DEM Computation of Flood Catchment Areas: Determining the Run-off and Maximum Discharge Time of Concentration in Uyo Urban

Abstract

Rainfall runoff modelling is a vital and an essential paradigm in flood risk management. This research sought to determine the run-off and maximum discharge time of concentration (TC) in Uyo Urban to help facilitate adequate and proper flood risk and management plan in the area. The topographic map and 3D surface of the catchment area were generated and the rational method employed to determine the time of concentration of runoff as well as the maximum discharge while Hydrology extension in ArcGIS 10.3 was used to model the river basin from DEM and identify locations. Detailed analysis of 39 years (1977-2015) rainfall data was recorded to determine inter-annual variability, monthly distribution pattern, mean total annual rainfall, mean maximum daily rainfall and standardized anomaly index (SAI). The computed discharge was calculated. The results of the analyses indicate a total discharge of 1573.54m3/s and takes approximately 40 minutes of runoff time evident of prolonged rainstorms in areas like IBB Avenue as opposed to the short-lived rainfalls that causes flash floods in areas like Brook Street. This means that it takes a longer time of about 2 km to travel to the analysed site to cause flood. The study recommends the need for creation of more risk awareness and flood warning signs to further educate the people.