Grade by Grade
E. Liveable Communities · Liveable Communities: Land Use and Sustainability in Canada

Planning for a Changing Climate

E1.2 A2.3 A1.5About 70 minutes
Learning goals
  • I can describe how climate change is affecting communities across Canada, such as heavier rainstorms, heat waves, wildfires, thawing permafrost and coastal erosion.
  • I can explain the difference between climate adaptation and climate mitigation in land-use planning.
  • I can calculate and compare stormwater runoff from different surfaces.
  • I can analyse a current event about climate and communities using the concepts of geographic thinking.

Words to know

climate change
Long-term change in temperature and weather patterns. Today's rapid change is mainly caused by greenhouse gases released when people burn fossil fuels.
adaptation
Changing how and where we build and live to cope with climate impacts, for example bigger storm sewers or moving homes away from eroding coasts.
mitigation
Reducing greenhouse gas emissions to slow climate change, for example compact communities that need less driving.
stormwater
Rain and snowmelt that flows over the ground and into drains, ditches, streams and lakes.
impermeable surface
A hard surface, like asphalt, concrete or a roof, that water cannot soak through.
green infrastructure
Natural or nature-based systems that manage water and heat, such as trees, wetlands, rain gardens, bioswales, green roofs and permeable pavement.
urban heat island
The effect that makes built-up areas warmer than surrounding rural areas.
resilience
The ability of a community to prepare for, cope with and recover from hazards and changes.

Hook: the pipes were built for a different climate

Many storm sewers in Canadian cities were sized decades ago, using rainfall records from the past. Today, scientists report that in many places, heavy downpours are becoming more frequent and more intense as the climate warms. When a storm drops more water than the pipes can carry, water backs up into streets and basements.

So planners face a new question: how do we plan land use for the climate we will have, not the one we used to have?

How climate change is affecting Canadian communities

  • Heavier rainstorms and flooding: more water than drains can handle, flooded underpasses and basements.
  • Heat waves: in late June 2021, Lytton, British Columbia, recorded 49.6 °C, the highest temperature ever measured in Canada; a wildfire destroyed most of the village the next day. Cities now plan cooling centres, shade and tree planting.
  • Wildfires: longer, hotter fire seasons bring evacuations and heavy smoke to communities far from the fires.
  • Thawing permafrost: in the North, warming ground can shift and crack buildings, roads and airstrips that were designed for frozen ground.
  • Coastal erosion and sea-level rise: low-lying parts of Atlantic Canada and the Arctic face stronger storm surges and shoreline loss. For example, the Chignecto Isthmus, the narrow strip of land joining Nova Scotia and New Brunswick, carries a highway and rail line protected by old dykes, and governments are studying how to protect it.
  • Changing lakes and winters: shorter ice seasons affect winter roads that remote communities in northern Ontario and other regions rely on for bringing in fuel, food and building supplies.

Two kinds of response

Mitigation tackles the cause: cutting greenhouse gas emissions. Land-use planning helps by building compact, mixed-use communities where people can walk, bike and take transit, and by protecting forests and wetlands that store carbon.

Adaptation deals with the effects that are already happening:

  • updating floodplain maps with future rainfall in mind
  • using green infrastructure: rain gardens, bioswales (planted ditches), permeable pavement, green roofs and protected wetlands that slow and soak up water
  • planting urban forests and adding shade to cool neighbourhoods
  • raising or flood-proofing buildings and critical services such as hospitals and power stations
  • managed retreat: in a few places, moving buildings and roads away from coasts or riverbanks that cannot be defended

Good planning often does both: a large park with a wetland stores carbon (mitigation) and holds floodwater (adaptation).

Where does 25 mm of rain go on 1 hectare? (example runoff coefficients)Parking lot (runoff coefficient about 0.9)asphalt: almost nothing soaks inrunoff to storm sewer: about 225 m³Grassy park with trees (about 0.2)runoff only about 50 m³most water soaks into the soil
Hard surfaces send most rain straight into storm sewers and rivers; soil and plants soak most of it up. The same storm makes about 225 m³ of runoff from the parking lot but only about 50 m³ from the park.
Worked example

Let's calculate stormwater runoff

A simple estimate used by planners: runoff volume = rainfall depth (m) × area (m²) × runoff coefficient. The runoff coefficient is the fraction of rain that runs off (about 0.9 for asphalt, about 0.2 for a grassy park; real values vary). Compare a 1 ha parking lot and a 1 ha park in a 25 mm storm.

