This document provides instructions for using ArcGIS tools to perform hydrologic modeling and watershed analysis on a digital elevation model of Bangladesh. It describes how to use the Spatial Analyst and Hydrology tools to: 1. Create flow direction, flow accumulation, and sink rasters from the DEM 2. Generate a stream network, stream links, and stream order rasters from the flow accumulation raster 3. Convert the stream links raster to a shapefile and delineate watersheds.

1. GIS in Watershed Analysis
Tutorial

2. How to turn on Hydrologic Modeling
1. First turn on Spatial Analyst

3. Hydrology Tools
Activate ArcToolbox
from window menu
Expand “Hydrology”
from “Spatial Analyst”
Tools

4. Digital Elevation Model
• Add digital elevation model of Bangladesh
• Click on + icon and select dem

5. DEM of Bangladesh
(Resolution 900m)
This DEM will be used
To calculate Flow direction

6. Flow direction using ArcToolbox
• Click flow direction and select dem as input surface raster

7. Flow direction raster

8. Flow accumulation using Arc Toolbox
• Click flow accumulation and select flowdir_bgd91 as input surface
raster

9. Flow accumulation raster

10. Identify sink using Arc Toolbox
• Click on Sink from hydrology
• Select flowdir_bgd91 as input flow direction raster

11. Sink raster
• A total of 4621 sinks found

12. Fill Sink using Arc Toolbox
• Click on Fill from hydrology
• Select dem as input flow direction raster

13. Filled sink DEM

14. Use filled sink DEM
Now create Flow direction raster aging using this filled sink DEM.
Create Flow Accumulation raster using this new Flow direction raster.

15. Flow Direction raster
using filled sink DEM

16. Flow Accumulation raster
using filled sink DEM

17. Stream Network using ArcToolbox
• Select Flow
accumulation as
input conditional
raster
• Set 1 as constant
value
• Expression: Value >
300

18. Stream Network raster

19. Stream network on Flow accumulation raster

20. Stream link using Arc Toolbox
• Select Stream network as input stream raster

21. Stream Link

22. Stream order using Arc Toolbox
• Select streaml_con_1 as input stream raster.
• Stream ordering method is STRAHLER

23. Stream Order raster

24. Steam as Shape object
• The stream link raster file can be converted into line
feature class.
• Streams can be represented as shape file.

25. Stream to Feature using Arc Toolbox
• Select Streaml_con_1 as input stream raster

26. Stream as Shape file

27. Water shed using Arc Toolbox
• Select stream link as input raster

28. Watershed

29. Change symbology of watershed
• Double click and change as Unique values

30. Unique Basins