Federal Emergency Management Agency (FEMA) Flood Map

FEMA has received a lot of criticism for its map making process- such as having a “backwards looking” methodology based on historic floods and not having maps of projective, future conditions that consider climate change.The current FEMA process of updating maps includes a patchwork of data updated through various times, process, contractors, and models which can lead to misleading maps that may not reflect the current conditions.The FEMA flood map for Boston was last updated in 2016. Hover over the chart below to see how the FEMA process currently works.

Sasaki

“Sea Change Boston” by Sasaki Associates in 2014 paints an alarming picture. Sasaki used a high-precision elevation data to create a simple “bathtub” model. This process adds projected sea level rise (for example, 21 inches by 2050) to the elevation of projected storm surges, then selects all dry land that falls below that level to predict what will be flooded. While this simple, intuitive process can be done quickly and without much computing resources, it does not take crucial variables into account that affect what areas get flooded, including land cover, flood infrastructure, and stormwater infrastructure. This model accomplishes Sasaki’s goal of creating a shocking visualization for an exhibition but it should not be used for policy or prediction because of the inaccuracies involved in the methodology.

Climate Ready Boston

Finally, flood modeling for Boston’s Climate Ready report derives from modelling done by the Woods Hole Oceanographic Institute (WHOI) and UMass Boston, using a model called ADCIRC. ADCIRC simulates the fluid dynamics of wave action during extreme weather, making it more precise than a bathtub model. WHOI also incorporated variables such as projected sea level rise and storm surge intensity that are missing from FEMA’s model, making them both projective and predictive instead of just predictive.

Damage Calculations

Damage calculations were estimated using FEMA's Hazus model, which accounts for elevation and depth of flooding to estimate economic loss. Click on the map to the left to see census block-level estimates of economic loss to buildings under each flood scenario.

Our Proposal

Our proposal stems from noted differences between the three “models” for East Boston with a particular focus on the area stretching from the East Boston Greenway to Suffolk Downs site. In lieu of a physical intervention, we are proposing to streamline the FEMA flood mapping process, inspired by the large discrepancies in the models and the obtuse ways in which the maps are currently produced and released. Each included flood map was curated by different actors, for different reasons, and have been disseminated to decision-makers and the public in various ways.