Experimental hydrological studies of processes of failure of beaver dams and pond draining

Abstract

Beaver dams on small rivers significantly alter their hydrological regime. Formation of maximum break discharges on small rivers and flooding of areas are one of the detrimental consequences caused by the failure of such dams. Based on our survey of 11 dams and ponds in the Vereshchaginskii district (Perm oblast), as well as on cartographic modeling of 20 ponds, the dependences of the pond basin volume on the length of the pond and the maximum height of the dam have been established, which can be used to estimate the approximate volume of these ponds. When the dam height changes from 0.5 to 3.4 m and its length changes from 5 to 50 m, the volume of the pond basin alters from 0 to 850 m3. According to the results of artificial dam failure, the following aspects have been established: the nature of simulated flood propagation, the dependence of hydrological characteristics on stages; runoff hydrographs and volumes, as well as the nature of the drained pond bed. It has also been found that the development of the closure channel in the body of dams is unlikely to take place and that erosion mainly occurs on riverbank soils. Based on calculations, it has been revealed that the quantities of natural full-scale break discharges are equal to the maximum rain flood discharge with a 10% probability of exceedance. Full-scale break discharges differ from those calculated according to the hydraulics formulas by 10 to 30%. The maximum discharge values during our experiment ranged from 50 to 500 L/s; the amount of time to empty the ponds varied from 100 to 180 min.