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In May of 2023 ASCE released Supplement 2 for the ASCE 7-22 Standard. The portion of this Supplement 2 relating to Chapter 5: Flood Loads has been vastly updated. Among the major changes are a new 500-year flood plain for Risk Categories II, III and IV which reaches much farther inland than the previous 100-year flood plain. Provision have been added for floating debris based upon proximity from site location and for anything from logs, vehicles, small vessels up to barges, ships and beyond. Hydrodynamic drag forces below the design Stillwater elevator must now be accounted for along with minor revisions to the scour around piles, piers and foundations. Additionally, the Stillwater flood elevation must be increased for future sea level rise out for the next 50 years. There are varying estimates for this increase for future but studies by the Army Corps of Engineers and UCONN Sea Level Rise GIS currently estimate this at approximately 16 or 20 inches.
These new requirements found in Supplement 2 go beyond the currently adopted ASCE 24 Flood Resistant Design and Construction which will create a discrepancy in design requirements between the two standards. Connecticut’s next code adoption at the end of 2025 or early 2026 will reference the ASCE 7-22 standard. However, the Supplement 2 in its entirely does not have to be adopted as part of this new Code iteration. CT Engineers and engineers around the country have expressed concern about the feasibility of designing to the new Supplement 2 Standard due to it’s large increase in resultant loads on structures which along the shoreline are mainly residential.
The full Supplement 2 can be found at no cost here:
https://ascelibrary.org/doi/epdf/10.1061/9780784415788.sup2
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