damage

control and assessment, flood insurance compensation, delivery of federal aid, and

repairs/replacement of damaged or destroyed infrastructure and buildings. 

5.3 Flood Protection Issues

An overview of current flood protection issues within the Southern Coastal Watershed is

given below. Included are strategies and actions to address these issues.

Data Management

Strategy: Enhance flood protection data collection and management.

Data management includes the collection, maintenance, update/revision and retrieval of

data required to understand the water resource systems within the watershed. This data

can be used to define and/or delineate flood prone areas. As watershed characteristics are

constantly changing, the data used should be the most up-to-date to represent the current

state of the watershed.
Comprehensive Watershed Management Plan November 2000

44

The ability of the District, government agencies, local governments and private consultants

to complete accurate flood prone area analyses is dependent upon the quality of the data

available. Limitations on the collection of quality data include the cost of data acquisition,

physical constraints and lack of knowledge of what data is needed during the data collection

phase of a project.

Actions:

1) Develop a data management system with appropriate standards to provide the

information required to define the flood prone areas.

2) Provide the requirements necessary, in an ARC/INFO based GIS format, to allow the

transfer and formulation of input and output data from numerical models to a GIS. This

will support further data development for other predictive models (i.e., water quantity,

water quality, ground water, natural systems). It will also provide access to the data and

modeling results for regulation within the watershed.

3) Encourage the development of data transfer tools by the developers of stormwater

management software. The goal is to have software with the capability to transfer the

input data and output results to SWFWMD standards or to translate the information to

data formats used by other stormwater management software and GIS.

4) Use of data management tools to update the database through the regulatory process

by requiring Environmental Resource Permit (ERP) submittals to include the data in the

District’s data standards.

5) Perform aerial mapping with contour information (paper and digital formats) for areas

in the watershed that have no such information or outdated information.

6) Promote cooperative agreements to build data collection responsibilities based on need

and the capabilities of the agency (FEMA, SWFWMD, Counties, Cities).

7) Levels of Service (LOS) objectives should be set within project areas. These LOS’s

could be based on 25-year or 100-year, 24-hour events, and the number of homes

affected, and length and classification of impacted roads, etc. could be used to develop

a decision support matrix to evaluate the merits of multiple projects.

Flood Prone Area Analysis

Strategy: Obtain additional floodplain information.

Flood characteristics of the watershed can be used to decide what current and future

actions are necessary. One of the primary issues concerning flood protection in the

Southern Coastal watershed involves generation of flood estimates for those areas of the

watershed with little or no available data. Those areas that have not already been studied

should be targets for future data collection and analysis.

Actions:

1) Perform flood studies on unstudied areas.

2) Set priorities based on current development pressures.
Comprehensive Watershed Management Plan November 2000

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3) Set priorities based on historic flooding problems.

Effective Flood Protection Regulation and Planning

Strategy: Address increased runoff volume due to development.

Development within a basin, whether in or out of the floodplain, increases the runoff from

a given rainfall event. Current regulations prevent post-development peak discharge rates

in excess of pre-development peak discharge rates. However, many areas still may

experience increased flooding as the result of development. This stems from the fact that

an increased volume of runoff is released from systems designed to regulate peak flow

rates.

Use of several different strategies can help address the problem of increased runoff

volumes. Analysis of various duration rainfall events for a specific return period can identify

which event results in the greatest amount of flooding. In addition, current regulations could

be modified to require detention or quicker release of increased runoff volumes so as not

to coincide with peaks flows in the receiving water. Reuse of storm water for irrigation

purposes primarily has water quality and water supply benefits. If built on an appropriately

large scale, the volume available in storm water reuse holding ponds could also afford some

flood protection.

Actions:

1) Require modeling of current tailwater conditions and impacts of upstream volumes and

timing on a site proposed stormwater management system and the proposed systems

receiving water for stormwater management system permits.

2) Permit applications should require "critical event" analysis.

3) Promote the reuse of stormwater for non-potable water uses to increase storage in flood

prone areas in stormwater management system applications.

Strategy: Effective Regulation and Management of Floodplain Functions.

Inadequate regulations are created by a lack of information or errors made in identifying

flood prone areas. Land alterations which have impacted the function of the flood prone

areas have been allowed because such areas were not properly depicted on Flood

Insurance Rate Maps (FIRM) developed by the Federal Emergency Management Agency

(FEMA). In the pre-development analysis of a project site, the site’s existing storage

calculations should include potential storage volume. If the floodplain functions of a site are

altered (post-development), any permitted stormwater management system will not provide

the same floodplain function as the pre-developed site. 

Actions:

1) Ensure that regulations are enforced. That is, lands necessary for the provision of
Comprehensive Watershed Management Plan November 2000

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compensatory storage should be available when needed, systems should be designed

to accommodate flooding during extreme events, and such systems should not increase

the level of flood waters either upstream or downstream of the site.

2) Regulations should require conservative estimates of seasonal high groundwater

elevations when determining the amount of compensating storage for encroachment into

the floodplain.

3) During permitting, consider cumulative impacts of increased runoff volume in the

watershed.

4) Include inspection of stormwater management systems for integrity of impoundments,

embankments and other components of the system in current enforcement and

inspection programs.

Strategy: Link water resource planning and land use planning.

The authority of cities and counties within the watershed, and the local decisions about the

use of land that derive from this authority, have important consequences for water

management. This is particularly true of flood-prone areas. Flooding problems occur where

these natural areas are developed for residential or commercial use. A cooperative

relationship is needed to link management of land and water resources to minimize flood

damages and the loss of natural flood storage areas.

Actions: 

1) Encourage local governments to establish levels of service for current (present) and

targeted (build-out) conditions for the watershed’s stormwater management

infrastructure facilities for flood protection using methods developed by the Stormwater

Level of Service (LOS) Conventions Committee.

2) Assist local governments in using LOS criteria in their comprehensive plans to measure

the watershed’s current flood management capacity. Cooperate with FDOT and local

governments on the design of roads. The roads should be designed to meet LOS.

Signage programs, including flood elevation levels, could be developed to warn drivers

of flooding conditions.

3) Back legislation to require deeds or other documents for real estate to indicate if land

is in a floodplain.

4) Determine and establish appropriate setbacks from riparian systems for any structure

(i.e., landward of 100-year flood plain) or some distance from 10-year flood plain or

wetland boundaries.

5) Coordinate with local and county governments to limit densities in floodplains.

6) Encourage current open land uses (i.e., agricultural, recreational corridors) in floodplain

to remain instead of land uses that allow alterations to the floodplain. 

7) Encourage conservation easements, green ways, and the efficient use of the required

stormwater management storage, and placement of mitigation areas within existing flood

prone areas.

8) Promote clustering of development outside the floodplain.

9) Encourage the use of density credits to cluster development outside flood plains,
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incentive-based regulation.

Planning and Development of Future Flood Management Systems

Strategy: Adequately plan for future flood protection efforts.

Flood protection should be incorporated as part of stormwater management planning

efforts. Some flooding problems in developed areas can be addressed without expensive

remedies. For example, maintenance efforts keep existing ditches clean and existing

detention facilities structurally sound. Acquiring lands to protect floodplains from alteration

can help reduce potential flood damage. In addition, stormwater management master

planning should address existing flooding problems with a focus on solutions that minimize

environmental impacts, improve water quality and contribute to the water supply.

Actions:

1) Convince local governments that the entire watershed should be examined using a flood

prone area analysis.

2) Encourage local governments to inventory existing drainage systems.

3) Encourage local governments to set goals for flood protection based on a consistent

LOS policy.

4) Incorporate other planning elements in the Stormwater Management Plan method, i.e.,

transportation, major developments of regional significance, Greenway/Wildlife corridors,

recreation/parks, agricultural development, water supply, and environmental

management.

5) The Districts requirements for Stormwater Management Plans should develop a

consistent framework for management throughout the watershed.

6) Pursue special development codes for building construction in floodplains (i.e., no fill for

house pads in floodplains, signage required for depth of flooding, etc.).

Operation and Maintenance Responsibilities for Stormwater Management Systems

Strategy: Determine ownership, operation and maintenance responsibilities for flood

management systems.

Flood management systems within the watershed provide stormwater conveyance and

storage functions. The existing network is a combination of natural and manmade systems.

Responsibility for the operation and maintenance of these systems varies, but may include

the District, counties, municipalities or private entities.

Actions:

1) Determine the ownership of identified stormwater management systems.

2) Determine the responsible entity for operation and maintenance of identified stormwater

management systems.
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3) Develop operation and maintenance plans for the flood management systems within the

watershed. This includes developing strategies for maintaining and operating the

systems, obtaining easements or ingress and egress agreements with property owners,

and naming the governments or other responsible parties to complete the work.

Revenues and Funding Sources

Strategy: Seek consistent source(s) of funding for flood management systems.

Revenues and funding sources are available for surface water management at the federal,

state, regional, county and city government levels. Cooperative funding programs are

available to help cost share on projects of special concern and for watersheds that extend

beyond jurisdictional boundaries. Local governments fund stormwater management

projects through a variety of funding mechanisms. A consistent source of funding is

provided by some entities, while others fund inconsistently. Master plans address funding

for problem areas without consideration of possible future funding from other entities who

propose development or alterations within the watershed. 

New development or land alteration projects require stormwater management systems.

