TreesNY’s Stormwater Vegetative Control project is designed to capture and remediate stormwater runoff in areas prone to flooding. In the Bronx, nine tree beds replaced 2,260 square feet of impervious surface along Bronx River Avenue, where the sewers frequently backup and empty into the Bronx River. The extra-large tree beds run 3 feet deep and are thickly covered with sustainable forbs, native grasses, shrubs and fast-growing trees.
This low-cost and easily replicable design reduces stormwater runoff, improves air and water quality and enhances the streetscape.
Concrete sidewalks and asphalt streets in New York City are generally impervious surfaces, which means that water cannot readily penetrate the material and enter the groundwater. Instead, water simply flows across the surface and into a storm drain. All city streets and sidewalks are engineered to guide water across the surface and towards a drain in the most efficient manner possible. At times this engineered path can change because of the ground settling underneath of the road surface or by litter blocking the intended drain. Either scenario can produce a flood event that forces pedestrians to cross through or take large detours around pools of water extending out from the curb, creating a miserable experience for walkers and motorists alike.
An effective way to reduce the quantity and speed of this runoff is by reducing the impervious surfaces within our urban environment. For the following projects, Trees New York combines three decades of experience of installing new tree beds with additional design elements to intercept, store, and evaporate storm waters before they have a chance to run into the storm sewer.
In 2010, Trees New York was awarded a grant from the National Fish and Wildlife fund to protect the Bronx River by reducing runoff into its watershed. The blocks that bound the river have histo.JPG)
rically featured a higher density of industrial activity and like most industrial zones in New York, are lacking in permeable surfaces. Excessive precipitation in the form of rain or snow can eventually lead to a combined sewer overflow (CSO). This occurs when antiquated sewer designs send all stormwater to the water treatment facilities, which can easily become overburdened by having to clean both sewage from tenant-occupied buildings as well as rainwater that runs over sidewalks and streets to storm drains. The extra water that cannot be processed by the treatment plants is diverted through outfall pipes into local waterways. Since the tainted waters contain pollutants that vary from road residues to human excrement, any outfall of the combined sewage into a water body is disastrous to aquatic life and prevents people from using the river for anything outside of boating.
The Stormwater Vegetative Con.JPG)
trol project on Bronx River Avenue features nine enhanced tree beds that include all of the modern design features that maximize water detention as well as provide a significant amount of green that this industrial area formerly lacked.
Enhanced tree beds are three feet deep, about six feet wide, and twenty-five feet long. This alone is a vast improvement over the standard tree bed that is mandated by the New York City zoning code. The additional volume not only allows more stormwater to enter the pit, but the space also allows the roots of the trees to grow with less impediment so that over time the trees will grow stronger and absorb more water.
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To learn more about our Trees & Stormwater program and enhanced tree bed design, contact TreesNY's Project Manager, Lucian Reynolds at lucian@treesny.org or (212) 227-1887.
