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2021 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.
Objective 3. Engage Missouri River Basin stakeholders through our University of Missouri Research and Extension partners to characterize water resource managers’ and producers’ behavior, attitudes, and economic considerations with respect to irrigation water use, conservation, and flood mitigation; and to introduce them to analytical based decision aides for evaluating new technologies, best management practices, and cost-benefit assessment.
Objective 4. Develop holistic stochastic optimization models, risk assessment, and decision support tools to improve sustainable agriculture production water management practices, while enhancing long-term landscape health in temperate environments. These models will focus on water availability, water storage, and flood mitigation with dynamic economic assessments. This objective will be met through a collaborative effort between HERU and our University of Missouri partners.
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
The progress made on Objective 1 included a continuation on the compilation of technical guidance documents, information, and case studies as it relates to the development of the internal erosion component of the Windows Dam Analysis Modules (WinDAM), a cohesive earthen dam erosion prediction model. In an effort to learn and understand the development of dam breach erosion models, on-going testing of multiple dam breach erosion models including WinDAM, Embrea, and Dam/Levee (DL) Breach was conducted. A comparison of model outputs as it pertains to internal erosion was made by scientists in cooperation with international scientists and consultants, other federal agency scientists and engineers, and academicians.
Research associated with Objective 2 commenced on a physical model of a unique stepped spillway planned for the rehabilitation of a dam in Oklahoma. A bridge supported by bridge piers is planned to span over the spillway crest. These bridge piers create impedance in the flow as the water spills over the crest and down the stepped chute. Water surface elevations and velocity profiles along the crest and pier sections were collected. Velocity profiles and flow depth measurements were collected along the stepped chute section. Preliminary examination of the data shows water surface elevations and velocity profiles are influenced by the entrance abutments and the first pier closet to the training wall. The velocity profiles followed boundary layer theory for the stepped chute section downstream of the crest and piers. The crest training walls and the first pier closet to the training wall appear to decrease the velocity along the first couple of steps before trending towards the boundary layer theory profile. The piers reduce the effective width of the crest by the total of the pier widths, but they add very little friction loss due to flow disturbances at the upstream and downstream ends of the piers. The weir discharge coefficient was determined for curved abutments, stepped abutments, straight wall abutments, and straight wall with ninety-degree headwall abutments with and without piers. Round nose piers and square nose piers were evaluated, and the results indicate only minor increases in the discharge coefficient with round nose piers.
A dam inspection application tool was developed for beta testing in support of Objectives 1 and 2 of the project. ARS scientists in collaboration with the ARS Partnership for Data Innovations (PDI) team worked with USDA-Natural Resources Conservation Service engineers and local sponsors of USDA-assisted watershed dams to develop the parameters necessary for inspecting and monitoring dams. Refinement of the tool is expected.
Accomplishments
1. Stilling basin design criteria applicable for stepped spillways adopted as standard. Roller compacted concrete (RCC) stepped spillways and associated stilling basins are commonly used to upgrade aging earthen dams. Traditional stilling basin design criteria was proven applicable as an outlet energy dissipator for RCC spillways. The USDA-Natural Resources Conservation Service (NRCS) is adopting the stepped spillway and associated stilling basin design guidance into their National Engineering Handbook. NRCS expects to apply the RCC spillway and stilling basin design criteria to 1,200 dams across the U.S. The total cost-savings anticipated by NRCS for use of this technology is $600 million to $1.2 billion when compared to other rehabilitation options. Furthermore, NRCS acknowledges this research assists with the preservation of $2.3 billion in annual benefits provided to the American public. Benefits include flood control, rural and municipal water supplies for economic growth, water for crop and livestock production, support for healthy ecosystems, and recreation and tourism. The U.S. Army Corps of Engineers anticipates integrating the RCC spillway stilling basin research results in their revised hydraulic design of reservoir outlet works technical manual (EM 1110-2-1602). These design criteria have become an industry standard among architectural and engineering consulting firms across the U.S.
Review Publications
Hunt, S., Kadavy, K.C. 2021. Inception point for stepped chute designs with multiple sections of different step heights. American Society of Civil Engineers Journal of Hydraulic Engineering. 147(4): 06021001. https://doi.org/10.1061/(ASCE)HY.1943-7900.0001848.
Ali, A.K., Hunt, S.L., Tejral, R.D. 2021. Embankment breach research: Observed internal erosion processes. Transactions of the ASABE. 64(2):745-760. https://doi.org/10.13031/trans.13701.
Hunt, S.L., Temple, D.M., Neilsen, M.L., Abdelfatah, A., Tejral, R.D. 2021. WinDAM C: Analysis tool for predicting breach erosion processes of embankment dams due to overtopping or internal erosion. Applied Engineering in Agriculture. 37(3):523-534. https://doi.org/10.13031/aea.14334.
Hunt, S.L., Kadavy, K.C. 2021. Lessons learned in stepped chute research instrumentation. Applied Engineering in Agriculture. 37(3):513-521. https://doi.org/10.13031/aea.14333.
Hunt, S.L., Kadavy, K.C. 2021. Types I, II, III, and IV stilling basin performance for stepped chutes applied to embankment dams. American Society of Civil Engineers Journal of Hydraulic Engineering. 147(6). Article 06021004. https://doi.org/10.1061/(ASCE)HY.1943-7900.0001877.
