Basic equations for siltation of riverbeds

Abstract

In alluvial rivers, suspended matter is deposited in the pore space of the riverbed during low and medium discharges, and at high flows the armor layer breaks up and the riverbed is flushed. During this cycle, the hydraulic conductivity decreases with time and then suddenly increases, so one can speak of a characteristic graph of siltation. In this paper, the results of a 3-year investigation at the Laboratory of Hydraulics, Hydrology, and Glaciology of the Federal Institute of Technology in Zurich are summarized. A wealth of long-term tests allowed the derivation of several equations concerning the siltation of riverbeds, including the reduction of the hydraulic conductivity with time, the limit of siltation, the conditions for desiltation, and the consequent increase in hydraulic conductivity. Simultaneously, the influence of the significant variables is shown. This research makes it possible to quantify the siltation process as well as the effect of specific changes in the river regime and the catchment area.