Coordinate system: NAD 1983 HARN StatePlane Florida North FIPS 0903 Feet
Theme keywords: boundaries, elevation, environment, basin, catchment, hydrology, watershed , elevation, environment, boundaries
Abstract: This layer delineates the boundaries of drainage basins in Leon County, Florida. Basins are the largest unit of drainage and typically drain into a major lake or river in cases where there is a significant drainage network of streams present. In areas where internal drainage is the dominant mechanism of water movement basin boundaries represent limits beyond which flow does not typically occur during normal hydrologic conditions.
Metadata elements shown with blue text are defined in the Federal Geographic Data Committee's (FGDC) Content Standard for Digital Geospatial Metadata (CSDGM). Elements shown with a green asterisk (*) will be automatically updated by ArcCatalog. ArcCatalog adds hints indicating which FGDC elements are mandatory; these are shown with gray text.
This layer delineates the boundaries of drainage basins in Leon County, Florida. Basins are the largest unit of drainage and typically drain into a major lake or river in cases where there is a significant drainage network of streams present. In areas where internal drainage is the dominant mechanism of water movement basin boundaries represent limits beyond which flow does not typically occur during normal hydrologic conditions.
This dataset was originally developed in 1999 to provide members of the Tallahassee/Leon County GIS Interlocal group with base data to use in their maps, projects and business processes. The ESA Watershed Refinement Project was initiated in 2005 as a consequence of the increased accuracy of topographic data acquired through the routine basemap update project (orthophoto and LiDAR capture). To maintain an internally consistent set of data layers requires that all layers derived from topographic data be updated to reflect the current Digital Elevation Model (DEM) data both because the new DEM data is more accurate due to technology advances (LiDAR) and because the new DEM data reflects structural on-the-ground changes (construction activity) since 1996.
The information depicted in this GIS layer is the result of digital analyses performed on a database consisting of information from a variety of governmental and other credible sources. The accuracy of the information presented is limited to the collective accuracy of the database on the date of the analysis. The information is believed accurate and reasonable efforts have been made to ensure the accuracy of the data. However, TLC/GIS expressly disclaims responsibility for damages or liability that may arise from use of this data. This product is the property of Tallahassee/Leon County GIS and its use is thereby restricted.
Leon County Courthouse
301 S. Monroe St.
ESRI feature type: Simple, Geometry: Polygon, Topology:
Data set has been visually inspected. All data produced strives to meet National Mapping Accuracy Standards (NMAS).
A 20-ft resolution LiDAR-derived DEM formed the base data for all subsequent processing. Pits and peaks in the 20-ft resolution DEM were filled using 1 ft parameter. In practice the county-wide DEM was too large to process the iterative filling algorithm in bulk, so the DEM was broken into smaller sections for this processing step and subsequently merged back together to form a seamless, filled DEM. This DEM is preserved as DEM20_500. The filled DEM was processed through ArcHydro to create "atomic catchments". As part of this process, a parameter was required to determine the 'granularity" of the catchment formation process, based on the number of cells required to contribute water to a given cell in order to create a stream. A value of 500 was used for this process, based on trials of a range of values. ArcHydro was designed for use in areas of dendritic drainage, so some adjustments were required to force the application to function in our areas of internal drainage. It was necessary to convert some of the remaining closed depressions within the surface into "false streams" strictly for the purpose of forcing ArcHydro to create catchments in these internally drained areas. Subsequent to this work ArcHydro has been enhanced by the developers and some of the Florida Water Management Districts to better handle internal drainage. The output from ArcHydro was 73,262 "atomic catchments". Due to variations in geomorphology throughout the study area the size of these catchments varied. These atomic catchments were aggregated into more meaningful final catchments by OPS staff by analyzing the catchments, DEM data, flow direction grid and drainage lines. Areas requiring additional hydrologic knowledge were marked for review. Senior TLCGIS staff reviewed the catchments and tentative basin/watershed attribution and made appropriate edits. Catchments were dissolved into Watersheds and Basins. Unresolved questions were passed to City and County engineering staff for review. Field inspection and expert knowledge resolved the remaining questions and appropriate edits were made to the final product. Temporary topology was contsrtucted and the layers were checked for gaps or overlaps. OVERVIEW OF WORKFLOW * Create polygon buffers of each 1996 Basin boundary using a buffer distance of 1500 feet. * Use polygon buffer to create 3D shapefiles of masspoints and breaklines through LiDAR clipper extension. * Create TIN then GRID from masspoint and breakline data. * Fill GRID using 1 foot criteria for SINKS/PEAKS. * Merge all filled grid products back into a single DEM. * Run resultant GRID through ArcHydro toolset to produce catchment polygons. * Convert catchment polygon shapefile into PGDB for editing. * Attribute catchments to indicate draft Watersheds, based on ArcHydro stream network and flow direction grid. * Edit catchments to obey pre-existing man-made drainage divides (roads/railroads). * Merge small catchments into reasonably sized catchments. * Merge catchments into Watersheds * Merge Watersheds into Basin * Tech Review * Final edits RULES/GUIDELINES: * If 1996 ESA boundaries follow a sharp, clearly defined man-made feature, such as a road or railroad the Refined boundaries will retain that boundary. * Closed Watersheds on the perimeter of a Basin will be checked to determine which adjacent Basin they pop off into. Watersheds on the perimeter of Basins will be grouped with the appropriate Basin based on this characteristic. * Watersheds that change by > 10% will be considered * Major Refinements" and will be referred back to engineering staff for review. * After Catchments, Watersheds, and Basins have been refined for the entire county a complete map showing all changed areas will be presented to the TopoPartnering Group for final review.
Internal feature number.
Name of basin.
Acrea of drainage unit, in acres.
Area of drainage unit, in square miles.
Basins are attributed as closed (CLOSED=Y) if flow generally remains within the boundaries of the basin during typical hydrologic conditions.
Basin is closed.
Basin is open.
There is a distinction between basins which are technically "closed" based on topography and those that are classified as closed for regulatory purposes. Basins which are technically open may be classified as closed for regulatory purposes (REG_CLOSED=Y) when existing downstream flooding exists or when the open basin discharges into a closed basin. Basins which are technically closed may be classified as open for regulatory purposes (REG_CLOSED=N) when the receiving waterbodies have the capacity to handle excess stormwater volumes or where stormwater treatment standards exist that function to retain excess stormwater volumes.
LC Growth Management
Basin is regulated as closed.
Basin is regulated as open.
Length of feature in internal units.
Area of feature in internal units squared.
301 S. Monroe St.
Leon County Courthouse