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─921大地震崩塌地對河川輸砂衝擊之研究
Date Issued
2003
Date
2003
Author(s)
徐美玲
DOI
912116M002027
Abstract
Preliminary research in the previous two
years concluded that 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
channelized debris flow. This study aims to
estimate the topographic change and the
fluvial sediment transport characteristics
induced by the Chi-Chi Earthquake.
The 1998 1: 5000 contour maps was
first digitized and then converted into 20 x 20
meter DEM by Arc/Info software. This DEM
represents the topography before the Chi-Chi
Earthquake. The topography after the
Chi-Chi Earthquake is represented by the
20 x 20 meter DEM produced by the
Ministry of Interior after the event. The
pre-event DEM was subsequently transferred
into the TWD97 projection for consistency,
and compared with the post-event DEM to
estimate the topographic change induced by
the Chi-Chi Earthquake. In the Gun-Chi
watershed, the estimated quantities of erosion
and deposition are about 841,000 cubic
meters and 289,000 cubic meters in
respective, which results in a sediment
transport rate of 552,000 cubic meters for the
watershed.
Hydrological data from three nearby
gauge stations were collected and analyzed.
By fixing the coefficient of the regression
lines, the intercepts derived from data
collected before and after the Chi-Chi
Earthquake were compared. It showed that
the sediment concentration before the
Chi-Chi Earthquake was slightly greater than
that after the earthquake indicating that
similar flow discharge carries more sediment
in the post-event period. However, the
estimated annual sediment transport rates
after the Chi-Chi Earthquake did not exhibit
significant change from pre-earthquake years.
It is thus concluded that fluvial conditions
may be more important in controlling the
total sediment transport.
Subjects
landslides
debris flow
intense rainfall
suspended sediment
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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