Optimal gate operation of a main drainage canal in a flat low-lying agricultural area using a tank model incorporated with a genetic algorithm

Chiyoda basin is located in Saga Prefecture in Kyushu Island, Japan. The total basin area is about 566 ha, which is a typical flat low-lying paddy-cultivated area. The main problem in this basin is the appropriate operation of drainage structures during flood events in order to avoid the local inundation that seriously damages the crop yield. This paper presents a mathematical model of a drainage system in Chiyoda basin for calculating the flood inundation and optimizing the operation of gates in a main drainage canal. The optimization of a gate operation was carried out by a genetic algorithm. The simulation process was executed using the rainfall with the return periods of 20, 50 and 100 years. The simulation results indicated that before the optimization of a gate operation, the inundation concentrates locally at some paddy tanks with a prolonged inundation time. The same situation occurred in river tanks. In the main drainage canal, there are some gates that play an important role in the drainage system. By optimizing the operation of these gates, the above issue can be solved. The result showed that the total inundation time in the paddy tanks decreased and the inundation distributed more equally.