3D Analyst - Watershed, Padang


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Deliniate Watershed in Padang Using ArcGIS Spatial Analyst
by Inda Merliana

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3D Analyst - Watershed, Padang

  1. 1. Deliniate Watershed in Padang Using ArcGIS Spatial Analyst Inda Merliana G051060081
  2. 2. Introduction <ul><li>Background </li></ul><ul><li>The major factor caused the damage is the existence of various activity convert the forest which heedless of the conservation aspect, like activity of forest didn't manage properly legal goodness </li></ul><ul><li>The bare land left from irresponsible forest activity has converted into critical watershed that have a high risk for being degraded and need a special attention. </li></ul><ul><li>Objectives </li></ul><ul><ul><li>Generate watersheds based on DEM from SRTM data </li></ul></ul><ul><ul><li>To understand the process of hydrological modelling using ArcGIS spatial analyst tool </li></ul></ul>
  3. 3. Data and Software Needed <ul><li>Data Needed </li></ul><ul><li>SRTM data (In this project using padang area {S01E099, S01E100, S02E100}) </li></ul><ul><li>River, Linriver and Watershed in shapefile format </li></ul><ul><li>Software Needed </li></ul><ul><li>3DEM Terrain Visualization </li></ul><ul><li>ArcGIS 9.2 </li></ul><ul><li>Cosmo Player </li></ul>
  4. 4. Procedural Steps <ul><li>Create DEM from SRTM data </li></ul><ul><li>Remove Error Sink in the DEM </li></ul><ul><li>Generate Flow Direction </li></ul><ul><li>Generate Flow Accumulation </li></ul><ul><li>Generating Channel </li></ul><ul><li>Generating Stream Link </li></ul><ul><li>Generating Watershed </li></ul>
  5. 5. Prepare the SRTM data <ul><li>Before starting 3dem software, we have to register the SRTM data first. </li></ul><ul><li>Open 3dem terrain visualization and load terrain model from menu file </li></ul>
  6. 6. Prepare the SRTM data (2) <ul><li>SRTM data will appear, but first convert SRTM data projection to UTM from menu operation >> change projection. </li></ul><ul><li>Select the small area from this SRTM data by clicking F8 or choose F8 from menu operation </li></ul>
  7. 7. Prepare the SRTM data (3) <ul><li>After the area being small then save it in tif format, but if it not, do the same process like before by clicking F8 >> drag the area and then press enter </li></ul>
  8. 8. Create DEM From SRTM Data <ul><li>Open the ArcGIS 9.2. Activate spatial analyst extention from menu tools >> extention </li></ul>
  9. 9. Create DEM From SRTM Data (2) <ul><li>Add the data (tif format) </li></ul>
  10. 10. Create DEM From SRTM Data (3) <ul><li>From padang.tif layer properties change the type to minimum-maximum from symbology </li></ul>
  11. 11. Remove Error Sink in the DEM (1) <ul><li>The DEM provided padang.tif is floating point real. Because elevations are whole numbers we convert the DEM to integer. Do this with the Raster Calculator under the pull-down menu Spatial Analyst. The output is a temporary GRID. To make it permanent right click the feature class and select Make Permanent. </li></ul>
  12. 12. Remove Error Sink in the DEM (2) <ul><li>To remove an error sink, we use the Fill tool in Hydrological Modeling Tools </li></ul><ul><li>Use ArcToolBox for this operation ArcToolBox is accessible in ArcMap. Navigate to Spatial Analyst Tools and select Fill Tool. The model asks for an input feature class and an output feature class. </li></ul>
  13. 13. Generate Flow Direction <ul><li>Use the tool Flow Direction to generate a raster grid showing the direction of flow </li></ul>
  14. 14. Generate Flow Accumulation <ul><li>Use the tool Flow Accumulation to generate a raster grid showing the direction of flow </li></ul>
  15. 15. Generating Channel <ul><li>Based on our flow accumulation, we can map stream channels where the water flows. This channel is based on the number of cells which flow into a specific cell. If we want large channels we use a larger number. For this project we will map all cells that has at least 500 cells that flow into it. </li></ul>
  16. 16. Generating Stream Link <ul><li>After we have mapped stream channels we have to assign each individual stream segments a unique number. This is done with the tool Stream Link tool </li></ul><ul><li>The model asks for two input stream raster and input flow direction raster and output raster. </li></ul>
  17. 17. Generating Watershed <ul><li>Next, we can generate watersheds as the final steps in hydrologic modelling. Use the tool Watershed from spatial analyst tool </li></ul>
  18. 18. Result <ul><li>By activate two layers, padang_wsd and padang_stl, we can see the result from this project </li></ul>
  19. 19. Result in 3D View <ul><li>Open ArcScene to view the watershed deliniation in 3D view </li></ul>
  20. 20. Result View In Cosmo Player
  21. 21. Thanks for your attention