Progress 01/19/12 to 01/18/17
Outputs
Progress Report Objectives (from AD-416): The long-term objective of this project is to develop stand-alone and integrated tools for engineers to evaluate allowable embankment overtopping; predict dam failure from overtopping and internal erosion for homogeneous and zoned embankments with simple and complex downstream embankment slope geometries; design alternative surface protection methods, including vegetation, riprap, and concrete blocks; and develop generalized design criteria for increased spillway capacity for small dams (i.e., less than 20 m high). Specifically, the objectives of this project are: Objective 1: Enhance the WinDAM model to predict erosion and breach of complex earthen embankment geometries and materials. Subobjective 1A: Quantify the impact of complex embankment geometries on erosion processes 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 on erosion processes and rates of earthen embankment erosion and breach. Objective 2: Develop engineering tools for design of earthen embankment protection alternatives and increasing the discharge capacity of small dams. Subobjective 2A: Develop guidelines for dimensioning stilling basins and downstream channel protection for non-converging RCC stepped spillways constructed over existing earth dams. Subobjective 2B: Develop guidelines for dimensioning stilling basins and downstream channel protection for converging RCC stepped spillways constructed over existing earth dams. Approach (from AD-416): Large-scale physical models will be used to develop knowledge on the protective capability of vegetation and/or riprap on embankment slopes with convergences and berms. Large and small-scale models will be used to develop knowledge of erosion resistance of zoned embankment materials and to develop key relationships related to earthen embankment erosion. Small-scale and large-scale physical models will also be used to develop knowledge on the impact of discharge, energy dissipation, flow depth, velocities, and downstream tailwater depth on stilling basin and downstream channel protection design for stepped spillways. Data and relationships developed from these physical models coupled with in-depth literature review will be used in the development of predictive and design tools for embankment erosion 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. The results from this research will be incorporated into evaluation tools, software, design criteria, and management practices that will allow the continued service and increased benefit of the nation's agricultural flood control infrastructure. ARS scientists in Stillwater, Oklahoma made significant progress on Objective 1: enhance the WinDAM model to predict erosion and breach of complex earthen embankment geometries and materials and Objective 2: develop engineering tools for design of earthen embankment protection alternatives and increasing the discharge capacity of small dams. During the life of the project, ARS in collaboration with the Natural Resources Conservation Service and Kansas State University completed code verification of WinDAM C, which incorporated the internal erosion module in the software. WinDAM C was released as a Certified Computer Examiner (CCE) software by NRCS. Additionally, ARS scientists released a comprehensive set of prediction relationships for design of stepped chute training walls and stilling basins associated with stepped chutes applied to embankment dams.
Impacts
(N/A)
Publications
- Hunt, S.L., Kadavy, K.C., Crookston, B.M. 2017. Discussion of "Simple design criterion for residual energy on embankment dam stepped spillways" by Stefan Felder and Hubert Chanson. Journal of Hydraulic Engineering. 143(5):0717001-1-3.
- Jia, Y., Hunt, S.L. 2016. Development of CCHE2D embankment break model. Transactions of the ASABE. 59(4):805-814.
