Equations for predicting the magnitude and frequency of floods in the Dallas-Fort Worth metropolitan area were developed from recorded data from 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 record for gaged streams in the area. Simulated and recorded annual-peak data were subjected independently to log Pearson III frequency analyses. The results were weighted to determine appropriate discharges for selected 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 variable 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 is accompanied by a 180% increase in discharge of a flood with a 5-year recurrence interval and about 100% increase in discharge of a flood with a 100-year recurrence interval.
