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GIS Applications in Watershed Analysis …..the watershed unit

GIS Applications in Watershed Analysis …..the watershed unit. Dr. Dennis L. Johnson Assistant Professor Michigan Technological University COMET Hydrometeorology 99-2 Friday, 25 June 1999. Today’s Purpose. Introduce the Concepts of a GIS Applications of a GIS Focus on the Watershed Unit

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GIS Applications in Watershed Analysis …..the watershed unit

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  1. GIS Applications in Watershed Analysis…..the watershed unit Dr. Dennis L. Johnson Assistant Professor Michigan Technological University COMET Hydrometeorology 99-2 Friday, 25 June 1999

  2. Today’s Purpose • Introduce the Concepts of a GIS • Applications of a GIS • Focus on the Watershed Unit • …. Get you thinking …... DLJ 99 - Juniata College

  3. What is a GIS ? • A GIS is a Geographical Information System • A series of data layers (maps) that represent some feature on the earth’s surface • Ability to “overlay” !! • All data is “georegistered” DLJ 99 - Juniata College

  4. Georegistered ? • Representing a curved surface in a flat plane • Locating that plane on the earth • 3 issues • sphere • datum • projection DLJ 99 - Juniata College

  5. Sphere & Datum Mathematically describe a sphere Lock it down by making it touch the earth somewhere NAD27- Kansas Use satellites in modern day NAD83 DLJ 99 - Juniata College

  6. Project to a Flat Surface Touches at the equator Touches at 2 lines of latitude DLJ 99 - Juniata College

  7. Unwrap the Cylinder One cylinder for each data layer Represent the data electronically A GIS!!! DLJ 99 - Juniata College

  8. GIS Layers Elevations Discharge Points Rivers DLJ 99 - Juniata College

  9. A DEM • A Digital Elevation Model or DEM is used to represent the elevations of a section or area of land. • The DEM is generally a gridded or raster data set. • A raster data set means a series of rows and columns with each grid cell representing a property such as elevation. DLJ 99 - Juniata College

  10. Create A DEM from a Topographic Map DLJ 99 - Juniata College

  11. A Bunch of Blocks to Represent the Earth DLJ 99 - Juniata College

  12. A DEMWhat the Computer Sees & What You See DLJ 99 - Juniata College

  13. Other Views DLJ 99 - Juniata College

  14. Assign Flow Directions DLJ 99 - Juniata College

  15. Our Simple Area DLJ 99 - Juniata College

  16. Each Cell Flows Into Another • Note that each grid cell flows into another grid cell and so forth. • One could tally or keep track of the total number of grid cells that flow into each “downstream” grid cell. • This is generally known as a flow accumulation data set. DLJ 99 - Juniata College

  17. Our Flow Accumulation DLJ 99 - Juniata College

  18. Let’s Look at an Example DLJ 99 - Juniata College

  19. Add Rivers Juniata College DLJ 99 - Juniata College

  20. Zoom In DLJ 99 - Juniata College

  21. Assign Flow Directions DLJ 99 - Juniata College

  22. Calculate Flow Accumulations DLJ 99 - Juniata College

  23. Overlay Streams DLJ 99 - Juniata College

  24. Let’s Delineate a Watershed Just Below Raystown Lake (dam) DLJ 99 - Juniata College

  25. Delineate Raystown Lake DLJ 99 - Juniata College

  26. Another View DLJ 99 - Juniata College

  27. Isolate Raystown Lake DLJ 99 - Juniata College

  28. Flow Directions in Raystown Watershed DLJ 99 - Juniata College

  29. South Facing Slopes DLJ 99 - Juniata College

  30. Buffer the Streams ~100m DLJ 99 - Juniata College

  31. Find South Faces < 100m from Stream DLJ 99 - Juniata College

  32. DEM DLJ 99 - Juniata College

  33. Flow Direction DLJ 99 - Juniata College

  34. Slope DLJ 99 - Juniata College

  35. Stream Delineation DLJ 99 - Juniata College

  36. K Values K = 1.2 K = 0.48 K = 2.1 DLJ 99 - Juniata College

  37. Velocity V = KS1/2 DLJ 99 - Juniata College

  38. Flow Length DLJ 99 - Juniata College

  39. Advantages of GIS • Time Savings • Replication -Precision not Accuracy!!! • Ancillary Data • Data Reuses DLJ 99 - Juniata College

  40. Lake Superior SWE • U.S. Army Corps of Engineers • Manage Lake Superior • Sault Ste. Marie Locks • Snowfall is major contributor DLJ 99 - Juniata College

  41. DLJ 99 - Juniata College

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