Stormwater Basics


A rainstorm in the woods

When it rains in a forest, leaves, tree trunks, flowers and shrubs catch much of the water before it even hits the ground. Water drops that do reach the forest floor land on a soft humus layer - the dead leaves, twigs, and sticks that crunch as you walk through the woods. Humus absorbs water - it captures the drops and expands much like your kitchen sponge. As the rainstorm continues, some water works its way into the tiny holes between soil particles and joins the groundwater that gradually flows towards streams.

During its slow journey towards a stream, groundwater is filtered and cleaned. Some pollutants stick to clay and other soil particles. Bacteria and other tiny creatures living in the soil break down other pollutants. And plant roots take up fertilizers and other chemicals. In the end, the groundwater seeping into a stream is cleaner than when it first landed in the forest. And it enters the stream so gently that it doesn't stir up the bottom or erode the stream banks.

This marvelous system is nature's way of protecting streams during storms.

A rainstorm in town

Compare this to a rainstorm in your neighborhood. In your neighborhood, raindrops strike the pavement and rush downhill. As rain streams across the ground, it picks up oil droplets, gasoline, dirt, and other pollutants before disappearing into a storm drain. More rain bounces against rooftops and falls into gutters. Downspouts release torrents of water on lawns, and this water runs across your grass picking up fertilizer, herbicides and pesticides before entering storm drains.

Underneath your street, pipes carry stormwater to a nearby stream, where the swift-flowing, dirty water is released. This high-speed water erodes stream banks, releasing still more sediment pollution.

The end results are fewer fish, more pollution downstream, and unhealthy trees.

Low-impact development

Houses and streets don't need to pollute streams. There are many simple ways to have vibrant, healthy towns AND clean creeks. The answer lies in designing our stormwater systems to work more like nature - to slow down water, filter it, and allow it to seep into streams gradually. Rain gardens, rain barrels, green roofs and other simple techniques can help us maintain healthy waterways and continue to develop our communities.

To learn more, follow these links.

Why do we need better stormwater management?

Why stormwater matters
Montgomery County's 10 most polluted streams
A boxing analogy for stormwater problems

What you can do

Homeowner's guide to stormwater
Stormwater do's and don'ts
Join the FOSC Stormwater Committee

Stormwater projects in and around Sligo Creek

Examples of stormwater management around Sligo Creek
Presentation about Sligo Creek Watershed Stormwater

Raingardens in the Sligo Creek Watershed

American Elm Park
Forest Park
Eastern Middle School

Alternative plans for Evans Parkway Neighborhood Park

Detailed information