These systems function, however, as facilities for local governments, but are not necessarily

funded, owned, or operated by the local government. Major conveyance systems and

storage areas are typically funded by a variety of sources within a watershed. Often, there

are no overall mechanisms to guide the development of stormwater management

infrastructure within a watershed. 

Actions:

1) Alternatives to general revenue sources should be considered for funding of stormwater

projects.

2) Encourage the establishment of stormwater management utility fees.

3) Encourage the establishment of special assessment districts.

4) Encourage contributions to regional facilities developed based on a Stormwater

Management Master Plan.

5) Develop an educational program implemented by the District for county and local

governments that illustrate the available funding.

6) Encourage cooperative projects or piggyback scenarios where many agencies contribute

to a project developed through a watershed-wide study. Possibly provide credits for

developers, roadway improvements (FDOT, Counties, Cities) who tie into regional

projects that provide efficient stormwater quality and quantity storage, wetland mitigation

and protection of the floodplain and its function. Provide mechanisms for maintenance

and operation funding. 

Flood Management Awareness and Education

Strategy: Facilitate public education and understanding of flood protection are necessary
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in order to build support for stormwater management projects or programs that

protect the natural floodplain and its function.

Actions:

1) Educate public and elected officials that developments are often designed to flood

relatively frequently (based on a probability of occurrence of a storm event), based on

the level of service provided.

2) Educate the public on the hydrologic cycle and its interaction with the water resource

and the impacts on water use.

3) Educate the public and elected officials that restricting development in the flood plain

may result in significant monetary savings and enhance natural systems in the future.

4) Clarify District flood protection responsibilities.

5) Clarify the role of FEMA and their responsibilities and contribution to flood protection.

6) Promote cooperation between the responsible jurisdictions on flood protection issues.

7) Provide educational talks to technical groups.
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LITERATURE CITED

Gee & Jenson. October 1997. North Creek Basin Master Plan - Draft Comprehensive

Report.

Gee & Jenson. March 1998. Curry/Hatchett Creek Basin Master Plan - Existing

Conditions Interim Report.

Kimley-Horn and Associates, Inc. August 1994a. Elligraw Bayou Basin Master Plan -

Final Report.

Kimley-Horn and Associates, Inc. September 1994b. Matheny Creek Comprehensive

Basin Master Plan.

Parsons Engineering Science, Inc. January 1996. Forked Creek Basin Master Plan -

Final Report.

Parsons Engineering Science, Inc. July 1997. South Creek Basin Master Plan

Hydrologic, Hydraulic and Water Quality Interim Report.

Sarasota County. July 1997. Apoxsee: Sarasota County’s Comprehensive Plan.

Southwest Florida Water Management District. November 1982. A Model Flood

Management Ordinance.

SWFWMD. February 1995. District Water Management Plan.

United States Department of Agriculture. 1997. Cow Pen Slough Basin Master Plan.
Comprehensive Watershed Management Plan November 2000

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CHAPTER VI

WATER QUALITY

6.1 Introduction

In 1988, Sarasota Bay was chosen by the U.S. Environmental Protection Agency as an

estuary of national significance. Subsequently, the Sarasota Bay National Estuary Program

(SBNEP) completed a technical diagnosis of Sarasota Bay. The results of this diagnosis

were compiled in the document "Framework for Action" (SBNEP, 1992), which set the stage

for the SBNEP's "Comprehensive Conservation and Management Plan," (CCMP) which

was completed in 1995.

In 1995, the Southwest Florida Water Management District (SWFWMD) selected Sarasota

Bay to be included in its list of priority water bodies for the Surface Water Improvement and

Management (SWIM) Department. Designation of Sarasota Bay as a SWIM priority water

body allowed monies to be spent on the restoration and/or protection of Sarasota Bay from

the SWIM Trust Fund, pending the approval of a Sarasota Bay SWIM Plan. 

However, Dona and Roberts Bay (the Roberts Bay located next to Venice, not the Roberts

Bay just north of Phillippi Creek) have not received the level of attention focused on

Sarasota Bay. Neither has Lemon Bay. Additionally, Gasparilla Sound has not been the

focus of any detailed examination of water quality or pollutant loads.

The challenge, therefore, of the Southern Coastal Watershed Management (SCWM)

Program is to examine the possibilities of applying research, monitoring, and restoration

techniques used in Sarasota Bay and other similar systems, and apply them (where

practical) to Dona Bay, Roberts Bay, Lemon Bay and Gasparilla Sound.

6.1.1 Previous Studies and Available Data

Before inclusion in the National Estuary Program, Sarasota Bay was the focus of many

studies. In the late 1980's, the National Oceanic and Atmospheric Administration's "Estuary

of the Month" program produced a summary document focusing on Tampa Bay and

Sarasota Bay. This document, "NOAA Estuary of the Month" (1987) contains seven

chapters dealing with water quality, pollutant loads, and management issues within

Sarasota Bay. These articles are listed in the literature cited section of this chapter.

In 1988, Mote Marine Laboratory summarized the results of ongoing and completed

research in Sarasota Bay. This document, "Sarasota Bay Area Scientific Information

Symposium" (1988) updated information from the earlier NOAA study, while focusing on

Sarasota Bay alone. Also called "SARABASIS,” this effort included preliminary

recommendations for improving the management of Sarasota Bay and its watershed.
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These articles are listed in the literature cited section of this chapter.

Four years after its inclusion in the National Estuary Program, SBNEP produced the

"Framework for Action" (1992). This document summarized the entirety of research on

Sarasota Bay conducted through the efforts of the SBNEP, and included over a dozen

chapters dealing with water quality, pollutant loads, circulation patterns, fisheries, marine

mammals and more. Again, these articles are listed in the literature cited section of this

chapter. At the end of each chapter, individual authors made recommendations about what

activities would best aid in the preservation and/or restoration of Sarasota Bay. These

recommendations were the basis for a second SBNEP document, the "Comprehensive

Conservation and Management Plan" (CCMP, 1995). The CCMP is meant to be the

document through which local, state and federal agencies work with the local population to

best manage the natural resources of Sarasota Bay. 

In June of 1997, the Sarasota Bay SWIM Plan was formally accepted by FDEP. This

document summarizes the information contained within earlier characterization efforts, and

updates this information where necessary.

In addition, nearly two dozen articles, chapters, and reports not associated with these efforts

have been published on the ecology of Sarasota Bay in the last two decades alone (see

literature cited section). As well, data from past and ongoing water quality monitoring

programs carried out by Manatee and Sarasota Counties must be submitted to the State

of Florida’s water quality storage and retrieval system, a.k.a. STORET, where they are

summarized by the Florida Department of Environmental Protection in its biannual 305(b)

reports. The electronic version of this report, accessible at http://ebase.dep.state.fl.us is the

source of the most recent water quality data, which was used to produce the updated

information on status and trends in water quality throughout the SCWM Program's area of

interest. 

For Dona and Roberts Bays, although water quality data are collected as part of ongoing

monitoring programs, the exclusion of these waterbodies from the SBNEP's management

boundaries is reflected in the smaller amount of summary documentation on issues of water

quality and habitat loss. However, Mote Marine Laboratory coordinated a thorough

investigation of the hydrology, water quality, and basic ecology of the Dona and Roberts

Bays system. A compilation of findings, "The Ecological Status of Dona and Roberts Bays

and its Relationship to Cow Pen Slough and Other Possible Perturbations" was published

in 1975. A compilation of management strategies is included in this document.

For Lemon Bay, the most comprehensive assessment of water quality, natural resources,

and potential management issues is the "Lemon Bay Aquatic Preserve Management Plan"

published by the Florida Department of Natural Resources (now FDEP) in 1991. This

document, which focused on identifying important management issues, is mostly descriptive

in its assessment of the status of water quality and natural resources. 

Very little information is available for Gasparilla Sound, even within the document “Charlotte
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Harbor SWIM Plan,” which was accepted by FDEP in 1993.

The most recent attempt to characterize the water quality within the Southern Coastal

Watershed area of interest (other than Sarasota Bay) was carried out by Coastal

Environmental, Inc. (1997). This project was funded by the Charlotte Harbor National

Estuary Program (CHNEP), and includes summaries of water quality for the entirety of the

Charlotte Harbor basin and watershed. Of interest to the SCWM Program, water quality

status and trends information was assembled for the area of Dona and Roberts Bays,

Lemon Bay, and Gasparilla Sound. However, Coastal Environmental, Inc. (1997)

concluded that there was insufficient information available to determine trends in water

quality in Dona and Roberts Bays, Lemon Bay, and Gasparilla Sound.

Clearly, the much higher level of funding available through the SBNEP has resulted in a

much more detailed assessment of pollutant loads, circulation patterns, seagrass coverage,

etc. for Sarasota Bay than for Dona, Roberts, and Lemon Bays and Gasparilla Sound.

6.2 Overview of Watershed-wide Issues

The Southern Coastal Watershed contains some of Florida's most beautiful and productive

estuaries. However, population growth in the watersheds of Sarasota, Dona, Roberts, and

Lemon Bays has been dramatic, especially in the post-World War II years. In 1989, the

population in both Manatee and Sarasota Counties was estimated at 425,400 (SBNEP,

1989). By the year 1995, that number was predicted to be approximately 513,900. As

population in these two counties was less than 150,000 in 1940, this represents nearly a

fourfold increase in population in just more than fifty years. In 1960, population in the two

counties was estimated at 163,000, showing a more than threefold increase in population

in the last thirty years. 

