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RI Coastal Resources Management Council

...to preserve, protect, develop, and restore coastal resources for all Rhode Islanders

Narragansett facility first to benefit from STORMTOOLS

PROVIDENCE – The R.I. Coastal Resources Management Council recently approved the Town of Narragansett’s application for a proposed flood-proofing barrier to protect the Scarborough Wastewater Treatment Facility. It was the first time CRMC staff utilized the new mapping tool, STORMTOOLS, to demonstrate future flooding and storm impacts.

The facility – owned and operated by the town – is located on Ocean Road, just south of the Scarborough State Beach and services 7,300 residents (according to the RI Department of Environmental Management). Currently at the site, there is little to protect the treatment facility from flooding and wave action from storms. The town proposed to construct a barrier consisting of driven sheet pile and cast concrete, with rip-rap stone on the seaward side of the structure.

The facility abuts CRMC Type 1 (conservation) waters, and although the activity was proposed was landward of the coastal feature, it was classified as shoreline protection (prohibited in these areas under the coastal program), and therefore required a special exception from the Council, which it approved.

Using STORMTOOLS, CRMC Supervising Engineer Richard Lucia advised the town as to the design life of the barrier in relation to increased future risk from storms, flooding, erosion and sea level rise. STORMTOOLS is designed to help homeowners and municipalities understand their risk from coastal storms and flooding, and prepare for the realities of sea level rise. With the tool, as well as the latest sea level rise figures in the CRMC Red Book Section 145 and the CRMC shoreline change maps, Lucia reported to the Council that he would expect the structure to withstand regular storm events (10-year and 25-year storms), and sea level rise in its 50-year design life.

Citing STORMTOOLS, Lucia told the Council that he’d expect as much as 2.5 feet of sea level rise toward the end of the structure’s design life, and for the area to experience a five-foot sea level rise, at which point the structure would be inundated, in 2085.

Lucia also noted, however, that using the maps showing 100-year storm events with sea level rise added, the site would be flooded with even a sea level rise of two feet; during a 50-year storm event, the area would flood only if there were five feet of sea level rise in addition to the storm.

With this knowledge, the town’s consultant designed the structure to extend vertically 20 feet to incorporate four feet of freeboard above the Federal Emergency Management Agency’s (FEMA) Flood Zone VE elevation of 16 feet, and 2.8 feet of freeboard above the modeled wave run-up elevation of 17.2 feet. The additional freeboard is added for the projected 1.5 feet of sea level rise and one foot of freeboard for wave run-up.

“This is the first time our professional staff has had the opportunity to utilize STORMTOOLS in evaluating an application, and the results are obvious,” said CRMC Executive Director Grover Fugate. “The tool provides reliable data that we can use to educate and advise applicants. In the case of the wastewater treatment facility, the town was able to tailor their design to reflect these models.”

For more information on the RI Coastal Resources Management Program Section 145, go to http://www.crmc.ri.gov/regulations_proposed/2016_0126_CRMP_145.pdf. For more information on the CRMC Shoreline Change Maps, go to http://www.crmc.ri.gov/maps/maps_shorechange.html. And for more information on STORMTOOLS, go to https://stormtools-mainpage-crc-uri.hub.arcgis.com/.

 

Stedman Government Center
Suite 116, 4808 Tower Hill Road, Wakefield, RI 02879-1900
Voice 401-783-3370 • Fax 401-783-2069 • E-Mail cstaff1@crmc.ri.gov

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