This is due to the Fill tool filling in the stream, causing the flow direction to not flow into the right area. Add the layer L:packgisforeststreams to the data frame You should start to see some patterns. The output raster should be set to C:UsersNetIDDocumentArcGISFlowDirfill1 (the default) Turn off display of the Filled dem layer. About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features Press Copyright Contact us Creators. Notice how they are very inaccurate compared to where the stream actually is on the DEM. Flow direction Open the Flow Direction tool. The blacklines are the stream lines created from the resulting inaccurate flow accumulation. Inaccurate Flow Direction made from depressionless DEM with inaccurate streamlines (black lines) created from resulting inaccurate flow accumulation (shown to display inaccuracy of flow direction):ġm DEM with clearly visible streams. The values for each direction from the center are: For example, if the direction of steepest drop was to the left of the current processing cell, its flow direction would be coded as 16. As a result, flow accumulation is inaccurate in these areas and as a result of that the stream network built from it is as also inaccurate in these areas. The output of the Flow Direction tool is an integer raster whose values range from 1 to 255. This results in an inaccurate flow direction because the streams are filled to the same elevation of the surrounding area. In these areas the Fill tool used in the depressionless DEM workflow fills in the streams on the DEM. This works very well except in some areas that are quite flat.
I have followed ESRI's guide (found here ) on how to create a depressionless DEM so that flow direction is accurate. I need this in order to build a flow accumulation raster, so I can use that to build a stream network. Delete ‘FlowDelete’ dataset from your output workspace. We need to create a new Flow Direction raster from our recently filled DEM. There is no option to select the geometric network from a layer drop-down list as input to the tool.I am trying to build a flow direction raster for an area from a 1m DEM created from LiDAR. How to Delineate Watersheds in ArcGIS for Desktop MD DoIT GIO of 13 Flow Direction 1. In ArcGIS, right click on the flow direction layer (fdr) Data Export Data Export fdr as GeoTiff (TIFF format). Using this information, you can import the flow direction raster from ArcGIS into GRASS GIS and convert it to the drainage raster. This video demonstrates how to take a dem and use the fill tool, flow direction tool, flow accumulation tool and basin tool to show the location of rivers an. Therefore, when using this tool in ArcMap, the geometric network must be selected from disk. Figure 1: ArcGIS flow direction encoding Figure 2: GRASS GIS drainage encoding. Unlike other datasets, such as topology or network datasets, geometric networks do not have an associated layer.
This tool can only be run with Foreground processing, it cannot be run using Background processing. Environment as of Metadata Creation: Microsoft Windows 7 Version 6.1 (Build 7601) Service Pack 1 Esri ArcGIS 10.3.1 (Build 4959) Service Pack N/A (Build N/A) The overlandflowdirectionUCRBMaurerresolution.asc ASCII grid is the D8 flow-routing grid for the UCRB, resampled to match the Maurer et al. This tool does not honor selections flow is set on every edge in the geometric network. I am interested to know why ‘Flow Direction Raster’, derived from ‘Filled DEM’, generates values ranges from 1-128, with pixel depth of 8 bit unsigned integer which is readily capable to store values 0-255, As such, in the Tool’s Help, it is clearly stated that the output of the Flow Direction tool is an. Geometric networks in enterprise geodatabases must be registered as versioned in order for this tool to be used. If one is not active when the tool is run, this tool will start an edit session. Learn more about flow_direction_in_a_geometric_networkįlow direction must be set within an edit session. Unlike the Utility Network Analysis toolbar, this tool allows you to set flow direction based on the digitized direction of network edges inĪddition to the sources/sinks defined in your network.