The rapid population growth that has occurred throughout Southwest Florida in the postWorld War II years has caused substantial impacts to those natural resources most

dependent upon careful management and the protection of water quality. To understand

these issues better, a comparison of watersheds and basins follows.

For the chapters on water quality and natural systems, the estuarine areas and their

associated basins within the Southern Coastal Watershed are delimited as follows (see Map

3 in Appendix): 

! Upper Sarasota Bay (USB) - includes Palma Sola Bay, Anna Maria Sound, and

Sarasota Bay proper south to Siesta Key Drive

! Lower Sarasota Bay (LSB) - includes Roberts Bay (the northern one), Little

Sarasota Bay, and Blackburn Bay

! Dona and Roberts Bay (DARB) - includes Dona and Roberts Bays, and the

mouth of Shakett Creek
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0 

20 

40 

60 

80 

100 

Ratio

USB LSB DARB LB

Figure VI-1 - Watershed to open-water ratio

1 

2 

3 

4 

5 

6 

N:P Ratio (by weight)

USB LSB DARB LB

Figure VI-2 - N:P Ratio of Water Samples

! Lemon Bay (LB) - includes Lemon Bay south to the Gasparilla Island Causeway

! Gasparilla Sound (GS) - includes from the Gasparilla Island Causeway to a line

roughly parallel between the southern tip of Cape Haze and the town of Boca

Grande, and includes Turtle Bay and Bull Bay

An important consideration, when evaluating the health of any estuary, is the relative size

of its watershed. Using this classification, the watersheds for the basins within the Southern

Coastal Watershed vary in size from 59 square miles (Upper Sarasota Bay) to more than

90 square miles (Lower Sarasota Bay). The amount of open water that these watersheds

drain into varies from just more than 1 square mile (Dona and Roberts Bay) to 45 square

miles (Upper Sarasota Bay). For Gasparilla Sound, the irregular and highly indented

shoreline creates much difficulty, when assessing both the area of open water, and the area

of contributing watershed. 

The watershed to open-water ratio varies

from less than 2 (USB) to more than 80

(DARB; Fig. VI-1). Consequently, even

without anthropogenic influences, surface

waters in the Upper Sarasota Bay system

would be expected to have lower nutrient

concentrations and greater water clarity

than is the case in the Dona and Roberts

Bay system, due to the greater degree of

terrestrial influence in the Dona and

Roberts Bay system.

Using data summarized in the 1994

FDEP's 305(b) report, nutrient data can

be compared between these systems. All

four systems have TN values less than

the Median Value for Florida's estuaries

(FDEP, 1994). Also, all four systems

have TP values above the Median Value

for Florida's estuaries (FDEP, 1994). 

As a result of the elevated levels of TP in

all four systems, N:P ratios vary from a

low of 3.6 in Dona and Roberts Bay to 5.6

in Lower Sarasota Bay (Fig. VI-2). As
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20 

30 

40 

50 

60 

70 

Trophic State Index

1988 1990 1992 1994 1996

USB LSB DARB LB

Figure VI-3 - Trophic State Index Values

such, all four systems are well within the range of N:P ratios that would suggest nitrogen

limitation of primary productivity (i.e., < 10). Nutrient reductions for nitrogen would thus be

of greater benefit than those for phosphorus, except (potentially) in those freshwater

streams and lakes located throughout the watersheds.

Using the FDEP's criteria for developing

Trophic State Index (TSI) values, the

relative health of water quality within the

estuaries of the Southern Coastal

Watershed can be calculated. TSI values

were downloaded from STORET, and

average values for each basin are shown

in Fig. VI-3. No data were available for

Gasparilla Sound. 

USB, LSB, DARB and LB all exhibit

trends of improving water quality over the

past several years, with most of the

improvements occurring between 1990

and 1992. Prior to 1990, the average TSI

values for all the systems were in the

range of “fair” (50-59), with a single annual average (Lemon Bay, 1990) in the “poor” range

(60-90). In contrast, post-1992 values only contain one annual average (Lemon Bay, 1994)

not in the “good” range (< 50). However, a more recent analysis of water quality data, while

supporting the finding of improved water quality in Sarasota Bay, showed that water quality

appears to have degraded in the northern portion of Lemon Bay (the portion monitored by

Sarasota County) during the period 1995 to 1998 (Dixon and Heyl, 1999).

The improvements in water quality that seem to have occurred between 1990 and 1992 are

concurrent with the completion of nutrient removal technology upgrades to the City of

Sarasota’s wastewater treatment plant (in 1991), as well as the movement toward deep-well

injection of effluent from facilities such as Manatee County’s Southeast Treatment Plant and

Atlantic Utilities discharge into Phillippi Creek. These changes in effluent quality and

effluent disposal practices were a result of the Grizzle-Figg Act (403.086, Florida Statutes)

which required advanced wastewater treatment (i.e., nutrient removal technology) for all

surface water discharges into Tampa Bay, Sarasota Bay, Lemon Bay and Charlotte Harbor.

Unfortunately, insufficient data are available for determining the status of water quality in

Gasparilla Sound.

(rest of page left blank intentionally)
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6.3 Priority Issues at the Basin Level

6.3.1 Sarasota Bay

Sarasota Bay, the most studied of the estuaries within the Southern Coastal Watershed,

has experienced the following perturbations (data from Sarasota Bay National Estuary

Program [SBNEP], 1992):

! Nitrogen loads have increased by approximately 300 percent, compared with

pristine conditions

! Tidal wetlands have decreased by approximately 39 percent, when comparing

1950 to 1990 estimates

! Dredging has degraded 14 percent of the bay bottom

! Dredge and fill activities, as well as reduced water quality, have caused a 30

percent loss of seagrasses, when comparing 1950 to 1988 estimates

! Fisheries have declined substantially

However, recent improvements to wastewater and stormwater have occurred, and several

habitat restoration projects have been completed. Regulatory actions and SBNEPsponsored "early action demonstration projects" have resulted in the following:

! Nitrogen loads have decreased 25 percent bay-wide, when comparing 1998 to

1988 values

! Restoration projects have increased tidal wetlands in Sarasota Bay by

approximately 3 percent

! Due to nitrogen load reductions at several locations (e.g., City of Sarasota,

Manatee County), seagrasses have increased by approximately 1,682 acres

between 1988 and 1996

For comparative purposes, the water body here after referred to as "Sarasota Bay" extends

from Anna Maria Sound and Palma Sola Bay, in the north, to Venice Inlet, in the south, a

total of 52 square miles of open water. The contributing watershed is approximately 150

square miles in size (Heyl, 1992). 

The watershed is split between Manatee County and Sarasota County, and encompasses

the City of Sarasota, as well as the island communities of Anna Maria, Holmes Beach,

Bradenton Beach, and Longboat Key. 

The largest tributary to Sarasota Bay is Phillippi Creek, which drains a watershed of 57
Comprehensive Watershed Management Plan November 2000

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quare miles, or 38 percent of the Sarasota Bay watershed. Other major tributaries include

South Creek, with a watershed of 20 square miles (14 percent of the total watershed), the

Bowlees Creek system, which drains 13 square miles (8 percent of the total), and Whitaker

Bayou, which drains 8 square miles (5 percent of the total).

During the post-World War II period of rapid growth, much environmental damage occurred,

as a result of large-scale dredge and fill projects. These projects included the conversion

of Bird Key into a finger fill canal community, and the dredging (in the 1960's) of the

Intracoastal Waterway. The dredging of the Intracoastal Waterway may have increased the

hydraulic instability of Midnight Pass, the movement of which resulted in its permitted

closure and subsequent failed reopening in the winter of 1983 (Sheng and Peene, 1992).

Water quality in Sarasota Bay is undoubtedly influenced by the amount of watershed that

drains into different parts of the Bay. In northern and central portions of the bay (i.e., Upper

Sarasota Bay), 59 square miles of watershed drain into 45 square miles of open water. In

the area of Roberts Bay south to Venice Inlet (Lower Sarasota Bay), 91 square miles of

watershed drain into 7 square miles of open water. Thus, the watershed : open water ratio

in the northern and central parts of Sarasota Bay (Upper Sarasota Bay) is 1.3, while in the

southern part of Sarasota Bay (Lower Sarasota Bay), this ratio climbs to 13.4, a roughly

tenfold increase.

When comparing segments against each other in terms of water clarity, a general pattern

emerges. Areas closest to flushing passes tend to have the greatest water clarity (e.g.,

Anna Maria Sound, Longboat Pass, etc.). Areas farther away from the influence of the Gulf

of Mexico tend to have the lowest water clarity (e.g., Palma Sola Bay, Little Sarasota Bay).

However, Roberts Bay has poor water clarity, despite its proximity to Big Pass, and the

waters just west of central Longboat Key have good water clarity, despite being located in

a null zone for circulation (Sheng and Peene, 1992). 

Using FDEP's methodology for determining "trophic state indices - TSI" (FDEP, 1994), and

excluding stations located in tributaries, all bay segments had TSI values in the "good"

range, except for Midnight Pass, which had a TSI value in the "fair" range (Lowrey, 1992).

Comparisons of TSI values suggest that overall water quality in Sarasota Bay is better than

upper and middle portions of Tampa Bay, and about the same as lower Tampa Bay

(Lowrey, 1992). Comparisons with Charlotte Harbor TSI values suggest water quality in

Sarasota Bay is roughly equivalent to that of Charlotte Harbor, but substantially better than

water at the mouth of the Caloosahatchee River (Lowrey, 1992). However, recent

improvements in water quality in Sarasota Bay (Fig. VI-3) may make the assessment of

water quality performed by Lowrey (1992) somewhat dated.

