Effects of Woody Vegetation on Levee Integrity during Full Scale Testing at Twitchell Island in Rio Vista, California

摘要

A full scale levee infiltration experiment investigates the effects of woody vegetation on levee integrity within the San Joaquin Delta in California. An 8 foot deep crown trench was excavated through the levee at a control segment and through root systems of landside and waterside oak trees. The crown trench was flooded to simulate a flood condition while instruments tracked the response. Burrow networks, stratigraphy, fracturing, and voids added complexity. Cracks and deformations were monitored throughout the test. A leaning waterside oak tree fell during testing. Computer simulations captured the observed landside and waterside tree responses. The impact of a tree on seepage-induced stability is explored through mass averaged limit equilibrium analyses, incorporating tree loading distributed across a root plate zone defined by pit sizes from empirical windthrow data. Global seepage-induced stability does not appear to be largely impacted by the presence of a tree.