From the Abstract: "This study provides relationships for estimating the magnitudes of annual flood peaks having selected recurrence intervals ranging from 2 to 100 years on streams in the Houston metropolitan area. Data on the size of the contributing watershed and the percent of impervious surface within the watershed are required for use of the relationships, which were defined by analyses of the flood peaks and watershed characteristics for 26 sites . In the analyses, a 60-year rainfall record was used in a rainfall-runoff model that had been calibrated for each site from a 4 to 10-year period of concurrent rainfall and runoff observations. Flood characteristics for each site were then determined from a frequency analysis of the 60-year synthesized flood record and related by multiple regression to the characteristics of each watershed. The relationships indicate that as urbanization increases the impervious surface from 1 to 35 percent, the magnitude of a 2-year peak is increased by a factor of 9 and the magnitude of a 50-year peak is increased by a factor of 5. Other analyses indicate that urbanization also significantly increases the magnitude of annual runoff."
Geological Survey (U.S.); United States. Department of the Interior