Location: Hydraulic Engineering Research2017 Annual Report
1a. Objectives (from AD-416):
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.
1b. Approach (from AD-416):
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.
3. Progress Report:
Progress was made in Objectives 1 and 2 of this project plan. Specifically for Subobjective 1A, construction began on the convergent and bench flow test facility with the construction on the embankment test sections completed. The water delivery system for the tests are in the planning stages. This research is intended to aid in the enhancement of WinDAM (Windows Dam Analysis Modules) software for predicting embankment failure. The development of the software is being done in collaboration with the Natural Resources Conservation Service (NRCS) and Kansas State University. A WinDAM C training workshop is scheduled in conjunction with the Association of State Dam Safety Officials (ASDSO) Annual Meeting. For Subobjective 2A, a three-dimensional physical model was constructed and testing has commenced to evaluate alternative chute geometry (i.e. 0 to 90°). Preliminary data indicates a simplified momentum control volume analyses relationship may be extended to a steeper chute slope of 2(H):1(V) and convergences up to 30 degrees. Additional data analyses is expected to determine applicability to other chute slopes. Additionally, the large-scale stepped chute facility was modified to evaluate several stilling basin configurations (i.e. Type I, II, III, and IV) for Subojective 2B. Data analyses for these tests are underway.