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Service Description: A map service layer (map image layer) containing hydro-corrected drainage basin, watershed, catchment and sub-basin boundaries for drainage areas that impact Tallahassee and Leon County, Florida. This map service was generated from the most recent digital elevation model of Leon County, Florida.
Basins: Local level basins are the largest drainage unit tracked by Tallahassee-Leon County government and reflect final destinations of surface water drainage. Lake Jackson is, for example, a natural lake where a substantial amount of surface water runoff ultimately collects. Ames Sink (Lake Munson Basin) is a natural swallet (a sinkhole where surface water enters the aquifer) where surface watercourses terminate into the Floridan Aquifer. Lake Miccosukee is a water feature in part created from infrastructure that controls water elevation (weir/spillway) and a berm that prevents the surface water from draining into the aquifer by way of a swallet.
Watersheds: Watersheds are groups of catchments aggregated (merged) to produce even larger more meaningful drainage units. The results are produced from storm-water inventory wherever possible and indicate where water ultimately collects. This could be a much larger storm-water facility, a natural area (lake or depression) or other area where a greater volume of surface water collects.
Catchments: Catchments are an aggregated set of data. Meaning groups of sub-basins (deranged areas) are merged to create larger more meaningful boundary areas. For natural areas this could be several shallow depressions being included with a larger nearby natural feature (lake, sink, etc.). Meaning depending upon rainfall conditions an entire area of interconnected lower elevation depressions coalesce into a larger drainage area. For developed areas, this could mean a series inlets direct surface drainage by way of conduits to a storm-water management facility. This information is processed by either known inventory data connection or by best assumption. Sub-Basins: The sub-basin data is identical geometry to the ‘deranged area’ boundaries produced by Archydro, an extension of ESRI ArcGIS software. The deranged area boundaries used to produce the sub-basins are themselves produced by hydro-correcting the DEM surface to reflect both natural environments and areas with human activity. Areas with more substantial human activity effect the drainage pattern of water and in particular storm-water runoff. This would include things like paved roads, paved parking lots and buildings. An effort has been made to produce deranged area boundaries at locations where storm-water runoff is directed (inlets, grates, storm-water ponds, etc.) and as well natural locations in the environment (sinks, depressions, confluences, etc.). Hydro-correcting involves a certain amount of modification and manipulation of the DEM surface to produce better results. For example, ‘burning’ in a channelized ditch along a road with many driveway aprons that obscure the subsurface ditch (driveway culverts) beneath. A deranged area boundary is created by leveling an area that approximates where the water would flow (inlet, pond, sinkhole, etc.) by way of gravity and infrastructure that directs it (ditches, curbs, etc.). From the leveled area the ArcHydro software uses the DEM to generate the drainage boundary (deranged area boundary) using the DEM surface. Project Summary
ESRI’s Arc Hydro toolset was used to “hydro-correct” a high-fidelity Lidar-derived bare earth DEM for the purpose of mapping all drainage areas that contribute water to Leon County. This process allowed for the mapping of actual surface drainage patterns on the ground, including natural areas of unaltered drainage along with areas where surface drainage has been engineered to not follow the natural topography. This process yielded a much more accurate delineation of the amount of water draining to a given location than would otherwise be possible using topographic DEMs alone.
Since one of the goals of the project was to map all drainage areas that contribute surface drainage to Leon County, the mapping area extends beyond Leon County to include an additional nine counties in Florida and Georgia. This effort marked the first time that all areas that contribute surface drainage to Leon County were mapped.
Hydro-Correction
Hydro-correction methods were used to modify the DEMs in order to take into account the presence of stormwater inventory. For this dataset, hydro-correction was accomplished by using 3 geoprocessing tools from the Arc Hydro toolset:
Build Walls: The Build Wall tool allows the user to superimpose a polyline on an input DEM to raise the elevation values in the output DEM by a user-specified amount. This tool was primarily used where drainage divides were not well expressed in the source DEM. Additionally it was used to force drainage to stop at a particular point of interest (such as a stream confluence).
