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New Advances In and Benefits of Green Stormwater Management

While I have written extensively for years on sustainability, I have emphasized energy, greenhouse gases, etc., and less on other important items, such as waste reduction and water conservation. So here I write about issues in stormwater management. As land becomes more developed, there is less natural area to absorb rain water. It must flow somewhere, and can be too intense to handle and cause damage as it flows. This will grow as an issue as the frequency of high-rainfall events increases. Savings from damage avoidance will result from implementing better stormwater management.

Historically, the philosophy of stormwater management has been to take the water from rain events and move water away. It is more efficient to have a single system to lead all of it away, such as swales, leading to a sewer system.

However, a paradigm shift has occurred. Now that it is better to spread water out. Spread it away, down, store water, reuse, etc. This involves increasing natural land to absorb water. Below are the relative fates of water in a developed vs. natural area.

Developed Land Runoff: 55% Evaporation: 30% Infiltration: 15%
Natural Land Runoff: 10% Evaporation: 40% Shallow Infiltration: 25% Deep Infiltration: 25%

Strategies to better manage and spread out the growing quantity of water include:

•   Swales (depression) with a cut at the curb to allow water flowing down a street to enter a sidewalk or a grassy area.
•   Green roofs.
•   Sidewalk rain gardens. Feed runoff from roof into rain gardens before running off.
•   Porous pavement, such as a parking lot or a sidewalk to allow rain to flow to structural soil below to feed trees while still providing integrity to the sidewalk. This also allows tree roots to move horizontally instead of up, buckling sidewalks.

Per the last point, porous pavement (concrete or asphalt) is now competitively priced with conventional pavement, and actually lasts longer than conventional pavement (less cracking) because water is led away and does less puddling.

Per the 2nd and 3rd points, use whatever opportunity possible to replace pavement with trees. It’s not just aesthetics (it’s “pretty”). Besides reducing the amount of stormwater to treat, there is growing evidence that trees have distinct beneficial health effects for those nearby ( and that trees, roof gardens, etc. have a distinct effect on cooling nearby buildings, saving AC usage and energy costs.

CCES has the experts to help you evaluate and upgrade your stormwater management program to reduce costs, potential damage from storms, and energy use, and to improve the long-term health of your workforce. Contact us today at 914-584-6720 or at

Marc Karell, P.E., CEM, Principal, Climate Change & Environmental Services, LLC



Reprinted with permission by CCES


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