The formation and dynamics of sediment waves

Overspill from submarine channels is known to be re sponsible for the formation and main tenance of sediment waves on backside levee slopes. T h morphology of these sediment waves is controlled by the distribution of channel overspill. There are cu rrently no published measurements of channel oversp ill, o little is known about the velocity or concentration structure. This paper presents the results from a series of ex periments in which saline gravity currents flowed o ver an erodible sediment bed in the base of a fixed form s ubmarine channel model. This resulted in the deposi tion of overbank sediment waves associated with channel ove rspill at the apex of channel bends. Ultrasonic Dop pler velocity profiling was used to quantify the flow fi eld responsible for the deposition of the sediment waves. The results from this study provide detailed insigh ts into the process of sediment wave initiation and lso provide quantified evidence for the structure of th e flow field responsible for the deposition of the sediment waves. The sediment waves were deposited in the lee of a hydraulic jump, where the hydraulic jump was formed as the fluid overspilling the channel model celerated at the break in slope at the base of th e overbank slope. The results of this study suggest that the presence of sediment waves on channel levees ar intrinsic to the process of channel overspill, where the backside levee slope is sufficiently large to induc e a hydraulic jump or where a single flow is large enough to initiate a hydraulic jump within the overspill flow .