Procedures from international guidelines for assessing seismic risk to flood-control levees

We synthesize engineering procedures for estimating the seismic performance of major flood-control levees as given in guidelines documents and design codes from Canada (British Columbia), China, Italy, Japan, New Zealand, and the United States. Some guidelines carry the weight of law whereas compliance is optional for others. Most procedures combine a probabilistic ground motion characterization with deterministic assessments of levee performance (uncoupled approach). Ground motions are typically described using peak accelerations for reference site conditions at return periods typically ranging from 100 to 2,475 years. Those motions are deterministically modified for soil conditions using numerical simulations or ergodic site factors. Accompanying hydrological conditions are either not specified or are taken at a frequently encountered water level (ranging from mean annual to a four-month flood event). These demands are used in combination with various soil properties to assess the potential for liquefaction, flow failure, and permanent shear deformations. Drawing upon best practices identified from this review, we recommend procedures for levee risk assessment at the section-level and for levee systems.