The result was a torrent of fresh water pouring into the oceans.
A Tumultuous Past
Marcy says it is likely that the initial episode of rapid sea level rise left the primitive coastal communities in its path with but one survival mechanism: retreat. However, for the early nomadic societies of the time, accustomed to migrating seasonally to whatever locales proved most hospitable to their lifestyle, the changing landscape may simply have been taken in stride.
Scientists say the rapidly rising sea levels calmed down about 5,000 years ago, to the more gradual, almost imperceptible, rate of change seen in recent centuries. With the coastline providing a semblance of stability, Marcy says, societies began to take advantage of coastal amenities such as ample marine food supplies, access to seafaring transportation, and moderate climatic conditions to nurture sophisticated civilizations, the legacy of which continue to this day.
Nonetheless, Marcy says, the telltale signs of the creeping seafront continued to manifest throughout this period as well; on visits to the Mediterranean region he has seen for himself infrastructure built during the Roman era, such as portside tanks for fish caught at sea, as well as other civic assets, abandoned and under several feet of water near the sites of ancient settlements, a silent testament to the transient nature of coastal stability.
Still, the illusion of stable shorelines continues to lure settlement and infrastructure development to the oceanfront. Following in that time-honored tradition, it is estimated that worldwide over 2 billion people (37% of the global population) live within 100 kilometers of a coastline. In the United States alone it is believed 155 million residents live along coastal plains at elevations within inches of the tidal sea level. In fact, the whole United States East Coast from the south of Maine to Florida is composed of sandy beaches and barrier islands, and, according to Andrew Ashton, a scientist with the Woods Hole Oceanographic Institution, “Almost all of it is developed.”
But scientists say it could soon become a lot more difficult to settle in on the coast. Climate change models predict rapid changes in sea level within decades. The International Panel on Climate Change (IPCC) estimated in a report published in 2007 that the global average sea level will rise between 0.6 and 2 feet (0.18 to 0.59 meters) in the next century. Other scientific estimates, which envision a variety of scenarios for melting glaciers in the polar regions, forecast even more drastic changes; some predict a sea level rise of nearly 2 meters. According to the US Environmental Protection Agency, the IPCC has concluded that the impacts of rising sea levels are “virtually certain to be overwhelmingly negative.”
We could all just pick up and migrate inland, but, alas, we no longer live in an age of ennobling nomadic calm and acceptance.
No Easy Choices
Rob Theiler, a research geologist with the US Geological Survey (USGS) at Woods Hole, MA, says our options boil down to just three basic responses. He says we can “armor the shoreline to protect assets where they are being threatened”; we can deploy “soft stabilization techniques, such as pumping sand or constructing groins to capture sediments” to rebuild vanishing shorelines; or, mirroring our forbears, “we can implement some kind of retreat.”
According to Theiler, deciding between these alternatives will require taking into account a series of tradeoffs. “If you’re committing to put sand on the beach, you must first find a source for that sand and determine whether there is enough economically viable sand to do that.”
In the alternative, when considering a hard-armoring strategy, localities will need to decide other tough nuts-and-bolts issues such as how long the seawall should be-“then you have to deal with flanking,” he says.
Complicating matters when it comes to attempts to prevent coastal erosion is the fact that any remedies applied at one location along the coast may have unintended consequences for neighboring locales.
No less, if a community were to adopt a policy that involved some measure of retreat, Theiler says, it would first need to decide “whether there is a way to reroute a road,” or which assets would be worthy of a move to higher ground. “And what happens to the assets that might be left behind?”
Theiler says that in the near future, numerous localities will need to begin to make these and many other major decisions with long-term consequences. And raising the stakes a bit more, he says, once these decisions are made, there will be little turning back. According to Theiler, the selection of any particular strategy in response to sea level rise, especially along the open ocean coast, will commit communities over the long term “to certain future activities,” while forever ruling out other alternatives.
