Hydrological and Morphometric Characterization of Anambra-Imo River Basin Using Remote Sensing

Environmental problems related to flooding, water management, and landslide often emanate from disruption of river basin within a geographical locality. In this study, the Anambra-Imo river basin which drains the five southeastern states of Nigeria and a part of Kogi State in the northcentral was studied by combining the remote sensing technique and geographic information system (GIS). With the aid of digital elevation model (DEM) of the geographical region, the linear and spatial morphometric attributes of the basins such as drainage density (Dd), drainage texture (Dt), circularity ratio (Rc), elongation ratio (Re), constant of channel maintenance (Cm), form factor (Rf), infiltration number (If), stream frequency (Sf), length of overland flow (Lo), and compactness index (Ci) were obtained. The results of the analysis showed that the basins have a well-developed dendritic and parallel-type drainage pattern with a NE-SW orientation suggesting a relationship between fracture orientation and physiographic features. Anambra Basin is a sixth-order basin having a total of 1462 streams with a length of 13,682.9 km, while the Imo river basin is a fifth-order basin having a total of 208 streams with a total length of 1320.57 km. Morphometric analyses yielded infiltration numbers of 0.3 and 0.11, elongation ratios of 0.35 and 0.29, and form factors of 0.26 and 0.54; compactness indexes of 1.4 and 1.06; lengths of overland flow of 0.46 and 2.18; circularity ratios of 0.49 and 0.84; constants of channel maintenance given of 0.93 and 4.34; relief ratios of 0.61 and 0.35; and ruggedness numbers of 0.19 and 1.5 for Anambra and Imo river basins respectively. These results have thrown light on the underlying factors responsible for flooding and gullying in the study area as a combination of climatic and geological characteristics of the study area.