Thesis (M.Eng.)--Chulalongkorn University, 2009

Flood problem is a chronic problem, which frequently occurs in Hua – Hin Municipality, where is the most famous of seaside tourism of Thailand. Flood problem directly affects the socio – economic and transportation system of this area and it trend to increase the severity if there is no plan to intentionally solve the problem. The main objectives of this research are study of the causes of flood problem, and determine the adequacy of drainage system of the city. The methodology was divided into 2 parts; 1) open - channel or waterway system, and 2) pipe system in downtown. According to the research, there are 10 existing natural canals in this area. In the first part, the total canals were analyzed the efficiency by calculating each canal individually. Then the results were compared to the existing condition of canals. The outcomes of the field survey indicate that all of canals were obstructed by the most of infrastructure of the city which include; 1) irrigation canal, 2) railway, and 3) highway No.4 (Petchkasem Road). The most of intersections - between canals and infrastructures are hydraulic structures which are channel, tunnel, or culvert etc. These hydraulic structures changed the cross – section of canal which was the result of decreasing the efficiency of drainage system extremely. In the conclusion, the effects of infrastructure could be separated into 2 main categories; 1) the effects of open channel or waterway system that there are the obstruction of channel of irrigation canal, the tunnel of railway, and Highway No.4 that are culverts. These infrastructures are the neck bottle of open - channel so that it cannot instantly drain runoff when it was in flood condition. And 2) The expansion of Highway No.4 - between the section 207+600 km to 235+800 to be 6 lanes road from the original 2 lanes road - affects directly to the length of culverts, so, runoff cannot be drained immediately when there is a heavy rainfall or flood condition