Technique For Estimating The Magnitude And Frequency Of Floods In Texas PDF Download

Equations for predicting the magnitude and frequency of floods in the Dallas-Fort Worth metropolitan area were developed from recorded data of streams with drainage areas ranging in size from 1.25 to 66.4 square miles. The U.S. Geological Survey urban rainfall-runoff model was used to generate long-term flood-discharge records for gaged systems in the area. Simulated and recorded annual-peak data were subjected independently to log Pearson Type III frequency analyses. The results were weighted to determine appropriate discharges for 2-, 5-, 10-, 25-, 50-, and 100-year recurrence intervals. These T-year values were then used as the dependent variables in a multiple-regression analysis. The independent variables determined to be statistically significant and retained in the resulting equations were drainage area and an urbanization index that expresses the degree of urban development. Analysis of the results shows that a land-use change from rural to fully urbanized was accompanied by a 180-percent increase in discharge of a flood with a 5-year recurrence interval and about 100-percent increase in discharge of a flood with a 100-year recurrence interval. (Author).