• Topics: Sea Grant  |  Coastal Waters  |  Swett, Robert  |  Fann, David A 

Bathymetric Data for Coastal Resource Management in Southwest Florida Waterways: Enhancement and Standardization of Field Collection Methods Used by the West Coast Inland Navigation District¹

Introduction

Pressures from a coastal population explosion and unprecedented waterway boating intensities are stressing many of our nations water bodies (Nordheimer 1993). Fifty-four percent of the U.S. population (135.1 million in 1991) lives in the coastal zone (U.S. Bureau of Census 1994). While population growth along our coasts has increased slightly above the overall U.S. growth rate since 1960, regions such as the Gulf Coast have experienced double the national rate of change. Florida's coastal population has increased 242 percent, from 4.9 to 16.4 million, four times the national rate. As a result, many inland bay waters in Florida have been transformed into “urban seas.”

Recreational boaters and eco-tourists now use thousands of miles of channels and basins that were originally dredged as by-products of coastal development. These waterways were never designed as a transportation system and since many postdate the latest NOS hydrographic surveys, they do not even appear on NOAA small-craft charts (Antonini, Fann, and Roat 1999). State and local governments in Florida recognize the need to retrofit the thousands-of-miles of dredged channels into an integrated waterway transportation system consisting of arterial, secondary, and feeder canals, and basins. This approach is necessary to address boat traffic management issues and to reduce stress on surrounding natural habitats and waterfront communities (Fann, Antonini, Doubeck-Racine, Grella, and Listowski 1999).

The West Coast Inland Navigation District (WCIND) commissioned Florida Sea Grant (FSG), in May 1995, to design a management system for southwest Florida waterways consistent with municipal, county, Florida Department of Environmental Protection (FDEP), and Federal goals of facilitating safe boating and reducing boating impacts on natural resources. The design criteria were: (a) fit channel maintenance to boat draft needs; (b) minimize impacts on bay habitats; (c) prioritize and evaluate management alternatives on a regional scale; and (d) identify information products for boaters and shore residents to encourage environmental awareness by users of the neighborhood waterways and boat access channels.

The WCIND and FSG have completed fieldwork for seven applications of this system, covering over 1000 miles of channels (Antonini and Box 1996; Antonini, Swett, Schulte, and Fann 1998; Swett, Antonini, and Schulte 1999; Swett, Fann, Antonini, and Alexander 2000, 2001). These studies include large-scale (1:4,800, 1:2,400) mapping of water depth, boat and facility characteristics, signage, and habitat. Detailed analyses delineate and quantify (a) levels of boat accessibility to the open bay, and (b) location and extent of channel depth restrictions within boat access channels. Results of these applications are providing the WCIND and the coastal counties with a rationale and method to implement waterway improvements and restoration using a Waterway Management System with the following elements: (a) dredging to maintain channel depth at user draft specifications; (b) locating signs by boat density and traffic patterns; (c) managing traffic, using boat distributions and travel routes; (d) siting habitat restoration to protect waterways; (e) permitting on a regional scale to accommodate water-dependent uses and to minimize environmental impacts; and (f) educating the public, using waterway maps and guide materials, to instill stewardship and best boating practices.

Current users of the Waterway Management System include Lee, Sarasota, and Manatee counties, the City of Sarasota, and the Town of Longboat Key. User organizations include natural resources, planning, public works, parks and recreation, and county extension service departments; neighborhood associations; and local boat owners. Waterway improvements are being undertaken at Shakett, Phillippi, and Gottfried Creeks (Sarasota County), based on the management criteria and project databases. A General Permit rule will be adopted by the FDEP on 4 August 2002 to provide for maintenance dredging of restricted access channels in a two county region, with significantly reduced administrative costs.

A number of events have occurred at the state and national level that highlight the success and the acceptance of the Waterway Management System. The FDEP agreed to utilize this methodology to implement a standardized regional approach to waterway planning and as a basis to review permit applications for maintenance dredging (MOA 1997). The 1998 Florida State Legislature enacted General Law CS/HB 3369, which broadened the mandate of the WCIND to engage in inland waterway management. Recognizing the value of the waterway management approach, the NOAA Coastal Services Center provided FSG with seed money to develop and implement this waterway management strategy.

