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HIGH-RESOLUTION BATHYMETRY OF FLORIDA BAY

Project Proposal for 1998

Program: FRAGILE ENVIRONMENTS
Project Title: HIGH-RESOLUTION BATHYMETRY OF FLORIDA BAY
Location of Study Area: Florida Bay
Project Start Date: FY95
Project End Date: FY99
Project Number: 7242-37650
Project Chief: Mark Hansen
Region/Division/Team/Section: Eastern/Geologic/St. Petersburg
E-mail: mhansen@usgs.gov
Phone: 813-893-3100 ext 3036
Fax: 813-893-3333
Mailing Address:
600 4th St. S.
St. Petersburg, FL 33701
Program Element(s)/Task(s) 6.2
Panel:
Collaborators, Clients: US Army Corps of Engineers - Numerical modeling ; NOAA - Mapping
The primary users of the data will be researchers who are applying numerical models to the Bay to understand water circulation patterns and gradients in sediment transport. These efforts are directly related to water quality issues in the Bay. Circulation models are being developed and applied by WES and sediment transport models are being applied by USGS researchers. The updated bathymetry will also serve as a reference for future research in the Bay.



BACKGROUND NARRATIVES

Project Summary: Detailed, high-resolution maps of Florida Bay mudbank elevations are needed to understand sediment dynamics and provide input into circulation models. The bathymetry of Florida Bay has not been systematically mapped in nearly 100 years, and some shallow areas have never been mapped. An accurate, modem bathymetric survey will provide a baseline for assessing future sedimentation rates in the Bay, and a foundation for developing a sediment budget. Due to the shallow depths of the Bay, an updated bathymetry grid (digitally derived from the survey) is critical for circulation models.

Project Justification: Numerical circulation and sediment transport models being developed for the South Florida Ecosystem Restoration Program will be used to address water quality issues in Florida Bay. Application of these models is complicated due to the complex sea-floor topography (basin/mudbank morphology) of the Bay. The only complete topography data set of the Bay is 100 years old. Consequently, an accurate and modern sea-floor or bathymetry map of the Bay is critical for numerical modeling research. A modern bathymetry data set will also permit a comparison to historical data in order to help access sedimentation rates within the Bay. Previous research suggests that the mudbanks are dynamic features which migrate, accrete and erode. Less is known about the sedimentation rates in the basins. Some experts suggest the basins are filling, in association with sea-level rise, while others suggest the basins are deepening relative to sea-level. This study will produce a detailed bathymetric data set of Florida Bay in order to help assess sedimentation rates and provide numerical modelers with an accurate bathymetry map.

Project Objectives: The objective of this research is to collect new bathymetry for all of Florida Bay, digitize the historical shoreline and bathymetric data, compare previous data to modern data, and produce maps and digital grids of historical and modern bathymetry. This information will be provided to other researchers involved in the South Florida Ecosystem Restoration Program so they can better address the water quality issues of Florida Bay.

Overall Strategy, Study Design, and Planned Major Products: The strategy is to systematically map the bathymetry in Florida Bay in order aid in the assessment of Bay sedimentation rates and to provide an accurate sea-floor surface for numerical models. The Bay will be mapped using a shallow draft boat equipped with a high-precision GPS coupled with a high-precision depth sounder. Data will be collected on a USGS 7.5 min quad-by-quad basis proceeding westward from Blackwater Sound. Sounding trackline spacing will vary depending upon the relief of the sea-floor, i.e. closer spacing in near mud banks - wider spacing in the basins. Digital sea-floor grids will be produced from the trackline data. Historical bathymetric data (1890) will be obtained from NOS archives, digitized, and entered into a GIS. Digital comparisons will be made between the historical data and the new data. The project will produce both hardcopy and digital map products and professional papers. Historical and modern bathymetric maps will be produced as well as maps of bathymetric change. Digital maps will be available on the Internet and distributed on CD-ROM's. CD-ROM format will conform to ARC/View and SDTS standards.

WORK PLAN

Overall: The parts of the Bay which are accessible by a shallow draft boat will be mapped using the System for Accurate Nearshore Depth Surveying (SANDS). This system, developed by the USGS, utilizes geodetic differential Global Positioning System (GPS) receivers, a digital fathometer, a digital heave/roll/pitch sensor, and a shallow draft boat. The system is accurate to ~10 cm vertically, ~4 cm horizontally, and can collect data in water depths as shallow as 50 cm. In order to achieve this accuracy, the boat must not rove more than 10 km from any one GPS reference receiver. Therefore, approximately 10 new ground control points (with 1-2 cm accuracy) will be established throughout the Bay for use as reference receiver sites. Soundings will be referenced to the GRS80/NAD83 horizontal datum and NAVD88 vertical datum (via the NOS GEODID96 geoid model). For areas not accessible by boat, mud bank tops and sensitive sea-grass areas, other non-intrusive (remote sensing based) methods must be employed to fully map the bathymetry of the Bay. One non-intrusive technique to map the boat inaccessible areas is the US Army Corps of Engineers SHOALS helicopter LIDAR system. Another method utilizes vertical photography or imagery in combination with water stage data to detennine the elevations of the mud banks. These two techniques and others are being investigated at this time. Utilizing a non-intrusive method(s) in conjunction with the SANDS system will provide basin and mud bank elevations for the entire Bay.

