A Thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 1992

Bangkok, the capital of Thailand, is located in the lower Chao Phraya river delta with flat ground elevation of 0 to 1.5 m MSL. Due to rapid urbanization in Bangkok, the existing drainage systems cannot work effectively. Flooding therefore occurs more frequently and last longer in the city during heavy rains. As the land subsidence and urban development continue, the flooding and flood damage to property would be increased every year if no improvement of existing drainage system was carried out. Therefore, in this study an area of the inner part of Bangkok is selected to evaluate the flood improvement problem. The study area is bounded by Klong Bang Sue in the north, Klong Sam Sen in the south, Klong Prapa (Rama VI Road) in the west and Phahon Yothin Road in the east. It is near to the Victory Monument and the area is about 3.5 km2 {u2022} In this study, the MOUSE software package was applied to calculate the flood discharges in the sewers and flood depths in the study area. The MOUSE model has two computational modules for runoff and for pipe flow. The pipe flow model encompasses a fully dynamic model for accurate simulation of surcharge conditions and backwater effects. The design storm of 2 years and 5 years return periods with duration of 2 hours are used for evaluation of storm sewer system. This design storm are based on the average intensity-duration-frequency (IDF) curves of Bangkok Metropolis station (BFCD, 1984). Six different alternatives for the improvement of the existing storm sewer system are carried out in this study. The hydraulic effectiveness of each improvement alternative is calculated and expressed in terms of flooded area, flooding depth, flooding volume and flooding duration.