LOCATION OF THE DAM ON KOSI RIVER USING GIS TECHNIQUES By Anil Kumar Hemant Singh Himanshu kashyap

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

INTRODUCTION The 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 course On 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 floods 2.34 lakh houses were destroyed and 527 persons died in the disaster. This was the eighth incident of its kind in the past 45 years.

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).discharge During floods, it increases to as much as 18 times the average. The greatest recorded flood was 24,200 m 3 /s (850,000 cu ft/s) on 24 August 1954.

DATA FROM INTERNET Designed discharge for dam is not less than 27,014 m 3 /s (954,000 cu ft/s)(2). Designed height of Dam 269-metre Designed catchment area around is 6*10 4 sq.km Designed production of electricity through constructing Dam is 3,000 MW

SCALE AND RESOLUTION Size represented by our SRTM raster DEM is 90 X 90 m Resolution of Google earth image = 1m (approx)

REQUIRED CONDITION 1. (Optimum V/H ratio) Maximum volume discharge corresponding to height of DAM 2. 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 to where we need ( Higher elevation )

DATA REQUIRED 1. 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 map 6. Bio diversity Map 7. Rainfall map 8. Soil map

INFORMATION TO BE COLLECTED FROM DEM AND SHAPEFILE 1. Drainage layer (line feature) - ID - Length (m) - Structurally control (completely, partially, non)

2. Contour 3. Hillshade 4. View shade 5. Slope 6. 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

STEPS 1. Get the thrust fault line map, geology map, seismic map of area enclosing Kosi river 2. Get the google map of the area for getting the coordinates 3. Make the DEM of the Kosi river 4. Register the maps and georeference them 5. Digitize the river 6. Digitize the fault lines, agricultural fields, rock geology and prepare the shapefiles 7. Provide the appropriate buffer area for the above Shapefile for taking and leaving the obligatory points 8. Then using the Analyst tool  Overlay  Intersection, Union, etc we will find out the approximate location of required area according 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 GeometryAttribute Area BoundaryPolygon FeatureID+ Area GridLine FeatureID + Length(m) RoadsLine FeatureID+ Type DrainageLine FeatureID + order + length BuildingsPolygon FeatureID + Type of building Remarkable building). Agriculture Point FeatureID + Type (Tree, shrubs).

9. Delineate watershed area 10. Using 3D analyst tool  Raster surface  required options 3D analyst tool  TIN surface  required options Spatial Analyst Tool  Hydrology  required options Spatial Analyst Tool  surface  required options

STEPS FOR WATERSHED DELINEATION 1. Fill DEM 2. Create flow direction 3. Create flow accumulation 4. Create watershed pour point 5. Delineate watershed 6. Calculate the catchment area This gives the span of the catchment area

SELECTING CATCHMENT AREA 1. 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

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