DEM Reconditioning: This tool allows the user to superimpose a polyline on an input DEM to reduce the elevation values in the output DEM by a user-specified amount. This is often referred to as “burning” and is the opposite of Build Walls.
Level DEM: This tool allows the user to superimpose a polygon on an input DEM to reassign cell values in the output DEM to a constant user-specified elevation. This tool was used to create pour point locations in the output DEM by reassigning the output elevation to be slightly lower than the surrounding input pixel values, thereby creating a “pit” in the output DEM. The area that drains to each “pit” is referred to as a Sub-Basin.
Drainage Area Delineation
The Arc Hydro tool Sink Evaluation uses the 3 hydro-correction feature classes, the pour point feature class and the base earth DEM to create the drainage areas. Four feature classes representing drainage areas were produced: Sub-basins, Catchments, Watersheds, and Drainage basins. Sub-basins represent the smallest units of coherent drainage that were mapped. The Sub-Basins were the “building blocks” for creating a nested hierarchy of drainage units that are designed to be used at local scales as well as regional scales. The Sub-Basins were aggregated into larger nested drainage units, referred to as Catchments. The Catchments were aggregated into still larger nested drainage units, referred to as Watersheds. Finally, the Watersheds were aggregated into still larger nested drainage units, referred to as Drainage Basins.
Drainage Boundary 3D
Drainage Boundary 3D is a Polyline Z feature class created by intersecting the Sub-Basin boundaries with the DEM. The purpose of this feature class is to provide a set of metrics for identifying the high and low points along a Sub-Basin boundary, as well as pop-off locations for areas of closed drainage.
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Copyright Text: TLCGIS
Spatial Reference:
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Single Fused Map Cache: false
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Spatial Reference: 102100
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Spatial Reference: 102100
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Units: esriMeters
Supported Image Format Types: PNG32,PNG24,PNG,JPG,DIB,TIFF,EMF,PS,PDF,GIF,SVG,SVGZ,BMP
Document Info:
Title: Hydro Corrected Drainage Boundaries - Maintained
Author:
Comments: A map service layer (map image layer) containing hydro-corrected drainage basin, watershed, catchment and sub-basin boundaries for drainage areas that impact Tallahassee and Leon County, Florida. This map service was generated from the most recent digital elevation model of Leon County, Florida.
Basins: Local level basins are the largest drainage unit tracked by Tallahassee-Leon County government and reflect final destinations of surface water drainage. Lake Jackson is, for example, a natural lake where a substantial amount of surface water runoff ultimately collects. Ames Sink (Lake Munson Basin) is a natural swallet (a sinkhole where surface water enters the aquifer) where surface watercourses terminate into the Floridan Aquifer. Lake Miccosukee is a water feature in part created from infrastructure that controls water elevation (weir/spillway) and a berm that prevents the surface water from draining into the aquifer by way of a swallet.
Watersheds: Watersheds are groups of catchments aggregated (merged) to produce even larger more meaningful drainage units. The results are produced from storm-water inventory wherever possible and indicate where water ultimately collects. This could be a much larger storm-water facility, a natural area (lake or depression) or other area where a greater volume of surface water collects.
