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Flooding

Flooding can lead to significant property damage, infrastructure disruption, and public health risks, resulting in loss of life and economic hardship for affected communities. Additionally, it causes ecosystem damage, soil erosion, and long-term recovery challenges, underscoring the importance of effective flood management strategies to enhance resilience.

To mitigate the impacts of flooding, projects under flood-resilient design must implement at least two of the indicated flood mitigation strategies, in accordance with FEMA 543 [66] and ASCE 24 [67], or their local equivalents. These standards provide minimum requirements and offer critical guidelines that enhance the safety and structural integrity of vulnerable sites and buildings located in flood-hazard areas. Projects can choose from any of the strategies listed under Critical Utilities, as well as flood resistant materials or certifying under a qualifying design standard.

Critical utilities It is essential to elevate critical utilities above the design or base flood Elevation (DFE/BFE) as well as include additional freeboard to prevent water intrusion. This elevation protects essential services such as water supply systems, sewage treatment facilities, communication systems, and electrical infrastructure from submergence, which could lead to costly repairs and service disruptions. Adding freeboard serves as a buffer and an additional safety measure, further enhancing the resilience of critical infrastructure. Positioning utilities above the DFE/BFE significantly reduces the risk of damage from floodwater, ensuring that communities have continued access to critical services during and after a disaster. This reliability is vital for public health and safety, as well as for emergency response operations.

Design new potable water and sewage systems to withstand flood conditions, ensuring uncontaminated drinking water and preventing sewage overflow during flood events. Elevating on-site wellheads above the surrounding landscape is essential to allow contaminated surface water to drain away effectively.

Plumbing conduits, water supply lines, gas lines, and electric cables extending below the DFE must be carefully designed and anchored to withstand flooding. In addition, rainwater storage tanks must be designed and secured to resist flood forces, ensuring they remain functional and protected during flood events. These measures help minimize damage to critical utilities and enhance flood resilience.

66 “Design Guide for Improving Critical Facility Safety from Flooding and High Winds”, FEMA 543, (2007), Federal Emergency Management Agency (FEMA), accessed April 4, 2025, https://www.fema.gov/sites/default/files/202008/fema543_design_guide_complete.pdf. 67 “Highlights of ASCE 24-14: Flood Resistant Design and Construction”, Federal Emergency Management Agency (FEMA), accessed April 4, 2025, https://www.fema.gov/sites/default/files/2020-07/asce24-14_highlights_jan2015.pdf.

U.S. Green Building Council LEED v5 Reference Guide for Building Design and Construction, April 2025 Launch Edition 135