In urbanized areas, small streams are often overlooked or forgotten, but these streams can reduce contamination, ease flash flooding, and improve the esthetics and livability of our daily environment. Contaminants, habitat destruction, and streamflow flashiness resulting from urban development disrupt biological communities, particularly sensitive aquatic species. Every stream is connected downstream to larger water bodies, including rivers, reservoirs, and ultimately coastal waters. Inputs of chemical contaminants or sediments at any point along the stream can cause degradation of water quality downstream, harming biological communities and economically valuable resources, such as fisheries and tourism. This web page provides an overview of USGS's research about urban land use and water quality. It includes related research, publications, news, and a collection of data and tools (Introduction).