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Progress 10/01/15 to 09/30/16
Outputs
Progress Report Objectives (from AD-416): The long-term objective of this project is to develop stand-alone and integrated tools for engineers to evaluate allowable embankment overtopping; predict dam failure from overtopping and internal erosion for homogeneous and zoned embankments with simple and complex downstream embankment slope geometries; design alternative surface protection methods, including vegetation, riprap, and concrete blocks; and develop generalized design criteria for increased spillway capacity for small dams (i.e., less than 20 m high). Specifically, the objectives of this project are: Objective 1: Enhance the WinDAM model to predict erosion and breach of complex earthen embankment geometries and materials. Subobjective 1A: Quantify the impact of complex embankment geometries on erosion processes 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 on erosion processes and rates of earthen embankment erosion and breach. Objective 2: Develop engineering tools for design of earthen embankment protection alternatives and increasing the discharge capacity of small dams. Subobjective 2A: Develop guidelines for dimensioning stilling basins and downstream channel protection for non-converging RCC stepped spillways constructed over existing earth dams. Subobjective 2B: Develop guidelines for dimensioning stilling basins and downstream channel protection for converging RCC stepped spillways constructed over existing earth dams. Approach (from AD-416): Large-scale physical models will be used to develop knowledge on the protective capability of vegetation and/or riprap on embankment slopes with convergences and berms. Large and small-scale models will be used to develop knowledge of erosion resistance of zoned embankment materials and to develop key relationships related to earthen embankment erosion. Small-scale and large-scale physical models will also be used to develop knowledge on the impact of discharge, energy dissipation, flow depth, velocities, and downstream tailwater depth on stilling basin and downstream channel protection design for stepped spillways. Data and relationships developed from these physical models coupled with in-depth literature review will be used in the development of predictive and design tools for embankment erosion 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. The results from this research will be incorporated into evaluation tools, software, design criteria, and management practices that will allow the continued service and increased benefit of the nation's agricultural flood control infrastructure. Progress was made in both objectives, which fall under National Program 211, Problem Area 2: Erosion, Sedimentation, and Water Quality Protection. Progress on this project focuses on Problem Area 2.4: Development and testing of cost-effective control measures for agriculture, urban, and turf systems. Under Objective 1, progress was made in the enhancement of the WinDAM (Windows Dam Analysis Modules) software with the incorporation of the internal erosion component of the embankment failure process. Code verification of WinDAM C was completed by ARS and National Resource Conservation Service (NRCS) personnel as well as a host of collaborators. WinDAM C was released as a Certified Computer Examiner (CCE) certified software by NRCS during this reporting period. In regard to Objective 2, scientists completed physical model studies evaluating the hydraulic jump performance of USBR Type III and Type IV stilling basins and the rock stability performance of the downstream rock apron protection for non-converging stepped chutes. Additionally, testing of a three-dimensional physical model of a 2(H):1(V) converging stepped spillway chute was completed. Construction is underway of a three-dimensional physical model of a 4(H):1(V) converging stepped chute. Data from this research will supplement one of the most comprehensive database on non-air entrained and air entrained flows in stepped chutes applied to embankment dams and will extend the applicability of design criteria of converging stepped chutes and associated energy dissipating stilling basins. Data analyses of these tests are underway. Accomplishments 01 Updated Windows Dam Analysis Modules (WinDAM) released. WinDAM, a Certified Computer Examiner (CCE)-certified software, is a computational tool originally developed to evaluate dam breach through overtopping. This software was released by National Resource Conservation Service (NRCS) in cooperation with ARS and Kansas State University. WinDAM C, an enhanced version of the software incorporates algorithms developed by ARS scientists for predicting failure of embankment dams due to internal erosion. Code verification was completed in a collaborative effort by NRCS, ARS, Kansas State University, and host of collaborators. Although further validation of the tool is required for the internal erosion component, WinDAM C has been tested against USDA-ARS physical model study data of embankment dam failures resulting from internal erosion. This technology is anticipated to assist dam safety engineers in the prioritization of aging multi-purpose embankment dams for rehabilitation. 02 Extending applicability of rock apron scour protection downstream of stilling basins associated with stepped chutes applied to embankment dams. A rock apron provides protection against scour downstream of an outlet structure like a stilling basin. The rock apron ensures high velocity, turbulent flow does not undermine the outlet structure or compromise the integrity of the dam or spillway. An ARS researcher in Stillwater, Oklahoma, completed physical model studies on rock aprons associated with USBR Type III and Type IV stilling basins for stepped chutes. Isbash and USBR methods for rock stability predict the minimum rock size required for an USBR Type III stilling basin, while the U.S. Geological Survey (USGS) method predicts a stable yet more conservative rock size in comparison. For the limited tests conducted under normal design conditions, the Isbash and USBR methods indicate suitable rock size for protecting an USBR Type IV stilling basin associated with stepped chutes.
Impacts
(N/A)
Publications
- Daly, E.R., Fox, G.A., Enlow, H.K., Storm, D.E., Hunt, S.L. 2015. Site- scale variability of streambank fluvial erodibility parameters as measured with a jet erosion test. Hydrological Processes. 29(16):5451-5464.
