Our Latest High-Water Mark - NYTimes.com WATER up to the attics on Staten Island. Flooded subway and commuter tunnels. Power lost to 8.5 million homes and businesses. We get it: this storm and its impacts are huge. What we may not be getting is why. When the debris is cleared away, we will be left with a new high-water mark. On Monday, sea levels in New York City reached about 14 feet above the average low-tide mark; more than 9 feet above the average high; almost 3 feet above the last record, set in 1821. In the future, we're going to see more of the same. Satellite measurements show that the oceans are growing; waters are warming. Both factors increase the effects of storms; warmer waters lead to fiercer storms, and sea levels punch up the surges. A popular myth about sea level rise is that it happens slowly enough that we will have plenty of time to react. Or there's the blockbuster legend of a thousand-foot wave sweeping Manhattan and changing the world all at once. Both are unlikely. Hurricane Sandy showed us how sea-level rise actually works. It comes up in spikes that top historic highs and then fall back to normal. The Marshall Islands experienced such a high in 2011 when La Niña swamped parts of the capital city of Majuro at high tide. Hurricane Katrina wreaked a similar catastrophe on the gulf coast. In every case, sea levels jump for a moment, setting records, and then fall back. The real danger here is not the surge itself, but the return to normal. We record a new high-water mark, but we call the crisis over because the waters have receded, our waterfronts are back, and we return to business convinced the worst is gone. In other words, we forget. We're doing it already. Hurricane Sandy was a fluke, right? A storm surged from 90-mile-per-hour winds of a hurricane colliding with a northeaster, perfectly timed with a maximum full-moon high tide. The statistical likelihood of this is once in every 500 to 1,000 years. And yet, it has happened, and the likelihood is increasing all the time. How long do we want our coastal cities, and particularly New York - where the Long Island Sound faces directly into the Atlantic and the mouth of the harbor leads storm surges into the urban interior - to remain this vulnerable? Regions like the Netherlands have been dealing with this question for a long time, answering it with storm surge barriers rather than crossing fingers and hoping it doesn't happen again. New York does not have any such barriers. It is open to whatever the sea throws its way. We have to start treating our coastlines as if we were actually living here for the long haul. Innovations do not have to be as enormous as surge barriers. We could design better water tunnels to route water out of cities, and build huge inflatable plugs to halt the inward flow during surges. We could seal off power equipment in times of flood; build sluices near the coast that can shut to block surges; and even plant coastal forests as barriers to rising waters. More than engineering solutions, we need to consider novel ways of living, commuting and consuming that use less energy and produce less carbon dioxide. We may not see another storm like this for another 50 or 100 years, or maybe 10 - but when this high-water mark is again exceeded, people will wish we had put our minds to solutions while the memory was fresh. It seems almost crass to bring climate change into the discussion, when we have such immediate problems to deal with as the shutdown of morning commutes, the loss of electricity. But this is exactly the time to start the harder task of remembering why this storm was so huge. We talk about life slowly returning to normal along the Eastern Seaboard, but ultimately, it never will. A new high-water mark has been set. In the aftermath, one fact stands out above all: seas are rising, and we are in the way. Craig Childs is the author, most recently, of "Apocalyptic Planet: Field Guide to the Everending Earth."