Author(s): Yuk San Liew; Fang Yenn Teo; Azman Mat Jusoh; Ahmad Sharmy Mohammed Jaafar; Mohd Abdul Nassir Bidin
Linked Author(s): Yuk San Liew
Keywords: 2-D Hydrodynamic Modelling; Erosion and sedimentation; Bed shear stress; Suspended sediment; Flow velocity
Abstract: Sarawak River Basin, Malaysia experiencing floods every year which invented major losses in properties and lives especially to the residents living in the City of Kuching. Due to serious flooding occurrences in Kuching, Sarawak River Regulation Scheme was implemented in 1997 to mitigate fluvial and tidal flooding around the city. In order to further protect the city from flooding, a flood bypass channel and a barrage have been proposed under the mitigation works. This paper aimed to assess on the potential of erosion and sedimentation patterns due to the proposed flood mitigation works, particularly at the areas within the ox-bow lake located next to barrage and bypass entrance. The assessment was conducted by simulating the flow behaviours using a 2-Dimensional (2-D) hydraulic model, which takes into account of the types of sediment, bed shear stresses and flow velocities within the study area. The development of numerical model also required extensive data such as hydrological and hydraulic data, catchment characteristic information on topographica l, contour and landuse in order to ensure the quality result that desired to be achieved. Apart, bed and suspended sediment sampling was carried out to make correlation with the velocity simulated within the oxbow lake. From the sampling analysis, it was found that the clay particles dominating 90% of bed particles. Six simulations were produced with the velocity vector and flood direction maps for the condition before and after the proposed mitigation work for the flows of frequent, 100-year and 10-year ARIs. Based on the finding, the particle sizes of d50, result demonstrates that the existing bed sediment within the lake has high potential to be transported to the inlet of the proposed works for all scenarios. For the suspended sediment, it applies the same principles where the d50 of grain size are relatively much smaller when compared to the d50 of bed grain sizes. Therefore the suspended particles are having relatively high potential to be transported due to its physical and chemical characteristic as mud particles. These findings are valuable for the local implementing agencies to review the design of these flood mitigation works or proposing a set of erosion and sedimentation measures.