Soil erosion risk in the Northeastern Thailand was predicted using the USLE model which the
value of some variable was determined from the available source with the support of the
experiment. Moreover, with the availability of software, LS-factor layer could be established with
satisfactory accuracy. The validation of the model involved the formulation and testing the soil
erosion risk followed by the iteration of the model to the geo-referenced ground information. The
overlay process to create the soil erosion risk was performed on the sub watershed. Attention and
attempts were carefully made on the preparation of the layers. The overall assessment was also
carried out by comparing with the existing maps and ground observation. It has become
increasingly apparent that computer-based GIS provide the mean to the planning process for
conservation. However there still exists errors in the prediction particularly the values for each of
the USLE factors. The potential source of the modeling error is not only the values defined for each
factor but also in the scale and software uses.