Global Phenomenon With a Local Flavor
Although sea level rise is a global phenomenon, experts say that the experience of sea level rise will not be uniform at all locations. William G. Thompson, an associate scientist at Woods Hole Oceanographic Institution, says that in a few select locales sea levels don’t seem to be rising at all. For instance, he says, at the extreme end of the spectrum, in Norway and Sweden, “sea level is falling like crazy because the land is rising.” In those regions, the landmasses are still bouncing back, like a seesaw, after shedding the weight of glaciers that began melting at the end of the ice age. On the other hand, he says, at Wood’s Hole, in Massachusetts, tide gauges show sea levels “have clearly gone up over a foot in the past 100 years.”
Thompson explains, “The entire solid earth of North America is flexing because of the unloading of ice over the Hudson Bay, with the greatest effect being measured along the mid-Atlantic coast near Virginia Beach,” where, he says, sea levels are rising faster than they are farther south still along sections of the Florida coastline.
Even global climate factors have differing effects on sea level depending on the location. Thompson says factors such as thermal expansion of seawater and changes in the speed and orientation of ocean currents contribute their own share to variations in sea level from place to place, while the effects of waves can differ widely at various points at a single site. “It’s all very complex,” he says.
With all of this variability, Thompson says, it’s nearly impossible to make sensible decisions to deal with a long-term change like sea level rise on a “short-term cycle.”
“The problem with sea level rise is that it is very gradual; unless you’re right at the water’s edge, it creeps up on you. It’s the problem they’re having in New Orleans. You keep building levees up higher and higher, then suddenly you realize you’re 6 or 7 or 10 feet below sea level. Because it happens so slowly, people say, “˜Just put up a little seawall and everything will be fine.’ And it is for 20 or 30 years, and then you’ve got to start adding to it. It’s these time scales that are difficult and deceptive and make it really hard to make sensible policy. It’s almost an intractable problem.”
While there are obviously valuable assets on the coastline-whether they be personal property, such as homes; infrastructure, such as roads and utilities; or amenities and ecological features so vital to society that it would constitute a substantial loss to a community should they fall to the encroaching sea-Thompson notes, “Almost always, the human reaction is to procrastinate-to wait until there is a real threat, or wait until a hurricane comes along and wipes out all this coastal property-and then what do we do? We rebuild it all.”
He says, however, that although it may sound like a small incremental change, “it’s important to realize that, globally, sea level is rising in the range of a few millimeters per year and to plan for that to continue if not accelerate for the next 100 years.”
Ashton, also an associate scientist at Woods Hole, amplifies the point. “Sea level rise is only going to exacerbate whatever coastal erosion problems are already going on. Actually, over the last 150 years, it’s been happening at a faster rate than it was for the preceding several thousand years before that. But the future sea level rise is going to be a lot larger.” Ashton says projecting “historic” erosion rates into the future is going to be “a conservative estimate of how much land you’re going to lose.” According to Ashton, as sea level rise accelerates in the coming decades, erosion in the real world is likely to be much more severe, and very few communities are ready for it.
He says policymakers have been hard-pressed to recognize that the coastline is in fact in a permanent state of change. “We don’t have a great plan for managing coastline; we have an approach based on land not disappearing over time,” he says.
Swapping Sand to Pay the Piper
Ashton makes the simple observation: “The beach will move inland as the coast erodes.”
Even moderate sea level rise can have a powerful impact on shoreline real estate, he notes. Because of the gentle slopes and low elevations along the coast, a meter of sea level rise can easily submerge 100 meters of beachfront. And, he says, under natural conditions the beach is always moving.
Not all communities or property owners will be willing to go with the flow and watch passively as beaches protecting their homes and businesses come and go under the influence of natural processes such as tides and storms. But, Ashton says, interceding in the natural oceanfront processes often does not yield the desired result.
“New Jersey is known for having put a lot of seawalls along the coast. Although that stopped the erosion process, their beaches disappeared, losing the economic benefit” that had inspired the seawalls in the first place-the recreational value of the beaches.
