There’s a whole world out there, right o utside your window. You ’d be a fool to miss it. ~ C h a r l o tte E r i k s s o n
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Our Coastal Ecosystems’ Shifting Reality By Dr. Lenore Tedesco, The Wetlands Institute Executive Director
Marsh flooding as seen from The Wetlands Institute on May 11.
or the past several years, sea level rise, beach erosion, nuisance flooding, and coastal resiliency have become increasingly common terms in everyday discourse. Here at home, the New Jersey coast is experiencing rates of sea level rise that are more than twice the national average, and rising seas are already causing changes to our marshes and beaches. Effects that were seen a few times per decade or only by scientists making detailed measurements are now occurring annually, and are readily apparent to the casual observer. Our climate is changing, and the chaotic manifestations predicted by those studying it are being seen more frequently. The Mother’s Day storm was a dramatic reminder that change is already here. I periodically write about the changes to our ecosystems and covered how our beaches work in the spring issue last year, and thought it would be interesting to share my perspectives on this most recent coastal storm. If you were at the shore, you would have experienced the brutal low-pressure system that set up off the coast. However, those who were even 10-15 miles inland were spared much of the storm’s impacts. In my 11 years here, I believe this is the longest-duration wind and elevated water level event that we
Water levels measured at Stone Harbor. The red line is the level when the marsh is underwater.
have had. The relentless winds blowing to gale force and near gale force (greater than 30 mph) – with persistent stronger gusts – started on May 6 and didn’t diminish until May 11. These winds were also notable in the persistence of the attack direction, coming steadily from the northeast. These two conditions are the ingredients for the perfect storm for Seven Mile Beach, the New Jersey shore, and significant portions of the East Coast.
Strong winds that consistently blow from the northeast push waves and water high onto the front beaches and into the tidal inlets. They also keep the water from receding, pushing each successive high tide higher onto the beach. With nowhere to go, the tidal currents accelerate, and water and eroded sand move to the south and offshore, lowering beach elevation and cutting dramatic dune scarps. Winds also blow sands into
the dunes fortifying protections. Following these storms, normal high tides now reach higher onto the beach because of the lowered elevation. Beaches can store sand in offshore bars in winter and during storms, so the ultimate volume of sand lost from the beach system is not fully known. Calmer summer waves naturally move this stored sand back onto beaches so there should be some natural healing and replenishment. It is likely that beaches that are typically narrow will be affected through the summer. The storm’s elevated water levels also caused dramatic flooding of the marshes and back bays through a process called tidal stacking. Winds blowing from the northern or eastern quadrants push water into the bays through tidal channels, and when persistent, they prevent the tide from going back out the inlets. The graph shows the measured water levels from a tide station located next to the 96th Street bridge. Tidal stacking is dramatic and can be seen with each successive day, when low tide was higher than the prior day’s high tide. Marsh surface elevation in the back bays behind Seven Mile Beach is at roughly 1.8 feet NAVD88 (a level used to compare ground elevation to water levels) and is shown as the continued on page 102
Seven Mile Times
July 2022
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