Worse than Sandy? Slow your roll.
There’s been a lot of Sandy talk lately. Just ask New Jersey Governor Chris Christie.
Last weekend’s blockbuster winter storm, which will go down as one of the all-time greats, also brought with it some major coastal flooding. Along the southern Jersey shoreline and into Delaware Bay high tides drowned coastal roads in frigid, waist-deep water. Streets became slushy rivers while ice floes cut through coastal communities.
Though incredibly well forecast, it wasn’t exactly the scene most expected to wake up to on Saturday. And while the peak storm surge this weekend fell well short of the Sandy benchmark, lingering scars from Sandy didn’t stop the comparisons:
Was the flooding last weekend worse than Sandy?
Mops and politics aside, here’s one thing Governor Christie got right. Overall — no. Not even close. Nor was it ever expected to be.
So why all of the Sandy-esque and Sandy-style headlines?
For starters, the flooding last weekend struck some of the same townships inundated by Sandy in 2012. And for those swamped by icy waters, the flooding shouldn’t be trivialized. In the lower reaches of Delaware Bay and the southern Jersey shore it was major. By National Weather Service definition, that means extensive and potentially life-threatening. Thankfully the major flooding was localized and, despite over 100 emergency rescues, no flooding deaths were reported.
But what about the Sandy comparisons? In a few spots our tide gauges did actually measure higher tides last weekend than during Sandy. But beware of the fine print. These spots were spared the brunt of Sandy’s highest tides in 2012.
Consider this: only two months before Sandy roared through the mid-Atlantic, Category 1 Hurricane Isaac came ashore in Louisiana. During that hurricane parts of southern Louisiana flooded that didn’t during Hurricane Katrina in 2005. But it would be unfair to say Louisiana saw worse flooding in Isaac than in Katrina. As a general statement it’s misleading, insensitive, and depending on the context borderline irresponsible. But for towns like LaPlace, only 30 miles west of New Orleans, Isaac felt worse.
Record tide vs. record flooding
The apples-to-apples sniff test isn’t the only place the Jonas/Sandy comparisons go awry.
Let’s look back at the the measurements themselves. Our tide gauges measure something called storm tide, not flooding. It’s an important distinction, which I’ll get to in a minute. But it’s the storm tide we use for record-keeping. Storm tide is simply the tide you see on a regular day plus a little something extra. The little something extra is storm surge, or the water pushed ashore by the strong winds of a coastal storm or hurricane. And the little something extra can be a lot of something extra if the storm is big enough.
Now here’s where trouble arises when using record-flooding to describe record storm tides. The official measurements of storm tide don’t consider the additional water from waves. Our network of tide gauges average water levels over a 6-minute period and when they do so, they effectively average out the instantaneous water level spikes from waves. Here’s an example from Sandy:
Overlooking waves isn’t a small thing— not for winter storms. A September 2015 study of northeast winter storms over the past 30 years found that waves account for 63% of total water levels. In other words, if we’re not measuring waves, we’re missing 60–70% of the flooding for a nor’easter like the one last weekend. That’s a lot of water. Without knowing the impact of waves (which we don’t — at least for now), it’s tough to say the flooding was worse than Sandy, even at the tide gauges that did see record storm tides.
What’s in a name
I’ve no doubt parts of New Jersey flooded last weekend that didn’t during Sandy. Water doesn’t always spill in the same direction. Some homes even took in more water than during Sandy. And for those homeowners the flooding certainly felt worse than Sandy. But let’s not lose sight of the forest for the trees.
Sandy may have jabbed those areas flooded last weekend back in 2012, but it landed a knockout punch farther up the coast in communities north of Atlantic City, including the biggest city in the United States.
Peak storm tides from Jonas pale in comparison to Sandy, as does the scope of the event and extent of the flooding. But regardless of location, when we evoke a name like Sandy, the public expects the impacts to be the same. Here’s the reality — they never are.
The flooding from Jonas was forecast exceptionally well — days in advance:
But in denial you’ll find a common thread. Those that said they didn’t expect the flooding from Jonas also said the flooding from Sandy was less severe. And that’s the point.
Jonas wasn’t Sandy. It wasn’t the December 1992 nor’easter. It wasn’t the Ash Wednesday Storm of ‘62, the Blizzard of ‘78, the Perfect Storm, or the Great Appalachian Storm of 1950. It wasn’t the 1944 Great Atlantic Hurricane. It wasn’t Hurricanes Gloria, Isabel, or even Irene. It didn’t need to be. For Stone Harbor, Wildwood, Ocean View, and Dewey Beach, it was heartbreaking. And that’s a feeling no tide gauge can measure.
