Storm water Runoff Revisited

Retain Nutrients, Reduce Environmental Damage By Managing Water

With the heavier rains we have been experiencing, we at Greener by Design have experienced and upsurge in calls regarding runoff issues in Pelham. One client has a small river flowing through their back yard coming off of a road on the adjacent property, another has mulch running off a hedge row at the bottom of their grassy slope, and some have heavy water penetration in their homes.

Pelham is a community of hills and slopes, worse still we are not on the top of the hill, but lower in altitude than many of our neighbors, which means a good deal of water runs downhill to our properties from neighboring up hill communities. The predictions for our region are more heavy rainstorms and less regular, lighter rainstorms than in the past, so dealing with storm water will be even more of a problem than it is already.

Water seeks the path of least resistance. Whatever can’t be absorbed by soil, will run over it and take topsoil and valuable nutrients with it. Indeed, what made the Nile basin a rich farmland was the occasional flooding of the Nile that would deposit silt, made up of rich topsoil that had run into the Nile from heavy rains up stream.

What this means is areas where water runs down a slope are regularly being stripped of nutrients and topsoil so that grass and other plants have a harder and harder time being sustained. Additionally, if any kind of pesticide or fertilizer has been recently applied, this will run be taken down the slope to sewers and drains and into Long Island Sound causing greater environmental damage.

The favorite routes of water are paths, walkways, and driveways. Next are rocky areas, and last are lawns. Lawns, thought they do absorb water have a limited capacity to do so and once saturated the water will run down the lawn.

Strategies for dealing with runoff are to create dedicated spillways channeling the water where you want it to go, or at least away from where you don’t want it. Basically your driveway is a spillway, and the problem with this approach is it is a short term solution to a long term problem. Spillways inevitably take chemicals and pollutants (like oil from automobiles) unfiltered into local waterways. For this reason, most sustainable systems, like LEED for example, recommend creating permeable surfaces for driveways and patios. Permeable surfaces are generally hard surfaces that allow water to pass through them at regular intervals.

The most traditional approach for storm water management is to create “French drains” or underground catch basins for excess water. These do fill up with silt over time and need to be cleaned out.

On grassy slopes, the most effective strategy is to plant berms with perennials and shrubs at regular intervals where runoff is flowing. These mounds of soil will catch the water, break its movement, absorb a good deal of it and catch nutrients before they can run down the slope. They also will reduce the amount of grass (and therefore maintenance costs) on the slope as well as beautify the slope with more textures and colors.

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