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CIVL 651 - Remote Sensing with Civil Engineering and Environmental Science Applications - Loyola Marymount University

Lab Exercise: Watershed Delineation

Objectives: Delineate watersheds from an elevation data

Task 1 Delineate Area-wide Watersheds

This task shows you the process of delineating area-wide watersheds using an elevation raster as the data source. emidastrm.shp serves as a stream reference.

1. Download the data to your folder Lab7.
2. Start ArcGIS Pro. Create a New Project Lab7 in your folder as Map.
3. In the Catalog pane, right-click Folders, and Add Folder Connection.
4. Click Lab7 folder. Right-click emidalat and emidastrm.shp layers, and Add to Current Map.

Calculate flow direction

1. First you will check to fill sinks if there are any.
2. Click Analysis tab on the ribbon and Click Tools. In Toolboxes, select Spatial Analyst Tools and then Hydrology.
Tip: If Spatial Analysis does not work for licensing issue, click Project tab on the ribbon and click Licensing. On the right-hand-side pane, click configure your licensing options. Then Licensing window pops up. Select Spatial Analyst and click OK.
3. Under Hydrology and click Flow Direction tool. Select emidalat for the input surface raster, enter temp_flow for the output flow direction raster, and click Run.
4. Under Hydrology and click Sink tool. Select temp_flow for the input D8 surface raster, enter
sinks for the output raster, and click Run.
5. Next step fills the sinks in emidalat. Click Fill tool from Hydrology. Select emidalat for the
input surface raster, specify emida_fill for the output surface raster, and click Run.
6. You will use emida_fill for the rest of this task. Click the Flow Direction tool from Hydrology. Select emidalat_fill for the input surface raster and specify flowdirection for the output flow direction raster. Click Run.

Calculate flow accumulation
1. Next you will create a flow accumulation raster. Click the Flow Accumulation tool from Hydrology. Select flowdirection for the input flow direction raster and enter flowaccumu for the output accumulation raster. Click Run.

Create Source for watershed delineation
1. Next you will create a source raster, which will be used as the input layer for watershed delineation. Creating a source raster involves two steps.
2. First select from flowaccumu those cells that have more than 500 cells (threshold) flowing into them. Click the Con tool in Conditional toolset under the Spatial Analyst Tools with the following parameters:
• Input conditional raster: flowaccumu,
• Expression: click New Expression and select VALUE is greater than 500
• Input true raster or constant value: 1
• Output raster: net
3. Second, assign a unique value to each section of net between junctions (intersections). Go back to the Hydrology toolset. Click the Stream Link tool with the following parameters:
• Input stream raster: net
• Input flow direction raster: flowdirection
• Output raster: source

Delineate Watershed

1. Now you have the necessary inputs for watershed delineation. Click the Watershed tool under Hydrology. Select the following parameters:
• Input D8 flow direction raster: flowdirection
• Input raster or feature pour point data: source

• Output raster: watershed
Click Run.

2. Change the symbology of watershed to that of unique values so that you can see individual watersheds.

Stream Order

1. In addition, to represent the order of each of the segments in a water network, click the Stream Order tool under Hydrology. Select the following parameters:
• Input stream raster: source
• Input flow direction raster: flowdirection
• Output raster: StreamOrder
Click Run.

2. Save the project.

Attachment:- Watershed Delineation.rar