A Perfect Storm: Our Coastal Ecosystems' Shifting Reality
Marsh flooding as seen from The Wetlands Institute on May 11.
For 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 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 red line, so that when the water level is above this, the marsh is inundated. When the levels are above 2.5 feet, the marsh is completely underwater and the marsh grasses fully submerged. During the recent six-day storm, the marsh was fully inundated for several tide cycles – even through some low tides – with only brief times when the marsh grasses were exposed. As a comparison, during Superstorm Sandy, the marshes were inundated for approximately three days. With most nor’easters, it’s typical to have up to three days of inundation (rarely more), and low tides uncover the marshes.
In addition to the prolonged flooding during this storm, there is also a massive amount of wrack being transported throughout the back bays and in the marshes. Wrack is the dead thatch of the marsh grasses, and is produced every year during the winter when the grasses turn brown and die back. The difference this year is that the winter ice events that are relatively rare here flattened the marsh grasses, froze around them, and then broke them loose. The amount of persistent ice on the marsh this winter rivals only two other such ice events I have experienced in my 11 years here. These wracks moved around extensively during the high-water events, and will continue to do so throughout the summer. They will play important roles as they move around – both causing smothering and loss of marsh and serving as valuable rafts for wildlife and some birds nesting in the marsh.
The storm’s unrelenting high winds and water and associated marsh flooding were damaging to coastal wildlife. Nesting season had already begun for several beach and marsh nesting birds – including many ospreys, with osprey moms dutifully hunkered down trying to protect their eggs. Unfortunately, we have received many reports of nest loss during this storm. These happened early in the season, so we are hopeful many of these birds will try to nest again. Rising seas have also driven the loss of high marsh and transitional upland habitat, and this was acutely felt by wildlife. Flooding pushed marsh-dwelling birds onto higher ground that unfortunately proved to be very dangerous for them. Stone Harbor Boulevard and Avalon Boulevard were littered with clapper rails and gulls that were struck by cars.
The Wetlands Institute works every day to understand the changes to our coastal marshes and beaches as they respond to the ever-accelerating rates of sea level rise, and how the wildlife that depend on those areas adapt. Through the Seven Mile Island Innovation Lab (SMIIL), we are working with federal and state partners to develop and implement projects to help our marshes mitigate some of the effects of sea level rise and create wildlife habitat where it is being lost. The benefit of these efforts was evident in this storm. Areas in the marsh where SMIIL has already created nesting bird habitats ended up being some of the only places that were above water, and they served as important refuges for wildlife.
Our research and conservation projects provide information to other scientists, coastal restoration practitioners, and our local municipalities to enable them to plan and prepare for the changes that are already occurring. Our education and visitor programs work to connect people with nature so they can better understand the function of our marshes and the coastal ecosystem, and their importance to our well-being. If you would like to learn more, stop by for a visit or explore our extensive online resources. My writings are also archived on the Institute website and through the Seven Mile Times website.
