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freshwater flows to the east coast >
Program: FRAGILE ENVIRONMENTS
Program: FRAGILE ENVIRONMENTS
Project Summary: A system of canals and levees (see map of study area) has been constructed over the last century for the purpose of drainage, flood control, and aquifer recharge. Strategically placed control structures allow the water management officials to move water from inland areas during high-rainfall periods and retain water in the dry periods. Freshwater discharged to tide through coastal structures not only affects the amount of water available for water supply in the lower east coast and the Everglades, but also affects the biota in the Intracoastal Waterways and Biscayne Bay. Therefore, it Is imperative that there be accurate ratings for these structures to predict the effects of various restoration alternatives. Although these coastal structures are a pivotal part of the man-made system, the discharge through most of them are computed only from theoretical ratings. Actual field measurements are needed in order to determine if the theoretical ratings are adequate, and to develop more accurate ratings.
Project Justification: Stage measurements are currently made by SFWMD or USGS at the east coast structures. The flows through the coastal control structures in Dade, Broward, and Palm Beach Counties can be computed by developing stage-discharge ratings from field measurements of flow, stage, and structure operations. Although theoretical ratings exist for the structures, no check as to the accuracy of these ratings has been made. In order to develop ratings from field measurements, discharge measurements must be made at the structure simultaneously with water level and structure operation measurements. Difficulties in making accurate discharge measurements arise from the slow flows and non-standard velocity profiles in south Florida canals. The Acoustic Doppler Current Profiler (ADCP), a new state-of-the art device for measuring flows, will be used to make these discharge measurements. The ADCP uses the Doppler shift in acoustic signals to determine water velocity and compute discharge. It is ideal for measurements in slow and spatially varying velocity fields. Statistical techniques will be used to determine the best-fit ratings for the structures and error analysis of the ratings.
Project Objectives: The hydrology of the lower east coast of Florida is highly regulated by man-made canals with hydraulic control structures (see map of study area). The SFWMD controls the operation of these structures. Flows through the eastern coastal structures affect the total amount of water retained inland for water supply, prevention of saltwater intrusion, and maintenance of natural wetlands. Structure operating decisions must be based on accurate determinations of flows through these structures in order to properly account for the entire South Florida water budget. In addition, significant modifications to the flow systems in the inland wetlands and water conservation areas are planned by the COE as part of Everglades Restoration. These modifications will be affected by, and have an effect on, flows through the coastal controls. Accurate knowledge of coastal flows will have a direct effect on the implementation of the Restoration goals.
Overall Strategy, Study Design, and Planned Major Products: Computed ratings for coastal structures (gated spillways, culverts, and pump stations) in Dade, Broward, and Palm Beach Counties have been developed. These ratings are based upon actual field measurements to better relate quantity of discharge to upstream and downstream water levels and structure operation conditions. The field measurements were completed for all three counties by FY 97. Any additional measurements can be made if data appears lacking for any structure. The first report on the coastal structures in Dade county has been completed. The final report on the structures in Broward and Palm Beach Counties has been written and will be published in FY 98. An open file video has been completed and is awaiting approval for release.
Overall: The major users of the product will be SFWMD and COE, who will utilize the developed ratings for computation of flows to the east coast. This will allow them to make better management decisions regarding structure operations, and modifications to the hydrologic regime. Other clients, such as the National Oceanic and Atmospheric Administration (NOAA), Everglades National Park (ENP), hydrologists for the coastal counties, and the local water and sewer authorities are interested in the flows effects on inland areas, wetlands, well fields, saltwater intrusion, and Biscayne bay.
FY 97 - All measurements were completed. The report for the Broward and Palm Beach Counties will be finished by the end of FY 97. The report on the Dade County measurements was approved, and the open file video was completed and is awaiting approval for release.
FY 98 - The report for the Broward and Palm Beach Counties and the open file video will be completed and approved for release. Numerical models will be created to describe the flow patterns at selected sites in Dade, Broward, and Palm Beach Counties that produced anomalous data. Models will be designed by January 1998 and calibrated by May 1998. In addition, analysis will be conducted on transitional flow, the flow regime that exists between orifice and weir flows. Any additional measurements can be made if data appears lacking for any structure. The report on the numerical modeling will commence in May 1998 and be completed by September 1998. The fact sheet on transitional flow will be completed in June 1998.
Planned Outreach Activities: Coordination with the chiefs of the other Fragile Environments Program projects, especially "Freshwater Flows to Florida Bay" will allow water deliveries not only to be adequate for the projects, but be efficient for supply and management. An open file video has been completed to educate the general public about current research and efforts to quantify flows to the east coast, including local middle school students. The computed coefficient ratings for submerged orifice flow, submerged weir flow, free orifice flow, and free weir flow will be available on the USGS web page. Other outreach activities include attending and presenting at various inter-agency meetings, such as the annual SFWMD Ecosystems Conference, the ENP Florida Bay Interagency Science and Research Conference and the USGS Southern Inland and Coastal System (SICS) Project meetings.
New Directions, Expansion of Continuing Project (if applicable): Numerical models will be created to describe the flow patterns at selected sites in Dade, Broward, and Palm Beach Counties that produced anomalous data. In addition, analysis will be conducted on transitional flow, the flow regime that exists between orifice and weir flows. Any additional measurements can be made if data appears lacking for any structure. The report on the numerical modeling and the fact sheet on transitional flow will be written and completed in FY 98.
Accomplishments and Outcomes, Including Outreach: All measurements have been completed and ratings developed. Results were shared with other Fragile Environments Program team members. Federal, State, and local agencies, such as COE, ENP, SFWMD and local authorities . It was determined that the theoretical ratings developed by the COE were comparable to actual flows in Dade, Broward, and Palm Beach Counties. An analysis between the theoretical ratings and computed ratings was conducted showing how significant the differences were. The volumetric difference between theoretical and computed flows for 1994 was calculated for the Dade County structures, resulting in a significant shift in flow to the southern portion of Biscayne Bay.
Deliverables, Products Completed: The report on the Dade County measurements has been approved and is being prepared for publication, and the open file video has been completed and awaiting approval for release. The report for Broward and Palm Beach Counties portion of the study has been completed and will be ready for approval by the end FY 97.
Required Expertise: Senior surface water hydrologist with extensive modeling experience and a junior level modeler with a surface water background.
Names of Key Project Staff:
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