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| When the drainage coverage feature objects are used to create a hydrologic model the area of the polygons can be determined and used in any of the supported hydrologic models. If the points/vertices used to create the feature arcs also have z values associated with them then WMS will make a rough estimate of the longest flow path and slope along such a path. Finally, if you have derived a watershed from feature objects, but have a background DEM you can compute most of the basin data parameters using the following steps:
| | #redirect [[WMS:DEM_Basins#Compute_Basin_Data]] |
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| :#[[WMS:Importing USGS DEMs|Import/Read the DEM.]]
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| :#[[WMS:Importing Flow Directions and Accumulations|Compute the flow directions]] using TOPAZ.
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| :#Use the [[WMS:DEM Basins|Polygon Basin IDs→DEM]] command found in the ''DEM'' menu in the Drainage module to assign DEM cells a basin id from the feature object polygons.
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| :#Choose the '''Compute Basin Data''' command from the ''Feature Objects'' menu of the Map module.
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| Of course, the results will only be approximate since the actual basin boundaries will not have been derived from the computed flow direction data, but it will provide a reasonable estimate. Ideally you will want to derive the basin boundaries from the DEM and flow direction data and then use the [[WMS:DEM Basins|Compute Basin Data]] command in the ''DEM'' menu of the Drainage module.
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| ==''Related Topics''==
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| *[[WMS:Feature Object Guidelines|Feature Object Guidelines]]
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| *[[WMS:DEM Basins|Computing Basin Data from DEMs]]
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| *[[WMS:TIN Basins|Computing Basin Data from TINs]]
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