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Progress 10/01/14 to 09/30/15
Outputs
Progress Report Objectives (from AD-416): The long-term objective of this project is to develop stand-alone and integrated tools for engineers to evaluate allowable embankment overtopping; predict dam failure from overtopping and internal erosion for homogeneous and zoned embankments with simple and complex downstream embankment slope geometries; design alternative surface protection methods, including vegetation, riprap, and concrete blocks; and develop generalized design criteria for increased spillway capacity for small dams (i.e., less than 20 m high). Specifically, the objectives of this project are: Objective 1: Enhance the WinDAM model to predict erosion and breach of complex earthen embankment geometries and materials. Subobjective 1A: Quantify the impact of complex embankment geometries on erosion processes 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 on erosion processes and rates of earthen embankment erosion and breach. Objective 2: Develop engineering tools for design of earthen embankment protection alternatives and increasing the discharge capacity of small dams. Subobjective 2A: Develop guidelines for dimensioning stilling basins and downstream channel protection for non-converging RCC stepped spillways constructed over existing earth dams. Subobjective 2B: Develop guidelines for dimensioning stilling basins and downstream channel protection for converging RCC stepped spillways constructed over existing earth dams. Approach (from AD-416): Large-scale physical models will be used to develop knowledge on the protective capability of vegetation and/or riprap on embankment slopes with convergences and berms. Large and small-scale models will be used to develop knowledge of erosion resistance of zoned embankment materials and to develop key relationships related to earthen embankment erosion. Small-scale and large-scale physical models will also be used to develop knowledge on the impact of discharge, energy dissipation, flow depth, velocities, and downstream tailwater depth on stilling basin and downstream channel protection design for stepped spillways. Data and relationships developed from these physical models coupled with in-depth literature review will be used in the development of predictive and design tools for embankment erosion 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. The results from this research will be incorporated into evaluation tools, software, design criteria, and management practices that will allow the continued service and increased benefit of the nation's agricultural flood control infrastructure. An ARS scientist and collaborator in cooperation with Kansas State University and the Natural Resources Conservation Service (NRCS) continues to develop the WinDAM (Windows Dam Analysis Modules) software for predicting earthen embankment erosion failure. WinDAM B is in current use by NRCS as an analysis tool for prioritization of embankment dams for rehabilitation. WinDAM B is for evaluation of embankment failure due to overtopping including evaluation of surface protection (i. e. vegetal or rock lined) and the erosion processes of the underlying surface protection. WinDAM is in further development as WinDAM C to incorporate the internal erosion component of the embankment failure process. Code verification and validation by ARS and NRCS personnel is nearing the end, and WinDAM C is expected to be released in the near future. The development of WinDAM pertains to Objective 1 of this project plan. Generalized design guidelines for stepped chutes is under development by an ARS scientist at Stillwater, Oklahoma. Under Objective 2, generalized relationships for predicting air entrainment inception point, clear-water and aerated flow depths, air concentration, and energy coefficient relationships have be published. Data analysis of expected water splash above the training walls of stepped chutes have been completed. Under sub-objective 2a, physical model studies to evaluate the performance of the stilling basin and the downstream rock apron for non-converging chutes are nearing completion, and data analysis of these tests are underway. Convergence adds complexity to stepped chute design as it creates significant bulked flow depths along the training walls of the structures, and it can significantly impact the design of the stilling basin and downstream rock apron. Under Objective 2, ARS scientists developed generalized theoretical relationships for determining training wall height necessary to contain flow within converging stepped spillways, and these relationship were validated for a 3(H):1(V) chute slope over a range of convergences. Under sub-objective 2b, construction of a 2(H) :1(V) stepped chute has been completed, and testing has commenced. Data analysis from these tests are on-going. Preliminary data from the 2(H) :1(V) stepped chute show similar trends to the data from the 3(H):1(V) stepped chute with regards to flow along the training walls. Results from these tests are expected to show the impact flow convergence has on stilling basin design. Accomplishments 01 Extending applicability of stilling basin design criteria for stepped chutes. A stilling basin is an outlet structure used for energy dissipation and provides protection of the downstream riverbed and banks from erosion. The intent of this outlet structure is to ensure high velocity, turbulent flow does not undermine other hydraulic structures such as a dam or spillway. An ARS researcher in Stillwater, Oklahoma, completed a physical model study on stilling basin design for stepped chutes as the original design criteria was developed for smooth chutes. The applicability for design criteria for the USBR Type III stilling basin was extended to a Froude number of approximately 3.5, which can potentially lead to a cost-savings in stilling basin design. 02 Training wall height to contain flow in stepped chutes. Training walls are used to contain flow in hydraulic structures. USDA-NRCS design criteria indicates that all flood flow should be contained within the spillway. Stepped chutes have the potential to create an increase (i.e. bulked) flow depth due to the air-water interaction of the flow. This increased flow depth can lead to significant splash over the top of the training wall. An ARS researcher in Stillwater, Oklahoma, conducted a physical model study to determine the significance of the increased flow depth and the contributing splash on the training wall height requirements needed to contain the flow within a stepped chute. Findings indicate that the training wall should be approximately 1.4 to 1.85 times the bulked flow depth depending on step height chute.
