Morphometric Analysis of Sub- watersheds in Oguta and Environs, Southeastern Nigeria Using GIS and Remote Sensing Data

Abstract

Morphometric analysis of the sub- watersheds in Oguta area, Southeastern Nigeria using GIS processed Remote Sensing data was carried out with the objectives of evaluating their morphometric characteristics and other landuse/landcover dynamics. The present study involved the measurement of the linear, aerial and relief aspects of the dimensions of the sub-watersheds. Analysis of the landuse classification revealed that Njaba drainage basin is made up of 37.32% farmland and grassland, 27.51% forest, 20.06% bare land, and 5.28% water, while the Orashi drainage basin comprises of 30.23% farmland, 10.35% urban settlement, 20.14% forest land, 15.13% bare land and 24.14% water body. It was also revealed from the study that Njaba drainage basin has a basin length of 21.48km2 while that of Orashi drainage basin was estimated to be 29.59km2. Similarly, whereas the former has an area of 21.48 km2 the latter has an estimated area of about 29.59km2. Further morphometric analysis revealed that the bifurcation ratio of Njaba and Orashi drainage basins were estimated at 1.80 and 3.92 respectively, while their drainage densities were put at about 0.54 and 0.51 respectively. Finally, the basin relief ratios of the basins were estimated at 0.0038 and 0.00367 respectively while their form factor was given as 0.31 and 0.189 respectively. The form factor values estimated from this study revealed that the Njaba drainage basin is circular while Orashi drainage basin revealed an elongated dimension. These morphometric characteristics are key indices that are invaluable in assessing the geo-hydrological behavior of the drainage basins and their vulnerability to flooding.