sea level rise

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February 29, 2012 | 7:00 AM | By

Rising seas don’t have to be bad news

This is the third story in our four-part series Cape Change: A Local Perspective on Global Warming.

NASA

The 'hook' or 'fist' of Provincetown is one of the few parts of Cape Cod that is growing.

The tiny village of Woods Hole is a mish-mash of million-dollar homes and renowned scientific institutions perched on the southern tip of Cape Cod. Much of the coast is clad in sea walls and jetties intended to hold the line against the forces of erosion. But they can’t stop the rising sea.

At a recent workshop hosted by Waquoit Bay National Estuarine Research Reserve, Greg Berman of Woods Hole Sea Grant showed off a three-dimensional animation of what a popular restaurant perched atop one of those seawalls might look like under various sea level rise scenarios.

“So here we are at normal high tide,” he said, walking attendees through the animation. “You can bump it up to one foot of sea level rise. Three feet sea level rise. And then six feet of sea level rise.”

Sea level around Cape Cod has already risen one foot in the past century, and that rate is increasing as global temperatures rise and melting of the world’s major ice sheets accelerates. Three feet of additional rise by 2100 is now considered a moderate to conservative estimate, and six feet is within the realm of possibility. At that point, the restaurant in the animation would be flooded at high tide. Add storm surge from a major storm, and the computer-generated water levels rise to absurd heights half-way up the first-story windows – a prospect that elicited nervous laughter from workshop attendees.

“So really is it worse getting flooded to here,” asked Berman. “Is that going to matter too much more?”

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FILED UNDER: Human Impacts, Cape Change, coastal change, sea level rise
December 9, 2011 | 2:18 PM | By

Is erosion Falmouth’s forgotten problem?

Heather Goldstone / WCAI

Stretches of Falmouth's Surf Drive lie just feet from the high tide line. Sand often washes over the road during storms and has to be plowed off, creating the pseudo-dunes seen here.

I’ve been trying for a week to track down what – if any – progress has been made on the recommendations made by Falmouth’s Coastal Resources Working Group some eight years ago. I have yet to conduct a single interview, but I think the process itself has been revealing. So I’ll share.

The very first recommended action was to “establish a Town Coastal Management Committee to review proposed coastal projects, coordinate coastal activities and to inform the public concerning coastal processes.” So I headed over to the Town of Falmouth website to peruse the list of departments (which also includes committees, working groups, advisory boards, etc.). There’s the Coastal Pond Management Committee, which a member I was subsequently put in contact with (that comes later) explained does not deal with erosion issues. There’s the Beach Department, whose mission includes beach maintenance but There’s a link to the now-disbanded Coastal Resources Working Group, itself. But nowhere on that list could I find anything that might be the recommended committee. So …

Since the Coastal Resources Working Group reported to the Board of Selectmen, I decided to try there next. I emailed the chair(wo)man of the Board, Mary Pat Flynn to request an interview. She explained that the Board hadn’t taken up erosion issues in several months, but likely would at their meeting in January when they develop the coming year’s strategic plan. In the meantime, she suggested I contact Selectwoman Melissa Freitag, who she referred to as the Board’s “liaison to the committee” (which I presume refers to the Coastal Resources Working Group, but we’ll come back to that) and very knowledgeable on the subject. So …

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FILED UNDER: Adaptation, Coast, coastal change, sea level rise
December 1, 2011 | 11:21 AM | By

Beaches, beaches everywhere but not a dune in sight

Google Maps

Falmouth's south coast, from Nobska Point in Woods Hole (far left, bottom) to Waquoit Bay (far right), was the subject of a 2003 report outlining future strategies to address sea level rise and erosion.

In 2003, Falmouth’s Coastal Resources Working Group (a group of local scientists and concerned citizens that has since been disbanded) provided its first of two reports to town officials, entitled “The Future of Falmouth’s South Shore.” In the introduction, the authors actually lay out two possible futures – one if we continue on our past path of attempting to ignore or stop the inevitable, and one if we get our act in gear and start making the tough decisions that the realities of sea level rise and erosion demand. Here’s what they call the ‘business as usual’ scenario for 2100 (my emphasis):

  • Beaches will be present only where maintained by beach nourishment; few, if any, dunes will remain. Beach nourishment will become progressively more expensive as nearby sand resources are depleted.
  • The loss of the protective beaches and dunes will expose both public infrastructure (roads, bridges, water pipelines) and private property to the damaging effects of storms. The maintenance costs to the Town and to individuals will rise, and those increases will accelerate as sea level continues to rise.
  • Beaches will have retreated landward, with the possibility of breaks through the barrier beaches becoming more likely. Such breaks would expose property on the salt ponds to the waves of the open water of Vineyard Sound, and potentially cause serious disruption to channels for navigation into and out of the south shore ponds.
  • The shoreline will be pervasively armored, which will decrease the usability of the shore.
  • The need for, and cost of, emergency reaction to storm damage will increase.