“Things like sea walls don’t get rid of the fact that sediment is being taken offshore, or moving along shore, which happens a lot as well,” he says.
On the other hand, observing these unfavorable side effects, authorities in states such as South Carolina and California have effectively banned the construction of new seawalls, further limiting the options for protecting coastal properties.
“It’s really hard to get people to do the right thing,” says Thompson. “The wind and the currents and the waves move the sand around, and that’s been going on forever, yet when people buy a beach house and they see sand in front of it, they think that sand ought to stay there. So people build sea walls and groins and jetties, and all that does is rob sand from downstream.”
He says that although such measures as jetties and groins installed to attempt to control the movement of sand and protect the property behind the beach may preserve a part of a beach, they can just as easily lead straight to a conflict. According to Thompson, sand generally moves down the coast in a specific direction. “If you put a jetty or a groin up in front of your house, it’s like a dam for the sand. And the sand will pile up there, and you’ll have a nice beach, but the guy right next door is going to lose all of his sand because you’ve taken all the sand that was flowing onto his property and you stopped it from going there.”
Keeping the Coastline Afloat
Another hurdle to protecting coastal assets and oceanfront property is, of course, the cost. Dr. Robert Young, director of the Program for the Study of Developed Shorelines, says that in an era of declining budgets, efforts to save seafront properties from rising seas come with an ever-increasing price tag. But, he notes, “Most coastal communities want to protect everything; they just don’t want to have to pay for it.”
He says, “It’s hard to add up all the costs that have gone into beach nourishment projects.
New Jersey alone has invested over $1 billion on beach nourishment.”
Although beach protection projects to date have received much of their funding from public sources, Young says, “Federal funds for beach nourishment projects are drying up,” and residents of communities from states and regions lacking coastal zones are beginning to balk at supplying taxpayer dollars to support the ever-mounting expenses of vacation properties. Ultimately, he says, in an era of financial constraint, the question of who is going to pay will be a major determining factor in what in what gets protected, and how.
But he says creative solutions can be found to finance coastal protection projects. According to Young, Hilton Head, NC, has implemented a local 3% hotel accommodations and beach preservation tax that allows the vacation spots and the patrons that benefit directly from aesthetically pleasing shorelines to pay the costs for beach nourishment projects.
Young acknowledges, however, that many communities with at-risk shorelines may lack the financial resources of a prosperous resort such as Hilton Head, and he says the erosion control industry, out of necessity, may be called upon to take on a major role in facilitating a transition to local funding for beach protection projects. “The sooner the industry helps local communities find ways to fund coastal protection projects at the local level, the better it will be for everyone,” he says.
Unseen Forces
Gary Griggs, director of the Institute of Marine Sciences and professor of earth and planetary sciences at University of California Santa Cruz, says it’s important to remember when dealing with coastal erosion that on the ocean there are major forces amplifying the effects of rising water. “Pretty much with a river it’s the height of the water that is a concern,” he says, but in contrast, along oceanfront, “the big concern is the impact of the water.”
“In the ocean, a 10-foot wave extends a ton per square foot of pressure; there are incredible stories of cobbles that have been thrown through restaurant windows or up into lighthouses over 100 feet above sea level. With the big El Niño winters of 1983, we displaced chunks of concrete weighing up to 20 tons that were on top of a breakwater that had never been moved for 80 years, and there are lots of similar accounts from England, where you’ve got a longer record, where huge blocks were displaced by big waves at time of high tide.” In this context he says, “Anything you build has a lifetime-nothing is permanent.”
Ashton, of Woods Hole, concurs. “The effects of rising sea level will not be the equivalent of simple flooding. One of the main things to think of about sea level rise is that it is not passively flooding like a bathtub overflows, but that the waves will pull more and more sand offshore,” he says.
