Last week the U.S. House of Representatives pumped the brake pedal on passing a federal aid package for states affected by Hurricane Sandy, sending politicians from New York and New Jersey in to a frenzy and Congress into a debate over how much money these areas need to recover. Solutions like sea walls, expanded treatment plants and reservoirs have been bandied about in New York City and the coastal areas of New Jersey since the historic storm, but another suggestion –not nearly as grand as a sea barrier but perhaps more effective and feasible– has been brought to the forefront by Dr. Franco Montalto, a professor in Drexel University’s College of Engineering.
Montalto, who is slated to testify at a series of New York State Assembly hearings on Sandy recovery and climate change, is a proponent of a more holistic, ecosystem approach to climate preparedness. His suggestion: Green infrastructure –a term that’s come into chic in recent years in urban areas that are working to “green-up” their cities. Cities are adding projects like green roofs, drainage swales and depressed green areas to their list of infrastructural improvements for a variety of reasons, among them is a push to better manage storm water and reduce the excess heat generated and trapped in cities by a localized concentration of carbon dioxide producers like cars, buildings and factories.
Urban green infrastructure system, before and after (Photos courtesy of Dr. Franco Montalto)
According to Montalto, there is ample evidence that green infrastructure can also play a big role in mitigating environmental effects of extreme weather events such as hurricanes.
One of the reasons that New York City and northern New Jersey are especially vulnerable during coastal storms is that many of their wetland areas have been filled in for building. In fact, since the 1900s more than 75 percent of the area’s wetland acreage has been eliminated due to construction – including three regional airports, the Port Newark-Elizabeth Marine Terminal and several sports stadiums.
The problem here is that when there are monumental amounts of rainfall, instead of being absorbed –at least partially- in wetland areas, the stormwater runs off the developed surfaces, causing flooding and overloading of water treatment facilities. Aside from the structural damage caused by the high winds and storm surge, a good deal of property damage that occurred during Hurricane Sandy was due to flood water that carried discharges from overloaded sewage treatment plants.
The question government officials now face is how to keep the low-lying New York/New Jersey estuary safe from more flooding in the future. Montalto, who is part of a NOAA-funded group of scientists that studies environmental issues related to climate change in the urban northeast, toured many of the hurricane-damaged areas to examine environmental factors that may have contributed to or prevented the destruction. His finding: elevation, more so than distance from the coast, was a key determinant of vulnerability. So the buildings that stood where wetlands once existed tended to be the ones that suffered the most damage, while others, that were buffered by wetlands and coastal sand dunes or located on higher ground, seemed to be spared despite their proximity to the coast.
One suggestion for coastal protection takes this example of natural buffering to an extreme. A storm surge barrier, similar to those used to block the North Sea from consuming the 20 percent of the Netherlands that is below sea level, is one proposed solution for protecting the low-lying coastal areas of the northeast. Drawbacks of this plan are its high cost and the lengthy timetable -on the order of years- to build it.
Montalto’s ecosystem approach suggests preserving the remaining wetlands, which number about 70,000 acres in the New York/New Jersey area, and adding green infrastructure to increase the overall permeability of the region for absorbing stormwater.
In recent years, New York City has committed to using green infrastructure to absorb the first inch of rainwater from 10 percent of the city’s impermeable surfaces. By enhancing the city’s ability to absorb rain water, green infrastructure helps take the load off of treatment plants during storms and acts as a wetland-like barrier on a local scale.
The additional advantage to the ecosystem approach is that it can be implemented quickly, even in phases, so that there are immediate benefits. It’s also a financially scalable plan, as more infrastructure can be added when funds become available –which is, of course, the question of the hour.