Flood Flow Frequency by SCS-TR-20 Computer Program

The U.S. Soil Conservation Service Computer Program for Project Formulation—Hydrology reproduces the highest recorded flood hydrograph and estimates statistically reliable flood flows for the North Branch Kawkawlin River in Michigan. The Kawkawlin River consists of two major tributaries with entirely different watershed characteristics. The input data required for this program were collected from topographic maps and field visits. Log-Pearson Type III analysis of the recorded annual peak flows shows that the results of this model compare very well and appear entirely within the 90% confidence interval. Variability of the skew coefficient affected by a low outlier is shown. Flows at the gaging station are attenuated by a wide flood plain and do not represent flows at other locations. Flooding of the main river is dominated by the south branch due to the high drainage density and short travel distance. Other methods applicable for the region are also used for comparison.