Army Corps Explains Sea Level Rise Plan

Shoreline homes are vulnerable to future sea level rise and flooding

Army Corps plan to elevate floodplain homes is argued as the most cost-effective solution.

Army Corps proposal to elevate homes and sea level rise projection maps presented at Beach SAMP meeting.

Westerly’s Matunuck shoreline has moved a lot further landward than was 80 years ago, and it will continue to move further landward — and more rapidly — in the future.

The exact timetable of the retreat is uncertain, said coastal geologist Bryan Oakley at a recent meeting at the University of Rhode Island, but “we’re going to get there eventually.”

Oakley, an assistant professor at Eastern Connecticut State University, presented maps projecting future shoreline change on December 1 at the Shoreline Change Special Area Management Plan meeting at URI’s Graduate School of Oceanography.

The maps, he said, do not represent “a line in the sand” but rather a band showing expected shoreline change that will occur more rapidly with increasing sea level rise. Though the exact numbers are difficult due to the unpredictability of the other major – and in Oakley’s estimation, more important – factor in shoreline erosion, storms.

“We don’t know what the storm future is,” he said, “Storms don’t follow a schedule, even if we assign them a term like ‘100-year storm.’”

He said the maps were to be used by stakeholders and planners to “guide sustainable development choices” not as part of a regulatory process. They will be available on the Beach SAMP website and he is working with Beach SAMP staff to ensure they correspond with existing tools on the site, specifically Stormtools, which looks at future flooding impacts under different sea level rise and storm scenarios.

Army Corps Cost-Benefit Analysis

Chris Hatfield from the U.S. Army Corps of Engineers, described at the meeting a plan for elevating homes in the coastal floodplain at highest risk from flooding. The plan has stirred some controversy with Save The Bay, among others, criticizing it for underestimating sea level rise and not adequately considering retreat, rather than elevation, as an alternative solution.

The public comment period on the plan ended earlier in the week, and Hatfield said he had received several comments along the lines of “Don’t spend tax dollars on anything to do with anybody’s home.”

That, however, is within the Army Corps’ purview, Hatfield said.

“We look at private structures and the damage that is being incurred. We look at that as a national resource—we are allowed to take structure damage, even though it is occurring to private owners—the government has decided that they were willing to go in and protect that. They have charged the Corps with reducing structural damage.”

Congress passed a bill in the wake of Superstorm Sandy in 2013 that funded the study, and Corps staff have spent two years looking at 4,000 flood-vulnerable structures in Westerly, Charlestown, South Kingstown, and Narragansett. The study, now in the “tentatively selected plan” phase, identified 341 primarily residential structures that were vulnerable to flooding based on a conservative sea level rise scenario and thus are eligible for elevation assistance.

Other solutions, said Hatfield, such as building seawalls or replenishing beaches, were not cost-effective, in part because many of the coastal areas were too sparsely populated to justify the expense of the work.

Although the elevation plan proposed by the Army Corps is estimated to provide $7.35 million in annual benefits, the costs of potential septic system upgrades is not included in the coastal storm risk management feasibility study.

For example, in Misquamicut, which is densely developed enough for the Corps to consider structural solutions, when the Corps ran models simulating what would happen if the beach were nourished over the course of 50 years, they discovered “you couldn’t build a beach big enough” to protect the area. The models found, he said, that if they were to “try to build the beach bigger … it eroded even worse.”

The Army Corps also evaluated the prospect of funding retreat—“acquisitions”—that some have advocated.

“The benefits are, all the damages go away,” Hatfield said, but “the cost is not the cost of buying the people out, it is the cost of putting them in a flood-free home up the street—property in New England is expensive.” He added, “We also added the cost of cleaning the site and making it open space.”

As to the charge that the Corps’ projection of sea level rise was unrealistically low, Hatfield said that that was the rate those in higher authority at the Corps had agreed to consider. But he admitted that the 341 structures are not the only ones at risk. He said that he has told people who have contacted him about their homes in the same area as the ones targeted for elevation that “it’s not that they are not at risk or that they shouldn’t plan.”

An audience member questioned whether the Corps should be assisting presumably wealthy coastal property owners when “the households that struggle to recover are lower income households.”

Hatfield responded that “We were blind to income, whether it was a first home or second home,” but that he has looked at the 341 targeted structures, and “they are modest.”

The Army Corps paid for the study and will be responsible for 65 percent of the costs of implementing the plan — which includes 100 percent of the design costs and a portion of the construction costs. The remaining 35 percent would be incurred by the non-federal sponsor of the project, which is currently the CRMC, though it may not remain the partner in the future, Hatfield said. That role might be assumed by the state or the municipalities.

While CRMC is currently a sponsor, Grover Fugate, CRMC executive director, said there are still a lot of concerns to be addressed, including the Corps’ use of the low curve for projected sea level rise.

“The state has already adopted the NOAA high curve,” Fugate said, “there is a thing called federal consistency the Corps … has to deal with … we don’t believe the historic (low) is a prudent way to go.”

Federal consistency, according to NOAA, generally “requires that federal actions, within and outside the coastal zone, which have reasonably foreseeable effects on any coastal use (land or water) or natural resource of the coastal zone be consistent with the enforceable policies of a state’s federally approved coastal management program,” which in Rhode Island is the purview of the CRMC.

Both presentations will be available on the Beach SAMP website, http://beachsamp.org. The Army Corps’ plan for the area, known as the Pawcatuck River Coastal Storm Risk Management Feasibility Study, is online at http://www.nae.usace.army.mil/Missions/Projects-Topics/Pawcatuck-River-CSRM-Feasibility-Study/.

The Beach SAMP is a project of the Rhode Island Coastal Resources Management Council, Rhode Island Sea Grant and the Coastal Resources Center at the University of Rhode Island Graduate School of Oceanography, and the Rhode Island Geological Survey. More information about the Beach SAMP is available at http://www.beachsamp.org/.

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Monica Allard Cox | Rhode Island Sea Grant Communications