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Thursday, June 15, 2023

Opinion | The Army Corps’s Flood Plan Could Ruin New York’s Waterfront. It Doesn’t Have To. - The New York Times

The Plan to Save New York From the Next Sandy Will Ruin the Waterfront. It Doesn’t Have To.

"Last September, the U.S. Army Corps of Engineers unveiled its proposal to protect the greater New York and New Jersey metro area from the next catastrophic flood. It is an epic plan that includes dozens of miles of floodwalls, levees and berms along the shoreline and 12 storm surge barriers — arrays of movable gates — across entrances to waterways throughout the region.

The plan is estimated to cost a staggering $52.6 billion. It’s by far the most expensive project ever proposed by the Corps.

The trouble is that despite its great ambitions, the Corps’s plan demonstrates the shortcomings of relying on massive shoreline structures for flood protection. If built, this plan could reverse the region’s decades-long effort to open up its waterfront for recreation while, at best, protecting only a small fraction of the region’s most vulnerable areas from devastating storm surge flooding.

Coastal storm flooding is a grave risk to the region, as we saw when Hurricane Sandy swept through, causing 60 deaths and more than $70 billion in damage. In terms of population at risk, New York City is the most vulnerable city in the country, according to Climate Central, a nonprofit research organization. As global warming raises sea levels, more of the region will be at risk, and the likelihood of Sandy-scale flooding will increase.

Other cities facing such risks — including Rotterdam, the Netherlands; London; and St. Petersburg, Russia — have built arrays of movable gates across the main entrances to their harbors. These highly effective and reliable harborwide surge barriers can protect large areas while leaving shorelines free for recreation and other uses. And they are an ideal fit for the geography of New York Harbor.

Central to the Corps’s proposal, by contrast, are 50 miles of 12-to-20-foot-high floodwalls, levees and other shoreline structures that would interfere with public access and connection to the water on long stretches of existing developed waterfronts and parks, including Hunters Point, Greenpoint, Manhattan’s west side and downtown Jersey City.

These visualizations illustrate how floodwalls proposed by the Corps could alter the region’s waterfront. The Corps has suggested that the positions for some walls could shift as the project moves forward but hasn’t yet indicated what those changes would be.

Hudson River Park

Hudson River Park

Hudson River Park

Gantry Plaza State Park

Gantry Plaza State Park

Imagine bicycling up the Hudson River Greenway in Manhattan next to a concrete wall between you and Hudson River Park. Or straining to see the United Nations through occasional gaps in a 12-foot-high floodwall at Hunters Point. Or strolling along Jersey City’s pleasant waterfront esplanade without cool breezes from the harbor.

To preserve a modicum of public access, the floodwalls and levees would have numerous pedestrian and vehicular gates, some crossing major highways, cutting off even emergency traffic for many hours during a storm. The gates would have to be individually closed whenever a major storm threatens, requiring an extraordinary level of coordination. Failure to successfully deploy one gate could lead to large-scale flooding.

Floodwalls will also require expensive modifications to New York City’s drainage system and costly pump stations to prevent neighborhoods behind the walls from being flooded by rainwater, according to a letter Rohit Aggarwala, New York City’s chief climate officer, sent to the Corps.

These and other deficiencies are so serious that New York City seemed to have second thoughts. Mr. Aggarwala warned, “The city will not accept austere floodwalls running through our neighborhoods.”

Greenpoint Public Park

Greenpoint Public Park

Red Hook

Red Hook

Despite its high cost, the Corps’s proposal would still leave about 40 percent of vulnerable areas at risk of coastal flooding. This is mainly due to a cost-benefit methodology that appears to be biased against protecting low-income or smaller communities with lower property values. Defending areas such as the South Bronx, Hallets Point, Queensbridge, parts of South Williamsburg and even Yonkers and Ossining from storm surge is apparently not worth the cost — a clear example of climate redlining. The Corps’s plan also wouldn’t protect many vital regional assets, including the Hunts Point Market, LaGuardia Airport and Governors Island.

Furthermore, many environmental groups are concerned that putting surge barriers across narrow waterways with very poor tidal flushing — some of them highly polluted, like Newtown Creek and the Gowanus Canal — will only exacerbate already unacceptable conditions.

Why would the Corps propose a plan with such glaring weaknesses? And why would New York State, New Jersey and New York City endorse it?

One reason may be that the Corps and its local partners have been inanely deferring to one another instead of seeking the best plan. The project is a partnership among state and federal agencies, in which the states would pay 35 percent of the costs and the federal government would pay the rest.