WCIND and Florida Sea Grant also are committed to collect soundings in 47 popular anchorages within a five-county area in southwest Florida. This work stems from a 1995 Memorandum of Agreement among the FDEP, FSG College Program, the Southwest Florida Regional Planning Council, and the Boaters Action and Information League. The Memorandum established a pilot 5-year self-regulatory anchorage management program. The bathymetry collected at anchorages, in conjunction with other data sources, is being used to produce large-scale, detailed photomaps for anchorage users and for resource managers (Boaters Action and Information League 1999).

View all of the Introduction here: Introduction

Goals and Objectives

The primary objective of the Waterway Management System, as developed by the WCIND and FSG, is to provide a comprehensive, regional, GIS-based planning tool for resource management and channel maintenance. The four-county region that comprises the WCIND provides an ideal setting to test and revise the Project methodology and to gauge the success of its objectives, results, and recommendations. As outlined above, the value and necessity of the Project has been recognized, as reflected by the political will that has been exercised, at the local, regional, state, and national level, to implement and expand upon project recommendations and goals. The initial implementation of the Waterway Management Project for three WCIND counties will be completed this year. Upon completion, FSG and the WCIND expect to work with local, regional, and state entities to expand Project efforts throughout the state of Florida.

The principal goals of this NOAA-sponsored project are: 1) to enhance and standardize the bathymetric data collection procedures that have been used by the WCIND and FSG during prior implementations of the Waterway Management Project, 2) to provide a reliable and recurring source of bathymetric data, for areas not covered by NOAA surveys, that meets NOAA standards and that can be included on NOAA nautical charts, and 3) to evaluate survey equipment and procedures that could be used by third-party organizations, such as the Coast Guard Auxiliary or United States Power Squadrons, to collect bathymetric data under supervision provided by the WCIND or FSG. Improving past bathymetric survey and quality control procedures and acquiring additional hydrographic survey equipment and software have accomplished these goals. The project integrated DGPS and echo soundings with hydrographic survey software, which resulted in an increase in the efficiency of field operations and an improvement in the quality of the data collected.

Soundings were collected for approximately 313 miles of canals and waterways in Lee County (Figure 1), within the Caloosahatchee River system, from its mouth (west), to the county line. The soundings were thinned to a 5-foot spacing, and the final dataset includes over 700,000 depth points. The survey area includes numerous shore-parallel channels and approaches to open water from boating facilities, canals, and tributaries. The procedures implemented during this study will be used by the WCIND, on a recurring basis, to maintain bathymetric data for Manatee, Sarasota, Charlotte, and Lee counties. WCIND will make available to other entities, such as the Coast Guard Auxiliary or Power Squadrons, the survey procedures and equipment purchased from project funds so that they may collect bathymetric data in other areas. All bathymetric data collected utilizing the project procedures and equipment are on a CD that accompanies this report.

View all of Goals and Objectives here: Goals and Objectives

Project Equipment

Computer--the bathymetric survey was accomplished using a Rocky II+ ruggedized notebook from AMREL Systems, Inc. The notebook is designed for field and in-vehicle applications. The laptop is certified to the MIL-STD 810C and E and is resistant to rain (4 in./hr/ 0.5-4.5 mm/drop 30 min. period), temperature (operating--0° C to 50° C; storage--20° C to 60° C), shock, vibration, salt fog (35° C 5% 48 hour period), and humidity (85-95% RH). The computer used for office related tasks was a Dell Dimension XPS T750r 750 MHz Pentium III with an 18GB SCSI hard drive. Appendix A contains complete specifications for project equipment.

Software--The software programs listed below were used during various project phases.

1. ESRI ArcInfo 8.x for Workstation

2. ESRI ArcView 3.x

3. SURVCORR and BASELINE2--tide correction programs (supplied on accompanying CDROM)

4. Microsoft Excel

5. Microsoft Access

6. Microsoft Word

7. Adaptec Easy CD Creator

8. Trimble Pathfinder Office 2.51

9. Trimble Asset Survey Software

10. Trimble TSIP TALKER (version 2.0)

Differential Global Positioning System--the Regional Waterway Management System, as originally designed, is intended as a planning tool. However, the bathymetric survey procedures and methods meet Class 1 standards as described in the U.S. Army Corps of Engineers (USACE) Hydrographic Survey Manual (U.S. Army Corps of Engineers 2001) and hydrographic survey specifications of the National Ocean Service (National Ocean Service 1999).

