Methodology for Estimating Wind Wave Erosion of Riverine Levees

Abstract

The objective of this paper is to provide a methodology to analyze potential wind wave erosion of rivervine levees during a single extreme event. Among various requirements in current U.S. Army Corps of Engineer standards for the certification of levees is that a levee must be able to maintain stability during large wind wave events. Existing methods for estimating wind wave erosion are generally dependant on empirical information from open coasts frequently exposed to wave events and do not readily apply to well vegetated rivervine levees. This paper provides a four part methodology developed for assessing the stability of levees surrounding the city of Sacramento, California during large wind wave events. The methodology includes determining 1) a theoretical maximum erosion profile from a single event, 2) the stability of grass slopes under wave attack, 3) the stability of rock slopes under wave attack, and 4) if potential levee overtopping by wave runup will induce erosion. A flow chart is then used to combine the results of each of the four steps to determine whether sections of levee are A) likely to erode and fail during a large wind wave event, B) likely to erode but not likely to fail during a large wind wave event, or C) not likely to either erode or fail during a large wind wave event. Included is a summary of important wind wave characteristics, as well as a brief literature review of published methods for evaluating wind wave erosion.