Ch. 17] PRYOKS ISLAND REACH, OHIO RIVER 301 



ing, an operation that has involved during the past 7 years the re- 

 moval of approximately 185,000,000 cubic yards of accumulated sedi- 

 ment each year at an annual cost of almost $50,000,000. In order to 

 reduce the scale of this public loss, the Corps of Engineers is vitally 

 interested in diminishing or preventing the sedimentation, or shoaling, 

 of navigation channels. And to further this objective they have 

 brought to bear on the problem in recent years the coordinated re- 

 sources of the best available in theory, experiment, and practical de- 

 sign. 



Laboratory experiment has contributed materially to the success of 

 the undertaking by providing, with the small-scale hydraulic model, 

 decisive information that cannot be derived either from existing theory 

 or from the precedent of past experience. The work of the Waterways 

 Experiment Station in this particular respect has been devoted mainly 

 to hydraulic-model analysis of specific sedimentation problems, for 

 purposes of devising improvements that might eliminate excessive 

 shoaling in the given problem areas. The urgency that usually attends 

 empirical solution of the individual problem has not permitted pro- 

 tracted research of a fundamental nature; nor can the results of a 

 given study be regarded as having universal application. Neverthe- 

 less, the experimental program over the course of time has resulted in 

 the development of laboratory procedures and techniques that have 

 proved encouragingly successful for the solution of many perplexing 

 types of sedimentation problems in navigation channels. As a co- 

 incidental benefit, the fundamental knowledge of basic processes has 

 been expanded. 



The types of problems are as many and diverse, perhaps, as their 

 geographic locations or the intricacies of their natural causes. Also, 

 because of inherently overlapping features, they cannot sensibly be 

 segregated according to any strict classification founded on either 

 their basic characteristics or the techniques employed for their solu- 

 tions-. It is not within the scope of this chapter, however, to discuss 

 all of them; nor is it intended here to treat the theoretical principles of 

 model analysis. It is intended, rather, to describe briefly certain prob- 

 lems that are typical, and to demonstrate by specific examples the ex- 

 perimental techniques applied to their solution. By inference, the 

 scope of this field of research, and its advantages, can then be defined. 



PRYORS ISLAND REACH, OHIO RIVER 



A problem quite frequently encountered is that 'of shoaling caused 

 by bed-load movement in an open river with relatively stable banks. 



