Spatial and temporal changes in flood hazard potential at coastal lowland area: a case study in the Kujukuri Plain, Japan

The spatial-temporal change in flood hazard potential in the coastal lowland area was analyzed in the Kujukuri Plain, Japan, where widespread occurrence of land subsidence, the expansion of urban area, and the change in land cover have been reported. The data on flood hazard potential factors (river system, elevation, depression area, ratio of impermeable area, detention ponds, and precipitation) at three different periods, i.e., 1970, 2004, and 2013, were integrated by using geographic information system. Main data sources used are airborne laser scanning data, leveling data, Landsat TM data, river watershed maps, and precipitation data from precipitation observation stations and radar precipitation data. The flood hazard assessment maps for each time were obtained by using an algorithm that combines the flood hazard potential factors with weighted linear combinations based on multicriteria decision analysis technique. By comparing each factor layer map and flood hazard condition maps of different periods, it was found that the changes in different factors were quite variable during different periods with different spatial distributions. From year 1970 to year 2004, most of the areas where flood hazard potential was increased were concentrated in the central and northeastern part of the study area. During the period from year 2004 to year 2013, the areas where flood hazard potential was increased moved to the north and east. This study provides a flexible method to study the spatial-temporal variation of the flood hazard and, hence, could help flood management and environment protection in similar coastal lowland areas.