Streams & Watersheds

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If you have a creek or stream in your backyard or a small ditch that collects water after a storm, that is part of a greater system of streams, lakes, rivers and ponds that make up a watershed. How you treat the land in a watershed has a great impact on the rest of the watershed. Even if you do not live near a water source, you are still part of the watershed, and it's very important to practice good watershed stewardship.

A watershed is the area of land that drains to a common stream or stream network. Water can reach this stream network by filtering, draining or seeping through the ground, marshes, lakes or other streams. This same water sustains plant and animal life and provides our drinking water.

Watersheds in Tredyffrin Township

The geography of Tredyffrin Township encompasses seven watersheds: Abrams, Crum, Darby, Gulph, Little Darby, Trout, and Valley Creek watersheds. Trout and Valley Creek watersheds are the two main watersheds in Tredyffrin.

Valley Creek has an exceptional value (EV) designation from the Pennsylvania Department of Environmental Protection and thus has special regulations for individuals wanting to do earth disturbance or construction activities in the watershed. The Valley Creek Restoration Partnership has been working for a number of years to maintain, improve, and enhance this valuable creek asset.

A Trout Creek study was completed in 2004 and supplemented with an implementation plan in 2009 that evaluated the conditions and possible solutions to improve water quality and raise the status of the creek.

Impact of development

Over time, development tends to impair watersheds. Rainwater runoff is the greatest cause of impairment. Rainwater hitting homes, street and driveway pavement, buildings or other impervious surfaces, runs off and carries chemicals, dust, trash, and other accumulated pollutants into our watersheds along with the excess rainwater. 

Impervious surfaces (those that do not allow water to penetrate) prevent water from seeping into the ground to replenish the aquifers. Soil compaction from grading and development of a site also reduces the amount of water able to infiltrate into the ground water supply.

Since water cannot percolate into the ground during heavy rainstorms, it flows into natural or man made channels and streams. The velocity of the water flowing over the ground and into these channels can do serious damage to the stream channel through the effects of erosion.

Streambank erosion causes stream channels to widen and straighten over time, reducing their ability to slow the force of the water in a storm and increasing the chances of flooding and property damage.

What Residents Can Do

There are many ways to help protect and improve the health of watersheds. The following are recommendations of the Chester County Water Resources Authority: 

  • Plant bushes and trees on your property and/or near streambanks to slow runoff and erosion by maintaining the soil's integrity and retaining water that replenishes the aquifers.
  • If you live near an above ground water source, leave a buffer of at least 20 feet of un-mowed grass adjacent to the water source. It will filter pollutants from runoff and protect the streambank from erosion.
  • Direct downspouts away from driveways and sidewalks and onto vegetation so water may be absorbed into the ground.
  • Do not allow fertilizer to settle on sidewalks or the driveway. Leave a buffer strip around the outer edge of your lawn to prevent excess chemicals from landing on the hard surfaces and being carried away in the next rainstorm.
  • Do not place yard waste or any other type of waste in a stream channel. Doing so can cause severe problems such as flooding or property damage.
  • Always properly dispose of household hazardous substances. Disposing hazardous products such as paints, oil, household cleaners and fertilizers in your storm drain or elsewhere on your property contaminates the groundwater.

For more information on tools for stormwater management for your property, please visit our stormwater management page.

What Tredyffrin is Doing...

Working with the Valley Creek Restoration Partnership to implement 2 grant funded projects: 

  • Install a green roof on Hillside Elementary School
  • Install outfall BMP's around Crabby Creek

Enforce ordinances to protect environmentally sensitive lands, maintain and/or enhance buffers near water sources, provide open space, protect steep slopes and design better stormwater management systems.

Working with and supporting the Open Land Conservancy, Valley Forge National Historic Park, Chester County and various property owners whose goals are protecting and preserving our watersheds through the purchase of land and coordination of projects that benefit watersheds.