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Storm Water Management

Updated: May 5, 2021

If it’s on the ground, it will be in the river.

When asked in surveys, most people do not know that the major source of water pollution in the United States is surface water runoff. (National Environmental Education Foundation) Rain water connects our yards and streets to the nearest river or bay.

In Riverdale, rain water that does not enter the ground carries gardening chemicals, oil and other motor vehicle fluids, soap, paint, litter and anything else left on the ground downhill to either a storm sewer or, if there are no storm sewers, the Hudson or Harlem River.

And even if the water makes it to a storm sewer, if there is enough rain to overwhelm the sewer, an overflow pipe carries the excess rain, combined with raw sewage, directly to the river. This is referred to as a Combined Sewer Overflow (CSO).

Minimize pollution of the rivers by helping water infiltrate the ground where it is naturally filtered and cleaned, and by keeping toxins and litter off the ground.

Help rain water infiltrate into the soil:

  • Use permeable paving materials. Ground cover plants, gravel, and paving stones with spaces between are common choices. Permeable pavements are also available. Learn the details.

  • Keep soil loose. Rainwater will sheet off the surface of compacted soil as though it were pavement.

  • Plant a rain garden. How? Download the NEMO guide here.

What is a rain Garden? A rain garden is a garden that collects rain water and allows it to slowly seep into the soil. Rain gardens are often located near a downspout or paved area. Simple formulas enable you to calculate the size of the garden you need for the amount of rain water you expect, and planting guides help you choose plants that will thrive in wet soil. In the Special Natural Area District, you may not change the grade of your landscape by more than 2 feet without a review by the City Planning Department. Keep this restriction in mind when planning your rain garden.

Keep chemicals and litter out of the water:

  • Garden organically – see our Garden Organically section, above

  • Think about where you wash your car. If possible, wash it in an area where the soapy water and grime will infiltrate into the ground. Use biodegradable soaps.

  • Park your car on a permeable surface so that auto fluids that drip are not washed away by the rain.

  • Remember that litter ends up in the river and collects on the shoreline. Take care that your personal floatables stay put in trash cans or recycling containers.

  • Participate in cleanups such as the Annual International Coastal Cleanup.

  • Do not dump toxic household chemicals or other waste down the drain or storm sewer.

Get all the details:

For a collection of tip sheets on the connections between your yard, household chemicals, and clean water, visit the Nonpoint Education for Municipal Officials (NEMO) program, and look for the last set of tip sheets on the page, under the heading Clean Water. These are geared to homeowners.

To see what New York City is doing to address pollution of local waterways, visit the Mayor's Office of Resiliency and PlanNYC.

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