Stream Channel Modifications and Reclamation Structures to Enhance Fish Habitat

The process of channel modification has played a major, although not always beneficial, role in the development of this country. Land drainage has been necessary to convert swampland into fertile, productive farmland. Dredging of our stream bottoms has led to the discovery of precious metals and also to the creation of navigable waterways to transport our people and products. As our cities developed, it was often found that the river that provided a ready source for water supply and waste disposal was also likely to periodically carry damaging flood waters. Hence, the need arose to redesign and, in some cases, relocate these streams. Channel realignment has also been necessary in numerous instances to provide suitable bridge crossings and right-of~ways for our highway system. Overgrazing of the riparian communities bordering our rivers and streams has led to possibly more subtle but nonetheless damaging impacts. In total. Arthur D. Little (1973) estimated that by 1972, over 200,000 miles of stream channel had been modified in the United States. Given the sheer magnitude of such river manipulations and an increasing awareness by the public of the environmental ramifications of such acts, it is little wonder that'engineers and biologists find themselves continually debating the pros and cons of channel modification. Whether it is called channelization, improvement, alteration, realignment, or stabilization, there will be definite impacts to the specific stream reach involved as well as possible upstream and downstream effects. Such impacts can be positive or negative depending upon the nature of the modification and the nature of one's interest in the river reach undergoing change. Potentially, the following characteristics of a reach could be altered: