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Sediment and Erosion

Erosion is the process of soil and rock being transported and deposited to other locations by water flow and/or wind.  Erosion is  a natural process and helped shaped the natural landscape of the County. The problem arises when human activities, such as construction projects, cause large amounts of erosion and sediment deposition in our streams.

 

Sediment and Erosion Problems in Our Watersheds 

Problems caused by excessive sediment in streams include:

  • Unsightly waterways

  • Loss of important topsoil

  • Stream bank instability

  • Smothering of the spaces between rocks where fish lay their eggs

  • Cloudy water, which prevents fish from seeing their food

  • Abrasion of fish and other stream life

  • Reduced flow-carrying capacity in the stream channel due to sediment settling (which increases the potential for flooding)

  • Diminished water quality

  • Other pollutants carried by or attached to the sediment (such as phosphorus and petrochemicals) 

Image of a frog in sediment Image of a clump of sediment
Sediment smothers living organisms and abrades or coats their skin. It also settles in the spaces in which fish and other creatures lay their eggs and it makes the water cloudy. Sediment in our streams not only is a pollutant but also carries other pollutants attached to the sediment particles.

 

Stream Bank Erosion

If you spot a stream bank with active erosion or collapse, and sediment is discharging into the stream, report it to 311. DEP investigates complaints and will refer the problem to the relevant partner agency.

Common complaints include:

  • Severe stream bank erosion on property. Often mowing, herbicide use, and tree removal up to the stream's edge make banks more vulnerable to erosion because of the absence of roots, which bind soil in place.

  • Erosion of stream channels, which exposes sanitary sewer infrastructure.

  • Stream channel erosion resulting from a water main or sewer main rupture. (Cases are referred to the Washington Suburban Sanitary Commission.)

  • Stream erosion that is causing damage to a public road. (Cases are referred to the Montgomery County Department of Transportation.) 

 

Image of an exposed sewer pipe. Image of a house at risk from stream bank erosion.

Stream erosion can expose utility mains.

At this home, the yard is caving into the stream. This type of problem is often caused by a lack of vegetation along the stream banks. The roots of trees and plants help to bind the soil and keep it in place.
 

Limits of Service 

Please note that if the erosion problem is on private property, the only assistance that DEP provides is some technical assistance on how owners can solve the problem themselves.

DEP does not deal with erosion gullies and dry channels. Erosion gullies and dry channels are normally the responsibility of the property owner, except when they are part of the public storm drain system. Then DEP refers the problem to the Montgomery County Department of Transportation.

DEP does not deal with lot-to-lot drainage issues. Those issues sometimes are dealt with by the Montgomery County Department of Housing and Community Affairs when they are the result of one property owner doing something to his property (e.g., moving a downspout discharge point, filling in a backyard swale) that causes damage to an adjoining property.

Contact DEP by calling 311 or submit an online complaint form. Indicate that you are interested in filing an erosion control complaint. It's helpful to provide as much of the following information as possible:

  • Your contact information, for follow-up contact

  • The location of the complaint with street address if possible

  • The frequency and full extent of the problem

  • Pictures or video 

 

Construction Runoff

If you spot a construction site or any other land-disturbing activity that requires a permit (greater than 5,000 square feet) with discolored or muddy water running off it, you should report it through  311! (Construction/land disturbance sites less than 5,000 square feet are not required to have a sediment and erosion plan and don't fall under the Department of Permitting Services jurisdiction.)

Here are some examples of sediment violations and problems you can report:

  • An abandoned construction site where sediment control measures, such as plastic silt fences, are frayed or worm out and not functioning as intended. These devices might need to be replaced to prevent sediment erosion and runoff.

  • Streams adjacent to construction sites or land-disturbing activities with excessive siltation where you can see a direct flow connection to the construction site.

  • Sediment control practices (such as silt fences) that have been breached because of excess water or sediment build-up.

  • Other failing, inadequate, or improperly maintained sediment control best management practices on a site that is permitted for construction or land disturbance. 

To report a potential violation, contact the Department of Permitting Services or 311.

 

Aerial image of a construction site. Image of a silt fence protection.
A permitted construction/land-disturbance site must have a sediment control plan as part of its permit. A permitted site should have adequate, functioning sediment control measures (such as silt fences) in place.
 

 

Image of gravel at the entrance to a construction site. Image of a sediment pond
One common sediment control measure is a gravel entryway, which prevents trucks from tracking sediment from the disturbed site onto the road. Another sediment control measure is a pond into which the site drains so that sediment can settle before water is allowed to discharge into nearby creeks.

 

Image of sediment flowing off a construction site. Image of a sediment flowing into a storm drain.
This sediment problem occurred during a rainstorm, when the sediment ran off the site and entered the storm drain system. The storm drain system flows directly into local creeks.