Catchments: Catchments are an aggregated set of data. Meaning groups of sub-basins (deranged areas) are merged to create larger more meaningful boundary areas. For natural areas this could be several shallow depressions being included with a larger nearby natural feature (lake, sink, etc.). Meaning depending upon rainfall conditions an entire area of interconnected lower elevation depressions coalesce into a larger drainage area. For developed areas, this could mean a series inlets direct surface drainage by way of conduits to a storm-water management facility. This information is processed by either known inventory data connection or by best assumption. Sub-Basins: The sub-basin data is identical geometry to the ‘deranged area’ boundaries produced by Archydro, an extension of ESRI ArcGIS software. The deranged area boundaries used to produce the sub-basins are themselves produced by hydro-correcting the DEM surface to reflect both natural environments and areas with human activity. Areas with more substantial human activity effect the drainage pattern of water and in particular storm-water runoff. This would include things like paved roads, paved parking lots and buildings. An effort has been made to produce deranged area boundaries at locations where storm-water runoff is directed (inlets, grates, storm-water ponds, etc.) and as well natural locations in the environment (sinks, depressions, confluences, etc.). Hydro-correcting involves a certain amount of modification and manipulation of the DEM surface to produce better results. For example, ‘burning’ in a channelized ditch along a road with many driveway aprons that obscure the subsurface ditch (driveway culverts) beneath. A deranged area boundary is created by leveling an area that approximates where the water would flow (inlet, pond, sinkhole, etc.) by way of gravity and infrastructure that directs it (ditches, curbs, etc.). From the leveled area the ArcHydro software uses the DEM to generate the drainage boundary (deranged area boundary) using the DEM surface. Project Summary
ESRI’s Arc Hydro toolset was used to “hydro-correct” a high-fidelity Lidar-derived bare earth DEM for the purpose of mapping all drainage areas that contribute water to Leon County. This process allowed for the mapping of actual surface drainage patterns on the ground, including natural areas of unaltered drainage along with areas where surface drainage has been engineered to not follow the natural topography. This process yielded a much more accurate delineation of the amount of water draining to a given location than would otherwise be possible using topographic DEMs alone.
Since one of the goals of the project was to map all drainage areas that contribute surface drainage to Leon County, the mapping area extends beyond Leon County to include an additional nine counties in Florida and Georgia. This effort marked the first time that all areas that contribute surface drainage to Leon County were mapped.
Hydro-Correction
Hydro-correction methods were used to modify the DEMs in order to take into account the presence of stormwater inventory. For this dataset, hydro-correction was accomplished by using 3 geoprocessing tools from the Arc Hydro toolset:
Build Walls: The Build Wall tool allows the user to superimpose a polyline on an input DEM to raise the elevation values in the output DEM by a user-specified amount. This tool was primarily used where drainage divides were not well expressed in the source DEM. Additionally it was used to force drainage to stop at a particular point of interest (such as a stream confluence).
DEM Reconditioning: This tool allows the user to superimpose a polyline on an input DEM to reduce the elevation values in the output DEM by a user-specified amount. This is often referred to as “burning” and is the opposite of Build Walls.
Level DEM: This tool allows the user to superimpose a polygon on an input DEM to reassign cell values in the output DEM to a constant user-specified elevation. This tool was used to create pour point locations in the output DEM by reassigning the output elevation to be slightly lower than the surrounding input pixel values, thereby creating a “pit” in the output DEM. The area that drains to each “pit” is referred to as a Sub-Basin.
Drainage Area Delineation
The Arc Hydro tool Sink Evaluation uses the 3 hydro-correction feature classes, the pour point feature class and the base earth DEM to create the drainage areas. Four feature classes representing drainage areas were produced: Sub-basins, Catchments, Watersheds, and Drainage basins. Sub-basins represent the smallest units of coherent drainage that were mapped. The Sub-Basins were the “building blocks” for creating a nested hierarchy of drainage units that are designed to be used at local scales as well as regional scales. The Sub-Basins were aggregated into larger nested drainage units, referred to as Catchments. The Catchments were aggregated into still larger nested drainage units, referred to as Watersheds. Finally, the Watersheds were aggregated into still larger nested drainage units, referred to as Drainage Basins.
Drainage Boundary 3D
Drainage Boundary 3D is a Polyline Z feature class created by intersecting the Sub-Basin boundaries with the DEM. The purpose of this feature class is to provide a set of metrics for identifying the high and low points along a Sub-Basin boundary, as well as pop-off locations for areas of closed drainage.
Subject: Hydro corrected drainage boundaries for areas that impact Tallahassee and Leon County Florida. These are typically derived from our latest Lidar DEM.
Category:
Keywords: ArcHydro,Drainage,ESA,Water,Drainage Basins,Watersheds,Catchments,Subbasins
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