Levee Erosion Screening Process

Abstract

The California Department of Water Resources ' Urban Levee Geotechnical Evaluations Program is evaluating urban levees in the Sacramento and San Joaquin river systems. A three-tiered Erosion Screening Process (ESP) has been developed to qualitatively assess the current risk of erosion failure on a levee's waterside slope. Erosion is caused mainly by a weakened geometric levee cross section or poor initial construction coupled with high flow velocity and/or wave action. Levees are evaluated through this three-tiered screening process until the erosion risk potential is determined. Each of the tiers progressively increases in detail. Tier one assesses overall geometry, fetch length, and historical performance. In the second tier, assessments are performed to evaluate the levee ' s surface resistance to velocity and wave shear stress. Also, field reconnaissance verifies expected levee performance and look for signs of erosion or unstable conditions. In the third tier, the ESP analyzes levee geometry, river geometry, soil and vegetation types, wind-wave impacts and river velocity impacts to categorize levee reaches into a high, medium, or low erosion risk.