From the Overview: "This guidance document supports the standards related to approving coastal protection structures to be shown as providing protection on Flood Insurance Rate Maps (FIRMs) and outlines methods for analyzing the stability and effects of coastal structures during the 1- percent-annual-chance flood conditions. Because coastal structures can significantly affect local topography and flood hazards, Mapping Partners must evaluate coastal structures as part of any flood hazard study. The evaluation should, where possible, determine whether a coastal structure will survive the 1-percent-annual-chance flood and what impacts it will have on upland flooding. Criteria for evaluating the stability and performance of coastal armoring structures for Flood Risk Project purposes are well-developed and are discussed in detail. Criteria for evaluating beach stabilization structures have not been developed yet, and only basic guidance is provided. Criteria for evaluating miscellaneous structures are not standardized, and only basic guidance is provided."
Guidance Document 42
U.S. Federal Emergency Management Agency: https://www.fema.gov/