The city and states need the Corps’s promise of federal money to fund any major coastal protection project, which probably explains their readiness to accept the Corps’s proposal. Yet the Corps can’t get construction funds without congressional approval for a specific plan, which requires local political support and advocacy. So the Corps may be proposing what it believes the city and two states want.

The Corps’s design for shoreline floodwalls and local surge gates is strikingly similar to the plan that New York City released in 2013 after Hurricane Sandy. The Corps then extended the strategy to New Jersey communities. This seemingly mutual deference has resulted in the destructive and inadequate plan now under consideration — a proposal that would hobble the region for decades. It portends an endless series of fights and litigation, community by community, over shoreline floodwalls and local surge gates.

Fortunately, when the Corps unveiled its preferred plan, it was accompanied by several alternatives.

One option would be to use a regional storm surge barrier system instead of shoreline floodwalls and local sea gates. A Dutch flood risk expert, Jeroen Aerts, the head of the department of water and climate risk at Vrije University Amsterdam, whom New York City hired to evaluate its plans against other alternatives, concluded in 2013 that a regional offshore barrier system is a better choice. “Don’t rule out yet the barriers,” he warned, referring to harborwide storm surge barriers, “because the sea level is going to rise very quickly, and then you need a barrier.”

A regional, harborwide barrier system could stop the largest storm surges while maintaining normal water levels in the harbor. And instead of manually operating numerous shoreline gates, the closure of offshore surge gates would be mechanized and centrally controlled. All communities within the harbor area would be protected equally.

The Corps examined two ways to protect the region using harborwide barriers. One plan, featuring a storm surge barrier stretching from Breezy Point to Sandy Hook at the entrance to the lower bay, would cover 96 percent of the region at risk of flooding. In the other plan, a storm surge barrier would likely extend from Brooklyn to Staten Island, with supplemental gates at Arthur Kill and Jamaica Bay and would cover more than 80 percent. Both alternatives would have a surge barrier across the harbor entrance at Throgs Neck.

Areas predicted to flood

Source: U.S. Army Corps of Engineers

One challenge of regional barrier systems is what to do about sea level rise. Using the surge barriers to stop increasingly frequent high tide flooding may be tempting. But by carelessly disrupting tidal flow, frequent gate closings might risk the health of the Hudson River estuary. So a plan featuring harborwide surge barriers must include a plan to raise streets and walkways near the shore, where necessary, to block flooding by high tides and smaller storms. The offshore barriers would then be used only for medium-size and large storms, closing for storms no more than about once every two years, on average, as the Corps promises.

The city resisted harborwide barriers in 2013 because of too many unanswered questions. Many of those questions have now been answered.

A major concern was whether the federal government would fund such a large project, then estimated at $20 billion to $25 billion. But recently, the Texas delegation obtained congressional funding for a $34 billion Corps coastal restoration and surge barrier project for Galveston Bay to protect Houston and the surrounding area. Perhaps that approval can provide confidence that our region’s powerful congressional delegation can do the same.

Another question is whether piers supporting the gates would affect tidal flow, salinity and sediment transport. New research from David Ralston, a scientist at the Woods Hole Oceanographic Institution, suggests that when the surge gates are open, the environmental effects would be modest.

To impede storm surges, some environmental groups suggest turning to nature-based solutions, such as coastal wetlands, dunes, barrier islands and oyster reefs. We agree that, wherever practical, nature-based systems, like the reinforced dune being built on the Rockaway Peninsula, should be the first choice. But to combat a large storm surge, like the nine feet of water pushed up by Hurricane Sandy, other nature-based solutions would require vastly more space than is available in New York Harbor. For example, about three miles of wetlands between the ocean and shore would reduce a storm surge by only about 1 foot, according to a widely cited study conducted by the Corps.

After a public comment period that ended in March, the Corps will decide in the next few weeks whether to continue with its current proposal or switch to a different alternative. The Corps, the states and New York City, perhaps with the encouragement of our congressional delegation, should set aside their flawed proposal and turn to something better.

Galveston-Houston and Miami-Dade, facing similar challenges, were able to make extensive changes to the Corps’s initial plans. Galveston-Houston added a large storm surge barrier to a Corps plan for coastal restoration. Miami-Dade rejected the Corps’s initial flood mitigation plan and, as a result, is now engaged with the Corps in devising a much improved design.

For the sake of our waterfront and the communities excluded by the current plan, we should insist that the same thing happen here."

Opinion | The Army Corps’s Flood Plan Could Ruin New York’s Waterfront. It Doesn’t Have To. - The New York Times

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