The Effectiveness of River Bank Normalization on Flood Risk Reduction

Abstract

One popular technique used to reduce flood risk associated witha flood mitigation scheme, is normalization of a river bank. This methodcan be effected done by adjusting the width of the river on the left andright banks, in order to increase channel capacity. The biggest obstaclemost often encountered in adjusting the river banks is insufficient landarea, both on the left and right sides. The capacity of the river channel cantherefore not be optimised, due to this limitation. This study intends toevaluate the effectiveness of river bank normalization to reduce flood riskin the Puna River, Central Sulawesi Province of Indonesia. The capacityevaluation was conducted under two conditions i.e. before and afternormalization of the river bank, using HEC-RAS Hydrodynamic Program, integrated with GIS. The level of effectiveness is measured by acomparison between the capacity of the river channel after banknormalization with the required channel capacity on 100 years returnperiod of discharge for important and high-risk river categories. Simulationresults in both conditions show that the normalization of river banks canincrease channel capacity from 270 m3/s to 470.2 m3/s, where the requiredchannel capacity is 590.71 m3/s. The effectiveness of the banknormalization is 100 %, included in the category of very effective