Lake Simcoe Science
Low Impact Development (LID)
A Recipe for Urban Sustainability
In previous issues of our Science newsletter, we’ve
explored the problems associated with urban stormwater
run-off, a major contributor of pollutants entering into
our rivers and ultimately into Lake Simcoe itself.
Urban stormwater run-off is responsible for around 20
per cent of the phosphorus entering the lake. Given this
large amount, staff at LSRCA are engaged in reduction
efforts focused on stormwater because we know the
outcomes will have a big impact.
A Diet Low In Stormwater is Good for Your
When land is developed, the natural water cycle is
changed. Clearing the land removes the vegetation
that intercepts and allows precipitation (rain/snow) to
seep into the ground. Paving makes surfaces hard and
actually increases run-off. The result? Lots of water
coming down in the form of rain and snow, but no way to
enter the ground. Instead, it travels along the hardened
surfaces, picking up contaminants along the way,
eventually draining into our rivers and streams.
Traditional stormwater ponds were designed to make up
for this change to the natural water cycle by holding the
water in reservoirs, quickly moving it away from homes,
and slowly releasing it to the rivers and streams.
In this way, it did work. However, over time, the
shortcomings of traditional stormwater
ponds became apparent:
- While a traditional pond can slow
the speed of stormwater entering
our rivers, it does not address the
additional volume that is generated.
It’s this increased volume to the
rivers that causes stream bank
erosion, degraded habitat and,
when combined with many other
such ponds, downstream flooding.
- Along with this extra volume of
water comes additional pollutants,
the most important of which in
the Lake Simcoe watershed is an
increase in phosphorus.
- Stormwater pond maintenance costs and requirements
were underestimated. A 2010 LSRCA study found
that ponds are filling up with sediments faster than
expected. Removing the sediment is expensive
because, often times, the pollutants it has
accumulated leave it as a contaminated waste, making
disposal costly. In addition, stormwater ponds that are
full of sediments are not operating at peak efficiency.
- During hot dry spells, the dissolved oxygen in pond
waters can be consumed by biologic processes. This
state of hypoxia (low oxygen) or anoxia (no oxygen)
can promote the re-release of phosphorus bound to
sediment. This was documented in many ponds in the
2010 LSRCA study and means that, at certain times
of the year, these ponds that we are relying on to
contain phosphorus may actually release additional
- Stormwater is often warmer than its receiving waters.
All this warmer water entering our streams and rivers
can be harmful to some forms of aquatic life, which
prefer cooler temperatures.
How Stormwater Ponds are "Supposed" to Work
A storm water pond is an artificial pond designed to collect and retain urban stormwater,
releasing it slowly to protect f looding downstream and reducing sediment. However, over time, the
shortcomings of traditional stormwater ponds became apparent. Graphic by the Watershed Company.
A New Cuisine for Streams:
Low Impact Development
As communities continue to grow
and expand, we know doing more of
the same thing isn’t going to work.
LSRCA staff and researchers have
been exploring alternative strategies to
manage stormwater run-off in a more
sustainable manner. They’ve come up
with a menu of choices that improve
upon the traditional stormwater pond
approach. Low Impact Development is
seen as a possible solution.
By no means a new concept, Low
Impact Development has not gained
significant traction in Canada yet.
LSRCA hopes to change this.
The Stormwater “Menu”
LSRCA researchers have been collaborating with organizations that have successfully implemented Low Impact Development projects in the US. Our goal is to take the
lessons learned from their experiences and apply them to the urban landscape here.
The strength of Low Impact Development is that it tries to mimic the natural hydrologic cycle. In other
words, help to move water into the ground the same way it did before houses or parking lots were
built there. As discussed above, the key function that development interferes with is the ability of
stormwater to soak into the ground. Therefore, Low Impact Development will rely heavily on methods
that address this extra volume of water through infiltration, storage, reuse and finally, filtration.
Low Impact Development
approaches use a “treatment
train approach”. This means
a number of measures will
be used throughout the
community to manage runoff and keep it as close to
its source as possible. This
starts on individual properties
managing their own run-off as
much as possible, then using
the next treatment technology
in the train to address excess
run-off until the required
amount has been addressed.
Changes in Hydrology and Run-off Due to Development
The natural water cycle is changed when land is developed. The amount of infiltration vs runoff in
various landscapes can be dramatic. Graphic: Atlanta Journal Constitution.
We need to manage growth
More than 12,235 hectares (122 km 2) of new urban area is anticipated to be built in the Lake
Simcoe watershed by 2031. Traditional stormwater management is not a viable option if we are to
try and reduce the pollution entering the lake.
Low Impact Development Benefits
- Mimics the natural
- Treats water at the source
- Allows water to infiltrate because it tries to more closely
directly into the ground
- Maintains groundwater community that has more green
space and native landscaping.
- Assists with flood control
- It can even fit into older have a role in providing flood communities that do not have the space for conventional stormwater controls
- Helps communities build
resiliency to climate change
- Cheaper in the long
run than conventional stormwater ponds
- It looks nicer (and can increase property values)
What Does Low Impact Look Like?
Low Impact Development begins in the planning stages,
well before any shovels hit the ground. It’s incorporated
into the design of the community, taking advantage of natural landscape features, minimizing impervious surfaces like pavement, and treating stormwater as a
resource rather than a waste product. For these reasons, it could best be described as more holistic in its approach
to stormwater management, because it tries to more closely mimic the natural water cycle.
The result is a more resilient community that has more green
space and native landscaping.
While stormwater ponds will still have a role in providing flood protection, these won’t need to be large stormwater ponds, because most of the run-off is being managed locally on
Low Impact Development Strategies
Four low impact development strategies - green rooftops (top left), rain gardens (top right), rainwater harvesting (bottom left), and permeable pavement (bottom right).
Challenges to Low
Because Low Impact
Development has been tried
in other jurisdictions, we have
the advantage of learning from others’ experiences. LSRCA is
working with these partners to develop strategies to overcome the challenges associated with Low Impact Development
in Ontario. Some challenges, such as how to deal with
cold weather and frozen soils, are easier to overcome.
Others though, like changing people’s way of thinking
and doing things, take much more time.
Making This Work
The reality is that we have no choice if we hope to
achieve the health targets set for Lake Simcoe. The
current stormwater approach is not feasible in the long
run given development will continue. We have to make
changes and we have to do it now.
To that end, LSRCA is actively engaging with the
development industry to drive a market transformation
in the way communities are designed and built.
So far the response has
been extremely positive,
and not just because
it makes sense to the
industry, but because there
is a demonstrated demand from the public.
The first such development
in the LSRCA watershed is the Mosaik Homes
community in Newmarket that saw properties
near or with Low Impact
Development features among the first to sell. More of
these communities are on the way and what is now the
exception will hopefully soon be the norm for all new
development in the watershed.
Urban Areas without Stormwater Control
Lake Simcoe has around 200 stormwater management facilities.
However, as much as 60 per cent of the urban area of the watershed has
no stormwater control at all. These areas would particularly benefit from
individual landowner participation in our RainScaping program. These areas are shown in purple in the map below.
Getting Involved with Low Impact
If you're thinking of buying a new home, ask
the builder what steps they’re taking to manage
stormwater. Take advantage of any extras that
they are offering in terms of “green” development.
Now’s the time to incorporate it into your property
rather than paying to have it added later.