A Trimble code phase DSM212H GPS receiver with an integrated MSK dual-channel receiver with Everest^TM technology (which improves results in high multipath environments and locations where other radio frequencies could jam the GPS signals) was used to record horizontal positions for the bathymetric survey. Under optimum conditions, the horizontal accuracy (RMS) for the DMS212H, using the RTCM radiobeacon transmissions, is 50 cm + 1 ppm on a second-by-second basis, which, for the 4-county area of the WCIND, is better than 1 meter (Trimble Navigation Ltd. 1998b). Under normal operating conditions the horizontal accuracy for 95 percent of feature positions is 2 meters or less, which conforms with USACE and National Ocean Service (NOS) accuracy standards.

Survey Vessel--a Key West model 1720 open fisherman with a shallow V fiberglass hull and a center console served as the survey vessel. The Key West has a 70hp, 4-stroke, Evinrude outboard; fuel capacity of 31 gallons; 8-inch draft; 17-foot, 2-inch length; 6-foot, 10-inch beam; and weighs 1050 lbs.

Depth Sounding Equipment--sounding equipment consisted of a Bathy-500MF multi-frequency, single-beam echo sounder (Ocean Data Equipment Corporation); a Standard Horizon DS150 singlebeam echo sounder (Standard Communications); and a fiberglass sounding pole, calibrated and marked at 0.01-foot intervals.

Soundings from the Bathy-500MF and the DS150 were passed to HYPACK Max hydrographic survey software (Coastal Oceanographics, Inc.) loaded on the AMREL Rocky II+ notebook computer. Soundings were recorded to the nearest 0.1-foot with the Bathy-500 and to the nearest 0.1- foot with the DS100. The sounding pole was used to verify any suspect echo sounder readings and to check depths in shallow areas (below 3.8 feet). Calibration of the depth sounders was accomplished using a bar, which consisted of a 1.25 ft. X 2.9 ft. lead-weighted aluminum plate. The bar was lowered below the transducer with 25-foot long, 1/8-inch diameter twisted stainless steel wire cables marked at 5-foot intervals, from 5 feet to 20 feet.

Tide Level Recorders and Stilling Wells--tide observations were necessary to correct soundings to chart datum (MLLW). Tide level recorders consisted of Model 220 solid-state, ultrasonic fl uid level sensors manufactured by Infinities USA, Inc. Each Model 220 data logger stores 3,906 records, which allows for 16 days of tide data at a logging interval of 6 minutes. Data fi les were downloaded, in the field, to an HP-48GX calculator.

Each gauge was mounted on a stilling well, the dimensions of which are shown in Figure 2. All sections of the stilling well were cemented together except for the cap, which is secured to the closet flange using two padlocks to protect the tide level recorder. The stilling well was secured to a piling using wooden I-beam mounts and stainless steel worm gear clamps.

View all of Project Equipment here: Project Equipment

Project Planning and Preparation

Project Planning Map

Large-scale (1:7200) maps of the study area were prepared to delineate salt-water-accessible canals, channels, and other waterways where centerline depths were to be surveyed. Planned waterway centerlines were drawn by Lee County Marine Services Program personnel with knowledge of travel routes actually used by boaters. USGS 1-meter DOQQs served as the map base, and other map themes included the locations and characteristics of signs, vertical benchmarks, hydrologic areas, tide gauges, locks, and boat lifts. Hydrologic areas are defined by project personnel to guide the placement of tide gauges and the scheduling of depth survey work. Their inclusion on the planning map was important for complex areas, as exemplified by the City of Cape Coral (Figure 3). The maps served to plan the work schedule, monitor field progress, and annotate areas as they were completed.

View all of Project Planning and Preparation here: Project Planning and Preparation

Field Procedures

Tide Gauge Installation

Once appropriate tide gauge sites were established, secure facilities were found where gauges could be installed. Each proposed gauge site was visited to confirm the presence of vertical benchmarks and their suitability to determine tide gauge elevation. The majority of benchmarks were located within sight of the tide gauge installation, such as on a seawall or on an adjacent road or structure. A licensed surveyor was hired to establish vertical control for one gauge installation.

Tide gauge stilling wells were securely fastened to a protected piling or other suitable mounting location (Figure 5F) using stainless steel straps, similar to automotive hose clamps, but available in lengths of 4 feet or longer. An I-beam of 2 x 4 lumber, securely screwed together and placed between the stilling well and piling, provided a stable mount with a suitable standoff distance. The field crew carefully monitored the gauges elevation relative to the piling to check for vertical slippage or other problems.

