Abstract
What is the horseshoe-shaped topographies in Kawashima-cho Hiki-gun seen on Landsat image? That is the origin of this study. This study is a good example that satellite remote sensing technoligy could have a potential to survey the large scale ruins of ancient river channel.
This report describes the formation and valuation of the geographical characteristics in Kawashima-cho Saitama which are investigated by image analysis, surveying the literature, principal component analysis and numerical simulation of overland flood model.
The results of this study are summarized as fol-lows :
1) The horeseshoe-shaped topographies are natural embankment which closely relate to the Arak-awa river channel of ancient times. In the present, these are used for road, field and residential area.
2) Principal component analysis using material datum of rainfall on and affter Meiji period indicate that amount of rainfall in upper stream from Yorii of The Arakawa river control the amount of flood damage in Kawashima-cho. Consequently, a. change of the Arakawa river channel in period Edo guided the amount of rainfall which determined flooded area and brought increasing of flood damage in Kawashima-cho. So it is necessary to give careful consideration to the design of improvement for river channel.
3) The result of numerical simulation of overland flood flow shows the horseshoe-shaped topographies work as embankmet against flood flow and lighten the flood damage. The natural embankmeent in seen on Landsat image defended residential and farm area against the overland flood flow of small scale.
