Stormwater Management: BMPs

What is a BMP?

Best Management Practices (BMP) are permanent facilities designed to collect stormwater runoff prior to releasing the water into a natural water way. A BMP is required by state law during development or redevelopment of residential, commercial and industrial properties to reduce pollution and control flooding associated with stormwater runoff from rooftops or pavement. 

Can I remove a BMP?

No. By law you may not remove or modify a BMP on your property without gaining permission from the City of Norfolk Storm Water Engineer or his designee. City code 41.1 requires stormwater BMPs to be installed and maintained as established in the approved site plan for development of the property. Additionally, a “Declaration of Covenants” (Declaration) is filed with the Clerk of the Court and attached to the Deed of your property that requires owners to maintain the BMP at their expense. The Declaration also allows the City Inspector to access your property on a routine basis to perform inspections and may require discrepancies be corrected within an allotted timeframe.

Why should I maintain it on my property?

Stormwater BMPs are required by state law and local law to be installed and maintained. These requirements are in place to assist with managing localized flooding, preventing pollutants such as nutrients, sediment, oil, etc. from running off the site and polluting downstream waters, and, in some instances, encouraging infiltration for groundwater recharge. 

If you have questions about your BMP, please contact:
Chrisi VanLear, Environmental Program Supervisor
Monday-Friday 7:00am-3:30pm at 757-823-4078

  1. Grass Channel - What is it?
  2. How does it work?
  3. How do I maintain it?

A grass channel (or ditch) is a broad, shallow area covered with turf or grass. Grass channels are typically located along the edge of a property, gently sloping toward the storm drain system. They are commonly found along roads, parking lots, or between residential properties.
Picture of Grass Channel for stormwater

  1. Dry Swale - What is it?
  2. How does it work?
  3. How do I maintain it?

A dry swale is a broad, shallow, vegetated channel that is located along the length of a property and gently slopes toward the storm drain system. Dry swales are designed to slow stormwater runoff an allow water to soak into the ground through layers of special engineered soil mix and stone. They increase pollutant removal through filtration and infiltration.

Dry swales can be seeded with turf grass or planted with more elaborate landscaping that includes tall meadow grasses or native plants and trees. They are designed to dry out between rain storms and typically hold water for up to six hours after a storm.

  1. Infiltration Trench - What is it?
  2. How does it work?
  3. How do I maintain it?

An infiltration trench is a small trench filled with stone that collects runoff from paved or impervious surfaces such as driveways or roofs and allows it to absorb into the underlying soil.

Picture of Infiltration Trench

  1. Rain Garden & Bioretention Areas - What are they?
  2. How do they work?
  3. How do I maintain it?

Rain gardens are shallow landscaped gardens designed to temporarily store and treat stormwater runoff from your roof, driveway, walkways and lawn. They consist of several layers: a gravel bed, a special engineered soil mix and sand, mulch, and planted with native grasses, flowers, shrubs, and sometimes small trees. 

Bioswales are similar in the way rain gardens are designed with layers of vegetation, soil and also have a perforated pipe, or underdrain, in the gravel bed to assist n filtering storm water into the soil and storm drain system.Picture of rain garden

  1. Permeable Pavement - What is it?
  2. How does it work?
  3. How do I maintain it?

Permeable (or porous) pavement are surfaces made from porous material that allows stormwater to flow through it into the underlying stone and soil below instead of flowing off it. Permeable pavement may be made from porous asphalt, pervious concrete, or permeable interlocking pavers.

Picture Permeable Pavement next to AsphaltUp close picture of permeable pavement next to asphalt

  1. Rain Barrel or Cistern - What is it?
  2. How does it work?
  3. How do I maintain it?

Rain barrels come in many different sizes, but a 55-gallon tank is the most common. Cisterns are tanks of 200-gallons or more. Water is captured from a surface, such as a roof, and conveyed to the rain barrel or cistern through pipes or gutters. This prevents stormwater from entering the storm drain system and can help with localized flooding. There is an overflow system that diverts excess rainwater when full. 

The stored water is then available for non-potable use through a spigot or hose. Gravity facilitates the water in the tank being dispensed, so the barrel may be elevated on a stand or blocks to improve flow through a hose.  

Picture of Rain Barrel

Picture of Cisterns

  1. Wet Pond
  2. How does it work?
  3. How do I maintain it?

Stormwater ponds, or retention ponds, are permanent pools of water that collect and store stormwater runoff from roofs, roads, and parking lots. They reduce pollution and improve water quality by filtering the runoff before it enters our local waterways. They also control water quantity to reduce localized flooding.

Picture of Stormwater Wet Pond

For detailed information on specific BMPs please refer to:
Virginia Stormwater BMP Clearinghouse