Between 1970 and 1992, the majority of Sarasota Bay had become less saline (Lowrey,

1992). This change has occurred despite the lack of a trend in rainfall in the immediate

watershed during the same period (Tomasko, unpublished data), and is thought to be

related to increases in the amount of impervious surface area that have accompanied the

increased urbanization of the watershed. 
Comprehensive Watershed Management Plan November 2000

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Out of 17 bay-wide segments used to delineate Sarasota Bay (SBNEP, 1995), 11 showed

trends of decreasing chlorophyll a concentrations (Lowrey, 1992), an indication of

increasing water quality. Additionally, 5 bay segments showed trends of increasing water

clarity, 5 showed decreasing trends for total nitrogen concentrations, 7 showed

improvements for total phosphorus concentrations, and 4 showed improving trends for total

suspended solids concentrations.

Areas with multi-parameter documented increases in water quality in recent years include

the waters offshore Tidy Island, the area influenced by the City of Sarasota's wastewater

outfall, and Little Sarasota Bay, respectively. Improvements to Manatee County's

wastewater irrigation practices are thought to be responsible for improvements in water

quality offshore Tidy Island, while upgrades to the City of Sarasota's wastewater treatment

plant are thought to be responsible for improvements in water quality in the area influenced

by the City of Sarasota's wastewater outfall. Determining the causes of recent increases

in water quality in Little Sarasota Bay is more problematic.

In contrast, water quality may be declining in the eastern portion of Sarasota Bay between

Stevens Point and Bowlees Creek. Water quality in Roberts Bay and Palma Sola Bay did

not appear to be either increasing or decreasing (Lowrey, 1992).

Sarasota Bay is characterized by areas with strong tidal influence in and near its major

passes, as well as areas with much reduced flushing. Areas of reduced flushing can be

associated with "dead ends" such as Palma Sola Bay, as well as "null zones" for circulation

where tidal waves coming in from adjacent inlets meet (i.e., Little Sarasota Bay).

Turnover times for the water within different bay segments vary substantially. Turnover

times in Anna Maria Sound and that portion of the bay adjacent to Big Pass and New Pass

average 12 to 13 days (Sheng and Peene, 1992). In the area off Tidy Island, turnover times

average 15 to 16 days, and in Roberts Bay, turnover time was estimated at 19 days. In

contrast, Palma Sola Bay and Little Sarasota Bay have turnover rates of between 32 and

37 days, respectively (Sheng and Peene, 1992).

Due to the closure of Midnight Pass, turnover times for the water in Little Sarasota Bay

increased from 14 to 37 days (Sheng and Peene, 1992). However, due to the shift from two

null zones between Venice Inlet and New Pass to one null zone in Little Sarasota Bay,

turnover time in Roberts Bay decreased from 19 to 13 days (Sheng and Peene, 1992).

The relatively low turnover time for the waters of Little Sarasota Bay (37 days) thus

coincides with the much higher watershed to open water ratio found in this area. From this

consideration alone, it would be expected that water quality in Little Sarasota Bay would be

lower than in the central and northern portions of the bay.

Seagrass coverage varies throughout the bay. Excluding passes, areal coverage ranges

from 51 percent of the bay bottom in Anna Maria Sound to 6 percent of the bottom in the

eastern portion of the bay offshore of the City of Sarasota. Bay-wide, seagrasses cover
Comprehensive Watershed Management Plan November 2000

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approximately 32 percent of the bay bottom (Kurz et al., 1999 - in press). The depth to

which seagrasses grow also varies bay-wide, from less than 50 cm below mean sea level

(MSL) in Roberts Bay, to more than 2 m (MSL) in Anna Maria Sound (Tomasko et al.,

1992). As water clarity is the primary factor controlling the depth to which seagrasses grow

in Sarasota Bay (Tomasko et al. 1992), improvements in water quality have the potential

to increase seagrass coverage by allowing seagrasses to grow down into deeper, farther

offshore portions of the bay.

Increases in seagrass coverage have been used as "bio-indicators" of improving water

quality in Tampa Bay (Johansson, 1991). In years past, the part of Sarasota Bay near the

mouth of Whitaker Bayou (segment 11) lost a substantial amount of seagrasses, a

phenomenon mostly attributed to the discharge of secondarily treated wastewater from the

City of Sarasota (Dr. Robert Orth, personal communication). Improvements to the City of

Sarasota's wastewater treatment plant during the early 1990's are thought to be responsible

for a dramatic improvement in water quality in these same areas.

Associated with the implementation of nutrient removal technology and increased re-use

of treated effluent, loads of nitrogen into Whitaker Bayou have decreased by approximately

95 percent during the past 10 years (Camp, Dresser, & McKee, Inc., 1992; Tomasko et al.,

1992). This load reduction amounts to a 43 percent decline in loads throughout the central

portion of the bay (Camp, Dresser, & McKee, Inc., 1992). During this period, nutrient levels

decreased in the waters offshore of Whitaker Bayou (Lowrey, 1992). Between 1988 and

1996, seagrass coverage in central Sarasota Bay increased by 669 acres (Kurz et al., 1999

- in press). Further reductions in nutrient loads have the potential to further increase the

amount of seagrass coverage in Sarasota Bay (Tomasko et al., 1992).

The engineering firm Camp, Dresser & McKee, Inc. was tasked by SBNEP to determine the

relative contributions of five sources of pollution (stormwater, point sources, atmospheric

deposition, baseflow, and septic tanks) for four different pollutants (nitrogen, phosphorus,

lead, and zinc). The information presented here is derived from three major reports

(Phases I, II, and III of Camp, Dresser, & McKee, Inc., 1992) and two summaries of these

data (Heyl, 1992; Tomasko et al., 1992). 

Nitrogen, rather than phosphorus, seems to be the limiting nutrient for algal growth in

Sarasota Bay, as N:P ratios (mg/l) average less than six (Fig. VI-2). Nitrogen loads are

thought to be approximately three times as high as that which would be expected from a

pristine, undeveloped watershed (Camp, Dresser, & McKee, Inc., 1992) Consequently, the

elevated nitrogen loads entering Sarasota Bay would be expected to result in increased

abundances of phytoplankton (capable of reducing water clarity and shading seagrasses),

epiphytic algae (capable of shading seagrasses and interfering with gas exchange across

seagrass blades), and macroalgae (capable of shading seagrasses and producing recurrent

hypoxia in shallow waters). 

Baywide, 46 percent of the nitrogen loaded into Sarasota Bay comes from stormwater

runoff (data from Heyl, 1992). Runoff from residential land uses accounts for 60 percent

of the 46 percent due to runoff, or approximately 28 percent of all loads. The high level of
Comprehensive Watershed Management Plan November 2000

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nitrogen loads coming from residential runoff is attributed to two factors: residential land

uses account for 42 percent of the watershed, and event mean concentrations of nitrogen

for residential land uses are second only to those from row crops, being higher even than

those associated with runoff from citrus groves (Camp, Dresser, & McKee, Inc., 1992; Heyl,

1992). 

Atmospheric deposition accounts for 27 percent of the bay-wide nitrogen load. However,

atmospheric deposition is the dominant loading source in the northern portions of the Bay,

associated with the low watershed to open water ratio in these areas. Overall, these same

portions of the bay where atmospheric loads are proportionally and quantitatively greatest

(i.e., Anna Maria Sound and areas just to the south) are also areas with the best water

quality (Lowrey, 1992), the greatest water clarity (Tomasko et al., 1992), and the deepest

growing seagrasses (Tomasko et al., 1992). As important as atmospheric deposition is in

terms of loading models, there is the potential that atmospheric loads of nitrogen do not

have the same biological consequences as sources such as stormwater and wastewater

(i.e., loading associated with low concentrations "applied" over large areas, as opposed to

high concentrations loaded into more restricted areas).

Baseflow, that portion of the nitrogen load coming from uncontaminated groundwater,

accounts for 9 percent of bay-wide loads (Heyl, 1992).

Although septic tanks only contribute approximately 10 percent of the bay-wide nitrogen

loads, they can be locally important in areas where they are the predominant means of

sewage disposal (SBNEP, 1995). In Roberts Bay, septic tank nitrogen loads are estimated

at 21 percent of the total (SBNEP, 1995). Due to the combination of locally important

nitrogen loads and recurrent health problems associated with dramatically elevated bacterial

abundances in Phillippi Creek, the replacement of septic tanks with central sewers in priority

areas is a recommendation of the SBNEP's Comprehensive Conservation and Management

Plan (1995).

6.3.2 Dona and Roberts Bay System

Undoubtedly, the largest human influence on the ecology of Dona and Roberts Bay was the

modification of the Cow Pen Slough Watershed in the 1960's. This modification changed

the size of the watershed from 68 square miles to nearly 90 square miles (Mote Marine Lab,

1975). This effort, coordinated through the combined efforts of the U.S.D.A. Soil

Conservation Service, the Sarasota Soil Conservation District, the Sarasota County Board

of Commissioners and the Manatee River Soil Conservation District, was designed to

reduce flood damage in upstream vegetable producing areas and pasture land (Mote

Marine Lab, 1975). Thus, the very high watershed to open water ratio of the Dona and

Roberts Bay system (Fig. VI-1) reflects both natural and human influences. 

