Protection from Floodwall Overtopping Scou
Kevin Chancey, sarah edens, Monica Murie, Jason Unruh
The United States Department of Agriculture (USDA) chief scientific research agency Agricultural Research Service (ARS) specializes in developing solutions to agricultural problems that affect Americans every day. Stillwater is home to a division of the ARS this unit is called the Hydraulic Engineering Research Unit (HERU). HERU has been in continuous operation since it was established in 1940. The lab has had a major impact on soil and water conservation engineering and is recognized nationally and internationally as a significant contributor of sound design criteria for soil and water conservation structures and channels. Most notable is the pioneer work in the design concepts for vegetated channels. The HERU conducts experiments and trials to develop criteria for the design and analysis of structures and channels for the conveyance, storage, disposal, and measurement of runoff waters. Also to develop fundamental knowledge of the hydraulics of surface flows for use in planning measures needed to control water for flood prevention, pollution abatement, and assessing the safety of existing measures. Other aspects the lab studies are the ability of vegetation and/or various natural and manufactured materials to prevent erosion when used to manage runoff waters. Floodwall overtopping is an example of the type of project that the HERU laboratory would investigate. Overtopping is a result of intense storm events that under the right conditions produce runoff that overtops floodwall structures. The process of overtopping can be devastating in several ways. The excess water can flood property that was intended to be protected by the wall, and also the force of the water coming over the wall can scour and deteriorate the materials and foundation of the wall on the downstream side causing failure. In accordance with the mission statement of the HERU laboratory, we will be looking at what materials can be used to reduce this erosion phenomenon called scour.
Floodwalls are designed to provide additional storage and protection against flooding, but when floods exceed the design recurrence interval of the floodwall, waters will overtop the floodwall resulting in a waterfall effect on the downstream side. The resulting downstream impinging flow may cause scour and erosion that can undermine or destabilize the floodwall, potentially resulting in a catastrophic failure. Steps must be taken to reduce or eliminate this scouring and erosion in order to secure the integrity of overtopped floodwalls.
Scope of Work
TDLP Inc. met with the USDA-ARS HERU in September to discuss the logistics of the design problem at hand, and design objectives for a generalized approach for preventing scour and erosion downstream of floodwalls. As seen in the customer requirements section, the HERU laboratory has asked TDLP Inc. to develop a generalized approach with consideration of an optimal ground application that would decrease scour from water overtopping floodwalls, increase ground stability in order to protect the integrity of existing floodwalls, and remain within economic constraints in order to keep the product easily applicable and marketable. TDLP Inc. will begin this process by investigating the specific issues and problems occurring with overtopping of floodwalls. In order for work to be considered complete for this project, TDLP Inc. is required to generate design concepts, build a model of floodwalls currently in existence using a flume provided by the HERU laboratory, determine experimental procedures for testing these concepts within the flume laboratory, model these concepts, and present concepts for evaluation.