Flood information is reported for 338 miles of the main stem and six tributaries of the Wapsipinicon River. The information will be of use to those concerned with the design of bridges and other structures and the conduct of various operations on the flood plains of the streams. Included in the report are flood-peak records, gaging-station records, frequency curves, and water-surface profiles.
Outstanding floods resulting from extremely heavy rainfall occurred in the upper basin in 1968 and 1969. Those in 1968 produced the highest flood of record at the gaging station at Independence. The flood of 26,800 cfs (cubic feet per second) at this station was the greatest in the period 1933-70. A number of the smaller tributaries experienced floods more than five times the computed 50-year flood.
The flood experience on the main stem downstream from Anamosa has not been outstanding. No flood of record has exceeded the 50-year flood in this reach.
Flood-profile sheets show profiles of actual flood occurrences and computed profiles of the 25- and 50-year floods at most locations. These sheets also contain tabulations of the flood discharges profiled. A low-water profile and tabulated discharge indicate the range in elevation and discharge along the streams.