MULTIPLE RESPONSES TO FRONTAL EROSION AND INUNDATION ON A BARRIER/HEADLAND SHORE, RHODE ISLAND

The south shore of Rhode Island is a microtidal (1.05 m mean, 1.17 m spring range) mixed wave/tide dominated shore subject to both tropical and extratropical cyclones. Storm surges range from 2.9 m above MHHW (1938 category 3 hurricane) to 0.9 m (Patriots Day 2007 extratropical). Sustained southeast winds may cause extratropical surges to extend over 5-8 tidal cycles. Relative sea-level rise is 27.5 cm . 100 yr-1 resulting in a 22 cm rise since 1929 and 17 cm since 1938. A 5 km tract of the combined barrier spit/glacial stratified-material bluff headland, the Moonstone/Matunuck reach, serves as an example of multiple responses by people to an area severely impacted by frontal erosion and storm-surge inundation. Total frontal erosion measures up to 68 m (1939-2006) at bluff locations and 41 m on the barrier.

The Moonstone barrier contains USFWS refuge land and private property. The Refuge is left natural for piping plover habitat, whereas the private section homeowners, with structures on the National Historic Register, have responded by: 1) dismantling and removing; 2) moving to an upland site; 3) trying a series of “soft” structural shoreline protection methods. The Matunuck headland section contains a private beach club with open space, a town beach, densely populated sections of small summer cottages on leased land, a small commercial district and town road infrastructure with water and sewer lines. Response has been: 1) 100 m setback of buildings at the beach club; 2) dismantling and loss of a 120 m long boardwalk at the town beach; 3) movement of structures landward in the summer cottage area; and 4) maintenance of rip-rap revetments along parts of the commercial area, installed before prohibition by the present coastal management plan (RICRMP). Additional input was the placement of 80,000 m3 of sand on the shallow shoreface in 2 areas, obtained from maintenance dredging of nearby Galilee harbor.

All areas are in imminent danger from additional frontal erosion and storm-surge inundation. Frontal erosion has removed much of the buffer that existed at the time of the 1938 hurricane, resulting in landward translation of FEMA V and A zones. The Town of South Kingstown and Historic Register homeowners can claim a special exception under the RICRMP to install “hard” structures, probably seawalls because older revetments are failing.