Tentative Design Procedure for Riprap-Lined Channels-Field Evaluation

As a result of the basic study outlined in the previous report (1)*, a field evaluation of riprap-lined channels designed in accordance with the procedures outlined therein was recommended to determine the effectiveness of the procedures at scales considerably larger than any that can be produced in the laboratory. Because drainage channels are constructed as the need arises, and the necessity for a riprap lining depends on the local circumstances, considerable time may elapse before a substantial number of channels is available for examination. In addition, hydrologic events of the magnitude necessary to provide an effective test of the riprap's stability are relative infrequent. These conditions have militated against collection of sufficient data to thoroughly test the procedures developed in the study. Specifically, five channels have been proposed since the completion of the report outlining these design procedures; four of these have been constructed and one is still in the planning stage. Of the four completed projects, two were intended for stream relocations involving relatively large discharges and two are roadside drainage ditches. Some data have been obtained for these four channels, but in only two cases has the discharge been large enough to approach the design discharge and provide a reasonably definitive test. A detailed description of each of these channels and the available data on the results of the discharges which have occurred are given in the appendices.