Flood Susceptibility Modeling of Megech River Catchment, Lake Tana Basin, North Western Ethiopia, Using Morphometric Analysis

Abstract

The present study intended to flood susceptibility modeling by using drainage morphometric investigations of the Megech River catchment, Lake Tana Basin, North Western Ethiopia. Drainage morphometric criterion study performs a critical aspect in recognizing the factual aspects of river catchment with concern to floods. In the present study, we depicted the Megech River catchment into four sub-watersheds, followed by clipping off the drainage grid by using ALOS-PALSAR (Advanced Land Observing Satellite-Phased Array-Type L-Band Synthetic Aperture Radar) digital elevation model, toposheets, and Landsat-8 Operational Land Imager coupled with the Geographic Information System (GIS) program. The drainage morphometric parameters, such as basic, linear, areal and relief, were calculated in the current research by using the standard formula. The morphometric parameters, such as bifurcation ratio, drainage density, length of overland flow and drainage frequency, have a direct connection with flood susceptibility. Hence, rank 1 assigned to the highest values of the above-mentioned parameters followed by second-rank to second-highest value and rank third given the lowest value of the above parameters. The morphometric parameters, such as circulatory ratio, form factor, elongation ratio, drainage texture and compactness coefficient, have a reverse relation with flood proneness. Hence, rank 1 assigned to the lowest values of those parameters, followed by rank two to the second-lowest value and rank three given to the highest value of the above parameters. The compound factor is computed by aggregating the assigned ranks of the morphometric drainage parameters mentioned above and then dividing by the number of morphometric criteria used for sub-watersheds prioritization. The results of the present study displayed sub-watershed 3 scored very high prioritization (Ist), including a compound factor value of 1.89, and sub-watershed 2 got the highest compound factor value of 3.11, and it scored the lowest rank (IVth). The found sub-watershed 3 in the current research area was acquired as a high-priority grade one, and it demands urgent flood regulation remedies for competent water budget devising and administration in the Megech catchment area. The current study demonstrates the capability of sub-watershedwise drainage morphometric investigations in the flood susceptibility analysis using toposheets, optical remote sensing data and digital elevation model associated with GIS tools.