氏名 NGUYEN THI MY QUYNH
学籍番号 201125021
題目：Mapping of Soil Erosion in the Binh Dien Reservoir Watershed using the RUSLE
Model in GIS and Remote Sensing
（GIS とリモートセンシングを RUSLE への適用によるビンディエンダム集水域
の土壌侵食量の地図化）
ABSTRACT
Vietnam is located in the humid tropical zone where water erosion and sedimentation
have become a seriously environmental problem due to human activities such as
deforestation, intensification of agriculture, and urbanization. Hence, an optimal land use
planning that contributes to improvement of vegetation cover is crucial for soil
conservation in high risk areas of water erosion. In the context of reservoir watersheds
where are covered mainly by forestry land, planning of protected areas plays an important
role in reducing soil loss and sedimentation in reservoirs that result in environmental
problem on both on-site and off-site.
The aim of this research is to seek an improvement of current forest land use planning
in Vietnam for soil conservation in watersheds by integrating soil erosion map. The Binh
Dien reservoir watershed which is located in Thua Thien Hue province, centre of Vietnam
was the selected case study of the research.
The Revised Universal Soil Loss Equation was used to generate soil erosion map
because of three reasons. Besides that, satellite images and availably digital data sets were
utilized as input parameters of the model. The computation and generation of soil erosion
map were processed in Geographic Information Systems (GIS) and remote sensing (RS)
interfaces
The study has found three results. Firstly, soil erosion map was simulated after
getting the computation result of 5 factors in the RUSLE model. The result showed that
the watershed comprised 50 % of total area classified in the nil and the slight classes,
15.8 % in moderate level, 22.26 % at high risk, and 12.6 % belonging to severe, very
severe, and catastrophic levels. Secondly, the spatially confusion matrix between soil
erosion risk level and classified map of protection forest land for soil conservation
indicated that currently forest land use planning for watershed protection forest had not
strongly corresponded with potential of soil erosion risk because the current qualitative
criteria for identifying the protected area were not complete in line with soil erosion risk.
By using the classified map of soil erosion risk as the quantitative criterion for high risk
area identification, we pointed out additionally potential areas where belonged to the nil
or the slight level which were able to convert to production lands instead of protected
areas as currently land use planning. Thirdly, it was found that conversion of shrub/grass
land into plantation caused an increase of soil loss due to practice disturbances. Thus, to
reduce soil loss rate on plantation, silvicultural measures which supported for soil
conservation was proposed to apply on where has high risk of erosion. On this
perspective, the classified map of soil erosion risk became a useful tool for plantation
planning, designation and management.
Although there are many social factors which are not involved in the RUSLE model
affect forest land use planning in terms of watershed, this research showed soil erosion
map generated by the RUSLE can make a useful contribution to watershed management
including forest land use planning, designation, and management.
Keywords: soil erosion, RUSLE, C factor, head watershed, forest planning