Structure elevation, which includes physically raising an existing structure, is one of the most common adaptation methods used by localities. Typically, structures are elevated to the base flood elevation plus an added amount of freeboard.
Retrofitting a structure to raise its foundation can provide protection from increases in storm surge & flooding, reducing the likelihood of damage. Although an important interim adaptation effort, because of its comparatively low political cost, elevating structures is a short term fix to a long term problem; we consider it a long term Band-Aid adaptation solution & strategy.
Poquoson: aggressive campaign to elevate vulnerable structures, as approximately 86% of the City is within the 100-year floodplain. Over 600 homes (15% of the city’s housing stock) are already elevated. City Council also approved 3 feet of freeboard.
Some localities are concerned with structures going above height limitations after elevation, which can result in a Board of Zoning Adjustment (BZA) review. Hull, MA has helped overcome this barrier by amending its code, allowing property owners to request a special permit to exceed height limitations for elevation retrofits.
Town of Hull Nantasket Beach Overlay District: 7.2.2:
"The Planning Board may…issue a Special Permit allowing new and existing buildings within a Special Flood Hazard Area… to be elevated beyond the… height limit to provide flood proofing by meeting or exceeding flood elevation requirements. Buildings cannot exceed the elevation required to comply… by more than four feet."
Building elevation is available for funding under the FEMA Unified Hazard Mitigation Assistance Grant Programs (HMGP, PDM, FMA, RFC, SRL).
A damaged structure may be eligible for an Increased Cost of Compliance claim, which can be used to help pay for an elevation project. Qualified structures have experienced flood damage twice in the past 10 years, with damages equaling > 25% of its market value during each loss.
Hull, Massachusetts: structure elevation incentive program that offers a $500 credit toward building permit fees for structures in the A zone 2 feet higher than BFE & V zone 4 feet above the BFE. Program has 83% participation rate in new development & at least 7 existing structures have taken advantage of the incentive (Schechtman & Brady).
La Crosse, Wisconsin: innovative program to combine funding opportunities for elevating homes. Directs CDBG funds (up to $25,000 per property) to low- to moderate- income homeowners for elevation retrofits & provides an additional $25,000 per property through newly established revolving loan fund. Loan payments are spread over 20 years & 50% of the loan can be forgiven if FEMA certifies the property is raised above the BFE. Point of sale incentives are offered in the form of a matching grant of up to $12,500 to raise the property before it is sold.
Shore Up Connecticut: First revolving loan fund for shoreline adaptation via elevating structures in floodplains. Program sunsetting.
Virginia Shoreline Resiliency Fund: Revolving loan program for shoreline protection. Although not yet funded, program will finance structural mitigation & other adaptation strategies. Modeled after Shore Up CT.
Some concern that FEMA funds are being used to raise vacation homes rather than primary residences (FEMA is unlikely to prioritize second residences) & many localities have issues funding elevation projects through FEMA. In addition to the process being complex & unwieldy, localities have noted issues specific to FEMA Region III. ICC funding is too low to cover the requirement to bring a structure up to code. Additionally, the current process does not allow for adjusting project budgets for unforeseen conditions. This is especially problematic for structure elevation, where additional complications often only arise once a structure has been lifted off of its foundation.
Localities have had issues with property owners wanting to use fill to elevate entire lots to mitigate flooding. Chesapeake Bay Boards are being asked to permit shoreline property fill. At least one Tidewater locality is interested in code language that would prohibit fill on any parcel both in & outside the SFHA, with no variances permitted. One city has issued CBPA variances for flood control projects, but variances for “land creation” are not allowed.
- Protects existing development = effective in urban localities with a high degree of build-out
- Reduces flood risk to property owners
- Can lower flood insurance premiums for shoreline homes
- Reductions in flood insurance premiums can subsidize the cost of structure elevation
- Height limitations (through building codes or historic district standards)
- Band-Aid solution that does not result in shifting structures out of highly-vulnerable areas
- Building costs increase substantially for higher elevations
- Can lead to the need for expensive infrastructure elevation
- Structure accessibility may be impacted
- Grants for elevation projects rarely cover other costs associated with flooding, such as floor rot or wiring issues
Elevation can occur through several methods: elevating continuous foundation walls, elevating on open structures (piers, piles, posts, etc.), or elevating on fill. NFIP requirements: if an existing structure (within the SFHA) receives flood damage over 50% of its fair market value, it qualifies as substantially damaged & must be brought into compliance with newest code requirements. Ensuring there is a stringent freeboard requirement within a locality’s floodplain ordinance can promote safer structures, even in developed areas.
Localities should consider the associated costs of structure elevation. Raising houses can create a need to elevate large road segments/ stormwater systems & create additional construction costs (reconnecting driveways & regrading). Norfolk spent over $1.1 million on infrastructure elevation for one block after 6 homes were elevated; the costs of this additional elevation outweigh the preservation of property tax revenues from these homes. Furthermore, localities must continue providing services to citizens following a home elevation, the cost of which could be compounded by increased flooding. After evaluating the drawbacks of structure elevation, at least one Tidewater locality has considered developing a policy against raising houses.
1: Up to 500 points (Activity 430, Freeboard (FRB), Manual pg. 430-10):
Credit for ordinances that require freeboard with specific conditions.
Code of Virginia, § 15.2-2280:
Zoning ordinances generally
FEMA. (2015). Hazard Mitigation Assistance Guidance. FEMA.
FEMA. (2010). Home Builder’s Guide to Coastal Construction: Technical Fact Sheet Series.
Silton, A., & Grannis, J. (2010). Stemming the Tide: How Local Governments Can Manage Rising Flood Risks . Georgetown Climate Center.
Schechtman, J. & Brady, M. Cost-Efficient Climate Change Adaptation in North America. Rutgers University.
Thomas, J., & DeWeese, J. (2015). Reimagining New Orleans Post-Katrina: A Case Study in Using Disaster Recovery Funds to Rebuild More Resiliently. Georgetown Climate Center.
US Army Corps of Engineers. (2015). North Atlantic Coast Comprehensive Study: Resilient Adaptation to Increasing Risk. USACE.