The design of avalanche protection dams. Recent practical and theoretical developments

Abstract

Recent experimental and theoretical studies of the flow of avalanches against obstructions have been used, in combination with traditional design guidelines, to formulate recommendations for the design of dams and other protection measures in the run-out zones of wet- and dry-snow avalanches. These recommendations deal with the design height of dams, geometry and layout of braking mounds and impact forces on walls and other obstacles. In addition, laws and regulations regarding hazard zoning below avalanche protection measures in different European countries are described. The main new features of this procedure to dimension dams are: • The dam design is based on a consistent dynamic description of the interaction of shallow granular flow and an obstruction. • Shock dynamics are used to derive run-up heights on dams, which determine the design dam height under some conditions. • The necessary dam height to prevent supercritical overflow is also used to derive runup heights on dams, which determines the design-dam height under other conditions. • A maximum allowable deflecting angle, derived from shock dynamics, limits the range of possible deflecting angles of deflecting dams. • Momentum loss in the impact with a dam is calculated from the component of the velocity normal to the dam in the same way for both catching and deflecting dams. • A valanche flow along deflecting dams becomes canalised, which may lead to a substantial increase in run-out in the direction of the canalised flow. • A consistent dynamic framework makes it possible to account for the slope of the terrain where a dam is located and a curvature of the dam axis in the dam design.