ABSTRACT
This chapter briefly outlines the process and effects of piping, and then discusses various aspects of sapping as they affect both large and small landforms. Piping was originally, and still is, a civil-engineering term used for the flushing of sediment from within, under or around the fill or footings of a dam by water seepage or flowage. This commonly creates internal pipe-like openings and sometimes results in catastrophic failure of the structure. In this sense, the term encompasses both piping and groundwater sapping as used here. R. J. Small, T. Dunne and others have discussed groundwater flow models to explain the development of hierarchical drainage networks according to subsurface flow lines, but valley-head sapping and extension may also influence surface runoff and creep simply by creating a local low in the topography.
