Hydrodynamic modelling of a proposed Lebir and Galas dam for flood hazard analysis

A massive flood event , which hit Kelantan in 2014, has contributed a major destruction particularly at Kuala Krai district. An alternative approach to overcome this flood episode is by constructing dams. In this study, two dams proposed at the upstream of Galas and Lebir river, near Kuala Krai . This paper aim s to assess the implementation of the proposed dams which is a structural approach at the upstream area to reduce flood hazard in Kelantan using a hydrodynamic model. A coupled of 1D and 2D hydrodynamic model have been tested to simulate the occurrence of flood events in Kelantan due to the proposed dams . The Digital Terrain Model (DTM) has been generated by combining the data sources ; i.e. from Airborne LiDAR and SRTM. The design of proposed dams were defined based on 50 years flood characteristics proposed by UPEN and simulated into the DTM with different magnitudes of flood. The flow hydrograph and water level for 25, 100 and 200 - year return period are generated as input data for initial and b oundary conditions. River cross - section s and hydrodynamic roughness value of Kelantan catchment area are also used in the model . The flood that has been observed is focused on Kuala Krai area before and after the construction of the proposed dams. The result s of maximum velocity and water depth from the hydrodynamic modelling results are then generated to produce flood impulse and flood hazard maps . The results obtained from the preliminary study of the hydrodynamic modelling at Kuala Krai after the development of the proposed dams showed that no flood occurred at the downstream based on the streamflow input consideration.