This research will utilize numerical modeling and conduct various experiments to understand flow fields around bedrock blocks in rivers

This $181,194 Cooperative Agreement awarded by the Bureau of Reclamation under the SECURE Water Act - Research Agreements program (CFDA 15.560) will fund research by the Regents of the University of Idaho to investigate the mechanics of bedrock erosion in unlined spillways of dams. The research will utilize numerical modeling and laboratory experiments to study the flow fields around bedrock blocks and the primary erosional mechanism of block plucking, which is critical for improving models of spillway and river bedrock erosion. The goal is to generate better predictions of erosion by plucking to assess risks and plan infrastructure for approximately 150 interagency dams managed by entities like the Bureau of Reclamation, Bureau of Indian Affairs, and National Park Service. This 3-year project will run from March 2024 through March 2027 and involves collaboration with the Bureau of Reclamation's computational fluid dynamics modeling efforts.

Erosion of unlined spillways can pose huge risks for DAM safety, where erosion can propagate upstream and put the reservoir at risk of breach. Current spillway erosion models work relatively well for cohesive rock or soil-covered unlined spillways, but their capabilities break down in scenarios with highly fractured rock where the primary erosional mechanism is by plucking. In contrast, the hurst 1D erosion model (H1DE model) is a one-dimensional numerical model that can incorporate the detailed mechanics of block plucking that will be explored here. Regents of the university of idaho will investigate the mechanics of block plucking using laboratory experiments by varying flow characteristics, block geometry, bed roughness, and fracture conditions. The detailed time varying forces and pressures on blocks due to turbulence will be measured, which is likely a primary cause of block plucking. In collaboration with united states bureau of reclamation (usbr), who will be conducting computational fluid dynamics (CFD) simulations, we will use the experiments and CFD modeling to explore a wide range of block arrangement and flow scenarios. We will use the data to inform models of spillway and bedrock river erosion to potentially generate better predictions of erosion by plucking. A more robust erosion model for unlined spillways could currently be applied to 150 interagency dams (united states bureau of reclamation (usbr), bureau of indian affairs (BIA), national park service (NPS), united states department of agriculture forest service (USFS) and bureau of land management (BLM) to better understand the current erosion risk and to better plan for future infrastructure.