2006 Volume 59 Issue 2 Pages 43-48
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 (LISLE) 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 25487 m3 corresponding to the model applied, while the value of the dam sediment was obtained as 25008 m3 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.