SOIL CONSERVATION PLANNING AT THE WATERSHED LEVEL USING THE UNIVERSAL SOIL LOSS EQUATION WITH GIS AND MICROCOMPUTER TECHNOLOGIES - A CASE-STUDY

Procedures were designed to integrate databases and geographic information in an effort to characterize the spatial distribution of the risk of soil erosion by water on agricultural land within the Black Brook Watershed of northwestern New Brunswick. The Universal Soil Loss Equation (USLE) was used to calculate predicted annual soil loss rates. Soil survey, land use inventory, property ownership, digital elevation data, and climatic atlases were used as resource data sets to generate USLE factor values. Data sets for the USLE factors, along with associated maps showing geographic distributions, were established on microcomputers and the Computer Aided Resource Information System (CARIS) geographic information system (GIS). Integration of these data sets resulted in a map of polygons with unique combinations of USLE factor values. Manipulation of the individual factor data sets allowed for production of various scenarios of conservation practices. Use of GIS and digital databases allowed for the assimilation of vast amounts of information and extensive data analysis that would not have been feasible manually. Based on USLE generated values of predicted soil loss, the watershed was then classified in terms of soil loss tolerance (T), a value at which soil starts to lose its productivity. Results show that combinations of low cost improvements in soil management could alleviate soil erosion problems on over 75% of the agricultural lands in the watershed area. Further use of less intensive crop rotations would amend the majority (15%) of the remaining high risk erosion areas, leaving less than 3% that require terracing. The remaining 7% consists of land that should not be used for row crops.