Physical Modelling for Flood Evaluation of Selangor River Under Tidal Influence Mohd Fauzi Mohamad, Mohd Kamarul Huda Samion, and Saiful Bahri Hamzah Abstract - The estimated area exposed to flood disaster in Malaysia is estimated around 29,000 km2 or 9% of the entire country, affecting approximately 15% of the total population. The purpose of this study is to developed a physical model under tidal influence for Selangor River and to assess the floodplain and water level for various flow conditions with and without tidal influence. The model was developed utilising a non distorted scale of 1:100. The test was carried out for various flow with (i) fixed low water, (ii) mean sea and (iii) high water, with and without tidal influence for all cases. The results showed that the water level increases as the the flow increases and causes the flood. Flooding does not occured at downstream under all conditions tested. Keywords – Floodplain, meandering, physical model, river channel, tidal effect. I. BACKGROUND LOOD is one of the disasters in this country. The estimated area exposed to the flood disaster in Malaysia is estimated around 29,000 km 2 or 9% of the entire country which affecting 2.7 million people or approximately 15% of the total population of Malaysia (Hiew, 1996). Flood can be categorized as: • Flash flood (very high intensity rain at very short period) • Monsoon flood (prolong rain during monsoon season) • Coastal flood (Due to High Tide effect) In facing the flood problem in tidal areas, construction of tidal control gates are commonly being used. In London, Thames Barrier which was built in 1982 is one of the approaches in controlling flood due to spring tide. Whilst in Malaysia, the construction of barrage in some of the rivers such as Sg. Muda, Sg. Kerian and Sg. Besut is to control the effect of high tide. However, it is crucial to have a clear understanding of the overall effect of this type of strucutre as a solution to flood problems in order to provide the best solution to the problems along the rivers. Mohd Fauzi Mohamad is with the National Hydraulic Research Institute of Malaysia (NAHRIM) (+603 89476400 ext 6542; fauzi@nahrim.gov.my) Mohd Kamarul Huda Samion is with the National Hydraulic Research Institute of Malaysia (NAHRIM) (kamarul@nahrim.gov.my) Saiful Bahri Hamzah is with the National Hydraulic Research Institute of Malaysia (NAHRIM) (saiful@nahrim.gov.my) Basically flood can occur at any reach of a river due to different factors. In the upstream area it usually caused by the discharge which exceed bankfull flow and that discharge cannot be sustained by river cross section and river bed. Whereas flood occur in estuary area is caused by the tidal influences. However, at the middle stretch of the open channel the occurence of flood is more complex to explain because of the combination of both factors. Presently there are still lack of research on open channel hydraulics which is under the tidal influenced. One of the main reasons to the lack of research in this area is the limited data available such as water level and flow along the river bed. The difficulty to produce rating curve in the tidal influence area also influence the calibration process. Therefore, only one value is normally used in hydraulic analysis, such as highest spring tide which will result in very high water level and is inaccurate. II. OBJECTIVE The objective of the study can be describe as follows: • To develop a physical model under tidal influence for meandering in river channel. • To assess the floodplain and water level for various flow conditions and tidal influence III. SCOPE OF THE STUDY To construct physical model at National Hydraulic Research Institute of Malaysia. This includes choice of materials, physical model scale, evaluating and setting up the instruments. Gathering the available data of Sungai Selangor for the simulation in the experiment. Running the physical experiment covering flow from low to high without tidal influence under low tide, mean sea level and high tide and flows with tidal effect. Fig. 1 shows the Flowchart of the study process F International Conference Data Mining, Civil and Mechanical Engineering (ICDMCME’2014), Feb 4-5, 2014 Bali (Indonesia) 102