Levee Overtopping Design Guidance: What We Know and What We Need

Hurricane Katrina revealed that earthen levees appear to be most vulnerable to erosion damage when water overtops the levee crown and flows down the protected-side slope. Prevention of overtopping damage on grass-covered levee slopes requires reliable engineering design criteria for specifying permissible overtopping rates. Where overtopping flows are expected to exceed the permissible criterion for grass-covered slopes, design guidance is needed for estimating hydrodynamic loading and response of proposed armoring alternatives. This paper summarizes existing guidance that can be used to design overtopping protection alternatives, and it describes what additional guidance is needed for situations where no design guidance is presently available.