The watershed of the Dona and Roberts Bay system is dominated by agricultural land-uses,

although the coastal fringe is mostly residential in nature. In the 1970's and 1980's various

projects were undertaken to improve water quality within Cow Pen Slough (Gary Reckner,
Comprehensive Watershed Management Plan November 2000

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pers. comm.) These projects included the fencing off of Cow Pen Slough to prevent cattle

from eroding the banks and contaminating the water with their feces. Perhaps associated

with these activities, TN concentrations within the Dona and Roberts Bay system have

declined in recent years (Fig. 3) and are presently lower than the Florida Median Value

(FDEP, 1994). The high TP concentration in the Dona and Roberts Bay system appears

to be responsible for the strong nitrogen limitation in these waters (Fig. VI- 2).

In addition to their influence on water quality, freshwater influxes from the Cow Pen Slough

drainage system disrupt the normal circulation and salinity distribution patterns throughout

the Dona and Roberts Bay system. The large and rapid fluctuations in salinity that occur

throughout the Dona and Roberts Bay system are thought to have created a depauperate

flora and fauna within the outer portions of the bays (Mote Marine Laboratory, 1975). 

Not only do fluctuations in salinity make it difficult for the long-term survival of seagrasses,

but during periods of high inflow, incoming tides can be kept from entering the bays

themselves. This phenomenon can reduce the settlement and survival in Dona and

Roberts Bays of larval and juvenile stages of those animals that spawn in the spring and

summer (Mote Marine Laboratory, 1975).

Also associated with the large influxes of freshwater during the wet season, large rafts of

freshwater plants such as Elodea sp. and Hydrilla sp. are brought into the outer bays. Once

these plants are exposed to the higher salinities of the outer portions of the Dona and

Roberts Bay system, they die en masse. The decay of these large quantities of plant

material usually occurs in the same parts of the Dona and Roberts Bay system where the

highest sediment organic contents and lowest bottom water dissolved oxygen levels are

found (Mote Marine Laboratory, 1975).

Clearly, any efforts to restore a more natural hydrology in the Dona and Roberts Bay system

would have beneficial effects on the ecology of this system. Additionally, the removal

and/or better management of the large rafts of soon-to-decay freshwater plants brought

down into the Dona and Roberts Bay system from the upper reaches of Cow Pen Slough

would also have beneficial effects.

6.3.3 Lemon Bay

Lemon Bay was designated an aquatic preserve in 1986. Designation is meant to ensure

that the water quality and natural systems of Lemon Bay will be protected even as the

contributing watershed continues to attract a growing population.

Elevated levels of fecal coliform bacteria have been detected in the tributaries to Lemon

Bay, and in the surface waters of the Bay itself (FDNR, 1991). Concerns over these

findings have prompted the Englewood Water District to propose that the approximately

9,000 septic tanks in the Lemon Bay watershed be replaced with centralized wastewater

treatment (Palermo, 1996).
Comprehensive Watershed Management Plan November 2000

62

0 

0.5 

1 

1.5 

2 

2.5 

Attenuation (k / m)

0 5 10 15 20 25 30 35 

Chl A (ug / l)

Figure VI-4 - Plot of attenuation coefficients vs.

chlorophyll a concentrations in Lemon Bay

Despite the potential role of septic tanks in contributing to bacterial contamination of

groundwater and surface waters, water quality in Lemon Bay is presently classified as

"Good" (see Fig. VI-3). Perhaps associated with the generally good water quality in Lemon

Bay, seagrass coverage is extensive in the Bay, where they can be found down to a depth

of 7 feet (FDNR, 1991). 

Ongoing studies by the District and FDEP

suggest that water clarity in Lemon Bay is

correlated with phytoplankton levels (Fig.

VI-4), which themselves appear to be

nitrogen limited (see Fig. VI-2). These

results suggest that increased nitrogen

loads (associated with increased

urbanization of the watershed) would be

expected to bring about a reduction in

water clarity, and thus a potential

decrease in seagrass coverage.

A recent assessment of nitrogen loads in

Lemon Bay suggests that urban

stormwater runoff is less important than

the nitrogen loaded into this system from

natural forested systems and range land

(Coastal Environmental, Inc. 1997). This loading assessment, however, did not include

loads from atmospheric deposition, septic tanks, and point sources.

The further refinement of a nitrogen loading model for Lemon Bay is thus necessary to

better understand the potential implications of increased nitrogen loads into Lemon Bay,

and how to best manage the water quality and natural resources of Lemon Bay.

6.3.4 Gasparilla Sound

As discussed above, the complexity of this area makes it difficult to establish even the most

basic information on watershed to open water ratios. Concerning water quality, the most

intensive assessment to date for this area (Coastal Environmental, Inc. 1997) concluded

that “No comprehensive data bases were identified which allowed a comprehensive

assessment of long-term and current water quality conditions . . . ”

Clearly, both Gasparilla Sound and Lemon Bay require more intensive assessments of

water quality and pollutant loading potentials.

6.4 Water Quality Issues

Monitoring and Data Management
Comprehensive Watershed Management Plan November 2000

63

Currently, water quality data are collected by the following entities: Manatee County,

Sarasota County, Florida Department of Environmental Protection (FDEP), Southwest

Florida Water Management District, and the U.S. Geological Survey (USGS). Manatee

County monitors water quality within the estuarine waters of Sarasota Bay on a monthly

basis, using county staff. Sarasota County monitors water quality within the estuarine

waters of Sarasota Bay, Dona and Roberts Bays, and the northern portion of Lemon Bay,

by subcontracting this work out to private contractors. In the southern portion of Lemon Bay

(the portion in Charlotte County), water quality monitoring is mostly performed by volunteer

efforts coordinated by FDEP staff. 

With the exception of the USGS, the other agencies are required to upload water quality

data into STORET, the official repository of water quality data for the State of Florida.

Numerous projects have downloaded water quality data from STORET to determine status

and trends in water quality in Sarasota Bay (SBNEP, 1992; FDEP, 1994), Dona and

Roberts Bay (FDEP, 1994), and Lemon Bay (FDEP, 1994). However, a more integrated

water quality monitoring program is called for, to ensure that ongoing water quality

monitoring programs are coordinated and are assured of continued funding.

Strategy: Continue ongoing monitoring and data management activities in Sarasota and

Manatee Counties.

Actions:

1) Through the District’s cooperative funding program, determine those water quality

monitoring programs in need of support and/or enhancement though the use of

District staff and/or funding.

2) Through the District’s cooperative funding program, continue to support efforts

focused on determining the status and trends (if any) in water quality.

Strategy: Expand ongoing monitoring and data management activities into Charlotte

County.

Actions:

1) Through the District’s cooperative funding program, and in coordination with the

Charlotte Harbor NEP, develop a coordinated water quality monitoring program for

Lemon Bay and Gasparilla Sound.

Improving Water Quality

The depth to which seagrasses grow in Sarasota Bay is related to water clarity and water

quality. A similar relationship probably occurs in Dona and Roberts Bays and Lemon Bay,

as well. Activities which reduce nitrogen loads, and thus improve water quality, would be

expected to increase the coverage of these important fisheries nursery habitats, thus

resulting in increased fisheries resources. Lemon Bay appears to be susceptible to
Comprehensive Watershed Management Plan November 2000

64

decreases in seagrass coverage, should continued urbanization of its watershed occur,

given expected population growth. In addition, hydrologic modifications to Cow Pen Slough

could potentially benefit living resources in Dona and Roberts Bays.

Consistent with the Sarasota Bay NEP’s Comprehensive Conservation and Management

Plan, and the Sarasota Bay SWIM Plan, the District should continue to work with local, state

and federal agencies to address ongoing issues of wastewater and stormwater.

Strategy: Determine the potential ecological consequences associated with further

development of the Lemon Bay watershed.

Actions:

1) In coordination with the Charlotte Harbor NEP and the SWIM Program, develop

a detailed pollutant loading model for Lemon Bay, with special attention paid to

generating potential scenarios associated with increased nitrogen loads into Lemon

Bay.

Strategy: Better understand the ecological impacts of present-day flood control practices

in Cow Pen Slough, and determine the potential for utilizing high flows as a

supplement to potable and/or non-potable water supplies in Sarasota County.

Action:

1) Through the District’s cooperative funding program, and in coordination with the

Charlotte Harbor NEP and the SWIM Program, develop a detailed hydrologic model

of Cow Pen Slough, Shakett Creek and Dona and Roberts Bays, to better

understand the ecological impacts of present-day flood control practices.

Strategy: Reduce wastewater-related point and non-point source pollutant loads to the

freshwater and estuarine waters of the Southern Coastal Watershed.

Actions:

1) Support local governments in their efforts to require wastewater treatment policies

consistent with either nutrient removal technology, or advanced secondary treatment

with effective reuse.

2) Develop a multi-county wastewater reclamation program to minimize the

discharge of treated wastewater to the freshwater and estuarine waters of the

Southern Coastal Watershed.

Strategy: Reduce stormwater-related non-point source pollutant loads to the freshwater

and estuarine waters of the Southern Coastal Watershed.
Comprehensive Watershed Management Plan November 2000

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Actions:

1) Promote pollution prevention through improved landscape design and

maintenance of residential areas.

2) Continue ongoing efforts to implement the Sarasota Bay NEP’s “Florida Yards and

Neighborhoods Program.”

