Modeling Sediment Concentrations during a Drawdown Reservoir Flush: Simulating the Fall Creek Operations with HEC-RAS
Abstract
PURPOSE: This U.S. Army Corps of Engineers (USACE) Regional Sediment Management Technical Note (RSM-TN) summarizes the history and objectives of the Fall Creek reservoir flushing operations and presents a one-dimensional (1D) morphodynamic model that simulates sediment dynamics during the flush. A USACE Institute for Water Resources (IWR), Hydrologic Engineering Center, River Analysis System (HEC-RAS), model was developed to simulate sediment flushing and was compared to downstream flush concentrations for three separate years (2012, 2013, and 2014). BACKGROUND: Dam construction in the United States peaked approximately 50 years ago (Randle and Bountry 2017) with more than 60% of U.S. dams completed between 1950 and 1979. Therefore, most U.S. dams are approaching or have surpassed their design life. As reservoirs are managed beyond their planning time horizon, sediment deposition can impact project functions and downstream ecology. Other countries are addressing aging infrastructure by experimenting with sustainable reservoir management practices like drawdown flushing (Kondolf et al. 2014; Morris and Fan 1997). However, these management strategies are rare in the United States. Out of more than 450 water storage reservoirs in the USACE portfolio, only at Fall Creek, Oregon, is the reservoir pool drawn down annually to run-of-river conditions, thus flushing sediment from the reservoir. The USACE National Regional Sediment Management (RSM) Program funded a USACE Portland District (NWP) and Hydrologic Engineering Center (HEC) team to develop a sediment model of the Fall Creek drawdown.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 30, 2019
- Accession Number
- AD1079682
Entities
People
- James Crain
- Stanford Gibson
Organizations
- Portland District, U.S. Army Corps of Engineers