Selecting Site For DAM Construction Using ArcMap (Watershed Analysis)

Often we need to construct sites for storage of water, i.e. DAM and likewise.

ArcMap can provide you with few very easy steps that scientifically selects suitable site.

Image Source: PixaBay

What these steps are? These are just few clicks that can be performed in GIS Software such as ArcMap

Adding Digital Elevation Model
Converting Layer to KML
Flow Direction
Flow Accumulation
Creating a new Shapefile
Snap Pour Point
Watershed Calculation

Software you need for this:

- ArcGIS 10.X

Data Set:

- Any DEM (Digital Elevation Model Data) available online of your area of interest.

Adding DEM

Start ArcMap

Right Click on layers and select Add Data

Browse to folder to Add DEM data set available with name .tif or any other of your AOI.

Change Symbology to your desired style just for understanding purpose

Layer to KML: Just to view your area in real world we convert DEM to KML layer to have a look of study area. To do so use search tab and type Layer to KML as shown in figure

Layer to KML tool

Layer to KML tool Interface

A window as shown appears

Output Scale=0

Output File = Your Desired Folder

Open Google Earth and view KML Layer

Go to File -> Open and view Data

Data will be added to Google Earth screen as shown Closer analysis of area showed me lowest elevation points, your data may have different view and analysis, (see fig below also), assisted by left watershed.

Google Earth DEM Visualization

· Stream to north not included in DEM will also contribute, But these are first assumptions let’s use ArcGIS tools and see what actually is prefer scientifically

DEM Analysis in Google Earth

Flow Direction

Tool flow direction will give you flow directional Raster on basis of which flow accumulation will be predicted.

Go to search tab type “Flow Direction”

A window as shown appears

Specify Input and output

Click Ok

Flow Direction Tool

Flow direction to KML
Using LAYER to KML TOOL IN ARCGIS as in 2^nd step again convert it to KML

Flow Accumulation Determination

Go to search tab type “Flow Accumulation”

A window as shown appears

Specify Input = Flow Direction Output

And output of your choice

Click Ok

Figure (below) explains step visually

Output will be added as shown in figure

Flow Accumulation tool in ArcMap

Change Symbology of Flow accumulation

For Good understanding convert Flow accumulation to KML and observe it in Google Earth

Google Earth Visualization

Mahran point shows greater water accumulation on Google earth, I observed elevation values near maximum accumulation point interesting thing was increase in elevation as we move towards Maro Katha this can be considered as a natural Wall for Dam .Best possible site for water storage as it receives all previous water of maximum accumulated points. See the figure below to have visualization of words

Best Dam selection till now analyses let’s move forward and observe more.

Create New Shapefile

I named it “yourname.shp” and select start editing

Select point features from create features tab (see Fig below)

And mark point we observed earlier

Snap Pour Point

Go to search tab type “Snap Pour Point”

A window as shown appears

Specify Input pour point = shapefile point

Input accumulation raster = Flow accumulation output

And output of your choice

Click OK

Snap pour point

Calculate WaterShed

Output Image

Go to search tab type “watershed”

A window as shown appears

Calculate water shed window appears as shown

Specify inputs and click ok

WaterShed Tool

Watershed to KML conversion

Although this area is on lower elevation but it does not includes Shinkar side to be in water shed

Layer to KML

Raster To Polygon Conversion of Watershed Layer

Copy DEM into Arc Scene for 3-D viewing

Go to properties -> Set base height -> floating on custom Surface and select Base height approximate value

Calculate Area in our case for 1^st snap pour point area is 0.00522.

Let’s make another snap point and calculate its water shed I observed that to be 0.00541

Doing same to third snap point area is 0.00833

Consultation with civil engineering Student finalizes this point.

Google Earth Visualizing

Stream Order

Go to Arc Hydro Tool Box and search Stream Order as shown

Click on Stream Order tool

Specify inputs

Stream Raster

Flow Direction

And your desired method

Click Ok

Stream order Tool

Stream order

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