Tide gauge vertical control, relative to NGVD29 or NAVD88, was determined by differential leveling (double running) conducted by project personnel. When the benchmark was located on a seawall, simultaneous measurements to the water surface from both the gauge and benchmark were used to establish gauge elevation. The average of three or more measurements, made under calm conditions, was used to establish the gauge elevation. From other benchmarks, not located on seawalls, the gauge elevation was established via differential leveling. The MLLW tidal datum was determined in reference to an historical NOS tidal benchmark located in the study area. The NOS tidal benchmark sheet provided elevations of tidal and geodetic datums referenced to MLLW (feet). Tidal benchmark sheets were obtained from the following NOAA web site: http://co-ops.nos.noaa.gov/station_retrieve.shtml?type=Bench+Mark+Data+Sheets

During installation of the tide gauge, critical parameters were recorded, including benchmark characteristics and a record of the procedures and measurements obtained during tide gauge calibration and leveling procedures. This information was of vital importance when correcting depth measurements to the MLLW tidal datum.

Tide corrections were performed by means of a computer program, Survey Tide Correction (SURVCORR.exe), developed by the University of Florida (UF) Coastal and Oceanographic Engineering program. SURVCORR was developed to correct depths within a winding canal or river system. The program, with inputs of spatially referenced soundings and tide gauge readings, determines and applies depth corrections based on time and relative location. Tide data are interpolated to each centerline, or user-constructed baseline point, by assuming a linear variation of the tide through the system. Weighting the interpolation by the distance from a gauge provides correction for non-linear effects, such as viscous dissipation. A more detailed description of the program can be found in the Appendix B.

View all of Field Procedures here: Field Procedures

Post-processing of Survey Data

Tidal Datum Determination

The NOS control tide station chosen to compute NTDE equivalent tidal datums for the project area is located at Fort Myers (Station ID: 8725520) on the Caloosahatchee River, and is part of the National Water Level Observation Network (NWLON). The tidal datums computed for Fort Myers are for the 1960-1978 Tidal Epoch, and are based on a series length of 18 years (1966-1984). The primary control tide station that was used to compute the Fort Myers tidal datums is located at St. Petersburg (8726520). The Fort Myers station was selected as the control station because it better reflects the local tidal influences within the Caloosahatchee River than does the St. Petersburg gauge. The NOS accepted tidal datums (feet), referenced to station datum, for the Fort Myers gauge are as follows (http://co-ops.nos.noaa.gov/data_menu.shtml?stn=8725520%20Fort%20Myers,%20FL&type=Datums):

View all of Post-processing of Survey Data here: Post-processing of Survey Data

Results and Conclusions

The bathymetric GIS data set contained on the accompanying CD has information on over 700,000 point depths recorded for all channel center-lines and approaches to boating facilities, in an area extending from the mouth to the Lee/Hendry County boundary, and the canals, rivers, and creeks that drain into this reach of the Caloosahatchee River. The mean depth of the study area is 6 feet. The data were collected by an on-the-water survey conducted between June 2001 and April 2002, using a Trimble DSM212H 12-channel receiver, with integrated dual-channel MSK differential beacon receiver and Bathy-500MF and Horizon DS150 sounders.

All depths in tidal waters are referenced to the navigation datum, mean lower low water (MLLW), and are rounded to the nearest 0.5-foot. In non-tidal areas (above locks), the datum is the National Geodetic Vertical Datum of 1929 (NGVD29). Tide gauges were installed at 28 locations (Figure 4) during the period of data collection, and depths were corrected to MLLW or NGVD29 using computer programs prepared by the University of Florida Department of Coastal Engineering.

Depths recorded with the Bathy-500MF were used to verify the soundings recorded simultaneously by the DS150. The DS150, a low cost sounder, was evaluated for potential use in future shallow-area surveys conducted by third party entities under the supervision of the WCIND and FSG. Survey results revealed that the DS150 provided depths that were more consistent and reliable than those provided by the Bathy-500MF. The Bathy-500MF was subject to regularly occurring, short series of depths that were several feet deeper or shallower than were actual depths. Scripts were developed to identify and clean the anomalous depths recorded by the Bathy-500MF, however the procedure was tedious and time consuming.

