Communities with coastal management programs in place may feel they are ready for whatever sea level change may throw at them (within reason). Should the level rise, they can adapt by increasing the height of the beach and dunes to compensate for both higher tides and stronger storms.
But for those communities who are on islands or on barrier beaches, what about the non-beach side? Is it ready for any rise in tides? What other vulnerable areas need to be looked at? It does you no good to have a high-and-dry beachfront if your mainland access is under water.
Communities around the country are facing the very real sea level change impacts already, as flooding that once was rare now becomes far too common. Often, these calamities make themselves felt on the non-beachfront side first, in a variety of subtle ways that can easily sneak up on you due to their slow progression.
How will you know there’s a problem — and what (if anything) can be done?
Flooding: First and foremost, increased flooding (in both depth and frequency) is a dead giveaway that sea level is on the rise. Often the first indication there is a problem is that streets inundated more frequently, by waterfront properties complaining that their lawns are being attacked by seawater, and by seeing flood levels creeping higher and higher are clear warning signs. What can you do? Elevate, of course, buildings, roadways, you name it; improve drainage in low-lying areas (assuming your drainage is not being similarly affected); even consider ways to create either barriers or distance on the non-beach side between high water lines and upland structures or infrastructure using wetlands, vegetation or other soft or hard structures.
Septic systems: If your community still relies on these systems for wastewater treatment, changes in sea level that push the groundwater levels higher will soon have an impact on their effectiveness. Most septic systems rely on drainfields to treat waste and must have significant separation (24 inches, as a rule) from the underlying groundwater. If those drainfields are inundated or holding tanks are sitting in ground water, you have a problem. What can you do? Nothing cheaply… moving to so-called performance systems (which clean wastewater above ground before releasing it into the ground) are pricey and take a lot of work to keep them running effectively. The alternative may be a move to sanitary sewer, which is a major public works effort requiring both time and money aplenty.
Potable or irrigation water: Wells also feel an impact from rising ground water, either through salt water intrusion or increased pressure on the freshwater “lens” or aquifer your wells are accessing. What can you do? Move away from relying on wells or expect to install desalination devices on them. If you’re not on a central water system now, you will be soon… and either looking for a purer source or figuring out your options to remove the salt. That may also push your community toward a re-use or “gray water” system, to avoid having to use increasingly expensive potable water for irrigation.
Stormwater management and drainage: If levels are higher and storms are stronger, your community will need to be able to hold back higher levels or water… or retain more stormwater before needing to drain it immediately away. And if some of your current drainage outfalls are starting to go under water, their ability to work when needed will be increasingly compromised. What can you do? Higher berms for retention or to forestall flooding, move outfalls higher and install one-way gates so water goes out but will not be drawn back in.
Non-beachfront barriers: Holding back any rising tides on the bay side will take either barriers or buffers (as noted above). But you’ll also need to look at what’s already in place to see if they’ll be able to stand up to higher water levels. What can you do? If you’re using seawalls, they may need to be modified to both go higher and to avoid failure through overtopping or undercutting. And hard structures may need to be replaced with “living” shorelines, which create both a better buffer and give you the ability to move them further inland as waters push them there.
Natural vs. human resources: An island is finite and, as waters around it rise, there’s less land to go around. Prized coastal ecosystems that rely on a delicate mix of conditions – especially between fresh and salt water – will be squeezed… hard. What can you do? It will be necessary for your community to eventually make some tough choices to balance natural and human needs… and these will not be just environmental choices but economic ones, should rising water levels start pushing costs equally higher. It’s better to start that conversation sooner, before options are limited and change is imminent.
Some coastal experts may quibble about how much sea level is likely to change, but no one ever says there won’t be change. So coastal professionals charged with keeping their communities safe and prepared for any pending sea level change must look at all the potential vulnerabilities in order to be effective at their jobs. In many communities, the most vulnerable points may be far away from the sandy beach – and the solutions may be both complicated and costly to implement. This makes it even more imperative that your community begin the planning process now. Developing a management plan will be even more critical in years to come.
That’s why understanding these pressure points for sea level change is crucial, and having a clear-eyed assessment of vulnerability and timeframe is essential.
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