Date of Award
Doctor of Philosophy
Civil, Construction, and Environmental Engineering
The degradation of stream channels in western Iowa has resulted in scour and erosion problems at most of the bridge crossings of these streams. As a result, frequent maintenance, extension of spans, and reinforcement of bridge piers have been required. The cost has been a burden to the counties and the state. The critical streams are those which have been straightened in the past for flood control and land reclamation purposes. Willow Creek, the study watershed, is typical of these straightened streams;Grade stabilization structures have been designed to control the degradation at great cost. However, the optimal engineering solution to the problem depends highly on an adequate understanding of the mechanics of erosion and sediment transport, and of the upstream progression of degradation;The ultimate, future equilibrium profile is the fundamental and determinng factor when designing grade stabilization structures for controlling degradation. A channel equilibrium profile model to estimate the final equilibrium profile of Willow Creek, a stream with a drainage area of 130 square miles (337 sq. km) is presented;The computer model components are based on the hydraulic and hydrological characteristics of the stream. The deepening and the widening of the stream cross section were included in the formulation of the model, and these results and the equilibrium profile constitute the computer output;The model was applied to Willow Creek, and the final equilibrium profile of the stream was estimated for three trial "dominant discharge" values and for one value of the critical tractive force. The "dominant discharge" for Willow Creek was determined to be the magnitude of the 5-year frequency flood;The simplicity and flexibility of the methods used make them applicable to other streams in western Iowa. Data requirements for ungaged streams are drainage area and land use characteristics, stream slope, stream bed and channel characteristics and existing profile data.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Massoudi, Heidargholi, "Hydraulics of river bed degradation, Willow Creek, Iowa " (1981). Retrospective Theses and Dissertations. 7447.