Reliability Analysis of Coastal Rubble Mound Structures

THESE TOOLS PROVIDE $100+ THOUSAND SAVINGS PER POST-CYCLONE ASSESSMENT IN ADDITION TO BETTER DESIGNS

For the last 20 years, the U.S. has averaged nearly one catastrophic tropical cyclone per year. This chronic coastal storm risk has provided impetus for the Corps to quantify the coastal storm hazard with improved analytical and statistical accuracy. These cyclones damage and weaken infrastructure, such as more than 1,000 coastal rubble mound structures in the Corps’ vast infrastructure portfolio. In 2019, Corps’ engineering and design efforts included billions of dollars of new or modified structures; however, existing guidance is outdated. The Coastal Hazards System (CHS) and StormSim are two research products that provide tools and data to compute accurate, risk-informed reliability for coastal rubble mound structures. CHS is a national probabilistic coastal storm hazard resource that accurately quantifies detailed and comprehensive storm hazards on a national scale. StormSim is a suite of stochastic analysis and probabilistic modeling tools for coastal engineering that applies CHS modeling suites. Together, these research products save time and costs associated with local and regional studies, facilitating more efficient rubble mound structure design and quantification of risk.

PROBLEM: Corps manuals do not include comprehensive and prescriptive safety-level metrics for coastal rubble mound structure design. International practice has moved to prescribing safety levels for these structures. The result is unknown risk and uncertain approaches for engineering design and assessment, leading to widely varying levels of over- and under-design. The Corps’ existing state-of-practice guidance in its Coastal Engineering Manual provides a reliability framework, but there are no prescriptive safety factors, so the guidance is difficult to use.

SOLUTION: The CHS provides essential forcing data to develop target safety levels, with a large portion of the U.S. East and Gulf Coast complete so far. The CHS and StormSim provide the tools and data necessary to compute reliability for Corps coastal structures. Developing prescriptive guidance follows present civil engineering practice of computing reliability for existing structures, comparing reliability to performance, and establishing prescriptive safety levels corresponding to varying levels of performance.

IMPACT: Using automated probabilistic tools with existing CHS data provides accurate stochastic response and saves time and the cost of regional coastal storm modeling that typically ranges in the hundreds of thousands of dollars. These approaches have been applied to a wide range of Corps coastal structures to develop essential generalized safety levels. The results and tools facilitate accurate risk estimates, more efficient designs, and maintenance management of the Corps’ inventory of coastal rubble mound structures.