HRPDC staff recently launched a new Esri Story Map on HRGEO.org that provides an interactive summary of the organization’s multi-year effort to develop building first floor elevation data. First floor elevations (FFE) are important for identifying individual structures and areas of communities that are most at risk of flood damage. FFE data ultimately supports flood mitigation planning and evaluating solutions for communities and individual structures, such as installing flood vents or elevating homes.
FFE data has historically not been widely available in the Hampton Roads region. FEMA Elevation Certificates are the primary source of this information, but the certificates can be time intensive and costly to collect. To help address this data gap, the Hampton Roads Planning District Commission (HRPDC) undertook a three-year effort to develop FFE data in support of flooding vulnerability assessments. The primary goals of the project included: (1) developing a database of existing and estimated FFE data, (2) applying the data in a regional flooding vulnerability assessment that considers current and future flood risk, and (3) coordinating with other organizations to develop recommended practices.
Map displaying building locations and the 1% annual chance flooding scenario.
To develop the regional database of FFE data, HRPDC staff used multiple methods. These included predictive modeling, stair counting using Google Street View imagery, and integrating existing data sources, such as elevation certificates (data available on HRGEO.org) and data produced through other efforts in the region. The resulting database focused on single-family residential structures in current high-risk flood zones (the Special Flood Hazard Area) and included nearly 34,000 structures. This data was then used to assess potential damage in dollar amounts under different flood scenarios, including the current 1% annual chance flood, and future flood risk with 1.5ft and 3ft of sea level rise.
The importance of accurate FFE data was underscored by the resulting damage estimates, which changed based on the FFE value. Sea level rise also substantially increased the number of structures likely to be damaged, as well as the severity of damage to individual structures. Based on the lessons learned during this project, the HRPDC has recommended that local governments consider maintaining digital copies of elevation certificates and improving local assessor data. This project will also serve as a resource for the upcoming 2022 Hampton Roads Hazard Mitigation Plan update.
For more details about the project, check out the full report on the HRPDC’s website and the new Story Map. The Story Map is divided into 6 key sections that the user can navigate through. This project was funded, in part, by a Virginia Coastal Zone Management Program grant from the National Oceanic and Atmospheric Administration.