SOUTH KINGSTOWN — Aerial photographs taken in 1939 show a Matunuck coastline rimmed by a generous swath of beach. Overhead shots taken in 2006 show a shoreline transformed into a mere sliver of sand.

Now, the town is exploring ways to reduce the threat storms pose to the Matunuck area, particularly after waves submerged portions of Matunuck Beach Road during storms in the past several years, cutting the beach community off from road access.

About 100 people attended an informational meeting, prepared by engineers from the Pare Corporation, at Matunuck Elementary School last night that touched on options for protecting the region as well as their estimated cost.

Prospective actions ranged from taking no action, to building a breakwater or seawall, to erecting an emergency bridge that would connect Atlantic Avenue to Prospect Road. Costs ranged from zero to more than $20 million.

The Town Council in December hired Pare to look at the South Kingstown’s shoreline management as part of its multi-hazard mitigation plan. Every community must complete a plan, detailing how it would reduce risks from natural disasters, that must be approved by the Federal Emergency Management Agency.

Pare’s work focused on the area south and east of the Vanilla Bean ice cream shop extending to Matunuck Point that encompasses about 500 properties valued collectively at $160 million. And while the Foxboro-based firm did not make recommendations, its engineers explored a variety of possibilities.

First identified were options not in the running, namely bulkheads, floating breakwaters, shifting development away from the water, creating groins — jetties extending out from shore — and raising the grade of Matunuck Beach Road.

Next up were cost-free alternatives, including changing development practices in coastal areas to incorporate future conditions such as rising sea levels and changing storm patterns and taking steps to exceed national floodplain standards, which in turn would make homeowners eligible for discounts on their flood insurance premiums.

Pare estimated that retrofitting structures to elevate them above the flood level would cost as much as $47 per square foot.

An option that sparked some of the most impassioned discussion was building an emergency evacuation route just north of Mary Carpenter’s Beach Meadow and a bridge over wetlands that would connect Prospect Road and Atlantic Avenue.

Pare projected the road construction cost at $100,000, not including land acquisition fees or the expenses associated with moving cottages, and the bridge at $1.25 million, also without figuring in land costs.

Some residents dismissed the idea as a “bridge to nowhere,” noting that sections of Prospect Road already flood in moderate rain. Others worried it would open up the neighborhood to more traffic.

Other alternatives named were beach nourishment with an $8 million to $12 million pricetag; placing sausage-like tubes underneath dunes at $6 million to $8 million; and erecting beachfront berms of coconut fibers and sand for $8 million to $10 million.

Karl W. Hammond, a Pare engineer, said he would not recommend the berms because of their short lifespan and vulnerability.

Pare also explored “hard-armor” structures, estimating that an offshore breakwater about 5,000 feet long would cost more than $20 million. A breakwater, like the one near Sand Hill Cove, would alter surf patterns and habitat, Hammond said.

A riprap revetment was projected at $5 million to $7 million, with a concrete seawall on steel sheet pile coming in at $15 million to $17 million and a concrete gravity seawall estimated at $13 million to $16 million.

During the public comment period a resident suggested that the remnants of the former Jamestown Bridge trestle could be disposed off offshore. Another suggested a coastal building moratorium.

Several expressed concerns about the impact a breakwater might have on Green Hill or Roy Carpenter’s Beach. Jon Boothroyd, a University of Rhode Island geology professor, told them not to worry because sand moves east from Charlestown, but that the beach would be diminished behind such a structure.

Asked who would bear the cost of any measures, Principal Planner Raymond Nickerson said he imagined it would be paid for through a partnership with the government and area property owners.

Completing the hazard plan would make the town eligible for funding, Town Manager Stephen Alfred said.

“Our main concern right now is what would we do if there was a catastrophic event” and road access to Matunuck is cut off, Alfred said. The town needs to find out “what works, what’s allowed and funding,” adding that he did not foresee the town using a bond to pay for any measures.

Pare is expected to complete its work in coordination with the state Coastal Resources Management Council and Department of Environmental Management by the year’s end. It will include a cost-benefit analysis and pinpoint responsible parties, funding sources and time frames.

Pare’s study is being paid for by a $75,000 grant from the Rhode Island Emergency Management Agency that is matched by the town with $25,000 through in-kind services, according to Nickerson.

kmulvane@projo.com