New topographical maps of Martha’s Vineyard with updated, detailed flood zone information are now in the proofing stage and should be finished by fall. The new maps, called Flood Insurance Rate Maps (FIRM) could result in changes in flood insurance rates for homeowners and businesses in low-lying areas. Town zoning and building regulations in those areas may also be affected.
The Island is being remapped by The Federal Emergency Management Agency (FEMA) as part of a nationwide, hi-tech effort to bring the agency’s maps of coastal and inland flooding areas up to date, according to Dennis Pinkham, external affairs officer for the Boston FEMA office.
The new maps will replace coastal maps first made in the 1980s, according to Joanne Taylor, Martha’s Vineyard Commission coastal planner. She said the new maps will be much more precise.
A group of Island town representatives attended a briefing on the map project in December at the Vineyard Transportation Authority building at the industrial park, where a FEMA representative asked their help in proofing draft copies of the new topographical maps. These drafts are a prelude to the preliminary maps that should be made public before the end of March.
Ms. Taylor, Tisbury building inspector Kenneth Barwick, Jane Varkonda, conservation agent with the Tisbury Conservation Commission, and Edgartown Building/Zoning Inspector Leonard Jason,were among those who attended the meeting. Mr. Jason said they were asked to suggest corrections to names and to see if the high water markings were consistent with their records and memories.
“It is a huge expensive nationwide project and some of the changes are pretty significant. Sometimes the changes put people into flood zones and sometimes they take them out,” according to Mr. Pinkham. Changing weather patterns, erosion, and development can affect floodplain boundaries, he said.
Mr. Pinkham said the latest in mapping technology and information gathering techniques are being used to create the new maps. Chief among these is called LIDAR, for light detection and ranging. It is an aerial mapping system that uses an optical technology to measure topographical features by illuminating the target with laser light and analyzing the backscattered light. The end product will look similar to seafloor maps, he said.
The most recent available data on water flow and draining patterns of both ebbing and flooding tides are also important components of the new maps, Mr. Pinkham said. The new maps will show continuous gradations rather than the one meter increments of the old maps, so modeling of water flow will be much improved.
The preliminary maps will be used in community coordination meetings where the public will have the opportunity to ask questions and comment on the maps. There will then be a required 90-day appeal period when anyone effected by changes in the special flood hazard areas or the base flood elevations can appeal what is on the maps.
The appeals must be accompanied by scientific and technical evidence, according to FEMA’s Community Consultation Officer, David Mendelsohn. “We spend a lot of time and energy and there is a lot of expertise that goes into these maps, which doesn’t make them infallible, but there must be scientific data to appeal,” he said. “We have come a long way from ‘well, it hasn’t flooded in my lifetime.'”
He said that information used to make the new maps has come from more and better sources than was used to make past maps. There is much better statistical storm data, more complete buoy information on tide and wave activity during storms, much better and more detailed measurements of topography and the actual elevations as well as better river flow and rain data.
“We have a much better understanding of hydrology, the study of water and how it interacts with land masses, a much better understanding of bathymetry, the depth of the water, the land under the water and how waves build up and their effects on the land above the water,” he said.
The final maps will not be available until the fall.
One of the chief uses of the FIRM maps is to help assess risk in low-lying, flood-prone areas for insurance purposes, to help insurance professionals and homeowners make informed choices about flood insurance protection. The maps also help governmental agencies establish safer building codes and plan for emergencies.
The maps are an important part of the National Flood Insurance Program (NFIP) which sets the regulatory basis for local floodplain management and is also the primary source of insurance protection for the flood prone. The NFIP has maximum coverage limits of $250,000 for homes and $100,000 for contents, a small portion of the value of many homes in Vineyard coastal zones, according to Kathy O’Sullivan of Martha’s Vineyard Insurance. But she added that the limits can work for people in at-risk areas who have built their houses in ways that protect much of the home’s value from flood damage.
Ms. O’Sullivan said that flood risk is not the reason many Vineyard homeowners have had to resort to the Massachusetts FAIR Plan, known as the insurer of last resort, for their homeowners insurance. She said that many private insurance companies do not offer homeowners insurance on the Vineyard because of the high risk of wind damage and that flooding has not been the cause of their refusal to insure Vineyard properties.