ASCE updates ASCE/SEI 7-22 standard to protect against 500-year flood events

June 6, 2023
New provisions to the standard include a new requirement tying flood hazard mitigation design to Risk Category, as well as a new requirement to plan for relative sea level change.

The American Society of Civil Engineers has added new flood load provisions to its standard ASCE/SEI 7-22 Minimum Design Loads and Associated Criteria for Building and Other Structures.

ASCE says that the new provisions will protect against 500-year flood events, an improvement to the 100-year flood hazard reference in the previous version.

The update is available in a supplement as a free download.

“ASCE continuously seeks to update its standards using the latest scientific and engineering knowledge, to assure the standards remain relevant to society’s needs and an appropriate basis for design and construction” said Ronald Hamburger, Senior Principal with Simpson Gumpertz & Heger Inc., and chair of the ASCE 7-22 committee. “Proper implementation of the Supplement to ASCE 7-22’s Chapter 5 is a dramatic change to the current standard but will help residents and businesses feel secure despite weather-driven challenges.”

The primary technical updates relative to climate impacts include a new requirement tying flood hazard mitigation design to Risk Category, which is consistent with other environmental hazards in ASCE 7. The new provisions require Risk Category II structures and above to use the 500-year floodplain to determine flood loads.

Risk Category II structures, the most commonly used category, include one- and two-family buildings, low to medium occupancy businesses, or recreational facilities. Risk Category I structures, including agricultural buildings such as barns and sheds, could still follow 100-year flood provisions.

The supplement also introduces a new requirement for relative sea level change as it relates to each individual structure. The sea level rise estimated over the service life of the structure must be added to the design’s flood mitigation plans.

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