Impacts
(N/A)
Publications
- Hunt, S.L., Kadavy, K.C., Hanson, G.J. 2014. Simplistic design methods for moderate-sloped stepped chutes. Journal of Hydraulic Engineering. 140(12) :04014062-1-15.
- Hunt, S.L., Kadavy, K.C. 2015. Discussion of "Aeration, flow instabilities, and residual energy on pooled stepped spillways of embankment dams" by Stephen Felder and Hubert Chanson. Journal of Irrigation and Drainage Engineering. 141(2):07014038-1-3.
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Progress 10/01/13 to 09/30/14
Outputs
Progress Report Objectives (from AD-416): The long-term objective of this project is to develop stand-alone and integrated tools for engineers to evaluate allowable embankment overtopping; predict dam failure from overtopping and internal erosion for homogeneous and zoned embankments with simple and complex downstream embankment slope geometries; design alternative surface protection methods, including vegetation, riprap, and concrete blocks; and develop generalized design criteria for increased spillway capacity for small dams (i.e., less than 20 m high). Specifically, the objectives of this project are: Objective 1: Enhance the WinDAM model to predict erosion and breach of complex earthen embankment geometries and materials. Subobjective 1A: Quantify the impact of complex embankment geometries on erosion processes 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 on erosion processes and rates of earthen embankment erosion and breach. Objective 2: Develop engineering tools for design of earthen embankment protection alternatives and increasing the discharge capacity of small dams. Subobjective 2A: Develop guidelines for dimensioning stilling basins and downstream channel protection for non-converging RCC stepped spillways constructed over existing earth dams. Subobjective 2B: Develop guidelines for dimensioning stilling basins and downstream channel protection for converging RCC stepped spillways constructed over existing earth dams. Approach (from AD-416): Large-scale physical models will be used to develop knowledge on the protective capability of vegetation and/or riprap on embankment slopes with convergences and berms. Large and small-scale models will be used to develop knowledge of erosion resistance of zoned embankment materials and to develop key relationships related to earthen embankment erosion. Small-scale and large-scale physical models will also be used to develop knowledge on the impact of discharge, energy dissipation, flow depth, velocities, and downstream tailwater depth on stilling basin and downstream channel protection design for stepped spillways. Data and relationships developed from these physical models coupled with in-depth literature review will be used in the development of predictive and design tools for embankment erosion 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. The results from this research will be incorporated into evaluation tools, software, design criteria, and management practices that will allow the continued service and increased benefit of the nation's agricultural flood control infrastructure. The WinDAM (Windows Dam Analysis Modules) software for predicting earthen embankment erosion failure is under development by an ARS scientists and collaborators in cooperation with Kansas State University and the Natural Resources Conservation Service (NRCS). WinDAM B was released by NRCS for evaluation of embankment failure due to overtopping including evaluation of surface protection (i.e., vegetal or rock-lined) and the erosion processes of the underlying surface protection. WinDAM C is an updated version of WinDAM B that incorporates the internal erosion component of the embankment failure process. Code verification and validation is being conducted by ARS and NRCS personnel. ARS scientists at Stillwater, Oklahoma, have for several years conducted research to develop design criteria for the cost-effective application of roller compacted concrete (RCC) stepped spillways used for increased spillway capacity and to provide overtopping protection of embankment dams. Physical model studies of a 2(H):1(V), 3(H):1(V), and 4(H):1(V) stepped chute tested over a broad range of discharges and step heights have been completed. Generalized air entrainment surface inception point, clear-water and aerated flow depths, air concentration, and energy coefficient relationships have been optimized from the data and compared to data available from literature. Additional testing of the stepped chute under high air entrained flow conditions was completed to evaluate the water splash expected from these structures and the effect the splash has on the design of the training