Our Endangered Shoreline

The process of shoreline erosion. It never stops at the shore.

By Thomas Neuburger

We have to adapt to a shoreline that is shifting inland for the first time in human civilization. —John Englander, here Half the world's citizens live on sea coasts. So they're going to have to move. Where they going to go? And who's going to pay for it? —Bill Nye, here No one will pay for it. The rich aren't rich enough yet. —Yours truly

I recently wrote a deep dive into James Hansen’s working paper on “Global warming in the pipeline”. That piece is here.

Today I’d like to address just a few of the common misconceptions about sea level rise and how dangerous it is. In short, I want to answer this question…

My house is on the shore, but a full three feet above sea level. If the sea only rises a foot, I’m safe, right?

…with brief reasons why the answer is “No, you’re not safe at all.”

• When sea level rises, the land behind it erodes

Notice, in the image at the top, that the sea doesn’t have to rise much for quite a bit of land behind it to erode and collapse. As John Englander points out in this TED talk (3:36):

It makes sense that every time sea level goes higher, the shoreline is going to move inland. But the ratio is surprising. For each foot of rise, the average global shoreline moves inland about 300 feet — the length of a football field.

Keep that ratio in mind. To answer our original question, one foot of sea level rise moves the shoreline inland by something like 300 feet, or more if you live in a low coastal zone like most of Florida.

• When sea level rises, the water table rises with it

When salt water from the ocean rises, it forces the fresh water — and thus the water table — to rise as well.

This shows the effect on wells:

Sea level rise also affects drinking water. Florida is already constantly fighting the intrusion of salt water into its water system.

Imagine Florida’s future, even if escapes a monster storm. Not good. More on Miami’s fresh water problems here and here.

• When sea level rises, high tide is higher and storm surges overcome previous defenses

A higher sea level means higher storm surges and dikes that used to be effective are overrun.

• In addition, high tide can cause salt water to flood streets through water drains

Yes, you read that right. Salt water. As John Englander says in the TED Talk quoted above (emphasis added):

The other phenomenon we're starting to see is flooding streets on a regular basis, every 28 days, along with the lunar tide cycle. Flooding streets without rain, without storms. And in some neighborhoods, they're actually storm drains installed that were designed to take excess rainfall and move it over to the nearest waterway. Those storm drains now work in reverse. Every month, and some months worse than others depending upon the alignment of the planets, the salt water is backing up through the storm drain. It's happening from Key West and in Broward County and up toward Palm Beach County and out in Seattle — all over the world [in] low-lying coastal areas. That didn't happen a few decades ago, when those streets were designed[.]

So no, we’re not safe during “modest” sea level rise. A rising sea level shouldn’t be counted in vertical inches and feet, but in horizontal feet, yards and miles, measured from the previous shoreline to where our towns and cities will be safe for the next 50 years or more.

Those plans ought to start now.

How long will it take to effectively move New York? Mumbai? Jakarta? Shanghai? San Diego? Forever, if the planning never starts.

Videos

John Englander’s entire TED Talk is below. Note, however, his optimism, saying none of this will happen in this century. Others disagree.

And Bill Nye’s contribution to this subject is here:

Another good video on sea level rise: