The American Society of Civil Engineers has rolled out a sweeping update to its flood-resistant design standards, marking what many experts call a turning point in how the U.S. prepares for flood disasters. According to floodplain manager Tom Little, the new ASCE 24-24 standard represents the most impactful revision since the guidelines were first issued in 1998.

“If we want to protect our nation’s homes, businesses and critical infrastructure, we must adapt to [Mother Nature's] unpredictability,” said Little, who also serves as president and CEO of Floodproofing.com and was part of the committee that developed the revised standard.

ASCE 24-24, released earlier this year, introduces 29 key changes compared to its 2014 predecessor. The most transformative? A broader definition of flood hazard areas: rather than limiting requirements to the traditional 100-year floodplain, the new rules extend to 500-year floodplains, expanding the scope of buildings subject to regulation.

“This is not an arbitrary decision by the committee that wrote the ASCE 24-24 standards... it is a decision based on field experience and lessons learned from storms such as hurricanes Harvey, Ida, Ian and others,” Little said.

The update also redefines minimum elevation standards, tying them to the structure’s Flood Design Class. In practice, this means higher-risk structures like hospitals and schools must be built to even more rigorous elevation requirements — sometimes at levels corresponding to a 1,000-year flood event — while homes may still follow less stringent, yet elevated, guidelines.

“This provides greater protection for those critical infrastructure facilities which are vital to restoring normalcy to our communities after major flooding events,” Little explained.

For the first time, dry floodproofing systems must now undergo standardized performance testing to be approved for use in flood-prone areas. Under ASCE 24-24, these systems must meet the ANSI/FM 2510 standards, proving they can withstand water pressure and debris impacts — a move aimed at enhancing the reliability of such solutions.

“Companies that invest in performance, compliance and innovation are helping raise the bar and build trust in the marketplace, setting a clear standard for what reliable flood protection should look like,” Little said.

Based on hard-learned lessons from past disasters, the new standards also require annual inspections, maintenance, and deployment drills for dry floodproofing systems. According to Little, many committee members had seen these systems fail — not because they were poorly designed, but because they weren’t activated in time, or at all.

“Too often... buildings equipped with dry floodproofing solutions... were devastated by storms because those solutions were not properly deployed, or in some cases, were not deployed at all,” he said.

To prevent these failures, ASCE 24-24 mandates the use of flood warning systems that give between 12 and 36 hours' notice for manual deployments, depending on the building type and risk category.

Despite industry concern over construction costs, especially from the residential sector, Little argues that failing to build smarter comes at a higher price.

“Our nation has become stuck in a continual cycle of homes being destroyed by flooding and rebuilt on the same land according to the same outdated standards. This cycle eventually costs homeowners — and our nation — more than adopting the new standards,” he said.

While additional refinements may come in future years, Little believes ASCE 24-24 lays a strong foundation for more resilient development.

“With these new standards, we can make significant progress in building stronger, more resilient communities to take an important step in breaking the economy-draining cycle of disaster and recovery in which our nation is currently stuck,” he concluded.

Originally reported by Tom Little in Construction Dive.