Stability analysis of the L-575 levee failure on the Missouri river

The breach of a levee can be a devastating event, with each occurrence possibly resulting in millions of dollars in damages. Despite the destructive potential associated with a breach, there is a great deal of uncertainty associated with the current conditions of levees in the United States. Not only do soil parameters often vary a great deal throughout an earthen structure, but there is also very little information available on the soil parameters and design techniques used in the design and construction of these levees. This is particularly the case for levees that are 50 years old or more. This study focused on one such levee failure: the June 13, 2011 breach of levee L-575 near River Mile 552 on the Missouri River. A two-dimensional model of the levee was constructed using the SLOPE/W and SEEP/W software. Geometry of the levee and the site characteristics at failure were established through investigation of public domain information. The likely mean strength parameters of the soil were established through sensitivity analysis. A probabilistic analysis was then performed to evaluate the probability of the levee's unsatisfactory performance, as defined by incipient instability and as defined by the U.S. Army Corps of Engineers' minimum criteria. The probabilistic analysis revealed that there was less than a 20 percent probability of instability in levee L-575. However, there was more than a 90 percent probability that L-575 would perform unsatisfactorily with respect to the U.S. Army Corps of Engineers' minimum criteria.