The John Muir Institute for the Environment, at UC Davis, is using Esri ArcInfo and ArcView GIS to develop a predictive model of roadway-generated sediment. This research project, located in the Navarro River watershed, is significant in two respects. One, the Navarro River is identified as a USEPA Total Maximum Daily Load watershed, thus requiring the specific identification and quantification of nonpoint source inputs. Two, the watershed is critical habitat to coho salmon and steelhead, both federally threatened anadromous salmonids. This GIS-based model will help managers, specifically Caltrans, better identify and mitigate water quality problems.