3) Develop and implement stormwater management master plans for tributaries

identified as “hot spots” for toxic and/or sediment loadings.

4) Continue ongoing efforts to maintain stormwater management and treatment

systems for maximum efficiency in reducing pollutant loads.
Comprehensive Watershed Management Plan November 2000

66

LITERATURE CITED AND PREVIOUS STUDIES

NOAA Estuary of the Month Series

Clark, P.A., and R.W. MacAulay. 1987. Geography and economy of Tampa Bay and

Sarasota Bay. Pp. 1-17. In: E.D. Estevez (ed.). Tampa and Sarasota Bays: Issues,

Resources, Status, and Management. NOAA Estuary of the Month Seminar Series. No.

11. U.S. Department of Commerce, NOAA, Estuarine Programs Office, Washington,

D.C.

Dixon, L.K. and M.G. Heyl. 1999. Trend analysis of water quality data for the Sarasota

Bay National Estuary Program. Draft Final Report for: Sarasota Bay National Estuary

Program. Sarasota, FL. 

Estevez, E.D. 1987. Water quality trends and issues, emphasizing Tampa Bay. Pp. 65-

88. In: E.D. Estevez (ed.). Tampa and Sarasota Bays: Issues, Resources, Status, and

Management. NOAA Estuary of the Month Seminar Series. No. 11. U.S. Department of

Commerce, NOAA, Estuarine Programs Office, Washington, D.C.

Estevez, E.D., and J. Merriam. 1987. Resource status and management issues of

Sarasota Bay. Pp. 186-206. In: E.D. Estevez (ed.). Tampa and Sarasota Bays: Issues,

Resources, Status, and Management. NOAA Estuary of the Month Seminar Series. No.

11. U.S. Department of Commerce, NOAA, Estuarine Programs Office, Washington,

D.C.

Flannery, M.S. 1987. Tampa and Sarasota Bays' watersheds and tributaries. Pp. 18-48.

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Management. NOAA Estuary of the Month Seminar Series. No. 11. U.S. Department of

Commerce, NOAA, Estuarine Programs Office, Washington, D.C.

Giovannelli, R.F. 1987. Stormwater impacts to Tampa and Sarasota Bays. Pp. 144-156.

In: E.D. Estevez (ed.). Tampa and Sarasota Bays: Issues, Resources, Status, and

Management. NOAA Estuary of the Month Seminar Series. No. 11. U.S. Department of

Commerce, NOAA, Estuarine Programs Office, Washington, D.C.

Goodwin, C.R. 1987. Circulation of Tampa and Sarasota Bays. Pp. 49-64. In: E.D.

Estevez (ed.). Tampa and Sarasota Bays: Issues, Resources, Status, and Management.

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Haddad, K.D. 1987. Habitat trends and fisheries in Tampa and Sarasota Bay. Pp. 113-

128. In: E.D. Estevez (ed.). Tampa and Sarasota Bays: Issues, Resources, Status, and

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Comprehensive Watershed Management Plan November 2000

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Kurz, R.C., D.A. Tomasko, D. Burdick, T.F. Ries, K. Patterson and R. Finck. (1999). 

Recent Trends in Seagrass Distributions in Florida Coastal Waters. Pp. 157-165. In:

S.A. Bortone (ed.). Subtropical and Tropical Seagrass Management Ecology. CRC

Press, Inc. Boca Raton, FL.

Perry, M.J. 1987. Perspectives on management of Tampa and Sarasota Bays. Pp. 207-

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Phillips, T.D., Mahadevan, K., Tippin, S.B., and R.D. Garrity. 1987. Heavy industry of

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Sarasota Bay Scientific Information Symposium

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Edwards, R.E. 1988. Fishes and fisheries of Sarasota Bay. In: E.D. Estevez (ed.).

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Heyl, M.G., and L.K. Dixon. 1988. Water quality status and trends (1966-1986) in

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Lewis, R.R. III. 1988. Seagrass meadows of Sarasota Bay: a review. In: E.D. Estevez

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Bay. In: E.D. Estevez (ed.). Proceedings: Sarasota Bay Scientific Information

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Charlotte Harbor Watershed. Draft Report to the Charlotte Harbor National Estuary

Program. North Fort Myers, Florida.
Comprehensive Watershed Management Plan November 2000

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DeGrove, B.D., and J. Mandrup-Poulsen. 1984. City of Sarasota wasteload allocation

documentation. Fla. Dept. Environ. Reg. Water Qual. Tech. Ser.

Deming, J., R.S. Schwarz, P. Carender, D. Delahaye, and J.R. Williams. 1990. An

historic resources survey of the coastal zone of Sarasota County, Florida. Report to the

Sarasota County Board of County Commissioners, Sarasota, Fl.

Dendrou, S.A., C.I. Moore, and R. Walton. 1983. Final Report, Little Sarasota Bay

circulation study. Prepared for County of Sarasota Coastal Zone Management Division

and Environmental Services Dept. 

Dixon, L.K., and G. Kirkpatrick. 1995. Light attenuation with respect to seagrasses in

Sarasota Bay, Florida. Final Report to Sarasota Bay National Estuary Program,

Sarasota, Fl.

Estevez, E.D. 1988. Sarasota Bay, Florida. Identification of resource management

problems and issues. Final Report to U.S. EPA (Region IV). Mote Marine Laboratory

Tech. Rept. No. 117A.

Estevez, E.D., and D.A. Bruzek. 1986. Survey of mollusks in southern Sarasota Bay,

Florida, emphasizing edible species. Mote Marine Laboratory Tech. Rept. No. 102.

Florida Department of Natural Resources. 1991. Lemon Bay Aquatic Preserve

Management Plan. Florida Department of Natural Resources, Tallahassee, FL.

Florida Department of Environmental Regulation. 1986. Proposed designation of

Sarasota Bay and Lemon Bay as Outstanding Florida Waters. Rept. to Envir. Reg.

Comm.

Florida Department of Environmental Protection (1994). Southwest Florida District Water

Quality 1994 305 (b) Technical Appendix. Florida Department of Environmental

Protection, Tallahassee, FL.

Leverone, J.R. and M.J. Marshall. 1992. Seagrass bed faunal utilization study. Final

Report to the Sarasota Bay National Estuary Program, Sarasota, Fl.

Mote Marine Laboratory. 1975. The ecological status of Dona and Roberts Bays and its

relationship to Cow Pen Slough and other possible perturbations. Final Report to the

Board of County Commissioners, Sarasota County.

Palermo, T. 1996. Sewer project moves ahead. Englewood Sun Herald, January 22,

1996.

Patton, G.W. 1987. Studies of the West Indian Manatee: Anna Maria to Venice, Florida.

Mote Marine Laboratory Tech. Rept. No. 105.
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Pierce, R.H. and R.C. Brown. 1986. Naled toxicity to intertidal estuarine organisms. Final

Rept. to Sarasota Co. Mosquito Control Off., Sarasota, Fl.

Sarasota County, Florida. 1984. Blue Ribbon Panel for Midnight Pass. Summary Rept.,

April 24. 6 pp.

Sauers, S. 1980. Seasonal growth cycles and natural history of two seagrasses

(Halodule wrightii Aschers. and Thalassia testudinum Konig) in Sarasota Bay, Florida.

Section A, In: (W.J. Tiffany III (ed.). Environmental Status of Sarasota Bay: Selected

Studies. Mote Marine Laboratory Tech. Rept. No. 66.

Sauers, S.C., and R. Patton, 1981. A comparison of 1948 and 1979 seagrass bed

distribution in the vicinity of Whitaker Bayou, Sarasota Bay, Florida. Office of Coastal

Zone Management, Sarasota County, Florida.

Sheng, Y.P. 1994. A study on the effect of Manatee River discharge on circulation and

transport in Sarasota Bay. Final Report to the Sarasota Bay National Estuary Program,

Sarasota, Fl.

Sheng, Y.P., and S.J. Peene. 1993. A field and modeling study of residual circulation in

Sarasota Bay and Tampa Bay, Florida. Proceedings of the 3rd Int.'l Conference on

Coastal & Estuarine Modeling, ASCE.

Tomasko, D.A. 1993. Assessment of seagrass habitats and water quality in Sarasota

Bay. Pp. 25-35. In: L.J. Morris and D.A. Tomasko (eds.). Proceedings and Conclusions

of Workshops on: Submerged Aquatic Vegetation and Photosynthetically Active 

Radiation. Special Publication SJ93-SP13. St. Johns River Water Management District,

Palatka, Fl.

Tomasko, D.A., Smith, H., and M. Alderson. 1993. A watershed strategy for reducing

toxin and nutrient loadings from stormwater runoff in Sarasota Bay, Florida. Pp. 73-78.

In: C. Dye and B. Rushton (eds.). Proceedings of the Third Biennial Stormwater

Research Conference. Southwest Florida Water Management District, Brooksville, Fl.

Tomasko, D.A., Dawes, C.J., and M.O. Hall. (1996). The effects of anthropogenic

nutrient enrichment on turtle grass (Thalassia testudinum) in Sarasota Bay, Florida

(USA). Estuaries 19: 448-456.
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CHAPTER VII

NATURAL SYSTEMS

7.1 Introduction

Much of the variation in water quality affecting the numerous estuarine and riverine

systems in the Southern Coastal Watershed can be explained by two basic factors: the

watershed to open water ratio, and the degree of urbanization of the contributing

watershed. As discussed in the Water Quality chapter, areas with relatively low watershed

to open water ratios tend to have the best overall water quality (e.g., Upper Sarasota Bay,

Lemon Bay) while areas with high ratios tend to have lower overall water quality (e.g.,

Lower Sarasota Bay, Dona and Roberts Bays). However, the degree of urbanization of the

watershed strongly influences the quantity and quality of stormwater runoff from these

landscapes.