View all of Results and Conclusions here: Results and Conclusions

GIS Data Sets and Imagery

A CD-ROM accompanies this report and contains all geographic data sets as ARC/INFO® export files and ArcView® shapefiles (ESRI). The geographic data sets include: 1) soundings, reduced to Mean Lower Low Water (MLLW) or NGVD29 in areas behind locks, and recorded to the nearest 0.5-foot, 2) the location of the water level recorders used to correct soundings to MLLW, and 3) channels, created from soundings and represented as line features. Collection times are recorded in Coordinated Universal Time (UTC) for soundings. The projection parameters for all geographic data sets are as follows:

Projection: Albers

Datum: NAD83

Units: Meters

Spheroid: GRS1980

1st Standard Parallel: 24.0

2nd Standard Parallel: 31.5

Central Meridian: -84.0

Latitude of Projections Origin: 24.0

False Easting (meters): 400000.0

False Northing (meters): 0.0

The CD-ROM contains resampled USGS Digital Orthophoto Quarter Quadrangles at 1, 3, and 6-meter resolutions in JPEG format. Metadata, compliant with standards outlined by the Federal Geographic Data Committee, is provided on the CD-ROM for each geographic data set. The ArcView project (e.g., /ProjectDataCD/leephase3.apr) was created with a view containing all data sets and imagery. The included JPEG imagery requires that the JPEG (JFIF) extension be invoked from the available extensions.

The data sets and imagery that are included are described as follows:

View all of GIS Data Sets and Imagery here: GIS Data Sets and Imagery

References

Antonini, G.A., D.A. Fann, and P. Roat. 1999. A Historical Geography of Southwest Florida Waterways, Volume One: Anna Maria Sound to Lemon Bay. SGEB-47. Gainesville, FL: Florida Sea Grant College Program.

Antonini, G.A., R. Swett, S. Schulte, and D. Fann. 1998. Regional Waterway Management System for South Sarasota County. TD-1. Gainesville, FL: Florida Sea Grant College Program.

Antonini G.A., and P. Box. 1996. A Regional Waterway Systems Management Strategy for Southwest Florida. TP-83. Gainesville, FL: Florida Sea Grant College Program.

Boaters Action and Information League. 1998. A Guide to Anchorages in Southwest Florida. Second Edition. SGEB-48. Gainesville, FL: Florida Sea Grant College Program.

Center for Operational Oceanographic Products and Services. 2000. Computational Techniques for Tidal Datums Handbook. U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, National Ocean Service, Silver Spring, MD.

Fann, D., G. Antonini, J. Doubeck-Racine, M. Grella, and C. Listowski. 1999. Using GIS to Create Educational Products. GeoTools 99 Conference, Charleston, SC.

MOA. 1997. A Memorandum of Agreement Among the Florida Department of Environmental Protection, Florida Sea Grant College Program, and West Coast Inland Navigation District relating to a Regional Waterway Management System. Tallahassee, Florida. September 1997.

National Ocean Service. 1999. NOS Hydrographic Surveys, Specifications and Deliverables. April 23, 1999. Accessed on-line at http://chartmaker.ncd.noaa.gov/ocs/text/hsd-0.html

Nordheimer, J. 1993. Boom in Boating Crowds the Summer Sea. The New York Times, Sunday, July 4, pp. 1,9.

Swett, R.A., G.A. Antonini, and S. Schulte. 1999. Regional Waterway Management System for North Manatee County. TD-2. Gainesville, FL: Florida Sea Grant College Program.

Swett, R.A., D.A. Fann, G.A. Antonini, and L.C. Alexander. 2000. Regional Waterway Management System for Lee County, Phase 1. TD-3. Gainesville, FL: Florida Sea Grant College Program.

Swett, R.A., D.A. Fann, G.A. Antonini, and L.C. Alexander. 2001. Regional Waterway Management System for Lee County, Phase 3. TD-4. Gainesville, FL: Florida Sea Grant College Program.

Trimble Navigation Limited. 1998. Pro XR/XRS Receiver Manual. Revision A. Sunnyvale, CA: Trimble Navigation Limited.

U.S. Army Corps of Engineers. 2001. Engineering Manual, EM 1110-2-1003, Hydrographic Surveying. Washington, DC: Department of the Army.

U.S. Bureau of Census. 1994. Adopted from Soundings, November, p.127.

Appendix A

Equipment Specifications

View all of Appendix A here: Appendix A

Appendix B

Survey Tide Correction Program

Conceptual Description

View all of Appendix B here: Appendix B

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer-Chancy, Interim Dean.

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