Chie KUROIWA and Shinya HIRAMATSU
Many hillside landslides and debris flows occurred by typhoon T OSQP in Miyagawa
village ithe present Odai townj on SeptemberQX, QOOS. These caused severe sediment]related
disasters. In this study, several findings on the influence of precipitation,
slope angle and forest practice on hillside landslides caused by typhoon TOSQP
were shown in Miyagawa]dam basin as followsFPjCorrelation between precipitation
and collapsed area ratio was not clear. QjAngle of collapsed slope in deforestation
sites was T|POlower than those of non]forestation and reforestation sites.
RjCollapsed area in deforestation sites occupied TV in total collapsed area.
SjMost of landslides were occurred since PO to QO years after deforestation.
TjMore hillside landslides observed in larger deforestation area. UjA prediction
model of slope stability changes considering forest practice iKuroiwa and Hiramatsu,
QOOSj was applicable to Miyagawa]dam basin. As the result of this simulation,
collapsed area is generally in proportion to collapsing possibility area ratio
index iAPhritjj. VjAngle of collapsed slope and APhritjand collapsed area ratio
showed significant correlation.