Coastal flooding can be caused by different processes (i.e., hurricanes, storm surge, rapid accumulation of rainfall), and just because a property has never flooded in the past, doesn’t mean it won’t flood in the future. Flood hazard conditions are dynamic and can change over time, whether due to new development or natural changes in the environment. To accurately identify and classify risks associated with these changes, the Federal Emergency Management Agency (FEMA) identifies flood hazards and assesses flood-related risks through its Flood Hazard Mapping Program. Flood Hazard Mapping is an important part of the National Flood Insurance Program (NFIP), and is used regulate floodplain development and determine requirements for flood insurance. FEMA maintains and periodically updates the Flood Insurance Rate Maps (FIRMs) to reflect changes in flood risk. These remapping activities allow FEMA to identify emerging risks, provide more accurate information needed to identify flood insurance requirements, and target hazard mitigation planning to help reduce risk associated with flooding.
Recent FEMA Changes
In light of recent natural disasters and resulting changes to national legislation concerning flood insurance, FEMA’s flood mapping program has become a critical issue for many coastal communities and landowners. In the aftermath of Hurricane Sandy, Congress approved the Biggert-Waters Act, designed to keep the NFIP financially solvent. The Act called on FEMA and required insurers to amend rates to reflect true flood risk. The goal of this Act was to make the program more financially stable by phasing out government subsidies for flood insurance. In New England, changes were amplified because at the same time flood insurance rates were being raised at a federal level, FEMA Region I (New England) was in the process of remapping many of the coastal counties through their Risk MAP program (Figure 1).
Figure 1. Status of FEMA’s Risk MAP Program
For many coastal communities, remapping resulted in expansion of the Special Flood Hazard Area (100-yr floodplain) as well as higher Base Flood Elevations (BFEs). The combination of these two events alarmed coastal communities and landowners, as many new properties were now included within the 100-yr floodplain, and those mapped in the SFHA were now facing higher insurance rates. Massachusetts Senators Elizabeth Warren and Edward Markey warned these changes would have "economically devastating impacts". In response to such outcries, in March 2014 President Obama signed the Homeowner Flood Insurance Affordability Act into law, repealing and modifying certain provisions in the Biggert-Waters Act. Although this new law lowered rate increases on some policies mandated by Biggert-Waters, the recent remapping conducted in FEMA Region 1 still left many New England homeowners who never needed flood insurance before, with a requirement to purchase a new flood insurance policy.
FEMA’s coastal flood hazard mapping studies are supported by scientific and engineering analyses designed to quantify risks associated with the 100-yr storm event. In New England, storm surge levels are determined through statistical analyses of long-term tide gage data, local tidal information, and highwater marks from historical storms of record. FEMA also performs overland wave modeling to determine changes in wave height as a function of water depth, vegetation, development, etc. At barriers along the coastline, such as dunes, seawalls or steep shoreline features, FEMA evaluates the processes of wave runup and overtoppoing that occur when waves interact with steeper landforms. As part of the RiskMAP program, wave setup is now included in all coastal flood hazard mapping studies. Wave setup refers to an increase in the water level near the shoreline due to the presence of breaking waves. FEMA’s flood hazard maps then show risks associated with the combination of waves, runup, storm surge, and wave setup created during the 1%-annual-chance flood.
Expansion of the SFHA and increases in the BFEs on the new FEMA maps are the result of two primary factors: updates to storm surge levels; and inclusion of wave setup. While FEMA Region I is updating the coastal flood maps using improved data, they still rely on traditional, one-dimensional models used by FEMA for decades to quantify flood risks. FEMA offices in other Regions now utilize a tightly coupled hydrodynamic and wave model, combined with advanced statistics, to calculate 100-yr storm surge levels and wave setup for use in coastal flood hazard mapping studies. Results from this type of dynamic modeling provide more accurate and highly resolved predictions of coastal flooding associated with storms.
Potential Community Response
If a community or landowner believes FEMA’s FIRMs contain errors, there are a number of avenues to appeal or request for map revision. In the case of new maps, there is a formal process for review between the time the Preliminary FIRMs are published and adoption of the Effective FIRMs. Once the Preliminary FIRMs are released, which is done on a county-by-county basis, a 90-day statutory appeal period begins. During this time, the communities and their citizens can review the maps and, if warranted, develop and submit technical information to support an appeal. Once the 90-day appeal period closes, FEMA reviews the appeals received and potentially revises the maps accordingly before issuing a Letter of Final Determination (LFD). Issuance of the LFD initiates a 6-month period during which the communities must update their local ordinances, flood hazard plans, etc., and ultimately adopt the new maps. At the end of the 6-month period, the updated maps become Effective. Even if communities are still dissatisfied with FEMA’s Effective maps, it is crucial they formally adopt these plans; communities that fail to adopt the Effective FIRMs within the 6-month period are out of compliance with the NFIP, and are no longer eligible for flood insurance, flood hazard related grants, etc. FEMA also considers revisions to Effective FIRMs through applications for Physical Map Revision (PMR), Letter of Map Revision (LOMR), or Conditional Letter of Map Revision (CLOMR) when they are supported by the required technical documentation.
