Drainage Basin Morphometry and Landforms Characteristic in Talata Mafara, Zamfara State, Nigeria Using Remote Sensing Approach

Resumen

Issue: Landsat MSS image transparency for hydrologic mapping by Procum 2 device manual analysis framework, was used to generate drainage basin morphometry data in Talata Mafara, Zamfara State, Nigeria. Method: The device enlarges and registers image transparency at optional scales to collect primary data while secondary data used consists of pre-existing data online, in textbooks, journals, etc. The mapped details recorded from projected image registered on a topographical base map were mapped and used to define the drainage basins, sub basins and features for morphometric analyses. Findings: Bakolori Dam reservoir was the most prominent change detected with streams/rivers outflow that recorded decrease in the total drainage area from 20, 803.30 km²⁾ (Image-A) to l7, l39.50 km² (Survey map -B). The values of Image-A Stream order indicate 4^th order matured basin and the analysis of bifurcation ratio (Rb) is of low value between 0.14-0.68. This was due to the attribution of less structural disruptions which have not impacted the drainage pattern. Index of drainage Density (IDD) values of 2.50-8.10 (10^-3) in the sub-basins show low basic complexity within the terrain sub-basins, which is an indication of high vulnerability to erosion. Drainage density (Dd) shows low mean values of 0.227, which is an indication of the existence in the sub-basins of high permeable subsurface materials under sparsely covered vegetation with average relief that is prone to high erosion and gives the computative measurement of the topography analysis and high runoff potential. Stream frequency (Fs) shows high figures, 5.8-14.0 (10^-3) in the sub-basin, which is reflective of more captured streams using image. This also shows permeable geology, numerous tributaries and ephemeral streams. Length of over land flow (L) of 1.43-14.29 and T value of 3.26 indicate that the values of T is dependent on the soil texture of porous composition of the basic geology. Form factor (F) shows sub-basins having low F figures of (A) 0.03-0.025 to (B) 0.03-0.025, which is indicative of pervious geology, average relief with few stream flows of lower period and high major flow of higher duration prevails and does not cause elevated peak flows. Circularity ratio (Rc) figures, (A) 0.03-3.14, and (B) 0.78-3.14 approach one (1), which shows that the basin is matured due to their compact and near circular shape. Therefore, it gets confined for even infiltration and it takes considerable time for overflow to reach basin outlet. The elongation ratio (Be) analysis shows that the basin has high Re figures from 153.34-1030.32 with equal high infiltration capability and low runoff. The basin topography of the sub-basins is over 40/m estimates, which indicates high water infiltration and gravity flow with low runoff conditions. Conclusion: The implication of Rc figures approaching one (1) or unity is that, the basin is matured and in state of equilibrium, of compact shape and promotes synchronization of tributary flows. Hence, shorter duration for stream flow to reach the basin outlet. It also promotes high and rather sharp peak flows resulting from elongated basins.