walls. Analysis of the data is on- going. Further physical model studies are underway to evaluate the performance of the stilling basin for stepped chutes. Although convergence adds an element of complexity in stepped chute design, some stepped chute designs are anticipated to include convergence due to topographical and geological formations as well as land right constraints. ARS scientists developed generalized theoretical relationships for determining training wall height necessary to contain flow within converging stepped spillways. The relationships were validated for a 3(H):1(V) chute slope over a range of convergences. Construction of a converging 2(H):1(V) stepped spillway is nearing completion, and initial testing will soon commence. The expected outcome of this research is to further validate the relationships developed for training wall design as well as to determine the impact flow convergence has on stilling basin design. Accomplishments 01 Code verification and validation of WinDAM C. Dams provide many benefits, including flood protection, irrigation water for agricultural land, recreation, municipal and rural water supplies, and wildlife habitat among others. Although dams have excellent safety records, on occasion dams do fail, placing life and property at risk downstream. ARS scientists at Stillwater, Oklahoma, cooperated with Kansas State University and the Natural Resources Conservation Service (NRCS) for the continuous development of the WinDAM (Windows Dam Analysis Modules) software for prediction of earthen embankment erosion and failure. WinDAM C, a pre-alpha version of WinDAM, allows for the evaluation of internal erosion processes of embankment dams in addition to the evaluation of embankment dam overtopping. Case histories and results from physical laboratory modeling provide test sets for on-going code verification and validation of WinDAM C. Advancements in prediction tools and increased knowledge of embankment breach erosion and failure processes due to overtopping and internal erosion can lead to improvements in 1) risk assessments, 2) emergency action plans, 3) prioritization of dam rehabilitation projects, 4) inundation maps, 5) flood warning systems, and 6) flood zoning. 02 Developing design guidelines for roller compacted concrete (RCC) spillways and associated energy dissipator basins. Aging embankment dams are often faced with hazard creep, a change from low hazard to significant or high hazard classification due to changing demographics and increased infrastructure in the vicinity of the dam. Hazard creep can lead to inadequate spillway capacity, a common deficiency in dams that can lead to increased flooding downstream of these embankment dams. The Natural Resources Conservation Service (NRCS) anticipates 1100 embankment dams to utilize RCC spillway technology. ARS researchers at Stillwater, Oklahoma, are developing generalized design criteria for RCC stepped spillways used for overtopping protection and increase spillway capacity. Enhanced and quantifiable design relationships (i.e. , air entrainment surface inception point, clear-water and aerated flow depths, air concentration, and energy coefficient) for stepped spillways have been developed and validated with data obtained from literature. Additionally, a relationship to account for the expected splash created in the aerate flow region is anticipated. Stilling basin design for stepped chutes are under further testing to determine the applicability of traditional stilling basin design procedures or to determine whether new design criteria is required. These relationships provide the necessary design tools for determining training wall height and stilling basin requirements for stepped spillways. Increased knowledge and improved prediction relationships of stepped spillway design have great potential to extend the design life of thousands of embankment dams worldwide.
Impacts
(N/A)
Publications
- Hunt, S.L., Kadavy, K.C., Hanson, G.J. 2013. New flow depth relationships for embankment dam stepped spillway design. Dam Engineering. XXIV(1):53-70.
- Fell, R., Hanson, G.J., Herrier, G., Marot, D., Wahl, T. 2013. Relationship between the erosion properties of soils and other parameters. In: Bonelli, S., editor. Erosion in Geomechanics Applied to Dams and Levees, Chapter 5. John Wiley and Sons, Inc., and ISTE Ltd. p.343-381.
- Morris, M.W., Hassan, M.A., Wahl, T.L., Tejral, R.D., Hanson, G.J., Temple, D.M. 2012. Evaluation and development of physically-based embankment breach models. In: Klijn, F., and Schweckendiek, T., editors. Comprehensive Flood Risk Management: Research for Policy and Practice, Boca Raton, Florida: CRC Press. p. 90-92.
