401-829-4870 info@harboreng.com

Floodplain Mapping & Consulting

Homeowners and companies who own property along the coast are familiar with FEMA’s Flood Insurance Rate Maps (FIRMs).  In simple terms, a FIRM shows the potential extent of flooding in a region.  Base Flood Elevations (BFEs) are the elevations noted within defined areas on each FIRM that take into account storm surge and local effects including erosion and wave action.  These BFE’s need to be considered when building a new structure, modifying an existing structure or evaluating the level of risk an existing structure has to being flooded/damaged due to a significant storm event.

Over the years FEMA has been working hard to improve their data and FIRMs however it is important to recognize the results shown on a FIRM may not accurately represent the conditions for each and every location/site.  The best way to determine the flooding for a site is to have a Professional Land Surveyor develop a topographic survey and have a coastal engineer run the various programs required by FEMA to identify the Base Flood Elevations (BFEs) for the site.



Harbor Engineering’s principal has had much success reducing the BFEs for various properties along the coast by filing Letter of Map Revision (LOMR) applications.  These applications take into account more accurate topographic data and/or include the certification of a coastal structure that can help mitigate the effects of flooding.  Once approved by FEMA, a change to the flood zone(s) on a site may be able to avoid having to construct a more expensive type of foundation, reduce how high a structure needs to be elevated and/or reduce future insurance premiums.  Any one of these results leads to significant savings to the property owner.

Services offered by Harbor Engineering related to Floodplain Mapping & Consulting Services include:

  • Performing coastal flooding assessments using programs including CEDAS, ACES, CHAMP, WHAFIS and RUNUP
  • Designing shoreline structures to reduce the impacts of coastal flooding
  • Preparing applications to FEMA to change the FIRM via Letter of Map Revision (LOMR)
  • Consulting with homeowners, architects, structural engineers and municipalities on interpreting FEMA’s flood regulations and guidelines

Source: FEMA Coastal Construction Manual, 2005