Journal of the Japan Society of Erosion Control Engineering, Vol.59,No.2,2006
Application of the USLE and sediment delivery models in a mountainous catchment
Ambika DHAKAL@Satoshi TSUCHIYA@Okihiro OHSAKA
Abstract
This research aims to study the sediment delivery estimation models for upland
mountainous catchments, which are subject to soil erosion, and sediment delivery
to downstream areas every year. A method that combines the Universal Soil Loss
Equation (USLE) and sediment delivery ratio (SDR) model and use Geographic Information
System (GIS) techniques to estimate soil loss and sediment delivery at the watershed
scale was applied to Higashi]gouchi catchment, a forested mountainous catchment
located at the upper part of the Ohi River basin. Many landslide sites are present
in the catchment. The USLE was used to estimate mean annual soil loss. Required
GIS data layers for the input included rainfall, soil characteristics, elevation
and land use. The value of the dam sediment for the study area was calculated
from the sediment data deposited in the Ikawa dam. The estimated sediment delivery
for the study area in 1997 varied from 14799 to 25487m3 corresponding to the model
applied, while the value of the dam sediment was obtained as 25008m3 based on
the Ikawa dam sediment. The result obtained from the SDR model developed by Vanoni
showed an encouraging correspondence with the dam sediment. Further study applying
the method for the whole Ikawa dam catchment extending the analysis for several
years will be done to clarify whether the method can be used for catchments of
larger scale and for the long term.
Key words: Sediment delivery, USLE, sediment delivery ratio, dam sediment, GIS
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