Drainage areas of Iowa streams

Abstract

The drainage area of a stream at a specified location ordinarily may be defined as that area, measured in a horizontal plane, which is enclosed by a topographic divide such that direct surface runoff from precipitation would drain by gravity into the river basin above the specified point. One of the most important factors in the hydrologic computation for the design of structures on or over watercourses is the drainage area upstream from the point under consideration. Other hydrologic studies such as low-flow, flood-frequency analyses, rainfall-runoff correlations, stream density, and area-distance make use of this factor as a basic premise for computation. In order that the drainage-area information of the interior streams of Iowa be of uniform accuracy and available to all users of these data, this report has been compiled, and the drainage areas of all streams in excess of 5 square mies are listed. For the larger streams, drainage areas have been determined at numerous intermediate points. As a result of this report much basic background material has been compiled that will he useful in future hydrologic studies of drainage basin characteristics. This publication is limited to the presentation of the drainage-area data for the interior streams of the State. The methods of application of these data to the study of streamflow characteristics, and the design of related structures are properly the function of the design engineer and are not discussed herein.