Given the significant financial implications for property owners, it is vital that coastal landowners and municipal officials fully understand the current and future risks to their property or community associated with coastal flooding. Evaluation of FEMA’s updated FIRMs during the 90-day appeal period, or even after the maps become Effective, can often result in a reduction to the SFHA, as well as the BFEs. With the new maps released in FEMA Region I, there are a number of technical issues that may warrant closer examination, such as development of the 100-yr stillwater level, application of wave setup, and the development of wave conditions in sheltered water bodies. Whenever large areas are analyzed and remapped, some flood area designations can be conservative. Increases in risk can be real, but there are often opportunities to revise the maps to more accurately reflect available data. Because FEMA’s remapping area evaluates an entire county, their approach is necessarily coarser, and can overlook small topographic changes at a local level that may influence whether a property is in or out of the SFHA. With these issues in mind, Woods Hole Group has supported communities at three difference phase in the FEMA remapping process.
Figure 2. Results from the MassDOT BH-FRM model
showing water levels, wind velocities,
and directions associated with a coastal noreaster.
- During the 90-day appeal period: Woods Hole Group supported the communities of Scituate, Marshfield and Duxbury (Plymouth County), as well as other private groups in Barnstable County, to perform technical reviews of the Preliminary Flood Insurance Studies (FIS) and FIRMs. Through these reviews, we developed the technical basis for four appeals reducing the extent of the SFHA and associated BFEs (one in Barnstable County and three in Plymouth County). FEMA has accepted the appeal in Barnstable County and the Plymouth County appeals are currently being reviewed. In two other Barnstable County locations, we concluded there was no basis for an appeal of the Preliminary FEMA maps.
- In advance of the 90-day appeal period: Woods Hole Group is currently performing a multi-phase review of the Preliminary flood maps for the City of Boston (Suffolk County) in advance of the opening of the appeal period. Phase I involves a detailed evaluation of FEMA’s coastal mapping study, looking at storm surge levels, wave setup, overland wave propagation, wave runup and overtopping, using FEMA’s standard methodologies. Phase II of WHG’s review will produce more detailed, site-specific model inputs by incorporating the results of a tightly coupled hydrodynamic (ADCIRC) and wave model (SWAN) developed by Woods Hole Group for MassDOT (Figure 2). This approach follows the same methods utilized by FEMA in other Regions of the US. If warranted, results of the Phase II analysis will be used to refine the Preliminary FEMA FIRMs and support a formal appeal once the 90-day appeal period officially opens. There are also plans to expand the City of Boston evaluation to the three other communities in Suffolk County: Chelsea, Winthrop and Revere.
- After the close of the 90-day appeal period: In Quincy (Norfolk County), the 90-day appeal period closed. In this case, Woods Hole Group is evaluating the FIRMs that will become Effective on June 9, 2014. If errors are found, we will work with the City of Quincy and their engineering consultants to submit a Letter of Map Revision (LOMR) at the appropriate time.
Figure 3. Comparison of the area within the
100-year flood plain in FEMA’s Preliminary FIRM for
Marshfield and in Woods Hole Group’s updated analysis.
Our work evaluating the Preliminary FEMA FIRMs for the Town of Marshfield, showed lower BFEs for many of the areas studied, and also significantly reduced the number of parcels within the SFHA. In some cases, areas designated by FEMA as a VE zone were remapped into the lower risk AE zone. As seen in Figure 3, BFE’s were reduced from AE (El. 15-18’) to AE (El. 9-10’) throughout much of the area highlighted. Flood map changes submitted to FEMA with the appeal package for this area of Marshfield show a change from 685 parcels in the SFHA on the Preliminary maps to 489 parcels on the revised maps. These map changes were primarily the result of revisions to storm surge levels and attenuation of wave setup as it propagates inland away from the coastline. Due to the scope of the revisions, the reductions in flood risk are expected to have significant economic consequences for the community and the private property owners affected by the Preliminary FIRMs.
Flood Risk and Climate Change
Once verified and finalized, FEMA’s FIRMs are a critical tool for determining the current flood risk for coastal communities. However, communities cannot rely on FEMA’s flood maps to identify areas vulnerable to future climate change since FEMA’s analyses do not, by definition, incorporate sea level rise. For planning purposes it can be valuable to consider these issues, flood risk and climate change, in tandem. They are closely related issues and the same tools used to predict flood elevations can also be used to project risk and vulnerability into the future. While communities are responding to recent FEMA changes and making necessary reassessments of flood risks, they can be proactive and evaluate the risks associated with future climate change simultaneously. Not only does the modeling overlap, but the resulting community planning decisions are interwoven as well. For example, evaluating future climate change impacts associated with sea level rise can identify areas that might fall into FEMA’s jurisdiction in the future, and can identify mitigation actions that if enacted now, can avoid flooding risks in the future. The time for communities to start preparing for future climate change vulnerability is now. Combining these types of evaluations is cost effective,and provides the most complete picture of risk for future community planning decisions. Upgrades to critical infrastructure, such as waste water treatment, drinking water supply, utilities, and roadways all should factor climate change in the planning process.
Leslie Fields M.S., CFM, Coastal Scientist
Elise Leduc M.E.M., Coastal Scientist
Woods Hole Group – Falmouth
81 Technology Park Drive
East falmouth, MA 02536