Almost 3,200 buildings on the Vineyard sit on land which could be inundated by the storm surge of a category four hurricane. Even a category one storm would put almost 400 buildings at risk.

The daunting statistics come out of work done by the Martha’s Vineyard Commission, which plotted the location of structures on the Island against so-called SLOSH (Sea, Lake and Overland Surges from Hurricanes) maps from the National Oceanic and Atmospheric Administration.

And the list of structures at risk includes not only some of the Island’s most expensive properties, but also some of the most vital, including emergency services.

That’s the bad news. The good news is, having identified them, having finished work on a pre-disaster mitigation plan, which has been approved by the Federal Emergency Management Agency (FEMA), the towns in Dukes County are now in a position to start applying for large amounts of money available to help prepare for possible natural catastrophes.

The plan, some five years in the making, was endorsed about three months ago by the county and the Island towns and recently ticked off by FEMA.

It canvasses natural risks ranging from fires to earthquakes, but it makes clear that of all possible threats, those posed by flooding from storms are the greatest here.

It identifies critical facilities at risk from either storm surge or hundred-year floods and notes that “many of the identified facilities are essential, most of those critically important for response to natural hazards, so that their significance goes far beyond the dollar value attached to the facility.”

It makes for sobering reading. Even the surge from a category one hurricane, for example, would affect the school on Gosnold. A category three storm would likely would take out the Tisbury fire department and the Edgartown public well. Category four would hit the alternate emergency operations center in Tisbury and the Edgartown courthouse.

And a big winter storm poses an almost equal threat.

The document assesses the vulnerabilities of Dukes County to various natural disasters according to their likelihood, the size of the area which would be affected and the degree of damage.

It sets out four categories of damage. A minor event would involve limited, scattered property damage; a serious one would include minor infrastructure damage, brief interruption of essential services and some injuries or fatalities. Extensive means major property and infrastructure damage, and many injuries or fatalities and catastrophic would see infrastructure destroyed, essential services stopped and hundreds of injuries and fatalities.

The categories for likelihood range from very low frequency, one in a thousand years

or more, through low — one in a hundred to one in a thousand, to medium, 10 to 100 years, to high, more than once in 10 years.

A composite hazard index rates storms and northeasters highest at 9.4, ahead of hurricanes (9) for flood hazards. The impacts are not considered as great as for hurricanes, but the likelihood is higher.

In Edgartown, for example, the likelihood of a hurricane is rated medium, the area which would be affected is extensive and the impacts catastrophic. The hazard index is 10.

But individual towns rate differently. Hurricanes (10) are a greater risk to Aquinnah than winter storms (9). In Chilmark the opposite is true.

Nor does the fact that 3,199 structures fall within the Slosh map for a category four hurricane mean that many would necessarily be flooded.

Christine Seidel, the cartographer who compiled the maps for the commission, said it is a worst-case scenario and there are many variables, such as tides.

But the picture she came up with is nonetheless alarming and the commission, in association with the various emergency managers of the Island towns then went about identifying the vulnerabilities of critical facilities and possible ways to reduce the risk.

Commission coastal planner Jo-Ann Taylor said the scene is now set for the Island to begin applying for money to mitigate the possible effects of a disaster.

“By having an approved [pre-disaster mitigation] plan, the towns are eligible for up to 75 per cent funding for these projects. There’s a lot of money that has been awarded to other cities and towns around the country,” she said, adding:

“It’s competitive, but we have a number of good projects in our plan.”

Furthermore, the 25 per cent which must come from non-federal sources does not all have to be cash; in-kind contributions could make up half.

Thus work done by town departments can count.

“Or it could come from private owners who are vulnerable, depending on the project. For example the East Chop Bluff is privately owned, but the town could apply for funding [for works to protect the bluff] and the owners could put up the rest of the money,” Ms. Taylor said.

She said there are specific constraints on what FEMA would find, “but it’s a lot of money.

“You have to want what they want to pay for. Do that and you’re in like Flynn.

“What’s in there is what the emergency managers wanted. Several towns wanted emergency generators for storm shelters, shutters for storm shelters, that kind of thing. FEMA loves to pay for those.

“The result of this will be that we get a lot of structural mitigation that will achieve increased personal safety and protection of property, next time there’s a hurricane or a northeaster or one of the other hazards.”

The wish lists of the various towns are extensive. Edgartown, for example, is looking to get money to upgrade the Chappaquiddick ferry, making it less susceptible to interruption by storms. Oak Bluffs could seek money to fix stormwater drainage which has caused damage to Inkwell beach. Tisbury could seek money toward the relocation of its emergency services out of the flood zone. And towns in general could seek money to upgrade roads, bridges, culverts and the like.

All of that is yet to happen, of course.

“But I think we as a group have really achieved something major here, getting the plan approved, because you don’t get anywhere without that.”

The whole plan can be viewed on the commission Web site, mvcommission.org. Search for the PDM plan.