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Progress 10/01/12 to 09/30/13
Outputs
Progress Report Objectives (from AD-416): The long-term objective of this project is to develop stand-alone and integrated tools for engineers to evaluate allowable embankment overtopping; predict dam failure from overtopping and internal erosion for homogeneous and zoned embankments with simple and complex downstream embankment slope geometries; design alternative surface protection methods, including vegetation, riprap, and concrete blocks; and develop generalized design criteria for increased spillway capacity for small dams (i.e., less than 20 m high). Specifically, the objectives of this project are: Objective 1: Enhance the WinDAM model to predict erosion and breach of complex earthen embankment geometries and materials. Subobjective 1A: Quantify the impact of complex embankment geometries on erosion processes 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 on erosion processes and rates of earthen embankment erosion and breach. Objective 2: Develop engineering tools for design of earthen embankment protection alternatives and increasing the discharge capacity of small dams. Subobjective 2A: Develop guidelines for dimensioning stilling basins and downstream channel protection for non-converging RCC stepped spillways constructed over existing earth dams. Subobjective 2B: Develop guidelines for dimensioning stilling basins and downstream channel protection for converging RCC stepped spillways constructed over existing earth dams. Approach (from AD-416): Large-scale physical models will be used to develop knowledge on the protective capability of vegetation and/or riprap on embankment slopes with convergences and berms. Large and small-scale models will be used to develop knowledge of erosion resistance of zoned embankment materials and to develop key relationships related to earthen embankment erosion. Small-scale and large-scale physical models will also be used to develop knowledge on the impact of discharge, energy dissipation, flow depth, velocities, and downstream tailwater depth on stilling basin and downstream channel protection design for stepped spillways. Data and relationships developed from these physical models coupled with in-depth literature review will be used in the development of predictive and design tools for embankment erosion 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. The results from this research will be incorporated into evaluation tools, software, design criteria, and management practices that will allow the continued service and increased benefit of the nation's agricultural flood control infrastructure. ARS researchers at Stillwater, Oklahoma, along with cooperators from Kansas State University and the Natural Resources Conservation Service (NRCS) have for several years been developing the WinDAM (Windows Dam Analysis Modules) software for prediction of earthen embankment erosion failure. WinDAM is under continuous expansion and development as additional knowledge is gained from embankment breach erosion and failure process due to overtopping and internal erosion. WinDAM was updated to include algorithms to evaluate dam breach through internal erosion. WinDAM C, the pre-alpha version for internal erosion, is currently being tested, and a case history has been developed for evaluation. The next expansion of WinDAM is to include algorithms for predicting erosion processes for surface areas under extreme hydraulic attack (i.e., convergence zones and embankment toes and berms) during an overtopping event. Construction of outdoor physical models for conducting convergent and bench flow tests have been completed with one year of growing season on the Bermuda grass completed. The water delivery system to the convergent and bench flow testing facility is currently under construction. The outdoor facilities for conducting zoned embankment tests is ready for construction of the first test section. ARS scientists at Stillwater, Oklahoma, have for several years worked to develop design criteria for the cost-effective application of roller compacted concrete (RCC) stepped spillways used to increase spillway capacity and to provide overtopping protection of embankment dams. Data collection from a 2(H):1(V) stepped spillway has been completed and coupled with the data collected from 3(H):1(V) and 4(H):1(V) stepped spillways, making it one of the largest databases for stepped spillways. Data analysis and development of generalized air entrainment inception point, flow depth, air concentration, and energy dissipation relationships have been substantially met for 4(H):1(V), 3(H):1(V), and 2(H):1(V) stepped spillways. Limited data from literature is providing independent validation of these broader use of these relationships. Flow depth, velocities, and energy dissipation provide parameters for the design of stilling basins and riprap size for downstream channel protection for smooth chute spillways. Additional testing to evaluate the stilling basin and riprap size for downstream channel protection will allow verification of these relationships in the design for stepped spillways. Accomplishments 01 Incorporating algorithms into WinDAM to evaluate internal erosion of embankment dams. Dams have excellent safety records, but on occasion, dams do fail, placing life and property at risk downstream. ARS scientists at Stillwater, Oklahoma, cooperate with Kansas State University and the Natural Resources Conservation Service (NRCS) in the development of the WinDAM (Windows Dam Analysis Modules) software for prediction of earthen embankment erosion and failure. Algorithms were incorporated into WinDAM for the evaluation of internal erosion in embankment dams, and this pre-alpha version of WinDAM, known as WinDAM C, is being tested. Further enhancement of WinDAM is expected to evaluate dams prone to extreme hydraulic attack and erosion along convergence zones and embankment berms and toes during an overtopping event. Construction of physical models are nearing completion to evaluate these erosion prone areas. Advancements in prediction tools and increased knowledge of embankment breach erosion and failure processes due to overtopping and internal erosion can lead to improvements in 1) risk assessments, 2) ranking systems for prioritization of rehabilitation, 3) emergency action plans, 4) inundation maps, 5) flood warning systems, and 6) flood zoning. 02 Developing design guidelines for roller compacted concrete (RCC) spillways. Inadequate spillway capacity that can lead to increased flooding is a common deficiency for aging embankment dams. ARS researchers at Stillwater, Oklahoma, are developing generalized design criteria for RCC stepped spillways used for overtopping protection and increase spillway capacity. Enhanced and quantifiable design relationships (i.e., air entrainment inception point, flow depth, air concentrations, and energy dissipation) for stepped spillways have been developed. These relationships provide the necessary design tools for determining training wall height and stilling basin size for stepped spillways. An estimated 1100 embankment dams administered through the Natural Resources Conservation Service (NRCS) are expected to utilize this technology. Increased knowledge and improved prediction relationships of air entrainment properties within stepped spillways have great potential to extend the design life of thousands of embankments dams worldwide.
