| Summary: | The northeast monsoon season, which is characterised by significant and protracted rainfalls, frequently sees major floods in Pahang, Malaysia, including the Pekan area. With the gradual effects of urbanisation, farming, and logging in the upstream catchment, as well as the rise in riverbank platform level from development projects, the flood flow is becoming more concentrated in the main Pahang River. Because of this, the flooding is likely to be worse in the area downstream, especially in Pekan Town. This study established a simulation of the 30 ARI flood level by using the XP-SWMM 1/2D hydraulic model for the overall river networks with the proposed flood levees of Parcel 2 and existing Parcel 1 of Pekan. The study was conducted to determine the pumping station capacities and the corresponding maximum water levels within the ponder bund. Topography maps and IFSAR are used as reference maps to construct the river network in the XP-SWMM 1/2D model. Rainfall runoff modelling using HEC-HMS modelling analysis has been carried out in order to derive the discharge at Pekan. Seven (7) different cases were established according to different conditions: Case B1: pumping system at Genuk and South End; Case B2: pumping system at Genuk only; and Cases B3C1 to B3C5: isolation levee, pumping at Genuk and South End with various pumping capacities and an initial pumping water level of 1.8 m, a storage pond (300 m x 1000 m), and water discharged to the South End Sungai Air Tawar outlet. Based on this river hydraulic modelling study, estimations of pumping capacity and pumping operational levels were carried out. The most optimal solution is to pump at Sungai Genuk and South End with an isolation levee. With 28 m3/s and 21 m3/s pumping capacities at Sungai Genuk and South End, respectively, the maximum water levels at both locations recorded are 2.42 m (pumping station N.209) and 2.45 m (pumping station N.178). The peaks between the rainfall events will occur infrequently. As a result, it is critical that the pumping operation continue to continuously lower the flood level to the proposed drawdown level of 1.6 m after the flood level has receded. © 2023 IAHR – International Association for Hydro-Environment Engineering and Research.
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