Flood mitigation measures in urban areas of Malaysia using the integrated catchment modelling approach

Abstract

Integrated catchment modelling has been used to provide non-structural measures for the mitigation and management of urban flood prone areas. This paper aims to demonstrate a model-based approach through flood mapping that generates multiple simulation results of flood mitigation alternatives for the Sungai Gombak basin. Hydrological and hydraulic analysis, as well as hydrodynamic modelling were carried out using Infoworks Integrated Catchment Modelling (ICM) to evaluate the changes of flood extent caused by different structural components. Rainfall analyses were carried out through the computation of rainfall-runoff and design storms at various return periods and durations. Historical rainfall and stage data were used in the calibration process before the design storm events were fed into the hydrological model. Simulation of the design floods were run under different return periods, storm durations, and land use conditions. The results show that the existing rivers downstream of Sungai Gombak can only provide a flood protection level of 5 to 20-year Average Recurrence Intervals (ARIs). The main cause of frequent flooding can be attributed to the rapid change in catchment land use as development has far exceeded the Kuala Lumpur Structure Plan 2020, and the lack of compliance to the practices recommended in Manual Saliran Mesra Alam (MSMA). The findings suggest that bridge constriction removal is the key solution and that its combination with other flood mitigation works would significantly reduce the flood levels. In conclusion, the study provides useful results and a technical proposal for the authority, and successfully recommends further improvements in flood mapping practices for future studies.