IMPACTS OF URBANIZATION ON SURFACE RUNOFF OF THE DARDENNE CREEK WATERSHED, ST. CHARLES COUNTY, MISSOURI

Accurately documenting urban growth and evaluating its hydrological impact are of great interest for urban planning and water/land resource management. St. Charles County, a suburb of St. Louis, Missouri, has undergone significant urban expansion in recent decades. Rapid urban sprawl in the Dardenne Creek watershed within the county has had a profound influence on surface runoff. We examined the patterns of land use/land cover (LULC) change in this watershed using Landsat TM/ETM+ imagery in 1982, 1987, 1991, 1999, and 2003. Calibrated with the observed hydrological data in 2003, a Long-Term Hydrologic Impact Assessment (L-THIA) model was used to evaluate the effect of LULC change on surface runoff. Results indicated a rapid increase of urban areas in the watershed, from 3.4% in 1982 to 27.3% in 2003, dominated by changes in the lower portion of the watershed close to the metropolitan area. Model simulations suggest >70% increase in average direct runoff in the watershed from 1982 to 2003, and the runoff increase is highly correlated with urban expansion. This work helps raise awareness of the scale of hydrologic impacts of urbanization in this watershed, and provides a simple calibrated tool for local planners to assess potential hydrological impacts of future planning and development activities.