Through the mid 1970's, the southern Appalachian Mountains have been sparsely populated and largely forested. Unprecedented and largely unregulated development over the past 30 years (projected to increase over the next 50 years) is causing the construction of numerous mountain communities and unpaved roads on extremely steep terrain in a region that receives 70 to over 100 inches of rainfall per year. This region is the headwaters for municipal watersheds that serve millions of people in the large population centers surrounding the mountains. To determine the potential impacts of development in this region on source water quality, we have been monitoring stream flow and sediment from small watersheds - each having a predominant land use of forested, agricultural, or residential and commercial development. We use these data to validate and test a GIS based sediment model that is being used extensively for the establishment of sediment TMDLs in this region. We tested model sensitivity to input data quality and resolution. Results of model validation and water quality monitoring will be presented.