Fuzzy logic in polder flood control operations in Bangkok

The flood situation in Bangkok and the way in which it has evolved is described in this study. The present approach to flood control involves use of the polder concept. Since excess water in a polder has to be disposed of either through gravity drainage or pumping, the way in which the gates and/or pumps are operated becomes very important. In practice, operators of such facilities tend to be risk averse and favor operating according to fixed rules. Fuzzy logic programming was investigated as a way to improve operations, while not departing too far from the fixed rule operation that operators prefer. Some simple experiments were first done to find the most suitable alternative to present methods of incorporating fuzzy information. A new fuzzy algorithm was proposed and tested. Due to unavailability of actual data, a simple, but reasonably representative flood control situation, typical of those in Bangkok was used. Operating procedures were developed based on synthetic rainfalls and runoffs. Then, fuzzy operating rules were derived, and a fuzzy rule base was set up. Next, simulations were used in which flood hydrographs were generated and the system was “operated” using fuzzy logic programming and the fuzzy rule base which was developed. The results were compared with three other systems: fixed rule system, a time varying rule curve, and “optimal” operation. Besides the main experiments, which involved only pump operations, additional sets of experiments were conducted for the cases with combined pump and gate operations and with tides. Fuzzy logic programming was demonstrated to be a very promising tool for improving flood control operating procedures for polder systems such as those in use in Bangkok. The procedure can be looked upon as an extension of the fixed rule operating procedures presently being used by the operators. Further extensions are possible, including the use of flow forecasts. However, the main purpose of this study was to investigate the feasibility of using fuzzy logic programming to improve on existing operating procedures.Applied Science, Faculty ofCivil Engineering, Department ofGraduat