After reading through this a few times, I couldn’t shake the feeling that there was a “1″ in the wrong place. Maybe they meant 2010? After all, the shoreline is already “pervasively armored,” a good storm is all it takes to cover Surf Drive with sand, and I can’t remember the last time I saw a natural dune on Falmouth’s south coast, with the possible exception of Waquoit Bay – which the report notes is the only significant stretch of natural coastline remaining on Falmouth’s south shore. But perhaps I was overreacting, misremembering.

So I took a little drive, starting here in Woods Hole and ending just shy of Menauhant Beach, whose dunes have been significantly reconstructed, and Waquoit Bay. Along the way, I snapped photos of seawalls and jetties, as well as the remains of a couple homes already claimed by the sea. But my main target was dunes. Here’s what I found.

FILED UNDER: Coast, Human Impacts, coastal change, sea level rise
November 28, 2011 | 10:49 AM | By

What tree stumps say about ancient – and future – coastlines

I mentioned this last week, but The Cape Cod Times’ take on the ancient forest that is now South Cape Beach has some interesting additional facts and tidbits, like:

  • Around 200 tree stumps were uncovered on South Cape Beach by a strong storm in spring of 2010 (that’s when the Cape Cast video above was made).
  • Scientists selected just 12 stumps to sample for carbon dating because of the cost – each individual test costs $350.
  • The “mangrove-like” trees have been identified as red cedars.
  • The oldest are between 1,210 and 1,270 years old, while the youngest are in the range of 340 to 400 years old … meaning there was a cedar forest there when the Pilgrims landed.
  • Scientists are also trying to map the soil and geography under the beach, to get a sense of where the trees may have stood relative to ancient coastlines.

400 years seems like a long time, but not quite so long when you consider that forests don’t often sit right on the beach. There’s also the fact that sea level is rising faster now than it has at any time in the past 400 years (and more), and is expected to continue accelerating.

The scientists doing this work told the Cape Cod Times they’re hoping to turn this into a scientific paper over the winter. That’s one I’ll keep my eyes peeled for next year.

FILED UNDER: Human Impacts, coastal change, sea level rise
November 2, 2011 | 2:34 PM | By

What Massachusetts plans to do about sea level rise

Chris Devers / Flickr

The coast of Scituate, MA has been walled, but the town still faces erosion, flooding, and storm damage that is likely to get worse as sea level rises.

Last week brought a small spate of news about efforts to plan for the three feet or more of sea level rise that scientists say we can reasonably expect this century, thanks to rising water temperatures and melting ice sheets. In North Carolina, state officials’ recommendations that local governments plan and regulate development with this amount of change in mind has brought resistance from coastal communities and businesses who fear growth restrictions. The news from Texas was even more dire. A report by Rice University oceanographers recommends that the west end of Galveston Island should be abandoned and the city consolidated on higher ground behind a seawall in order to weather rising seas.

All this may have left you wondering: What about Massachusetts? The Commonwealth boasts some 1500 miles of ocean coastline and faces among the most rapid rates of sea level rise and erosion. So what are we going to do about it?

Massachusetts Office of Energy and Environmental Affairs recently released a comprehensive climate change adaptation report. The final chapter is dedicated to coastal and ocean issues, primarily sea level rise. I came away with four major themes, which we’ll explore over the next few days.

1. Build for tomorrow, not today

When you build a road, or a house, or a wastewater treatment plant, or a _____ (fill in the blank here), you expect it to be around for a while. So why build it in an area that’s likely to flood or wash away? Massachusetts has a variety of laws, codes, executive orders (you get the idea) that discourage or outright prohibit new development in vulnerable or dangerous areas. The report recommends continuing with or strengthening those measures. But the definitions of those areas are often based on current or even historic data.

