"The problem of rock erosion in unlined emergency spillway channels is described in this first-of-a series report. Recent CE and non-CE case histories which illustrate the potentially hazardous impacts of excessive erosion in discharge channels are described as are the various factors controlling erosion and other responses to emergency spillway overflow. Research programs designed to improve geotechnical capabilities with respect to selection of cost-effective preventive and remedial measures in discharge channels where the risk of excessive erosion appears high are also discussed" (abstract, para. 1).