The options, in brief:
1. Armor the coast: Sea walls protect coastal properties, but are expensive and take a heavy toll on beaches and marshes.
2. Reinforce beaches: Adding sand and planting dune grasses is a temporary and expensive way to maintain beaches and dunes that naturally protect what’s behind them.
3. Retreat: Abandoning or moving coastal development allows coastlines to move naturally, but is economically and emotionally fraught.
In the past century, sea level around the Cape has risen nigh on a foot and a further three feet of rise is considered by many scientists to be a reasonable expectation for the coming century. It’s entirely possible that we could see a foot rise by 2050. Add to that predicted increases in the severity of storms, and you’ve got a recipe for serious coastal erosion. Then add the fact that over half of Americans live within 50 miles of the coast … you get the idea.
The only way to slow or limit sea level rise is to cut greenhouse gas emissions that are driving the warming responsible for sea level rise. But even if we went cold-turkey on fossil fuels today, we’d still be facing a century – possibly a millenium – of warming and sea level rise due to the carbon dioxide already accumulated in the atmosphere. So adapting to rising sea levels – finding ways to protect human lives and properties, and ensure the resilience of our coastlines – is a must. Here are the options, broken down into three major categories:
1. Armor the coastSea walls, jetties, groins, and any manner of hard, semi-permenent structures were the answer of choice in the early 20th century. The idea was to stop the movement of sand and protect the property behind the armoring. The practice has largely fallen out of vogue because of the side-effects. Armoring disrupts the normal flow of sand along a coastline and starves nearby coastlines of the sand necessary to maintain beaches and salt marshes. Town Neck Beach in Sandwich, MA is a striking example of this phenomenon.
Still, as Beth Daley recently pointed out in her coverage for the Boston Globe, much of Massachusetts’ coast was walled decades ago and property-owners behind the walls are increasingly dependent on their armoring to stave off flooding and storm damage. But Massachusetts’ sea walls are aging in need of a lot of work – more than an a billion dollars worth – if they’re to stand up to rising seas.
2. Reinforce beaches
Also known as beach nourishment, this option usually involves dredging sand from offshore and adding it to eroding beaches to maintain a sandy beach and dune system for recreation, wildlife habitat, and natural storm protection. In its worst form, it resembles World War I tactics: hold the beach at all costs, throwing tons of sand and millions of dollars at a beach knowing full well it will wash away and you’ll have to do it again in a matter of years. But this option also holds the greatest promise for the application of that ultimately human trait: ingenuity. Planting dune grasses and other dune-adapted plants can help hold sand in place and extend the lifespan of nourishment efforts. Going a step further, there’s an intriguing option known as ‘biodegradable erosion control.’ Basically, dunes are built over semi-hard but biodegradable structures that are designed to give the dunes a lifetime longer than the homes behind it – protecting both human development and the natural environment. It’s been fascinating to watch a local project in progress on the blog of the Woods Hole Group, the environmental engineering firm responsible.
3. Retreat, retreat!
The final option is to get out of the way: move or abandon homes, roads, and other infrastructure in the path of shifting coastlines. This is a permanent solution – perhaps the only one – but is economically and emotionally fraught. Should homeowners be bought out? By whom? And where would they go? Then there’s the bigger question: how far from the coast is far enough?
If you think that all sounds awfully militant, well, it is. While seaside life is supposed to be all about peace and tranquility, human development along the coast puts us in a position for direct conflict with Mother Ocean. And, as with many aspects of climate change, there is no silver bullet – just lots of brass BB’s, and lots of hard choices. Rob Theiler, one of Woods Hole’s experts in sea level rise and coastal change, puts it this way:
“Mother Nature bats last at the coast. If we wait long enough, she’ll make the decisions for us. But they may not be very pleasant.”
In other words, it’s time to start talking seriously and thoughtfully about the future of our coasts.
If you’re a coastal property owner, tell us: what do you you think we should do?