Real time rainfall and flood hazard modeling in Bangkok city | |
| Author | Ahmad, Aftab |
| Call Number | AIT Thesis no. WM-02-04 |
| Subject(s) | Floods--Thailand--Bangkok Rain and rainfall--Thailand--Bangkok |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | Urban flooding is an inevitable problem in highly urbanized cities of Asia in wet season. Flood events in Bangkok occur from two sources; heavy rainfall and the high water level in the Chao Phraya River. The frequency of flooding from the Chao Phraya River has been minimized by construction of dikes along the river in low elevation areas. However, flooding from heavy rain events occurs on regular basis due to limited capacity of the drainage system in the city and lack of hydrological information. Hydrological information with maximum details and high accuracy plays a vital role in decision making to control the consequences of heavy rain events. The short-term rainfall and flood forecast has high level of quantitative and qualitative accuracy and very useful information for minimizing loss in terms of time and money due to heavy rainfall in the city. The aim of this study was to develop and evaluate procedures to transform rain gauge and radar data into hydrological information including rainfall and flood risk maps, calibrated radar images, and forecast of rainfall and expected flood risk in the city of Bangkok. Point data interpolation techniques named station averaged method, inverse distance weighted (IDW), Theissen Polygon method and Spline interpolator were applied and evaluated for accurate interpolation of rain gauge data to prepare rainfall maps in real time. IDW with its parameters; distance exponent equal to 4 and number of neighboring points equal to 3, was found to be the best rainfall mapping approach using rain gauge data. A procedure was developed for preparation of online flood risk maps based upon the criteria given by BMA on the classification of rainfall intensity for its potential for flooding in Bangkok. A relationship was also derived between rainfall intensity and the duration of floodwater in the streets of Bangkok. The comparison of rainfall amounts on radar images with corresponding rain gauge observation showed that the radar images must be calibrated. The overall average value of adjustment factor is 1.81, which shows that radar is generally underestimating the rainfall. However, the value of adjustment factors highly varies (ranging from 1.07 to 4.32) from location to location therefore use of one average value for the adjustment of entire radar image in not recommended. A rainfall forecast model was developed and tested using radar data. The forecast model provided approximately 80 % accurate results. There is potential of improvement in the forecast algorithm to increase the forecast time from 15 minutes using the radar data. The model forecasts rainfall in the form of a rainfall map, which is similar to the radar image that provides aerial distribution of rainfall, and can be used for hydrological purposes including flood forecast and management of urban drainage system. |
| Year | 2003 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Water Engineering and Management (WM) |
| Chairperson(s) | Mark, Ole |
| Examination Committee(s) | Tripathi, Nitin Kumar ;Sutat Weesakul ;Tawatchai Tingsanchali |
| Scholarship Donor(s) | Japan |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2003 |