Mechanics of Log Movement in Streams: Effects of Propagating and Standing Waves

It is now recognized that large woody debris (LWD) in streams and rivers can provide important benefits to aquatic and riparian ecology and habitat while locally controlling hydraulic grade. Consequently, river engineers are considering the use of LWD as an integral component of stream stabilization and river restoration projects. The complex interaction of multiple logs among themselves and with the stream environs determines in the end the overall behavior of LWD. However, unraveling the dynamics of that interaction must start with a correct specification of the equations of motion governing the movement of individual logs. This paper reports analytical and experimental results from laboratory studies on drag and inertial forces exerted on cylindrical logs by flowing water.