Data collected will be checked for errors then entered in a sophisticated contouring package (CPS3) for contour and digital grid generation. This information will then be passed into ARC/Info for map production and data archiving. All raw (field) data will be stored and archived on magnetic-optical disks. Bathymetric survey data will continue to be collected through 1998. Preliminary hard copy and digital maps will be produced on an annual basis. Data will be provided to clients after it has been internally reviewed for accuracy.

Historical bathymetric data will be obtained from NOS historical archives. The only complete historical bathymetric data of the Bay is from the 1890 time period. All sounding will be digitized using standard digitizing practices. In order to compare this data set to the modern it must be projected into a modern horizontal datum (NAD83). Projecting the historical data into a modern datum is not straightforward as there was no national horizontal datum before 1920. However, the USGS has obtain a unique data set of control points from NOS archives which have both the 1890 positions and NAD83 positions. This information allow us to accurately compare the historical to the modern.

Historical, moderm and change maps will be produced at a scale of 1:24000 and will conform to USGS I- Map standards. Map production will be performed using ARC/Info and data archiving will comply with SDTS standards.

Timeline:
FY98 Hansen -PI, Dewitt - Field Data Collection/Processing, Thomton - GIS expert
Collect field data including establishing new ground control points when necessary.
Process field data.
Produce draft maps and digital grids of moderm data.
Complete digitization of historical data.
Produce draft maps of historical data.
Produce draft maps of sea-floor change.
Professional Paper - Use of SANDS for Mapping Florida Bay.

FY99 Hansen -PI, Dewitt - Field Data Collection/Proccssing, Thomton - GIS expert
Complete collection of field data including establishing new ground control points when necessary.
Process field data.
Produce final maps and digital grids of moderm data.
Produce final maps of historical data.
Produce final maps of sea-floor change.
Produce USGS Open File report - Summary of historical sea-floor change in Florida Bay.

Planned Deliverables/Products:
FY98 - All map products will be in draft form
Modern sea-floor maps of Florida Bay at 1:24000 (7.5 min USGS Quadrangle) overlaid on DOQ
Digital grids of modem sea-floor bathymetry
Historical (1890) sea-floor maps of Florida Bay at 1:24000 (7.5 min USGS Quadrangle)
Sea-floor change maps (1890-199x) of Florida Bay at 1:24000 (7.5 min USGS Quadrangle)
FY99 - All map products will be in final form
Modem sea-floor maps of Florida Bay at 1:24000 (7.5 min USGS Quadrangle) overlaid on DOQ
Digital grids of modem sea-floor bathymetry
Historical (1890) sea-floor maps of Florida Bay at 1:24000 (7.5 min USGS Quadrangle)
Sea-floor change maps (1890-199x) of Florida Bay at 1:24000 (7.5 min USGS Quadrangle)

Planned Outreach Activities: The US Army Corps of Engineers (WES) will receive digital sea-floor grids after they have been reviewed internally for accuracy. The grids will be used for numerically modeling Bay water circulation and sediment transport. In the past year, we have assisted (5.field days) NOAA in collecting water level data using the SANDS system. NOAA is using our data to establish ground control for a variety of research projects related to the South Florida Restoration Program. We plan to assist NOAA in the future when requested.

Prior Accomplishments in Proposed Area of Work:

New Directions, Expansion of Continuing Project (if applicable): None

ACCOMPLISHMENTS, OUTCOMES, PRODUCTS, OUTREACH

Accomplishments and Outcomes, Including Outreach:
Florida Bay has been systematically surveyed from Buttonwood Sound to Calusa Key basin.
Four new ground control points were established.
All historical shoreline and bathymetric data of Florida Bay has been digitized.
NOAA has been provided field assistance for 5 days and processed water level data.

Deliverables, Products Completed:
FY97 products will be for the area from Blackwater Sound to Calusa. Key basin. All map products will be in draft form.
Modern sea-floor maps of Florida Bay at 1:24000 (7.5 min USGS Quadrangle).
Digital grids of modern sea-floor bathymetry.
Historical (1890) sea-floor maps of Florida Bay at 1:24000 (7.5 min USGS Quadrangle).
Sea-floor change maps (1890-199x) of Florida Bay at 1:24000 (7.5 min USGS Quadrangle).

NEEDS

Required Expertise:
FY98
    oceanographer           for      Bathymetric surveys
    Field Assistant         for      Bathymetric surveys/data processing
    GIS experts             for      Historical data processing
FY99
    Oceanographer           for      Bathymetric surveys
    Field Assistant         for      Bathymetric surveys/data processing
    GIS experts             for      Historical data processing

Names of Key Project Staff:

FY98
    Mark Hansen				l6pp
    Nancy Dewitt			22pp
    Lance Thornton			13pp
FY99
    Mark Hansen				26pp
    Nancy Dewitt			22pp
    Lance Thornton			13pp

Major Equipment/Facility Needs:
The SANDS system is comprised of high-precision instrumentation valued at ~$150K, operated on a boat worth ~$50K. This equipment has been provided to this project without incurring major equipment purchase costs. The requested repair and replacement (R&R) funds are to cover the cost of R&R which frequently occurs when instrumentation is subjected to vibration and humid salt air in a small boat.

FY98
    $10K        Small boat expenses
    $15K        Field/travel expenses
    $20K        Equipment repair and replacement
FY99
    $5K	        Small boat expenses
    $10K        Field/travel expenses
    $20K        Equipment repair and replacement
    $25K        Map publication expenses


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Last updated: 24 April, 2014 @ 01:01 PM (KP)