Low Impact Development - An Old New Idea
Many people have never heard of Low Impact Development (LID) but likley have seen it on city streets without knowing what it was.
LID is a simple idea that strives to return rainwater back to the ground. As cities pave over large areas of the
landscape, rainwater that would naturally be abosrbed back into the ground is instead washed away by paved surfaces
such as roads and parking lots and into storm sewer systems.
Storm sewers redirect the runoff into natural creeks and then rivers turning them into concrete gutter systems carrying off
pollutants typical of urban environments such as car exhaust. It also bloats natural waterways contributing to enbankment erosion.
LID was designed initially by conservation authorities and university civil engineering departments to improve water quality
but it has the potential to make expensive storm sewer facilities obsolete. This is great news for wildlife and especially
those species that are dependent on meandering creeks to survive.
It is also great news for beavers, as beavers are often killed when they occupy a storm sewer holding pond and attempt to dam sewer outlets pipes.
The environmental consequences of washing away rainwater are tremendous. It prevents groundwater recharge and the ability to
grow large landscape trees in cities because there isn't enough rainwater to feed their roots.
Specifically LID is a stormwater management technique that uses simple designs and landscape features at the lot level to infiltrate,
filter and retain runoff close to its source. Examples include rain gardens, permeable pavement and bioswales.
Below is a LID design installed in the Glen Carin neighbourhood in London Ontario:
In Toronto, a desire to improve tree health has increased surface area and soil depth for tree planting areas. These larger
planting areas will also absorb and prevent rain runoff.