Hydroinformatics Support to Flood Forecasting and Integrated Flood Management Model in Sarawak River

In recent years, river floods in Sarawak River seemed to occur more frequently and had been causing more and more economic and social damages. One of the greatest deficiencies of the current flood management system for Sarawak River basin is its inadequate optimization of the existing structural measures. This optimization may be achieved by application of some of the models and the framework developed recently for enhancement of participation of various local stakeholders in flood management. Hydrological simulations had been conducted and carried out using HEC-HMS for Sg. Sarawak catchment. The model was calibrated and validated using years 1976 and 2000 flood events. The rainfall-runoff hydrographs generated from calibration and validation processes showed Nash-Sutcliffe values of 0.78 and 0.71, respectively. The calibrated hydrological model was then used as inflow hydrographs in InfoWorks RS model. Two hydraulic models, namely, Pre-barrage Sarawak River Model and Post-barrage Sarawak River Model were developed, calibrated and validated by modifying Manning’s n values corresponding to field observations. Years 1976 and 2000 flood events were used for calibration and validation purposes, and showed to have an accuracy of approximately 90% for both processes. The hydraulic model was intended to integrate the existing flood mitigation structures available in Sarawak River Basin. Flood Bypass Channel modeling scenario was carried out using the models developed to investigate the performance of the existing flood mitigation measures in Sg. Sarawak basin. The results revealed that the existing structure, Sarawak River barrage was able to trim down the backwater due to King Tide or the flood flow from the upstream. However, the barrage had insignificant on water level during king tide and flood event. The modeled results were used in Logical Framework Analysis to look into the possible alternatives that may help reduce the damage. The outcomes of this study showed that the existing condition could be significantly improved once the Flood Bypass Channel and Early Flood Warning System are constructed. An analytical logical framework for Early Flood Warning System is presented in this paper