Thursday, September 26, 2019

Paved paradise and put up single-family housing and parking lots. Impervious surfaces in Metro Vancouver.

Earlier this week, I posted about the importance of the urban tree canopy in Metro Vancouver’s urban areas. Trees provide ecological services which support human, environmental, and economic health.

The Metro Vancouver Regional District recently released a report about the urban tree canopy and impervious surfaces in our region. Langley City is near the bottom of the list with a lower amount of tree cover. To learn more, please read my previous post.

While a healthy tree canopy is good for our region, impervious surfaces degrade the health of our region. Impervious surfaces can include buildings, roads, driveways, paths, and parking lots.

Impervious surfaces have a negative impact on environmental and human health. When it rains, stormwater goes directly from parking lots and roads into streams. This water is unfiltered which means it is full of chemicals and garbage from impervious surfaces that end up directly into our ecosystem.

Stormwater should be allowed to filter through the ground which helps remove toxins before they end up into our ecosystem, and eventually eaten by us as these toxins work there way up the food chain.

The urban heat island effect is also exacerbated by impervious surfaces. This is why it always feels warmer in parking lots than in parks.

One of the things that I hear is that density is reducing greenspace and creating more impervious surfaces, the opposite is true. Lower density development whether it be strip malls, office parks, or single-family housing is what is creating the most impervious surfaces in our region.

The following chart shows that 30% of the impervious surfaces in Metro Vancouver are in areas with single-family housing. 25% of impervious surfaces are due to roads in our region.

Distribution of impervious surfaces among land use types within the Urban Containment Boundary. Select chart to enlarge.

While each single-family lot is 50 to 60% impervious surface, compared to around 70% for apartments, single-family housing takes up a much larger footprint. This mean that single-family zoning creates more impervious surfaces as an absolute number, and per person housed.

Surface parking lots are generally 90% impervious surface while road right-of-ways are 69% impervious.

The following table show the percentage of imperious surface by each municipality within the urban containment boundary.

Percentage of impervious surfaces within the Urban Containment Boundary by member jurisdiction (2014). Select table to enlarge.

As you can see, 62% of Langley City is imperious surface with most of it in the Langley Bypass, Willowbrook, and Industrial areas.

Map of impervious surfaces in Metro Vancouver by parcel. The darker the green, the less impervious. The darker the grey, the more impervious. Select map to enlarge.

In Langley City, we have a whole lot of surface parking lots. With modern technology and best practices, you can now build parking lots that allow stormwater to be filtered on-site. There are ways that parking lots can be greened, including by planting more trees and requiring significant planted areas.

We are currently in the process of updating our zoning bylaw in Langley City. I’m hopeful that we will have these best practices required in the new bylaw to reduce the amount of impervious surfaces in our community, and to better manage stormwater in areas with impervious surfaces.

No comments: