This investigation was undertaken as a part of the cooperative program with the Iowa Institute of Hydraulic Research, the City of Des Moines, and the U.S. Geological Survey. The purpose of this report is twofold:
1. To present water-surface profiles and rating curves for existing channel conditions in the 4-mile reach of Raccoon River upstream from the mouth, and
2. To show the effect upon water-surface profiles of raising the Fleur Drive roadway to eliminate road overflow.
The Raccoon River., having a drainage area of 3,630 square miles, borders the south edge of the Des Moines downtown business district before flowing into the Des Moines River at mile 201.6. A large residential area and the city airport are separated from downtown Des Moines by the Raccoon River (fig. 1). Five highway bridges and one railroad bridge span the river between the mouth and mile 205.75, the limits of this report (fig. 1). The river is confined to a narrow channel from the mouth to the Chicago, Burlington, and Quincy Railroad bridge (mile 202.6); upstream of this bridge the river is not confined and during high water spreads over a wide flood plain. Fleur Drive, a principal traffic artery to the downtown area, is the only roadway of the five that crosses this wide flood plain. It has been flooded 15 times during the period 1903, 1918-1965.
