DRAINAGE NETWORK EXTRACTION AND WATERSHED DELINEATION USING REMOTE SENSING AND GEOGRAPHIC INFORMATION SYSTEM OF IMO STATE, NIGERIA.
This study focused on drainage network extraction and watershed delineation using remote sensing and geographic information system Imo state Nigeria and then carried out extraction some of the hydrologic characteristics of the study area. Five major watersheds were delineated which were named WS1, WS2, WS3, WS4, and WS5, with the largest watershed basin having an area of 1744.86km2 to 567.01km2 for the smallest basin. The perimeter of watershed basins varies from one basin to another, where the circumference of the largest watershed basin reaches about 338.54 km, and the smallest basin about 187.53km. The longest flow length of the streams is very important in quantifying the volume of available surface water, the carrying capacity of the stream channels, and the urban floodplain extent as well. Figure 8 and 9 shows the watersheds and their drainage networks which is dendritic type, with the longest flow length ranges from 105.82km in WS1 to the smallest 40.21km in WS5. Analysis of land use and soil characteristics the study area was also done which could be used for watershed management.
Keywords: Watershed; stream network; GIS; remote sensing; DEM; topographic map