This study examines the relationship between land use/land cover (LULC) changes and surface runoff generation empirically to reveal how urbanization has altered the hydrologic characteristics of a watershed. A hydrological model, the Soil and Water Assessment Tool (SWAT), is employed to estimate the watershed runoff generation for two LULC scenarios from 2002 to 2010. The Cypress Creek watershed was chosen for the investigation because of its recent development pressure resulting from the rapid growth of Houston, Texas. This watershed is located within Harris County, 37 km from Houston. Results indicate that the mean annual runoff change was high for most sub-basins that experienced significant urbanization. The correlation coefficients between low, medium, and high intensity developed lands and the amount of surface runoff were significantly positive with values ranging from 0.5 to 0.8, while the correlation coefficient of greenspaces with surface runoff was -0.6. These findings reveal the importance of land use changes and development densities in managing stormwater and suggest local planners and decision makers on where and how to limit the future residential developments in rapidly growing suburbs.