Dona Bay WMP - Sarasota.WaterAtlas.org - University of South Florida

SWFWMD initiated mapping efforts in the early 1970’s and publishes aerial contourmaps for use by local governments and private entities. These topographic mapsdelineate contours at 1 ft intervals and also provide periodical ground point references at0.1 ft values. The maps provide water level elevation for wetlands and other waterbodiesdepending on the date of photography. These maps were used extensively for theSarasota County Cow Pen Slough/Shakett Creek Flood Study Update. Specifically, thetopographic information from these maps provided essential information in definingwatershed and subbasin ridge lines as well stage-storage relationships throughout thewatershed. In addition, it was used to then delineate the limits of the 100-year floodplain.Through cooperative funding efforts between SWFWMD, FEMA and Sarasota County,LiDAR (Light Detection Aerial Response) for the entire County has been obtained. TheLiDAR data provides digital information that can be manipulated to automate thedetermination of basin ridge lines and watershed storage through the use of currenttechnologies such as Digital Elevation Modules (DEM) and Digital Terrain Models(DTM). This LiDAR dataset is currently in quality review for use with these digitalterrain applications.Floodplain InformationThe Cow Pen Slough/Shakett Creek Flood Study Update included mapping of the 100-year riverine floodplain, as presented in Figure 6.2. The floodplain map includesdesignations consistent with FEMA’s flood zone definitions. Specifically, the FEMA“AE” zones, identified in dark blue, correspond to areas in the 100-year floodplaintypically associated with moving and/or deep water. The FEMA “AH” zones, identifiedin light blue, correspond to areas of shallow or ponded water, where average depths arebetween 1 and 3 feet. The adoption of the Shakett Creek/Cow Pen Slough Flood StudyUpdate assures that floodplain areas within the Dona Bay watershed will be recognizedand that the floodplain functions will be preserved when new development proposals areconsidered. In addition, the detailed hydrodynamic model provides a valuable tool forevaluating the effects of proposed land use changes and other watershed alterations onexisting flood stages.6-14