Sustainable Drainage

Find information on the most common residential drainage features in Surrey.

A sustainable drainage feature is any stormwater management structure that reduces the negative impact of change on the existing drainage system. This is also known as a:

  • Best Management Practice (BMP),
  • Low Impact Development (LID) feature, or
  • Sustainable Urban Drainage (SUD).

The objective of these features is to maintain the same runoff characteristics on a site that existed prior to development or change. With climate and environmental changes, the need to include sustainable drainage features into development becomes even more important.

Many sustainable drainage features are generic and can be implemented easily on any lot. Homeowners and developers can improve sustainability by providing trees and increasing the depth of absorbent topsoil on lots.

Sustainable drainage features can be implemented at the individual lot level, local community level, city wide, and regionally.

Common sustainable residential drainage features

Disconnected downspouts

When it rains or snow melts, a lot of water flows off of your roof. The downspout helps capture that water and send it to a place other than inside your home.

Downspouts help direct the water to safer places to protect your home. Typically, the downspouts are connected to the perimeter pipes around your house that go straight to the storm system, and then local streams.

In a sustainable development, the downspouts are disconnected from the storm system and instead have a splash pad below them so that most of the water that hits your roof can be directed to grassed areas or gardens where most of the water can be used by plants or it can soak into the ground.

Rock pits

Another way of slowing down the flow of water over a property is to dig a hole in the ground and fill it with rocks. The spaces between the rocks in the pit provides room for water to be stored.

Water gets channelled into the rock pit where it percolates into the ground. It can be pretty slow depending upon what kind of soil is in the ground. These pits, sometimes called French drains, hold the water while it soaks away into the ground where it can become part of the groundwater.

Porous driveways

When rain hits a driveway, it sits on top in puddles or it rolls right off the asphalt towards a storm drain or creek. This can cause flash flooding because water can’t trickle into the ground and all the rainwater rushes to the nearest creek instead.

What if a driveway could absorb water? It could be made from gravel, concrete blocks or even something called, porous asphalt or concrete. The more rain that can be directed to flow through the driveway and get absorbed by the ground, the less water that flows into the pipes that are connected to nearby creeks.

Drainage swales

A swale is like a ditch, but shallower and wider. You usually see these beside roads. When there is a lot of water, it fills up and slowing down the flow of water on its way to the creek. When the weather is dry, the swale is empty and grass and other plants grow.

By holding the water temporarily in a swale, it allows some water to soak into the ground, some to evaporate and mostly it slows the water headed for the neighbourhood creek or stream.

This helps protect the habitat at the creek or stream so little critters, like toads and newts don’t get swept away in the swift current that occurs in typical developments.

Perforated pipes

Perforated pipes are simply pipes with holes in them. The pipes get laid down under the ground and can drain a whole back or side yard. The pipe works in a system and is sort of like a reverse maze.

Water from the soggy yard enters any of the pipes under the ground and as water moves through the pipes, it can drain out the holes and eventually run to the lowest pipe and run into the ground.

Detention ponds

Another way to slow water down after a rainstorm is to send it to a settling pond. The water gets to sit there slowly draining towards the creek or into the ground. If the water going into the pond is dirty, the pond lets the water slow down so that the dirt can settle down to the bottom of the pond instead of flowing to the creek.

While the water is sitting, larger and heavier particles sink to the bottom of the pond so the nearby stream receives cleaner water.

Sustainable drainage features provide many benefits such as providing water quality treatment, reducing channel erosion, controlling flooding by reducing peak flow and flow volume, and recharging the groundwater.

Additional resources

Other associations involved in sustainability policy and practice: