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The effects of urbanization on flood-frequency relationships in the city of Wichita, south-central Kansas, were determined from a study of five drainage basins with varying degrees of urbanization. A rainfallrunoff model was calibrated for these basins with an average calibrated model error of 27.5 percent. The calibrations were used to synthesize 69 water years of peak-discharge record for each basin, and a log-Pearson Type-Ill flood-frequency analysis was performed on each record. Results of four other methods of determining flood frequencies were evaluated by comparison with modeled results. The four methods used were analysis of a short-term record of observed annual peak discharges, the modified Soil Conservation Service method, the Oklahoma method, and the National method. Flood-frequency estimates from the rainfall-runoff model were considered to be the most reliable for the five basins in this study. Comparison of the model estimates with the estimates made by the other flood-frequency techniques indicated that the National and Oklahoma methods could be used on ungaged basins with comparable results. Evaluation of all methods revealed the necessity of including a basin area-channel length factor for urban basins. An analysis of the effect of increasing imperviousness on peak flows indicated an average factor of 6.3 between the 2-year rural and urbanized flood and an average factor of 2.3 between the 100-year rural and urbanized flood.

Concentrations of dissolved calcium, iron, magnesium, sodium, silica, and strontium in in grids 2, 3, and 4 of the forebay of Lake Powell and outflows (draft tubes