Impacts
(N/A)
Publications
- Hunt, S.L., Kadavy, K.C. 2012. Closure to "Inception point relationship for flat-sloped stepped spillways" by Sherry L. Hunt and Kem C. Kadavy. Journal of Hydraulic Engineering. 138(11):1004-1005.
- Hunt, S.L., Kadavy, K.C. 2013. Inception point for embankment dam stepped spillways. Journal of Hydraulic Engineering. 139(1):60-64.
- Al-Madhhachi, A., Hanson, G.J., Fox, G.A., Tyagi, A.K., Bulut, R. 2013. Deriving parameters of a fundamental detachment model for cohesive soils from flume and jet erosion tests. Transactions of the ASABE. 56(2):489-504.
- Al-Madhhachi, A.T., Hanson, G.J., Fox, G.A., Tyagi, A.K., Bulut, R. 2013. Measuring soil erodibility using a laboratory "mini" JET. Transactions of the ASABE. 56(3):901-910.
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Progress 10/01/11 to 09/30/12
Outputs
Progress Report Objectives (from AD-416): The long-term objective of this project is to develop stand-alone and integrated tools for engineers to evaluate allowable embankment overtopping; predict dam failure from overtopping and internal erosion for homogeneous and zoned embankments with simple and complex downstream embankment slope geometries; design alternative surface protection methods, including vegetation, riprap, and concrete blocks; and develop generalized design criteria for increased spillway capacity for small dams (i.e., less than 20 m high). Specifically, the objectives of this project are: Objective 1: Enhance the WinDAM model to predict erosion and breach of complex earthen embankment geometries and materials. Subobjective 1A: Quantify the impact of complex embankment geometries on erosion processes 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 on erosion processes and rates of earthen embankment erosion and breach. Objective 2: Develop engineering tools for design of earthen embankment protection alternatives and increasing the discharge capacity of small dams. Subobjective 2A: Develop guidelines for dimensioning stilling basins and downstream channel protection for non-converging RCC stepped spillways constructed over existing earth dams. Subobjective 2B: Develop guidelines for dimensioning stilling basins and downstream channel protection for converging RCC stepped spillways constructed over existing earth dams. Approach (from AD-416): Large-scale physical models will be used to develop knowledge on the protective capability of vegetation and/or riprap on embankment slopes with convergences and berms. Large and small-scale models will be used to develop knowledge of erosion resistance of zoned embankment materials and to develop key relationships related to earthen embankment erosion. Small-scale and large-scale physical models will also be used to develop knowledge on the impact of discharge, energy dissipation, flow depth, velocities, and downstream tailwater depth on stilling basin and downstream channel protection design for stepped spillways. Data and relationships developed from these physical models coupled with in-depth literature review will be used in the development of predictive and design tools for embankment erosion 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. The results from this research will be incorporated into evaluation tools, software, design criteria, and management practices that will allow the continued service and increased benefit of the nation's agricultural flood control infrastructure. Dam safety is of high importance worldwide, and although dams have excellent safety records, dams do fail, creating a potential risk to life and property downstream. ARS scientists at Stillwater, OK, along with cooperators from Kansas State University and the Natural Resources Conservation Service (NRCS) have for several years been developing the WinDAM (Windows Dam Analysis Modules) software for prediction of earthen embankment erosion and failure. To expand on the development of WinDAM, outdoor physical models for conducting convergent and bench flow testing have been designed, constructed, and configured; vegetation has been placed for testing of Bermuda grass and will be allowed to mature for 12 months prior to testing; and a water delivery system is in the process of being modified to handle the necessary flow. Laboratory bench testing for characterizing erodibility of the soil materials to be used in field testing is complete. The outdoor facilities for conducting zoned embankment tests have been substantially reconfigured to conduct tests. Construction of the first test section is nearly ready to begin. Aging embankment dams are vulnerable to changes in hazard