City expansion is a major driving force altering local and regional hydrology and increasing nonpoint source (NPS) pollution. To explore these environmental consequences of urbanization, longterm runoff and NPS pollution were assessed in Beijing, P. R. China. The assessment was based on landuse types, soil hydrology, and long term precipitation data. The environmental impact model LTHIA was used. The outcomes indicate that the area likely would be subjected to impacts from urbanization on runoff and some types of NPS pollution. Urban sprawl will increase runoff volume considerably and significantly increase losses of COD and certain heavy metals such as Pb, Zn in runoff. The results of this study have significant implications for urban planning and decision making efforts to protect and remediate water and habitat quality in the Beijing area. The techniques described herein can be used in other areas.