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2020 Annual Report
Objectives
Objective 1: Improve the WinDAM model to predict the erosion of complex embankment geometries and composite materials, and the allowable overtopping flows for alternative materials, including articulated concrete blocks or riprap integrated with vegetation.
Subobjective 1A: Quantify the impact of complex vegetated embankment geometries on erosion process during overtopping including: convergence zones at the intersection of the earthen embankment and valley walls and embankment berms and toes.
Subobjective 1B: Quantify the impact of changes in soil materials (specifically zoned vs. homogenous) on erosion processes and rates of earthen embankment erosion and breach.
Objective 2: Develop engineering guidance to determine hydraulic performance of alternative stepped chute designs.
Subobjective 2A: Develop guidelines for alternative step and/or chute geometry for stepped chutes constructed over existing earth dams.
Subobjective 2B: Improve engineering design guidance for stilling basin design for stepped chutes.
Approach
Large-scale physical model testing on intergraded surface protection (i.e. vegetation or vegetation integrated with riprap and/or ACBs) of steep embankment channels coupled with data from vegetated channel databases will be used to develop knowledge on erosion of complex embankment geometries (i.e. berms and convergence zones) and the materials (i.e. vegetation, riprap, and/or ACBs) intergraded within the embankment as surface protection. Large and small-scale models will be used to evaluate and to develop knowledge of fundamental processes and rates of erosion of zoned embankment materials. These tests will provide knowledge to develop key algorithms related to earthen embankment erosion. Large and small-scale physical models will be used to develop knowledge on the affect step and/or chute geometry has on the design of stepped chutes and stilling basins. Data from these physical models will be used to develop new relationships and/or tools or expand the use of existing technology for embankment erosion prediction and spillway and stilling basin design. USDA-ARS HERU scientists will collaborate with other ARS, government, university, international scientists, and consultants to carry-out these objectives. Research results will be integrated into new or existing evaluation tools, software, design criteria, and management practices; thereby, allowing for the continued service and increased benefit of our nation's multi-purpose agricultural infrastructure.
Progress Report
Objective 2: Research continued to enhance the development of engineering guidance on converging (i.e. narrowing of the spillway from the crest to the toe) stepped chutes as well as stilling basins associated with stepped chutes. For Subobjective 2A, data analysis indicates that empirical and theoretical relationships for predicting the centerline flow depth and flow depth along the training walls for stepped chutes are applicable for 2(H):1(V) and 4(H):1(V) chute slopes with converging training walls ranging from 0 to 52 degrees. Additional data from literature is under review to determine the extent of chutes slopes the equations are applicable. Testing of stilling basins associated with converging stepped chutes is on-going. Under Subobjective 2B, testing of various United States Bureau of Reclamation stilling basin types was completed for non-converging stepped chutes. Data analysis shows that the use of energy dissipation features like blocks and end sills dampen wave fluctuations in the stilling basins. Dampening the wave fluctuations lessen the downstream channel erosion.
Research associated with Objectives 1 and 2 is adapting to field scale monitoring and inspecting of dams. Initial stages of a pilot program for dam monitoring and inspection network is in development. This pilot program is proposed to incorporate the monitoring of an ARS-owned dam that will be rehabilitated with a roller compacted concrete stepped spillway in 2021, along with dams in north central and southwest Oklahoma. This research includes the use of unmanned aerial vehicle technology for inspecting dams, spillways, and channel erosion and evaluating sedimentation of reservoirs; sensors for water-level recording, and review of historic and current data (e.g. soil parameters, hydrology, changes in land use, among others) relative to dam design. This research is a collaboration of multiple ARS research units and the USDA-Natural Resources Conservation Service. The data collected from this project will likely allow for the evaluation and enhancement of the software, WinDAM (Windows Dam Analysis Modules) for dam breach prediction that is associated with Objective 1. In addition, the dam monitoring and inspection network can provide real-time data for evaluating the hydraulic performance of structures like stepped spillways and associated stilling basins, cantilever pipe outlets and associated plunge basins, and earthen spillways and information on whether additional physical model research is needed related structures like these.
Accomplishments
