Development of Potential Floodwater Retention Zones using AHP and GIS: A Case Study in the Chi River Basin, Thailand

要旨

The Chi River always faces floods and water shortage problems in the rainy season and subsequent dry season, respectively. The Royal Thai Government emphasizes on construction of floodwater retention reservoirs to store more water along the Chi River. This water is to be used mainly for agriculture in the subsequent dry season. A methodology was developed to identify potential floodwater retention zones using the Analytical Hierarchical Process and GIS-based data. They were surface water, drainage density, landform, land use, soil drainage, salt crust, geological formation, lineament density, vegetation index, and groundwater yield. The result was the potential water retention zones map, which was categorized as excellent, good, moderate, poor and very poor classes. The map was validated with a field survey of floodwater retention site. The results agreed with the field check. The hydrodynamic model (MIKE11) was employed to simulate diversion of discharges from the Chi River into retention reservoirs. The results of simulation revealed that the proposed reservoir (Kud Dok) could retain floodwater at the maximum storage capacity of 8.13 million m3 for return periods of 3, 5, 8 and 25 years.