In this chapter, the variation in landscapes between different watersheds will be

examined, with particular attention focused on the types of natural systems found

throughout the Southern Coastal Watershed.

7.1.1 Previous Studies and Available

Data

Information used to assess general patterns of the locations and amounts of natural

systems in the Southern Coastal Watershed came from several sources. For the Sarasota

Bay watershed (i.e., USB and LSB) information was derived from Heyl (1992), Estevez

(1992), and Beaman (1992). For Dona and Roberts Bays and Lemon Bay, data came

from Coastal Environmental, Inc. (1997). Other sources of information included "The

Ecological Status of Dona and Robert's Bays," produced by Mote Marine Laboratory in

1975, and the "Lemon Bay Aquatic Preserve Management Plan," published in 1991 by the

Florida Department of Natural Resources. The U.S. Department of Agriculture's "Soil

Survey of Sarasota County" (1991) was also used. In addition, much emphasis is placed

on GIS-based data analysis of aerial photography acquired by the District in 1995.

7.2 Overview of Watershed-wide Issues

This chapter will focus on two overall categories of natural systems - inland systems (i.e.,

those associated with upland communities and freshwater systems), and coastal systems

(i.e., salt marshes, mangroves, and seagrass and unvegetated benthic communities).

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Inland systems

A variety of land uses are found within the watersheds of each of the major basins within

the Southern Coastal Watershed (Map 4 in Appendix). Table VII-1 summarizes land use

characteristics for each of the four major basins within the Southern Coastal Watershed. 

Table VII-1. Estimated 1995 land use / land category percentages (Data from

SWFWMD). 

Land Use USB LSB DARB LB GS

Residential 73 57 22 44 43

Commercial 43310

Agricultural 8 19 37 21 6

Forested 4 12 21 19 9

Wetlands 10 9 17 14 42

Other 10010

For the watershed of Upper Sarasota Bay (USB), the percentage of the watershed within

the residential land use category is the highest of the four Southern Coastal Watershed

basins. Upland forests account for the smallest percentage of the four basins.

For the Lower Sarasota Bay (LSB) basin, residential areas accounted for the second

highest percentage of land use of the four basins. The percentage of the watershed

consisting of wetlands was the smallest of the four basins.

In the watershed of the Dona and Roberts Bays (DARB) basin, residential areas were the

lowest percentage of land use of the four basins within the Southern Coastal Watershed.

Forested areas were a larger percentage of the watershed than any other basin.

Agricultural areas were also the largest percentage of land use of any of the Southern

Coastal Watershed basins.

In Lemon Bay’s watershed, commercial areas were the lowest percentage of land use of

the four basins. Wetlands accounted for the second highest percentage of the watershed

of the four basins. The percentage of the LB watershed in the forested land category was

second only to DARB’s watershed. 

The Gasparilla Sound watershed had the largest percentage of land cover as wetlands.

A major issue in this watershed, is the amount of platted land that was partially developed

and then abandoned. For example, large tracts of land in the area south and east of

Rotunda have been cleared of native vegetation, access roads have been constructed,
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but no houses have been built. As such, while these areas are mapped as "urban and

built-up" land use categories in the District's 1995 land use/cover mapping efforts, they

tend to have little in common with most people's perception of this land use classification.

Significant tracts of natural systems include the substantial amount of upland forests

(mostly slash pines and southern slash pines) in the LSB basin, particularly in the area of

Oscar Scherer State Park. In addition, large areas of upland forests are found in the

Lemon Bay watershed; particularly in the headwaters of Forked, Godfrey, and Oyster

Creeks (Map 4 in Appendix). Large tracts of rangeland exist in the DARB watershed,

especially in the headwaters of Cow Pen Slough.

Non-forested freshwater wetlands are found in significant quantities in the USB and LSB

basins, especially in the upper reaches of South Creek. Non-forested wetlands are also

common in the DARB basin, and as fragmented parcels in the eastern portions of the LB

watershed. A large area of non-forested freshwater wetlands is found in the northern

portion of the GS watershed, where a weir placed across the upper reaches of the West

Branch of Coral Creek has resulted in the formation of an extensive marsh system

dominated by cattails (Map 4 in Appendix).

Beaman (1992) noted that the rate and quantity of loss of freshwater wetlands in Florida

far exceeded those for saltwater (or tidal) wetlands. In the Sarasota Bay watershed,

freshwater wetlands declined by approximately 35 percent between 1975 and 1991, with

rates of loss in the USB basin exceeding those for the LSB basin. Beyond outright loss

and/or destruction, Beaman (1992) also documented the impacts of physical damage to

existing wetlands (e.g., altered hydrology) and also impacts from invasion by exotic

species such as Brazilian Pepper and Australian Pine.

Coastal Systems

For the purposes of this chapter, coastal systems will be divided into the following

categories - salt marsh and mangrove systems, seagrass meadows, and non-vegetated

creek and estuarine benthic communities.

While much work has been done on the distribution of salt marsh and mangrove

communities in Sarasota Bay (USB and LSB), not much detailed information exists for

DARB, LB and GS. For the Sarasota Bay area, Estevez (1992) estimated that 39 percent

of saltwater wetlands (both salt marshes and mangroves) had been lost between 1950

and 1990. In addition, remaining tidal wetlands tend to be smaller and more fragmented

than in years past. Besides impacts from mangrove pruning, tidal wetlands are also

adversely affected by infestation by exotic species such as Brazilian Pepper and

Australian Pine.

Along the shoreline of Lemon Bay and its tributaries, mangrove forests are a common

feature. While the relatively steep shoreline prevents extensive mangrove development,

mangroves are a dominant coastal feature on the mainland shoreline north of Forked

Creek, on the northern portion of Manasota Key's eastern shoreline, and along the barrier
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island shoreline from Stump Pass to Gasparilla Sound (FDNR, 1991). Much of the

shoreline and adjacent uplands in the Gasparilla Sound watershed consists of existing

conservation areas and “Strategic Habitat Conservation Areas” identified by the Florida

Game and Freshwater Fish Commission (see Map 6 in Appendix).

Seagrasses are found throughout the shallow estuarine waters of the Southern Coastal

Watershed. While much information exists on the status and trends of seagrass coverage

in Tampa Bay and Charlotte Harbor, less information is available for Sarasota Bay and

Lemon Bay. Little information is available for Dona and Roberts Bays. However, the

SWIM Program has mapped seagrass coverage in the Southern Coastal Watershed area

for 1988, 1994 and 1996, to examine the status and trends of this important benthic

community. Listed below are estimates of the abundance of seagrasses (in acres) for

USB, LSB and LB for the years 1988, 1994 and 1996.

Segment 1988 1994 1996 1988-1996 Change

 USB 7,377 7,920 8,856 20 % increase

 LSB 1,273 1,344 1,477 16 % increase

 LB 2,606 2,653 2,605 <1 % decrease

The increased coverage of seagrasses in the Upper Sarasota Bay is mostly attributed to

two major activities - improvements to the disposal and reuse practices of the Manatee

County Southwest Regional Wastewater Treatment Plant, and upgrades to the nutrient

removal processes of the City of Sarasota's Wastewater Treatment Plant (Tomasko and

Ries, 1997). For Lower Sarasota Bay, 184 of the 204 acre increase in coverage between

1988 and 1996 (90 % of the total increase) occurred in Little Sarasota Bay, which might

reflect a recovery of this system from the stresses it initially received after the closure of

Midnight Pass in 1983. For Lemon Bay, the small change in distribution between 1988

and 1996 suggests a system in somewhat of an equilibrium status.

For non-vegetated creek and estuarine benthos, data from Sarasota Bay (Dixon, 1992)

suggests that oyster reefs are much more common in the LSB system than in USB,

although oysters can be found in significant quantities in the Palma Sola Bay sub-basin of

USB, and also along the mainland shoreline of USB near Bowlees Creek. The greater

coverage of oyster reefs in LSB, compared with USB, is most probably associated with the

higher watershed to open water ratio of LSB, which results in the lower salinity conditions

that favor oyster reef development.

While their distribution is not mapped as well as in USB and LSB, oyster reefs are a

common feature in the DARB system, again probably reflecting the fact that the DARB

system has the highest watershed to open-water ratio of the four basins within the

Southern Coastal Watershed.

Oyster reefs are not a dominant feature in the LB system, except in the tributaries along

the mainland shoreline. However, oysters can be found growing attached to the prop roots
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of red mangroves in all four basins.

7.3 Priority Issues at the Basin Level

7.3.1 Sarasota Bay

In the Upper Sarasota Bay (USB) basin, residential and commercial development has

resulted in the conversion of a substantial amount of natural systems to houses,

roadways, shopping centers, and associated land uses. As a result, the USB basin has

lost the greatest percentage of its original freshwater wetlands coverage, compared with

the other four basins in the Southern Coastal Watershed. The loss of these wetlands has

occurred mostly through traditional ditch and drain activities. As a result, the storage

capacity, water purification, and habitat value of these natural systems have been

reduced dramatically. The reduced acreage of freshwater wetlands would be expected to

alter the hydrology of the area such that tributaries to Sarasota Bay would exhibit more of

a "feast or famine" response to fluctuations in rainfall. That is, drainage of wetlands for

development accelerates the delivery of large pulses of freshwater to receiving water

bodies, which then decreases the ability of tributary systems to "cleanse" these pulses of

water through the processes of uptake and sedimentation. In addition, this drainage

activity reduces the volume of water discharged in the dry season, decreasing the amount

of critical low-salinity habitat needed for juvenile stages of various species of commercially

and recreationally valuable finfish and shellfish.

