In the city of Jau - SP, an artificial lake was built in 1995. In 1996, it was filled by sediments removed of a small watershed site in the urban area by erosion in the slopes, occupied with agricultural and urban use. To evaluate and to identify the sediments source areas of the watershed, geographical information system techniques and methods were used.

A digital cartographic database was built at 1:10.000 scale, using topographic charts, soil maps and land use map. The maps were digitized and inputted in the ArcView 1.0 and Idrisi 2.0 GIS, to create a digital terrain model (DTM) and soil/land use raster maps. The DTM was built using the TIN (Triangulated Irregular Network), the most efficient model to design the landforms in digital form.

A cartographic model for erosion prediction was implemented in the GIS to obtain a watershed susceptibility erosion areas map. To improve the visualization of the susceptibility erosion map, it was joined to the watershed landforms and used the 3D Analyst Module of ArcView GIS. Applying that technique, it was possible to create a 3D landscape erosion map, that permits to the user to visualize the entire area in all directions possible.