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Creating Watersheds and Stream Networks

Creating Watersheds and Stream Networks. Steve Kopp. Workshop Overview. Demo Data Understanding the tools. Elevation Data. Types DEM : Digital Elevation Model “bare Earth” DSM : Digital Surface Model Data Structure Raster TIN Terrain. Where do you get DEM data?. Sources

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Creating Watersheds and Stream Networks

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  1. Creating Watersheds and Stream Networks Steve Kopp

  2. Workshop Overview • Demo • Data • Understanding the tools Creating Watersheds and Stream Networks

  3. Elevation Data • Types • DEM : Digital Elevation Model “bare Earth” • DSM : Digital Surface Model • Data Structure • Raster • TIN • Terrain Creating Watersheds and Stream Networks

  4. Where do you get DEM data? • Sources • Global • SRTM and HydroSHEDS - 30m and 90m • ASTER - 30m (challenging for surface runoff modeling) • United States NED 30m, 10 m, and higher (ArcGIS Online) • LiDAR, IfSAR • Generated photogrammetrically • Created with interpolation tools • especially TopoToRaster Creating Watersheds and Stream Networks

  5. DEM Construction Considerations • Extent • Map Projection (use equal area) • Cell size and Resolution • Must be appropriate for the landscape and scale being modeled. • Source elevation data (accuracy, density, sampling) • Interpolation techniques (use TopoToRaster) • Special consideration for contour input • TopoToRaster interpolator – works well with contours, creates hydrologically correct DEM Creating Watersheds and Stream Networks

  6. Drainage System Watershed (Basin, Catchment, Contributing area) Watershed Boundaries (Drainage Divides) Pour Points (Outlets) Creating Watersheds and Stream Networks

  7. DEM FLOW ACCUMULATION FLOW DIRECTION STREAM ORDER STREAM LINE Apply Threshold SINK STREAM LINK No DepressionlessDEM Are there any sinks? FLOWLENGTH Yes FILL SNAP POUR WATERSHED Function Processing Creating Watersheds and Stream Networks

  8. Hydrologically Correct DEM • Sinks • Some sinks are real • Do not fill in the Great Salt Lake • Streams in the correct place? • To burn or not to burn… • Watershed boundaries in the correct place? • To fence or not to fence… Creating Watersheds and Stream Networks

  9. Filled sink Sink DEM Errors – Sinks and Spikes • Sinks: when sinks are (or are not) sinks • E.g. Lakes, depressions, karst and glacial landscapes • Global fill • Dealing with internal basins • Selective fill • Depth • Area Creating Watersheds and Stream Networks

  10. 78 72 69 71 58 49 74 67 56 49 46 50 69 53 44 37 38 48 64 58 55 22 31 24 68 61 47 21 16 19 74 53 34 12 11 12 Flow Direction 2 2 2 4 4 8 2 2 2 4 4 8 1 1 2 4 8 4 1 2 4 8 128 128 2 2 1 4 4 4 1 1 1 1 4 16 Flow Direction Elevation 32 64 128 16 1 8 4 2 Direction Coding Creating Watersheds and Stream Networks

  11. 0 0 0 0 0 0 0 1 1 2 2 0 0 3 7 5 4 0 0 0 0 20 0 1 0 0 0 1 24 0 0 2 4 7 35 2 Flow Accumulation 32 64 128 16 1 8 4 2 Direction Coding Creating Watersheds and Stream Networks

  12. DEM FLOW ACCUMULATION FLOW DIRECTION STREAM ORDER STREAM LINE Apply Threshold SINK STREAM LINK No DepressionlessDEM Are there any sinks? FLOWLENGTH Yes FILL SNAP POUR WATERSHED Function Processing Creating Watersheds and Stream Networks

  13. 1 1 1 2 2 2 2 2 2 2 2 Creating Vector Streams Value = No Data StreamToFeature RasterToFeature Creating Watersheds and Stream Networks

  14. Stream Link • Assign a unique value to each stream segment. • Can be used as input to Watershed tool Creating Watersheds and Stream Networks

  15. 1 1 1 1 1 1 1 1 1 1 1 2 2 1 1 1 2 2 2 3 4 2 2 3 7 3 Stream Ordering Shreve Strahler Creating Watersheds and Stream Networks

  16. Watershed Delineation • Identify the contributing area to a cell or group of cells. Creating Watersheds and Stream Networks

  17. Snap distance Stream Cell you clicked on The cell that will be selected(cell with highest flow accumulation) Snapping Pour Points • Use the SnapPour tool to snap the “pour point” of a watershed to the cell of highest flow accumulation within a neighborhood. • Prevents accidental creation of tiny watersheds on channel side slopes. Creating Watersheds and Stream Networks

  18. Flow Length • Calculate the length of the upstream or downstream flow path from each cell. Creating Watersheds and Stream Networks

  19. Where is this functionality? • Tools in the Spatial Analyst Toolbox • Global Watershed Delineation and Trace Downstream in ArcCatalog Ready to User Services, ArcGIS Online Analytics and Web AppBuilder • Sample tools, models, workflows and Arc Hydro tools) are available in GeoNet, Geoprocessing tool gallery, and Hydro Resource Center Creating Watersheds and Stream Networks

  20. Hosted Hydro Analysis Services • Watershed Delineation Service • Trace Downstream Service • Profile Service • Elevation Summary Statistics • Source • US – based upon 30 m elevation and vectors derived from NHDPlus V2 Global – based upon 90 m elevation from HydroSHEDS • New contributions welcome… Creating Watersheds and Stream Networks

  21. Thank you… • Please fill out the session survey in your mobile app • Select [Creating Watersheds and Stream Networks] in the Mobile App • Use the Search Feature to quickly find this title • Click “Technical Workshop Survey” • Answer a few short questions and enter any comments • Paper survey forms are also available

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