Severe flooding can endanger lives and cause billions of dollars in property damage. Even moderate levels of flooding can lead to destruction and disruption of building operations. Flood damage can occur from a variety of sources, including hydrodynamic/hydrostatic forces and debris impact, soaking, and sediment and contaminants. Flood water can destroy a building’s electrical infrastructure and mechanical systems, causing interruptions that can last from a few days to over a year.
Due to continued climate change and the 2016 revisions to the Federal Emergency Management Agency (FEMA) flood maps, many buildings not previously categorized as “at risk” are now subject to flooding. Because of this, if flood-proofing and mitigation steps are not taken, building owners face potential risks and associated increases in flood insurance coverage.
- Dry flood-proofing – A combination of measures that result in the building structure and its utilities being watertight and substantially impermeable to floodwater penetration. The building components should also have the capacity to resist flood loads.
- Wet flood-proofing – The use of flood-damage resistant materials and construction techniques to minimize flood damage to areas below the flood level of a structure. The area is intentionally allowed to flood.
- Floodwall / levee – Man-made barriers that are constructed to contain, control, or divert the flow of water so as to provide protection from temporary flooding.
Per NFIP regulations, non-residential buildings are only required to be protected to the base flood elevation (BFE), the elevation to which floodwater is anticipated to rise during the 1-percent-annual-chance (100-year) flood. However, extending the flood-proofing measures to the BFE +1 foot of freeboard can allow the non-residential building to achieve a favorable NFIP insurance rating. Flood-proofing to even higher elevations can result in savings in annual insurance premiums.
Design considerations when selecting flood-proofing measures may include performing a flood hazard evaluation of the site and a structural evaluation of the building. When considering flood-proofing measures that require human intervention, the implementation of a flood emergency operations plan is recommended to allow adequate flood warning time. A certified floodplain manager and registered professional engineer or architect can assist owners with regulatory requirements, building codes, guidance documents, and design standards.