  1. Convert rainfall to metres: 25 mm = 0.025 m.
  2. Convert the area: 1 ha = 10 000 m².
  3. Parking lot: 0.025 × 10 000 × 0.9 = 225 m³ of runoff.
  4. Park: 0.025 × 10 000 × 0.2 = 50 m³ of runoff.
  5. Difference: 225 − 50 = 175 m³. One cubic metre is 1 000 L, so that is 175 000 L, enough to fill several backyard swimming pools.

The parking lot produces about 225 m³ of runoff, the park about 50 m³: the hard surface sends about 4.5 times as much water into the sewers.

The urban heat island on a summer afternoon (model)warmercoolerRuralSuburbDowntownParkSuburbRuralcoolerpocket
Pavement, roofs, traffic and few trees make city centres warmer than nearby rural areas, especially at night and during heat waves. Parks and trees create cooler pockets. The curve is a model; it shows the shape, not exact temperatures.

Analysing a current event (A2.3)

When you read a news story about a flood, heat wave or wildfire, ask:

  • Spatial significance: Where did it happen, and why there?
  • Patterns and trends: Has this happened before? Is it becoming more frequent?
  • Interrelationships: How did the natural event interact with land use (paving, building in floodplains, forest edges)?
  • Geographic perspective: How do residents, governments, businesses, insurers, and First Nations, Métis or Inuit communities see the event and the response?

Then check the source: who wrote it, when, and what evidence it uses.

Just for fun

Riddle: I am a garden that loves bad weather. The harder it rains, the happier I am, and I keep your basement dry. What am I?

A rain garden!

Hands-on activity

Rain-garden test

You need: two identical baking pans or plastic trays, soil or potting mix, a sponge or some moss or grass sod (optional), a measuring cup, and a third container to catch water. Do this outside or on a towel.

  1. Tilt one empty tray slightly (prop one end on a book). This is your "parking lot". Pour 500 mL of water at the high end and catch what runs off the low end. Measure it.
  2. Fill the second tray with packed soil and, if you have it, sponge or sod on top. Tilt it the same way and pour 500 mL slowly. Catch and measure the runoff.
  3. Calculate a runoff coefficient for each: runoff ÷ 500.
  4. Explain your results in two sentences and connect them to green infrastructure.

What to look for: the soil tray should send much less water off the end (a lower coefficient). Students should explain that soil and plants hold and slow water, just as rain gardens and wetlands do.

Your turn

1

What is the difference between adaptation and mitigation? Give one land-use example of each.

2

Calculate the runoff from a 0.5 ha school roof (coefficient 0.9) in a 30 mm storm.

3

Why are city centres often warmer than nearby countryside?

4

Name three types of green infrastructure.

5

How can thawing permafrost affect a northern community?

6

Why might a community choose managed retreat?

More practice: warm-up

1

What is an impermeable surface? Give an example.

2

Convert 40 mm to metres.

3

What is a cooling centre?

4

Which absorbs more rain: a lawn or a parking lot?

5

What is the highest temperature ever recorded in Canada, and where?

More practice: on your own

1

Explain how replacing a parking lot with a park is both adaptation and mitigation.

2

A 2 ha subdivision has a runoff coefficient of 0.5. How much runoff comes from a 20 mm storm?

3

Why are winter roads important to some remote northern communities, and how does climate change affect them?

4

Use the urban heat island model to explain why planting street trees matters most in dense downtown areas.

5

Using a geographic perspective, name two groups who might view a plan to move homes away from an eroding coast differently, and how.

Challenge

1

A city replaces 3 ha of a 10 ha shopping-centre parking lot (coefficient 0.9) with a park (coefficient 0.2). How much less runoff will a 25 mm storm produce?

2

Some people argue that adaptation is a waste of money and we should only cut emissions. Evaluate this view.

3

Explain one way climate change interacts with land-use choices to make a disaster worse.

Check your understanding

Quiz

1.

Which is an example of climate ADAPTATION?

2.

Runoff from a 1 ha lot (coefficient 0.8) in a 10 mm storm is:

3.

The urban heat island effect means that:

4.

Why do bioswales and permeable pavement reduce flooding?

5.

Which climate impact most threatens buildings and runways in the Arctic?

6.

Which concept of geographic thinking asks how residents, governments and businesses see an issue differently?

For parents and teachers

Climate change can make some teens anxious. Keep the focus on solutions: this lesson is mostly about what communities are actively doing (rain gardens, trees, better flood maps). The runoff calculation needs unit conversions (mm to m, ha to m²); check these first if answers are off by a factor of 10 or 1 000. The tray experiment can get messy; do it outside or in a sink. Look up your municipality's climate action or climate adaptation plan together; most Ontario cities have one online.