Identification of Piping and Sapping Erosion of Streambanks

Abstract : The objective of this study was to investigate the erosion of river- and stream-banks by exfiltrating seepage, referred to as piping and sapping. This mechanism is widespread in occurrence and is a significant factor in bank stability, but it is often overlooked. The mechanism is complex and acts in concert with other bank erosion processes. Operation of those other processes often masks the processes and products of piping/sapping. Failures caused by piping/sapping may occur during periods of stream inactivity long after storm or flood events have ended. The piping/sapping process is described in detail, and the conditions necessary for piping/sapping to occur are discussed. A procedure to determine whether or not piping/sapping is operating at an erosional bank site is presented, along with guidance on filter use to prevent or remediate streambank erosion caused by piping/sapping.