ABSTRACT
Geographical information system (GIS) has emerged as an efficient tool in delineation of drainage pattern and hydrographic characteristics of a catchment. It is on this note that this study aims at analyzing the morphometric parameters; areal, linear and relief which influence runoff/discharge volumes and time lag of the Ossiomo river catchments. This analysis provides a better understanding of the morphometric characteristics within the catchment and its vulnerability to flood and flood related hazard. The potential hydrographic variables examined include: runoff, peak flow, time to peak, infiltration, and overland flow, nature of the bedrock etc. This study deals mainly with the geometry, more emphasis being placed on the evaluation of morphometric parameters such as stream order (Nu), stream length (Lu), bifurcation ratio (Rb), drainage density (D), stream frequency (Fs), texture ratio (T), elongation ratio (Re), circularity ratio (Rc),and form factor ratio (Rf) etc. Data used include 4 Shuttle Radar Topographic Mission Digital Elevation Models (SRTM DEM) maps with footprints that cover the entire catchment. These morphometric parameters were evaluated using ArcGIS 10.3 platform. Results indicated that the Ossiomo river catchment is a 6th order catchment with dendritic pattern thereby indicating homogeneity in texture and lack of structural control. The Ossiomo river catchment has a basin area 4948.25 km2, basin length 138.69 km, basin perimeter 351.37km, bifurcation ratio 3.304, length of overland flow 1.8km, form factor 0.26, circulatory ratio 0.50, relief ratio 0.90, drainage density 0.28, elongation ratio 0.57, total number of streams 478. An analysis of the linear, areal and relief parameters show that the basin has low flood vulnerability. The outcome of the study is fundamental for prioritizing proactive and sustainable urban floo management, appropriate land use planning and zonation especially along their flood liable areas at the mouth of the catchment and storm water management.
