For this study, we extracted the frequent inland inundation area in Osaka city using maps of flood damage during 1993–2012. The maps were drawn manually for each city as paper-based flood records. Because of the unfixed patterns and methods of drawing the maps, these maps have not been used for flood damage vulnerability analyses. We have translated these paper-based maps into digitized maps on GIS database, and have extracted the frequent inland inundation area. The result of analysis of the extracted area is the following: Frequent inland inundation area tends to be distributed in "plain" than "depression" areas, and sewer construction is conducted predominantly in “depression” areas. The “plain” and “depression” areas are extracted using the flood inundation model. Furthermore, results clarified that the frequent inland inundation area tends to be distributed to the area 1) with a small slope or low elevation; 2) around the structure which divides the land surface flow and sewer by such as road and rail; and 3) around the school spacing in a single line.

　In recent years, large-scale deforestation has increased in Nan Province, northern Thailand, and the impact on the hydrological environment due to deforestation has become a concern. In this study, historical changes in the rainfall duration curve and flow duration curve (FDC) were examined by statistical analysis using hydrological data for a 42-year period (1974- 2015) obtained from the upper Nan River watershed. Daily rainfall did not show any significant increasing trend over the study period. However, low-flow discharge and drought-flow discharge in the FDC both increased significantly. Especially, the drought-flow discharge, from 86 % to 96 % of the annual time flow exceeded (days 314-351), increased with a significance level of 0.001. According to previous research, natural forest decreased by about 41.5 % (from 856,246 to 500,439 ha) and agricultural land increased by about 51.5 % (from 342,997 to 518,257 ha) in Nan Province over a 17-year period (1995-2012). This largescale land-use change is thought to have influenced the change in the FDC.