LOCATION OF THE DAM ON KOSI RIVER USING GIS TECHNIQUESBy Anil KumarHemant SinghHimanshu kashyap

OBJECTIVE

To develop a viable methodology for producing GIS data model for preliminary location dams, using ArcGIS

INTRODUCTIONThe Kosi is known as the “Sorrow of Bihar”  when it flows from Nepal to India, as it has caused widespread human suffering in the past through flooding and very frequent changes in courseOn August 18, 2008, Kosi breached its eastern afflux bundh at Kusaha in Nepal, The floodwaters engulfed 35 blocks and 993 villages spread over five districts. Nearly 3.3 million people and 3.68 lakh hectares were trapped in floods2.34 lakh houses were destroyed and 527 persons died in the disaster. This was the eighth incident of its kind in the past 45 years

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The Kosi's alluvial fan has fertile soil and abundant groundwater in a part of the world where agricultural land is in great demand.The Kosi has an average water flow (discharge) of 2,166 cubic metres per second (76,500 cu feet/s).During floods, it increases to as much as 18 times the average. The greatest recorded flood was 24,200 m3/s (850,000 cu ft/s) on 24 August 1954.

DATA FROM INTERNET

Designed discharge for dam is not less than 27,014 m3/s (954,000 cu ft/s)(2).Designed height of Dam 269-metreDesigned catchment area around is 6*104 sq.kmDesigned production of electricity through constructing Dam is 3,000 MW

SCALE AND RESOLUTIONSize represented by our SRTM raster DEM is 90 X 90 m

Resolution of Google earth image = 1m (approx)

REQUIRED CONDITION1. (Optimum V/H ratio) Maximum volume discharge corresponding to height of

DAM2. Low drainage density (For reduction of soil erosion)3. Hard rock geology of the site of the dam.3. Higher rainfall.4. The dam-site is in lower part of valley, in order to collect water.5. Less evaporation. (lesser solar radiation)6. The largest catchments area is to collect the largest amount of water.7. Choose a place that we can use the gravity forces to transport water towhere we need (Higher elevation)

DATA REQUIRED1. DEM of the terrain (IIT Delhi website) 2. Thematic map of Fault lines 3. Topographic maps (Survey Department of Nepal)4. Drainage Pattern Shapefile (IIT Delhi website)5. Land use/Land Cover map6. Bio diversity Map7. Rainfall map8. Soil map

INFORMATION TO BE COLLECTED FROM DEM AND SHAPEFILE

1. Drainage layer (line feature)- ID- Length (m)- Structurally control (completely, partially, non)

2. Contour3. Hillshade 4. View shade5. Slope6. Aspect

Above information can be retrieved from 3D Analyst tool Raster Surface required tool

For further information , we go to Spatial analyst tool Hydrology required option In this we have the options for• Basin• Fill• Flow direction• Flow accumulation• Order of stream• Pour point• Watershed• Length of flow

STEPS1. Get the thrust fault line map, geology map, seismic map of area enclosing Kosi river2. Get the google map of the area for getting the coordinates3. Make the DEM of the Kosi river4. Register the maps and georeference them5. Digitize the river6. Digitize the fault lines, agricultural fields, rock geology and prepare the shapefiles7. Provide the appropriate buffer area for the above Shapefile for taking and leaving the obligatory points8. Then using the

Analyst tool Overlay Intersection, Union, etcwe will find out the approximate location of required areaaccording to the required conditions

THIS WILL GIVE AN APPROXIMATE REGION WHICH IS TO BE CONSIDERED FOR BUILDING DAM

OTHER THINGS TO DIGITIZE IN THE THEMATIC MAPS Layer Name Geometry Attribute

Area Boundary Polygon Feature ID+ Area

Grid Line Feature ID + Length(m)

Roads Line Feature ID+ Type

Drainage Line Feature ID + order + length

Buildings Polygon Feature ID + Type of building

Remarkablebuilding). Agriculture

Point Feature ID + Type (Tree, shrubs).

9. Delineate watershed area

10. Using 3D analyst tool Raster surface required options 3D analyst tool TIN surface required optionsSpatial Analyst Tool Hydrology required optionsSpatial Analyst Tool surface required options

STEPS FOR WATERSHED DELINEATION

1. Fill DEM2. Create flow direction3. Create flow accumulation4. Create watershed pour point5. Delineate watershed6. Calculate the catchment area

This gives the span of the catchment area

SELECTING CATCHMENT AREA1. Using the pour points, make watershed

2. Clip different basin rasters and make different layers of all basins

3. Calculate the area and volume corresponding to different heights of dam

4. Compare the V/H ratio of all the basins

The catchment having maximum increase in volume per differential increase in height is selected

RESULTWe are able to find a suitable site for DAM construction on Kosi river NEPALThe coordinates of the proposed DAM are (27°16’10”N,87°12’34”