A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering.

Thesis (M.Eng.) - Asian Institute of Technology, 2000

above mean sea level. The city always faces the problems of flooding during heavy rainfall. The flooding problem is well known and difficult to solve due to the lack of filed data in an urban catchment. The catchment in Don Muang district drainage area is selected to be the study area. Field experiment was carried out during September to October, 1999. Runoff coefficient of the study area was computed from the field experiment data. It shows to be 0.294-0.471 for developed residential area. Drainage in the study area is under the influence of backwater at Klong Prem Prachakorn. It delays the runoff duration up to 3.5 days for 3.5 hours rainfall duration. The SWMM model was then applied to the study area. The drainage system was schematized into 286 subcatchments, 233 nodes and 288 branches which is quite detail work. The model yields a fairly satisfactory agreement between the simulated and observed water level of a complex drainage system for residential area. From the model application, it was found that main flood problem in the study area is due to low capacity of the storm sewers which is caused by the hydraulic slope and size of the storm sewer.