With most of its natural landscape altered by the rapid and extensive development of its

watershed, the USB basin has the smallest percentage of its total land use in those

categories (uplands and wetlands) with the greatest habitat value to wildlife.

Somewhat in contrast, development pressures in the LSB basin have not yet resulted in

the degree of loss of natural systems that has already occurred in the USB basin. The

overall impacts are not quite as severe as in areas just to the north. Estevez (1992)

suggested that the USB basin was mostly affected by development pressures that

focused on the inland areas, while the LSB basin was mostly affected by development

pressures that focused on the shorelines and barrier islands. Thus, while the USB basin

has lost a greater percentage of its freshwater wetlands and native uplands, its shoreline

has remained mostly in a natural state. Conversely, while the LSB basin has lost a

significant amount of its tidal wetlands to development, significant areas of its freshwater

wetlands and native uplands have persisted, although most of them in a damaged state.

7.3.2 Dona and Roberts Bays

Without question, the biggest alteration to the natural systems of Dona and Roberts Bays

(DARB) was the development and expansion of the Cow Pen Slough drainage system in

the 1960's. Because of these activities, the watershed of DARB increased from 68 square

miles to nearly 90 square miles (Mote Marine Lab, 1975). The historic watershed to open

water ratio of DARB of 62: 1 was already much higher than that of the second highest
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ratio of the four Southern Coastal Watershed basins (LSB; 13:1). With the expansion of

the Cow Pen Slough watershed, coordinated through the combined efforts of the USDA

Soil Conservation Service, the Sarasota Soil Conservation District, the Sarasota County

Board of Commissioners and the Manatee River Soil Conservation District, this ratio

climbed to 89: 1, a value nearly seven times higher than the second highest ratio in the

Southern Coastal Watershed.

Large influxes of freshwater inflow from the Cow Pen Slough drainage system disrupt the

normal circulation and salinity distribution patterns throughout the Dona and Roberts Bay

system, which is associated with reduced water quality and the diminished abundance

and diversity of the flora and fauna within the outer portions of DARB (see Chapter VI -

Water Quality).

As much of the land use in the DARB watershed is in agricultural and upland forested

categories, potential areas might be available for developing "diversion marshes" which

might be capable of reducing peak wet season flows from Cow Pen Slough into DARB, as

was called for in Mote Marine Laboratory (1975) and Coastal Environmental, Inc. (1997).

In addition, the potential for diverting wet season flows and utilizing them to offset a

portion of the potable and/or non-potable needs for the City of Venice and Sarasota

County merits further investigation (see Chapter IV - Water Supply).

7.3.3 Lemon Bay

According to estimates from Coastal Environmental, Inc. (1997), the population of the

Lemon Bay watershed is expected to increase dramatically during the next 10 to 15

years. Using data supplied by the Southwest Florida Regional Planning Council, Coastal

Environmental, Inc. (1997) predicted that residential land uses, which comprised

approximately 44 percent of the watershed in 1995, would increase to approximately 84

percent of the watershed by the year 2010. This would represent an approximate

doubling of the amount of the watershed devoted to residential land uses. While

estimates of population increases must be viewed with skepticism, the implications of

such rapid growth, if they occurred, would be dramatic.

It would be expected that if Lemon Bay's watershed underwent a change as drastic as

that which is described above, several phenomena would occur: 1) remaining natural

uplands would be the most likely land use to be converted to residential purposes, 2) flora

and fauna dependent upon these natural upland communities would decline in number, 3)

remaining wetlands and surface water bodies would receive increased loads of

stormwater pollution from increased development, 4) water quality would be expected to

decrease in the tributaries to Lemon Bay and the bay itself, 5) natural systems that are

dependent upon good water quality (e.g., seagrasses, oyster reefs) would be expected to

decrease in abundance and vigor, and 6) fish and wildlife dependent upon these

estuarine systems would be expected to decline in number.

The above-described scenario is essentially the same process that has already occurred

in the more heavily developed areas north of Lemon Bay. Consequently, the degree of
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degradation of water quality and the loss of water quality-dependent benthic communities

that has occurred in Sarasota Bay (i.e., decline in seagrass coverage vs. historic levels)

might be expected to occur. As much of Lemon Bay suffers from the lack of a state and/or

local government-administered water quality monitoring program, the water quality data

collected to date was viewed as less than adequate for assessing the status and trends in

water quality for Lemon Bay (Coastal Environmental, Inc., 1997). More detailed water

quality and pollutant assessment studies are needed, to better understand the

consequences of potential development pressures in Lemon Bay.

7.3.4 Gasparilla Sound 

As with the assessment of water quality, the lack of detailed information (other than basic

land use mapping efforts), makes assessments of the natural systems of Gasparilla

Sound's watershed a casual exercise. However, completed, ongoing and planned

activities to purchase land in the Gasparilla Sound watershed (i.e., the State of Florida's

Charlotte Harbor Buffer Preserve, the potential addition of the "Cape Haze Parcel" via

CARL and SOR/P-2000) seem to be the best way to ensure that the functions associated

with the existing saltmarsh, mangrove and salt flat acreage of the Gasparilla Sound

watershed will be provided into the future.

7.4 Natural Systems Issues

Since 1950, intertidal wetlands in Sarasota Bay’s watershed have declined by

approximately 40 percent. Although not as well documented, similar losses have also

occurred in the watersheds of Dona and Roberts Bays and Lemon Bay. Wetlands loss in

Gasparilla Sound is not as extensive as in the other basins. These wetlands provide a

number of benefits to the Southern Coastal Watershed, including roles played in

shoreline stabilization, water quality improvement, and fish and wildlife utilization.

In addition, uplands habitats in the Southern Coastal Watershed have undergone

dramatic modification in recent decades, with much of the native upland communities

converted to residential and/or commercial land uses.

Strategy: Continue ongoing efforts focused on protecting and restoring wetlands in

the Southern Coastal Watershed.

Actions:

1) Through the SWIM Trust Fund, and the District’s Cooperative Funding Program,

continue ongoing efforts to enhance, restore and create wetlands throughout the

Southern Coastal Watershed.

2) Provide proactive, cooperative consultation to the private and public sectors on

development proposals and regulatory issues that impact wetlands.

Strategy: Protect natural systems within the Southern Coastal Watershed through

land acquisition (fee simple) and other land conservation methods (e.g.,
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conservation easements). 

Actions:

1) Identify and prioritize conservation lands within the watershed using the Florida

Game and Freshwater Fish Commission’s “Closing the Gaps” reports, as well as

recent efforts by local governments and the District’s SOR/P2000 Program.

2) Coordinate land acquisition and other conservation efforts among federal, state,

regional, and local governments.

3) Educate land owners of significant undeveloped areas (e.g., ranchers in eastern

Sarasota County) about protection and management of listed species habitats.
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LITERATURE CITED

Beaman, R. 1992. Freshwater wetlands. Pp. 6.21-6.32. In: (P. Roat, C. Ciccolella,

H.Smith, and D. Tomasko, eds.). Sarasota Bay: Framework for Action. Sarasota Bay

National Estuary Program. Sarasota, Fl.

Coastal Environmental, Inc. 1997. Synthesis of Existing Information for the Greater

Charlotte Harbor Watershed. Draft Report to the Charlotte Harbor National Estuary

Program. North Fort Myers, Florida.

Dixon, L.K. 1992. Bivalved shellfish of Sarasota Bay. Pp. 11.1-11.18. In: (P. Roat, C.

Ciccolella, H.Smith, and D. Tomasko, eds.). Sarasota Bay: Framework for Action.

Sarasota Bay National Estuary Program. Sarasota, Fl.

Estevez, E.D. 1992. Tidal wetlands. Pp. 6.1-6.20. In: (P. Roat, C. Ciccolella, H.Smith, and

D. Tomasko, eds.). Sarasota Bay: Framework for Action. Sarasota Bay National Estuary

Program. Sarasota, Fl.

Florida Department of Natural Resources. 1991. Lemon Bay Aquatic Preserve

Management Plan. Florida Department of Natural Resources, Tallahassee, FL.

Heyl, M.G. 1992. Point- and nonpoint-source pollutant-loading assessment. Pp. 12.1-

12.19. In: (P. Roat, C. Ciccolella, H.Smith, and D. Tomasko, eds.). Sarasota Bay:

Framework for Action. Sarasota Bay National Estuary Program. Sarasota, Fl.

Mote Marine Laboratory. 1975. The ecological status of Dona and Roberts Bays and its

relationship to Cow Pen Slough and other possible perturbations. Final Report to the

Board of County Commissioners, Sarasota County.

Tomasko, D.A. and T.F. Ries. 1997. Responses of Tampa Bay and Sarasota Bay

Seagrass Meadows to Nitrogen Load Reductions. Winter 1997 Newsletter. Estuarine

Research Federation.

United States Department of Agriculture Soil Conservation Service. 1991. Soil survey of

Sarasota County, Florida.