Back-bay flooding a growing problem
OCEAN CITY, New Jersey — Marty Mozzo gets a gorgeous show each night when the sun sets over wetlands near his property on the bay side of a barrier island.
When he and his wife bought the house in 2008, she looked at the marsh, where the only sign of water was a tiny trickle nearly a kilometre away.
“Do you think this will flood?” she asked.
“How could it?” he replied. “Look how far away the water is.”
Within weeks of moving in, a storm stranded them for two days with water on all sides. Theirs is one of several neighbourhoods in Ocean City, New Jersey, where residents have adopted unofficial flood etiquette: Don’t drive too fast through flooded streets or you’ll create wakes that slam into houses, scatter garbage cans, and damage lawns and gardens.
They are among millions of people worldwide whose lives and land are being dampened by back-bay flooding — inundation of waterfront areas behind barrier islands where wind and tides can create flooding during storms or even on sunny days. It’s a type of flooding that tends to be overshadowed by oceanfront storm damage that grabs headlines — and government spending — with dramatic video of crashing waves and splintered houses.
“This insidious flooding is increasing, and it is an important social issue, but it is not getting enough attention paid to it,” said S. Jeffress Williams, a coastal scientist with the U.S. Geological Survey. “Flooding is happening with increasing frequency in back-bay areas. It happens very rapidly; it’s just not as dramatic.”
Williams, who lives on Cape Cod in Massachusetts, said backbay flooding is happening just as frequently, if not more so, than oceanfront flooding.
“Over the past 15 or 20 years I have seen, especially when you get a full moon and a high tide,” he said, “roads, backyards and parks all get flooded, much more so than we ever had before.”
The problem of back-bay flooding is coming into sharper focus. Studies are underway, money is starting to flow toward the problem, and the realization that destruction of wetlands for development along such shores is partly to blame is leading to discussion about building codes.
As of January, the U.S. Army Corps of Engineers map of recent storm protection and navigation projects in New Jersey showed 10 either completed or underway, with six more planned. But none were done in back bays.
A 2010 study by the National Oceanic and Atmospheric Administration found that about 123 million people — or about 39 per cent of the U.S. population — lived in coastal zone counties, a number projected to grow by eight per cent by 2020. The greater proportion of those people live on or near the bay sides of barrier islands, scientists say, than on the oceanfront.
Unlike oceanfront flooding, in which crashing waves from storm-driven seas pound the beaches, back bays flood gradually and comparatively quietly as water levels rise. The effect is worsened during storms that continue through numerous tide cycles in which water piles up in the back bays without being able to drain out to sea.
Tides and wind can inundate some of these areas even when the sun shines.
“The water sneaks up the backside of barrier islands and the flooding you get is sometimes actually greater than on the ocean sides due to the topography of the islands,” said Guy Nordenson, a structural engineer specializing in climate change adaptation whose firm has worked with the U.S. Army Corps of Engineers on flood prevention projects.
Many traditional engineering solutions that are used along the oceanfront are of limited benefit against back-bay flooding. Houses are being elevated and roadways repaved to make them higher. But the bulkheads, sea walls and sand dunes used along the ocean can’t be replicated in many back-bay areas because of limited space and resistance from homeowners who prize waterfront views.
Any new homes need to be built in these areas with sea level rise in mind, said Princeton geosciences professor Michael Oppenheimer.
“They need to design buildings that are essentially floodable, where it’s OK that the first floor gets flooded every now and again,” he said. “These places do get wet on a regular basis.”
Globally, sea levels have been rising over the past century, and the rate has increased in recent decades. In New Jersey, seas have risen by 0.4 metres over the past 100 years. That is a faster pace than for the past 2,000 years combined, he said.
Researchers project that by 2050, seas off New Jersey will rise by an additional 0.4 metres.