But Ashton says there is a lot more that science needs to learn about the dynamic processes involved. Although there are several models scientists use to describe the interaction between erosion and sea level rise, they each have various shortcomings, and Ashton says there is little certainty over any rule that can be applied to all coastal erosion situations.
For instance, he says, one popular rule that gets a lot of attention in coastal erosion circles is known as the Bruun Rule. In simple terms, it states that as sea levels rise, the shoreline will retreat. According to this theory, the sand dragged by the surf from the receding beach will waft out just far enough to maintain the slope and depth of the environment offshore. As a result, the beachfront slope will remain unchanged while the water’s edge shifts gradually inland. One could imagine it as the bathtub itself gradually widening, with the edges moving inland as sea level rises.
However, as attractive as the conceptual image may appear, leading coastal scientists say that in reality it’s been difficult to find concrete examples to prove its validity.
According to Orrin Pilkey, professor emeritus of earth and ocean sciences at the Nicholas School of the Environment at Duke University, the Bruun Rule has nevertheless been used to shape subsequent erosion models and to guide coastal policy recommendations and projects. He argued in a 2004 paper entitled “Sea-Level Rise and Shoreline Retreat: Time to Abandon the Bruun Rule” that decisions based on this erstwhile rule risk ignoring complex and important factors that could drastically impact the effects of sea level rise on erosion. Pilkey says that although the rule, first published by Per Bruun in 1962, provided early and worthwhile insight into the processes involved in coastal erosion, the time has come to delve for a deeper understanding of erosion processes.
Ashton says the main challenge in developing models for coastal erosion is that “it’s often difficult to get exact values for sediment transport; it’s something we will understand more over time, but it’s also very nonlinear-you get potential for a lot of complicated behaviors in sediment transport.”
Rule or no rule, Ashton says, sometimes the best solution for coastal areas may be to do nothing at all. “Parks provide a nice example of the fact that you don’t need to feed a beach for it to exist, but of course you have to strike a balance between the infrastructure that we want to protect, as well and the value of that infrastructure.”
Keeping Cities Above Water
As much as sea level rise is expected to wreak havoc with beaches, it will be just as vexing when it comes to coastal cities.
Griggs says that protecting urban infrastructure from rising water is a major concern. For example, he says, during the 1940s and ’50s the San Francisco area made major investments in infrastructure that is now at risk due to sea level rise, including “highly developed military bases and sports and recreational parks.”
“When those were done back in the ’40s and ’50s, sea level rise wasn’t an issue,” Griggs says. “We built these up with fill, a few feet above high tide, but now we’re realizing that with about 16 inches of sea level rise, the runways of the Oakland and San Francisco airports start to go underwater. Those are huge multibillion dollar facilities that serve millions of people.”
He adds, “Many of our sewage treatment plants are at the lowest elevations in the community; sewage flows downhill and sewer lines are, in fact, buried beneath the beach. We’ve got highways, parking lots, and power plants, not to mention ports and harbors, that are virtually at sea level. Those are really large infrastructure investments that are not easy to pick up and move.”
If sea levels rise as forecast, cities located far inland from the coast along tidal estuaries will face substantial challenges staying above water as well. Key infrastructure of numerous major US cities lies within inches of current sea level, and few have developed long-term plans for dealing with rising waters.
Olympia, WA, however, has resisted the temptation to procrastinate and has begun putting together a plan to deal with sea level rise, one of the first in the nation-and for good reason.
No Time to Wait
“Olympia is built on hydraulic landfill excavated from Budd Inlet and placed along the shoreline about 100 years ago,” says Andy Haub, planning and engineering manager for the city’s Public Works Department. “Downtown is on that fill, and at high tide it is just a foot above tidal elevation.”
Haub says the terrain between the inlet and the rest of the city is so flat that “sometimes at high tide, seawater flows backward from Budd Inlet into the storm drains” and winds up seeping into downtown to flood city streets. “If we’re going to flood, we need to manage that,” he says.