classification due to changing demographics in the vicinity of the dam. As a result, many of these dams have insufficient spillway capacities due to changes in hazard classification requiring more stringent dam safety regulations to be met. ARS scientists at Stillwater, OK, over the past several years have developed design criteria for the cost-effective application of roller compacted concrete (RCC) stepped spillways to provide increased spillway capacity and overtopping protection of embankment dams. Air entrainment inception point relationships were optimized for stepped spillways having a broad-crested weir using data collected from a 3(H) :1(V) stepped spillway physical model. The relationships were further validated from data available from literature. Data collection of velocities, flow depths, and air concentrations from a 2(H):1(V) stepped spillway model are substantially complete. Analyses of these data are in the preliminary stages to further enhance relationships developed for air entrainment inception point, flow depth, energy dissipation, and air concentrations from a 4(H):1(V) and 3(H):1(V) stepped spillway models. Limited data from literature will provide independent validation for these relationships. Flow depth and energy dissipation are parameters for designing the stilling basin and riprap size for downstream channel protection. These relationships with additional testing will be used to optimize the design of the stilling basin and riprap size for downstream channel protection for stepped spillways. Accomplishments 01 Improving methods for predicting earthen embankment erosion and failure. Although dams have excellent safety records, dams do fail, placing life and property at risk downstream. ARS researchers at Stillwater, Oklahom along with cooperators from Kansas State University and the Natural Resources Conservation Service (NRCS) are continuing to enhance the WinD (Windows Dam Analysis Modules) software to provide a tool for predicting earthen embankment erosion and failure processes and impacts. Soil parameters are essential for improved model development. Laboratory ben testing for characterizing erodibility of the soil materials to be used field testing was completed. Physical models to evaluate convergent and bench flow on embankment dams have been constructed, so WinDAM can be further enhanced to evaluate erosion prone areas of embankment dams. Increased knowledge of embankment breach erosion and failure processes d to overtopping and internal erosion, resulting in enhanced prediction tools, has great potential to improve: risk assessments, ranking systems for prioritization of rehabilitation, emergency action plans, inundation maps, and flood warning systems. 02 Generalized hydraulic guidelines and tools developed for roller compacte concrete (RCC) spillways. Inadequate spillway capacity is a common deficiency for aging embankment dams. Researchers at the Hydraulic Engineering Research Unit, Stillwater, Oklahoma, are continually developing and enhancing generalized design criteria for RCC stepped spillways for overtopping protection and to increase spillway capacity f the rehabilitation of aging embankment dams. Flow depth, energy dissipation, air concentrations, and air entrainment relationships developed from 4(H):1(V) and 3(H):1(V) sloped RCC stepped spillway physical models are complete. Data collection from a 2(H):1(V) slope stepped spillway has substantially been completed, and preliminary analysis of the data is underway. These data will enhance generalized design relationships for inception point, flow, depth, energy dissipatio and air concentrations. These relationships will provide quantifiable design guidance for engineers to use in designing RCC stepped spillways. Additionally, these relationships will provide engineers economic justification on selecting particular design parameters (i.e., step heig while also keeping in mind the safety of the general public. Approximately, 1100 embankment dams constructed under the Small Watershe Program administered through Natural Resources Conservation Service (NRC are expected to utilize this technology. Increased knowledge of air entrainment properties within stepped spillways has great potential to extend the design life of thousands of embankment dams worldwide.
Impacts
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Publications
- Hunt, S.L., Temple, D.M., Abt, S.R., Kadavy, K.C., Hanson, G.J. 2012. Converging stepped spillways: Simplified momentum analysis approach. Journal of Hydraulic Engineering. 138(9):796-802.
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