Location: Hydraulic Engineering Research2018 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:
An ARS scientist in Stillwater, Oklahoma is making progress on Objective 2: develop engineering guidance to determine hydraulic performance of alternative stepped chute designs. Construction was completed on a three-dimensional model of a converging stepped chute, and testing has commenced. Additionally, stilling basin installation for a two-dimensional stepped chute was completed and testing commenced. Data analysis is underway for both the three-dimensional and two-dimensional stepped chute physical models.
1. Windows Dam Analysis Modules (WinDAM) C adopted by worldwide leaders in dam safety. WinDAM C, a CCE-certified software is a computational tool for evaluating dam breach through overtopping and internal erosion. In 2016, this software was released by NRCS in cooperation with ARS and Kansas State University. This software incorporates algorithms developed by ARS scientists for predicting failure of embankment dams due to overtopping or internal erosion including breach outflow and breach timing. Since its release, the software has been adopted by consulting engineers, academic researchers, and federal agencies (e.g. US Corps of Engineers, US Bureau of Reclamation, NRCS, Tennessee Valley Authority among others). In FY18, no fewer than ten countries across North America, South America, Europe, and Asia requested the software to incorporate into their educational and design analysis toolbox. This technology is assisting dam safety engineers in the prioritization of aging embankment dams and levees for rehabilitation for the purposes of preserving the $2.5 billion annual benefits provided by USDA-assisted dams. This technology helps emergency managers, city planners, and policy makers in making decision on establishing zoning regulations, developing flood inundation maps, and improving emergency action plans. It is anticipated that this technology will be used in the development of flood warning systems.
2. Mini-JET erosion test apparatus adopted to evaluate soil erodibility. The JET erosion test apparatus and methodology was originally developed as a laboratory research tool by an ARS scientist in the 1990s to study the soil erodibility properties of earthen spillways and embankment dams. Since that time, the apparatus has been adapted in to a smaller, more portable unit (e.g. mini JET) for field investigations. Because of its more user-friendly design, the mini-JET apparatus has been more widely adopted throughout academic institutions across the U.S. (e.g. Baylor University, North Carolina State University, Iowa State University, Kansas State University, Oklahoma State University, University of Tennessee among others), Europe, and Asia to evaluate soil erodibility of not only earthen dams and spillways but also levees, edge of agricultural fields, irrigation canals, channels, stream banks, and stream beds. In addition, consulting engineers across Europe (e.g. U.K., Belgium, France among others) and other federal agencies (e.g. US Bureau of Reclamation and US Army Corp of Engineers) have adopted the tool and methodology into their instrumentation portfolio to further examine the erosion resistance of soils.
3. SITES, Water Resources Site Analysis Software only earthen spillway erosion analysis tool today. SITES, Water Resources Site Analysis Software, is a computation tool for evaluating earthen vegetated auxiliary spillway erosion. The software was later adopted and deployed by the US Army Corps of Engineers as Sites Spillway Erosion Analysis (SSEA) tool. While the software development was initiated in collaboration between ARS, NRCS, and Kansas State University more than three decades ago, this technology remains the only computational tool available worldwide for predicting earthen spillway erosion and breach. Federal agencies (e.g. NRCS, US Bureau of Reclamation, US Army Corp of Engineers) and consulting dam safety engineers worldwide have adopted this tool as their tool of choice for evaluating earthen spillway erosion. Academic institutions use it as an educational tool for teaching the next generation of dam engineers. Extreme events like those created by Hurricanes Harvey, Maria, Irma, and Michael among others has generated more requests for this technology transfer and exchange of expertise over the past year.
4. Stepped spillway and associated stilling basin design criteria adopted for rehabilitation of aging embankment dams. An ARS scientist developed standardized step by step, comprehensive, user friendly design guidelines for stepped spillways and associated stilling basins used as an overtopping protection system for aging embankment dams. These design guidelines are known to have extended the planned service life and the annual benefits provided by the USDA-assisted dams in Oklahoma, Kansas, Texas, Pennsylvania, West Virginia, Kentucky, and Georgia. NRCS has adopted this design criteria and working to draft the technology into a chapter of the NRCS National Engineering Handbook. In addition, it has become an industry standard among architectural and engineering consulting firms across the U.S. designing stepped spillways applied to embankment dams. ARS has adopted this design standard for the future rehabilitation of ARS's only owned dam in Woodward, OK.Hunt, S.L., Kadavy, K.C. 2018. USBR Type III and Type IV stilling basin and rock apron associated with stepped chutes. Applied Engineering in Agriculture. 34(2):389-394. https://doi.org/10.13031/aea.12638.
Hunt, S.L., Kadavy, K.C. 2017. Estimated splash and training wall height requirements for stepped chutes applied to embankment dams. American Society of Civil Engineers Journal of Hydraulic Engineering. 143(11): 06017018. https://doi.org/10.1061/(ASCE)HY.1943-7900.0001373.