The report recommends updating maps and documents that delineate wetlands, dunes and beaches, eroding coastlines, and flood hazard zones so that they reflect not only current conditions, but future projections. Then, base decisions about where to build (or where not to, as the case may be) on those projections. The report also notes that, in cases where development will occur in flood- or erosion-prone areas, buildings should be constructed to withstand predicted storm/flood/erosion conditions and to meet a standard of ‘no adverse impact’ on surrounding properties.

2. Rebuild wisely

It seems to be an almost instinctual human response: if something we’ve built is damaged by the forces of nature, we rebuild. For those with significant financial and emotional investment in a property, it may seem like the only possible response. And, in cases where the natural disaster was a rare or one-time event, it may well be warranted. But sea level rise isn’t like that. It’s a constant, inexorable process that will only lead to greater and greater damage to structures in its path.

The report offers several recommendations for avoiding or decreasing “repetitive losses.” First and foremost, vulnerable structures that are being rebuilt or renovated should be raised, not just above current wave height (as currently required), but above projected sea level and storm surge. Rebuilds could also be subject to the updated erosion and flood hazard maps mentioned above. There’s also a recommendation to provide financial incentives, perhaps reduced insurance rates, to communities that are early adopters of climate change adaptation policies. That’s the easy part.

The hard part is this: in the long run, reducing repetitive losses means reducing the number of structures in harm’s way. The report contains two recommendations on this front. Both would warm the hearts of those who authored EPA’s recent guidelines for beating an organized retreat from rising seas. The first is to establish some variety (and they list a few possibilities) of funds for buying properties or otherwise compensating private owners for abandoning their coastal properties. The second is to establish a statewide rolling easements policy that would allow owners to develop their properties, but not take any action to hold back the sea or stop erosion. The word “rolling” refers to the fact that the zone covered by such a policy would “roll back” to match the changing coastline.

3. Armor sparingly

During the 1940′s and1950′s significant chunks of Massachusetts’ coastline were hardened, or armored, with a variety of structures intended to hold back the sea – seawalls, revetments, jetties, groins, bulkheads, and breakwaters. Over time, it became clear that these hard structures weren’t the panaceas they might seem. By disrupting the constant, natural flow of sand and sediments on, off, and between beaches and saltmarshes, they can actually exacerbate erosion problems. Thus, the construction of new coastal armoring has been severely limited – by state law – since the late 1970′s.

Still, as a comprehensive 2009 inventory made all too clear, there are a lot of homes in Massachusetts sitting behind aging – and often ailing – seawalls. The cost of repairing all those structures is estimated at more than $600 million. To actually upgrade them to meet expected sea level rise puts the price tag at more like $1 billion. So the Commonwealth faces some tough decisions about which structures to repair and which to let go. The new report says as much, and recommends a thorough cost-benefit analysis and consideration of all alternatives when deciding what to do with existing structures. It offers only one hint as to possible criteria for deciding which communities to protect, saying that densely populated urban areas – particularly low-income areas – are top candidates for structural engineering projects.

Actually, most of the section on coastal engineering focuses not on hard structures, but on so-called soft solutions, namely beach nourishment. Soft engineering gets treated as a necessary evil – made necessary by the disruptions in natural sand flow brought about by hard armoring. Recommendations focus on ensuring that the source of sand used for such projects is sustainable, not ecologically damaging.

On Monday … Protect natural coastlines.

FILED UNDER: Adaptation, sea level rise
October 28, 2011 | 4:50 PM | By

What we do and don’t know about sea level rise

New Scientist has been running a series of brief, paired articles on, alternately, Climate Knowns and Climate Unknowns. This pair seemed particularly germaine to a recent thread here:

Climate known: Sea level is going to rise many metres

The upshot here is simple:

Studies of sea level and temperatures over the past million years suggest that each 1°C rise in the global mean temperature eventually leads to a 20-metre rise in sea level.

The key word there is “eventually.” Despite the fact that we’re likely to hit, and quite possibly pass, the milestone of 2°C global warming this century, very few scientists think we’ll see 10 meters or more of sea level rise in that time. Here’s why: the ocean absorbs some 90% or so of the excess heat trapped by human greenhouse gas emissions, and that warming is one of the primary drivers of sea level rise. However, the ocean warms up slowly and can lag behind the atmosphere by decades. So it will take a long time for the full impact of atmospheric warming to be realized in the form of rising sea level. That said …

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FILED UNDER: Human Impacts, sea level rise
October 27, 2011 | 2:50 PM | By

Tough decisions about sea level rise face push-back

Vicky Sawyer / Flickr

Sea level rise could make low-lying towns like Elizabeth City, NC more prone to flooding, but suggested restrictions on development are meeting with opposition.

