Erosion, Drainage & Stormwater Management

BACKGROUND:
(written by Lee Schmidt, Ponds Trustee & Board Liaison to the Burke Centre Conservancy Open Space Committee)

Different entities have different goals regarding drainage. Chesapeake Bay Authority has the goal of no excessive disposition of soil or hazardous materials into RPAs (Resource Protection Areas), which are around the creeks and streams in our area. Burke Centre Conservancy (BCC) ARB (Architectural Review Board) Standards have goals of maintaining the natural appearance of properties and no (excessive) runoff from one property to another property. In preparing their drainage document, the BCC Open Space Committee has had a goal of preventing and repairing soil erosion from such drainage. However, the paramount goal has to be to prevent “residence” of accumulated water against building foundations so as to seep in. It is best to design and maintain grounds so water will naturally flow away from buildings, even if then it must flow to other properties (hopefully, without causing erosion or other damage). This is where conflict of goals occurs so all factors must be carefully considered.


The original intention of assembling information on this topic was to provide guidance to clusters on identifying erosion problems from drainage through their clusters and providing ways to resolve these problems. Following the Open Space Committee's review of this extensive topic, the Board of Trustees has determined that selected portions of the gathered information may eventually need to be added to certain ARB Standards.

Solving Drainage & Erosion Issues: A Guide for Homeowners

IMPACT ON HOMEOWNERS:

(written by Anita Musser, Oaks Trustee)

Erosion has been studied very carefully by the Open Space Committee and the members have provided some really good information. I have never really understood where to find help in addressing this issue until I read their report. I live on a slope where rain runs from Burr Oak Way down a path and open space area, through my neighbors’ yards and down into mine. I have a drain in my yard so that is understandable. However, over the years, the open space area has been cleared of brush and natural debris which served to slow down the rush of the water before. Now, the water rushes down like a river and brings mulch and leaves and everything else down with it. After a hard rain, I spend a lot of time just cleaning out my yard so I can mow. So what can we do about this?

One of the places you can begin is at the Northern Virginia Soil & Water Conservation District (NVWSCD). This is a wonderful site with topics such as Rain Gardens and More, Soils Information, and Wet Yard - Solving Drainage Problems (as excerpted below from NVWSCD), for example.


WET YARD - SOLVING DRAINAGE PROBLEMS:

(excerpted from http:/www.fairfaxcounty.gov/nvswcd)

If your yard dries out within a day or two after a rainstorm, that is considered normal. A yard with a wetness problem has puddles or soggy areas that persist for several days after storms or are always present.

If you have heavy flows of stormwater passing over your property during storms, but not persistent sogginess afterwards, please see Control Heavy Runoff.

My Yard is Wet for Several Days After Rain or Snow

[from NVSWCD) Wet areas that persist for several days after rain or snow are commonly caused by improper grading (low spots or depressions) or poor infiltration of water into the soil.

  • Grading problems on your property will prevent water from quickly flowing away into a storm drain or other suitable outlet. Areas around the foundation should slope away from the foundation walls; swales or other flow diversions between neighboring houses should be properly graded so that runoff does not stagnate on your property.
  • Poor infiltration (also known as percolation) can be caused by compacted soils, soil with high clay content or soils with a shallow depth to bedrock. Water can perch on top of these materials, either at the ground surface or slightly below it, causing sogginess. In addition to the solutions below, consider amending the soil.

Small wet area after stormsSmall Wet Area After Storms

[from NVSWCD] In small wet areas after storms, poor grading prevents stormwater from flowing off the yard. Instead, stormwater is held in small, well-defined depressions until evaporation or infiltration into the soil eliminates the wetness.

A practical and environmentally beneficial option is to replant the wet area with water-tolerant plant species, preferably native. If you wish to eliminate the soggy depression, you can do so by filling or re-grading the depression.

I. Replant with water-tolerant species. A soggy spot can be improved by replanting with water-tolerant plants. Plants will aesthetically improve the soggy spot, soak up the remaining water, attract beneficial pollinators, and they can also slowly improve drainage by loosening the soil with their roots and organic matter.

II. Fill in the depression. To eliminate wetness in small depressions, the depression can be filled in and graded. Here's how:

  1. Remove all leaves, plants (including grass) and other loose material from the depression.
  2. Fill the depression with topsoil (or if near the foundation of the house, with fill soil) and compact using a tamper or a similar device. Use soil with relatively high clay content.
  3. Grade the filled-in depression so that water will not stagnate. Soil should be graded so that water flows away from the foundation walls to prevent any water damage.
  4. Cover the depression with sod, grass seeds or other vegetation. If sod is used, make sure the final elevation does not cause water to collect on the up-slope side. If grass seeds are used, consider protecting the seeds with a thin layer of topsoil (approximately ¼ of an inch) followed by a thin layer of straw. This thin layer of soil and straw will help protect the seeds from birds and also enhance germination.

Widespread Wetness After StormsWidespread Wetness After Storms

Widespread sogginess near landscaping that is too large or difficult to simply fill in, re-grade or replant, there are other solutions. Runoff can be redirected or captured to minimize water accumulation.

  • Redirecting runoff safely takes it to a suitable area. This can be done using swales, French drains, catch basins or downspout extensions.
  • Capturing and storing runoff helps protect streams and rivers and reuses the water. This can be done using rain barrels, cisterns, dry wells, soil amendment or rain gardens.

Learn how to redirect runoff and how to capture and store runoff. »


Storm Drains and the Chesapeake BayStorm Drain Label: Drains to Potomac River, Copyright 2005 das Manufacturing, Inc.

(from Northern VA Soil & Water Conservation District)

Storm drain labeling is an effective, low-cost method of educating residents about water quality problems in our streams, lakes, rivers and the Bay. 
NVSWCD is currently recruiting volunteers to lead storm drain labeling projects.

Storm drains are located throughout the Potomac River and Chesapeake Bay watersheds. What we do in our yards and communities affects the Bay through the storm drainage system.

When it rains, the water running along the gutters in the street vanishes down storm drains. Where does the water go? The water in a storm drain does not go to a treatment plant. This runoff drains directly into a local stream. All our local streams in Fairfax County feed into the Potomac River, which empties into the Chesapeake Bay. Nothing is removed from the water. That means pet waste, yard debris, fertilizer, motor oil, pesticides and trash all have the potential to flow into our streams and the Chesapeake Bay.

Pollution that enters our water resources through the storm drains is called non-point source pollution because it comes from all our homes and communities - many diffuse sources, not a single "point" source. Non-point source pollution is the leading cause of water quality deterioration in the Chesapeake Bay.


RELATED LINKS:

   Northern Virginia Soil and Water Conservation District

  Pohick Creek Watershed Management Plan

  You and Your Land: A Guide for the Potomac Watershed

  Fairfax County Storm Water Management

  Storm Drain Safety