Rivers in the Oshima Peninsula can be classified into four types: A, B, C and D types. A-type rivers are steep ones less than 10 km in length and flow rapidly into the sea. B-type rivers are relatively steep ones in length from about 10 to 20 km and develop river beaches and terraces. C-type rivers are sluggish ones more than 20 km in length and develop alluvial plains with meanders. D-type rivers are along wetland in various lengths and flow very slowly into the sea. A-type rivers constitute

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... pids, falls and pools, then are recognized as "upstream" type. This type has frequently experienced natural disasters including debris flows, avalanches and bridge washouts. In turn, B-type rivers are recognized as "upstream-to-midstream" type. Upstream zones of this type are similar to those of A type, whereas midstream zones develop meanders, river beaches and terraces. Upstream zones of this type have frequently experienced natural disasters such as debris flows, whereas midstream zones have frequently been suffered by roads destructed, houses destroyed and fields inundated. C-type rivers can be divided into three zones, namely, upstream, midstream and downstream zones. Upstream zones of this type are similar to those of A type. Midstream zones of C type develop meanders, river beaches and terraces, whereas downstream zones develop many paddy fields with banks. Upstream zones of this zone have frequently experienced natural disasters such as debris flows. Midstream zones of this type have frequently experienced natural disasters such as roads destructed. Downstream zones of this type have frequently experienced natural disasters such as homes flooded. D-type rivers have frequently experienced natural disasters including homes flooded and fields flooded.