A debate in North Carolina over how best to plan for accelerating sea level rise could be instructive for those facing the same issue elsewhere (yes, that means us, here on Cape Cod). The Virginian-Pilot reports that state officials have recommended that local governments should plan – and regulate – for 39 inches of sea level rise by 2100. A group of coastal counties and businesses, known as NC-20, has sprung up to oppose the recommendation.

“This is a ‘what if,’ ” said Willo Kelly, president of NC-20. “We can understand seven inches in 100 years but not 39 inches. If this is reality, then why aren’t they building a sea wall along the entire coast of the United States?”

I’ll be honest. When I first read that quote, I scoffed. The whole wall-us-in idea is one I’ve toyed with in previous posts, but only as a means of provoking conversation about this crucial issue. The reasons not to build a sea wall around the entire U.S. – or even the Cape – seem too numerous and obvious to even begin listing. Cost, feasibility, environmental impacts …

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FILED UNDER: Adaptation, sea level rise
August 11, 2011 | 4:35 PM | By

Three spots to see before they’re gone

Since its creation nearly 15,000 years ago, Cape Cod has been shaped by the erosive forces of wind and waves. But rising sea level due to human-caused global warming is accelerating the pace of change, and fundamentally changing some of the processes that have shaped Cape Cod. Here are three dramatic examples along Cape Cod’s ‘great beach’:

1. Coast Guard Beach

Coast Guard Beach is a prime example of the eroding bluffs that typify Cape Cod National Seashore. The average rate of erosion along this stretch of the outer Cape is 3 feet per year, but a single storm can sometimes take more than ten feet in a matter of days.

Google Maps

The Life Saving Station that gave Coast Guard Beach its name has already been replaced once because of erosion. The current building likely has less than 75 years before it has to be moved or demolished.

Sitting atop that eroding bluff is the Coast Guard – formerly the Life Saving Service – station that gives the beach its name. The original Life Saving Station, built in the late 1800′s, was located about 350 yards southeast of the current building. There’s only ocean there now.

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FILED UNDER: Human Impacts, Cape Cod National Seashore, coastal change, sea level rise
August 8, 2011 | 8:07 AM | By

Cape Cod National Seashore a natural lab for change

This story was originally published in the Cape Cod Times as part of Nature in Balance, a week-long series produced in collaboration with WCAI.

National Park Service/Cape Cod National Seashore

Erosion at the Nauset Lighthouse parking lot of the Cape Cod National Seashore in October 1966.

Henry Marindin may not have the same name recognition as Henry David Thoreau, but he commands a dedicated following among local geologists.

Between 1887 and 1889, Marindin led a team of surveyors who traversed the length of what Thoreau called Cape Cod’s “great beach,” now the Cape Cod National Seashore. He recorded the details of the expeditions in 13 leather-bound journals.

Marindin’s work is more than a historical curiosity. The information he gathered is helping scientists predict how Cape Cod’s coastline will change in the future.

Using old but accurate surveying techniques, Marindin’s team generated beach profiles every 1,500 feet between Chatham to Provincetown.

“They came on the train,” explained Mark Adams, the geographic information specialist at Cape Cod National Seashore. “Then they hired a horse, and then they rode out to these stations on the coast and built tripods out of wood and sent rowers out in dories and sighted from their coastal tripod to the dory. They were able to triangulate using these old methods.”

Each of the 229 profiles the team created started at the top of a bluff or dune along the Outer Cape and extended approximately a mile offshore. Marindin compiled his topographic data and estimates of erosion rates in a scientific treatise with a title that resonates today: “Encroachment of the sea upon the coast of Cape Cod.”

Marindin’s survey – which found an erosion rate of about 3 feet per year – along with two more recent surveys conducted by Adams and Graham Giese of the Provincetown Center for Coastal Studies, has provided unparalleled insights into the evolution of the Cape’s coastline, particularly the rates and processes of change.
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FILED UNDER: Ocean Change, Cape Cod National Seashore, coastal change, sea level rise