“Our entire downtown is built on fill. It’s very flat, so we either devise a system to protect it or not-there’s really no incremental approach, or any approach that would sacrifice part of it and maintain others.”
Haub says a significant motivation for protecting the entire downtown is the fact that major regional transportation corridors are among the assets at risk. “If we want to keep those corridors open, we need to protect downtown,” he says.
With the higher-end forecasts for sea level rise calling for seas to rise almost 2 meters during the current century, Haub says, “The city council gave us directives in November 2010 to come up with conceptual strategies for protecting the city from 50 inches of level sea rise. We spent the first year of the project developing a better model of water elevations for Budd Inlet.”
He says the effort emphasizes practical matters rather than academic debate. “We go to our city council every year with a work plan for evaluating our next step in understanding sea rise. We’re not even suggesting we’re climate change or sea level rise experts, we’re simply responding to a flooding threat downtown, and we need to understand that risk.
“We propose a work plan every year that builds upon the previous plan, and at the end of the year we report back to the city council and host a community discussion on sea level rise in January of each year.”
According to Haub, studies indicate that if the city is to survive the projected sea level rise it will need to begin building, within the next 15 years, the various measures, such as sea walls, berms, and tidal gates, to protect its infrastructure. To illustrate the scope of the effort that will be required, Haub says that the initial section of sea wall is expected to cost $8 million and will protect just 10% of the most vulnerable part of the downtown area.
Although the plan is still in the conceptual phase, Haub says, “We’ve come up with maps that describe what type of sea walls to use at different locations downtown and how to phase those in over time.”
Models to the Rescue
Haub says detailed flood modeling for Budd Inlet also produced at least one surprising result.
Fairly high tidal waters are quite common on the inlet. “We understand that risk, and maybe accept it; but when you start quantifying the risks from a coastal engineering perspective, we have a new understanding of how vulnerable we are today. If we had an extreme high tide, with low barometric pressure or wind, we could flood downtown extensively.” And that realization gives the planning effort greater urgency, he says. “A lot of our work this year is focusing on managing our current risk. We’re working on emergency response planning and strategies for where we would deploy sandbags first, and so forth.”
For longer-range plans, Haub says, the city “has narrowed the choice” for coastal protection structures down to “earthen berms, concrete berms, or sheet pile” for various sections of the sea wall. But he says the city will keep open the possibility of using manufactured temporary barriers to provide protection to areas around port facilities used for ship loading.
Haub says projects already underway in response to flooding in Olympia are being integrated into comprehensive planning for sea level rise as well.
“As we build and do regular capital improvements, we’ve been consolidating storm pipes to give water fewer avenues to follow.” In addition, his department has plans to install tidal valves at strategic locations along Budd Inlet to help manage downtown flooding.
Although he is not certain when, or if, the city will take the monumental step of building sea walls capable of holding back 50 inches of sea level rise, with their consequent space requirements and questionable aesthetic appeal, Haub says a lot of progress has been made in “small steps” over what to do if that eventuality does come to pass. And he says making the transition from planning into action has been easier than expected.
“We’ve simply tried, a year at a time, to understand how sea level rise could impact the city. We started out by getting good LiDAR elevations of downtown, we took another step of understanding our infrastructure-our stormwater systems, wastewater systems, our different built systems downtown-then, this past year, we built a good marine model that allows us to simulate different tidal and wind dynamics in Budd Inlet, and now we’ve combined them all together,” he says.
“We have not spent much time trying to understand climate change, or sea level rise; rather we’ve dealt with it as a flooding issue.”
In addition to the LiDAR analysis to fill in the information gaps, Haub says planners have accepted state and federal and other government data and information on sea level rise, “incorporating that into the incremental building of our knowledge.”
He notes, “It’s not so much decision points on what to do or when to do it, it’s just increasing our knowledge and at the same time educating our community so that they can keep track of this too.”
As long as there are oceans and people who want to, or need to, be near them, coastal erosion will be a challenge. It is a force of nature that literally has no rival.