行政院國家科學委員會專題研究計畫成果報告:地震造成新山崩地質環境特性之研究─(子計畫四)921大地震崩塌地對河川輸砂衝擊之研究
Date Issued
2002
Date
2002
Author(s)
徐美玲
DOI
902116M002023
Abstract
The sediment derived from landslides in
the conglomerate formations in the
Ninety-Nine Peaks area, is transported to the
nearby channels by two major forms of
debris flows. One is the slope-typed debris
flow, the other is the valley-typed debris flow.
This study aims to deduce the geomorphic
thresholds for the two types of debris flows
from data derived from field investigation
and aerial photograph analysis of the Dry
Creek and the Ten-wei-ken Chi watershed.
Study shows that the valley-typed debris
flow always took place on converged convex
slopes. They usually had a bowl-shaped
appearance, with a constriction 4 to 6 meters
wide below the sliding area. The main axis
length, the depth of the slide and the size of
both the sliding area and its watershed for
slope-typed debris flows are all significantly
greater than those for the other slope
movements. Meanwhile, the watershed size
and the total area of landslides inside the
valleys where valley-typed debris flows took
place are significantly larger than those
without such phenomenon. It is discovered
that when the contributing area of a landslide
exceeds 1,000 square meters, and also
exceeds 2 to 6 times of the sliding area,
slope-typed debris flows are very likely to
take place. When a watershed is larger than
15,000 square meters, and the area of the
landslides within them exceeds 20% of the
watershed area, valley-typed debris flows
also tend to take place.
Subjects
Conglomerate formation
landslides
debris flow
geomorphic threshold
Publisher
臺北市：國立臺灣大學地理環境資源學系暨研究所
Type
report
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