Venting Turbidity Currents in Reservoirs

Abstract

Description Turbidity currents are generally understood to stand for stratified flows in lakes or reservoirs caused by the differences in density of suspended sediment concentrations between the inflowing and the standing water. Turbidity currents occur mainly during floods since high discharges and suspended sediment concentrations are often a consequence. What is significant about turbidity currents is the sudden submersion of the clear stagnant water by the turbid water, the plunge point. Subsequently, the turbidity currents layer at the bottom of a reservoir, continue moving toward the dam within the former streambed, and come to a halt when reaching the dam and transform in a so-called submerged muddy lake. The barrier of the dam causes the suspended material to settle, which is in many cases undesirably. The probability of turbidity current events is a matter of correlation between hydrological and sedimentological predispositions, as well of the topography of a reservoir, e.g., its geometry, which is decisive for the tolerance of turbidity currents; since the reservoir has to be relatively short and straight with a substantial gradient, the valley should be V-shaped with steep slopes with the bottom outlet situated at a low level in the vicinity of the dam. Fundamentally, such turbidity currents could be vented through a reservoir by opening low-lying gates like bottom outlets at precisely adjusted moments. The advantage of venting turbidity currents is in many cases the