Track 1: Effects of Climate Change in Warm Weather Coastal Regions
Flooding from recent severe coastal storms has caused significant cultural and economic losses in the Gulf Region and along the Atlantic Coast. Sea level rise and increased precipitation associated with climate change will continue to increase the regularity and severity of coastal flood events, as evidenced by the frequency of recent events exceeding the mapped 100- or 500-year floodplains in these regions. In response, owners, designers, and other built heritage stewards need to better understand their flood risk, even in previously unaffected areas, and determine practical options for mitigating flood hazards in the future.
Flood mitigation design and building code requirements are typically based on American Society of Civil Engineers (ASCE) 24-14 – “Flood Resistant Design and Construction”. The Federal Emergency Management Agency (FEMA) also publishes many guidance documents, including P-936 – “Floodproofing Non-Residential Buildings,” P-1037 – “Reducing Flood Risk to Residential Buildings That Cannot Be Elevated,” and Technical Bulletin 7 – “Wet Floodproofing Requirements”. These guidance documents prescribe the following general flood mitigation methods:
• Elevation: raise the structure above expected flood levels.
• Dry floodproofing: make the building substantially impermeable to floodwater and design the structural components to resist the flood loads, including hydrostatic uplift.
• Wet floodproofing: intentionally allow floodwater to enter the building to equalize the hydrostatic pressure and prevent damage to the building structure. This approach requires the use of flood-damage resistant materials such that the building may be inundated during floods without substantially damaging the structure or materials.
Each of these flood mitigation methods creates significant preservation challenges and flood mitigation guidance often conflicts with established preservation guidelines. Dry and wet floodproofing often require substantial modification to the original structure, building use, or building materials to be feasible – all in direct conflict with typical preservation guidelines. Elevating also presents challenges and conflicts with general recommendations in the Secretary of the Interior’s Standards for the Treatment of Historic Properties, thus limiting potential funding or national registry listing if this flood mitigation measure is considered.
In this presentation, we will discuss sources of flood risk within and outside of mapped floodplains, review the common flood mitigation concepts discussed above, and explore historical and contemporary flood mitigation solutions within the context of typical preservation goals and National Park Service (NPS) guidelines.