Author(s): Manisha Panthi; Brian Crookston; Michael Phillips

Linked Author(s): Brian Crookston

Keywords: climate change; local scour; floods; dam; non-linear weir; PKW; LW

Abstract: Atmospheric rivers, heat domes, anticyclones, and other climatic patterns are contributing to more frequent, more intense, and longer-duration weather conditions. Recent examples include the Omega Block over central Europe that caused historic flooding in Turkey, Greece and Libya; a generational snowstorm in the western USA ending a multiyear drought; and eight devastating floods on four continents in the first eleven days of September 2023. A changing climate causes significant economic and environmental impacts, disaster displacements, and loss of life. Challenging weather patterns also strain water infrastructure, particularly during periods of extreme floods where the resiliency of current spillways to safely pass excess flows is critical to avoid dam failure. For many projects, a labyrinth or piano key weir as the spillway crest is a viable option to increase discharge capacity for a given upstream water level, yet special consideration must be given regarding scour potential at the terminal structure. This paper presents the potential challenges related to local scour for spillway rehabilitations in the context of climate change. Results include laboratory local scour studies and real-world scenarios complimented with information from case studies and field observations. This paper provides an overview of local scour mechanics, an approach for predicting local scour at the toe of a PK weir for specific unit discharges, effects of gradation on non-cohesive material scour morphology, the potential effects on scour development from a flood hydrograph (vs steady-state laboratory experiments), and the reduction in toe scour due to a horizontal concrete apron.

DOI: https://doi.org/10.3929/ethz-b-000675921

Year: 2024