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

Building With Nature: How Landforms and Physical Processes Shape Land Use

E1.2 A1.4 A1.5About 70 minutes

Learning goals

I can explain how landforms, soils, water, climate and natural hazards limit or guide where communities build.
I can describe how physical processes such as flooding, erosion, landslides, wildfire and freeze–thaw affect land use and the built environment.
I can explain how Ontario and other Canadian communities use land-use planning to reduce risks from natural hazards.
I can use a simple overlay of constraint maps to choose a safer building site.

Words to know

built environment
Everything people have built: buildings, roads, bridges, pipes, parks and other structures.

natural hazard
A natural process or event, such as a flood, wildfire, landslide or earthquake, that can harm people and property.

floodplain
Flat land beside a river that is covered with water during floods.

erosion
The wearing away and removal of soil and rock by water, wind, ice or gravity.

permafrost
Ground that stays at or below 0 °C for at least two years in a row. It underlies much of northern Canada.

freeze–thaw
A process in which water seeps into cracks, freezes and expands, then melts, slowly breaking rock and pavement.

conservation authority
A local Ontario agency, organized by watershed, that manages and protects water and natural resources and regulates development near rivers, shorelines, wetlands and hazard lands.

constraint map
A map that shows areas where building is limited or unsafe, such as floodplains, steep slopes and wetlands.

setback
The minimum distance a building must be from something else, such as a property line, river or eroding slope.

Hook: why is there a long, narrow park here?

If you look at a map of Toronto, you will see long green ribbons winding through the city. Those are ravines and river valleys, and most of them have trails and parks, not houses. That is no accident.

In October 1954, Hurricane Hazel brought extremely heavy rain to southern Ontario. Rivers in the Toronto area flooded suddenly, and 81 people died. Many of the homes that were lost had been built in low-lying river valleys. After the storm, Ontario changed how it plans: much of the valley land was bought by public agencies and kept as open space, and the conservation authorities gained a bigger role in controlling development in floodplains. The natural environment had taught a hard lesson about land use.

How the natural environment guides land use

Before building anything, planners ask what the land itself allows:

Landforms and slope: steep slopes are costly to build on and can slide or erode. Flat land is easier to build on, which is also why it is often wanted for farms.
Soils and geology: good farmland soils are limited and valuable. Some clay soils are unstable. Bedrock close to the surface (as in much of the Canadian Shield) makes it expensive to dig basements and lay pipes.
Water: rivers and lakes attract settlement, but floodplains and shorelines can be dangerous. Wetlands soak up floodwater and filter water, so they are usually protected.
Climate: cold climates mean building codes require insulation and roofs strong enough for heavy snow. In the North, permafrost changes how everything is built.
Ecologically important areas: places like the Oak Ridges Moraine (a ridge of sand and gravel north of Toronto that stores and filters groundwater) and the Niagara Escarpment (a long ridge of rock from Niagara to Tobermory) have their own provincial plans that limit development to protect water, habitat and landscapes.

Planners in Ontario map the area a big flood would cover. Inside that floodplain they usually allow parks and trails, not new homes, and they keep buildings back from steep, eroding valley slopes.

Physical processes and events that shape communities

Flooding: spring snowmelt, ice jams and heavy rain can flood river valleys. Ontario's conservation authorities map hazard areas and regulate building in them.
Shoreline erosion: waves wear away bluffs and beaches on the Great Lakes, like parts of the Scarborough Bluffs in Toronto. Planners require setbacks so homes are not built too close to an eroding edge.
Landslides in sensitive clay: parts of eastern Ontario and Québec have a sensitive marine clay (often called Leda clay) that can suddenly turn almost liquid. The village of Lemieux, Ontario, was relocated in the early 1990s after studies showed its land was unstable, and in 1993 a large landslide carried part of the abandoned area into the South Nation River.
Wildfire: communities surrounded by forest, like many in northern Ontario and western Canada, plan for wildfire with fire breaks, cleared zones around buildings and evacuation routes. In 2016 a wildfire forced the evacuation of the whole city of Fort McMurray, Alberta.
Earthquakes: southwestern British Columbia has the highest earthquake risk in Canada, so building codes there require stronger structures.
Freeze–thaw: every Canadian knows potholes. Water gets into cracks in pavement, freezes and expands, then thaws, and the road breaks apart. Roads, bridges and foundations must be designed for it.

Heat from a building can thaw the permafrost under it, so the ground slumps and the building sinks and cracks. Raising buildings on piles anchored deep in the frozen ground leaves a cold air gap, so the ground stays frozen and solid. Climate warming makes this harder, which you will see in the next lesson.

Worked example

Let's choose a safer building site using overlays

A town wants to place 200 new homes on one of three sites. The constraint maps show: Site A is flat, outside the floodplain, on good farmland. Site B is half inside a floodplain beside the river. Site C is flat, outside the floodplain, on land already used for an old parking lot near the town centre, but next to a steep valley slope along one edge. Rank the sites and explain.

Overlay the constraints: think of each map as a transparent layer stacked on the others (this is what GIS software does).
Site B: half the land is in the floodplain. Building there puts people and property at risk, and Ontario planning policy generally directs development away from hazard lands. Worst choice.
Site A: safe from flooding, but it uses up good farmland, which is a limited resource and hard to get back. Possible, but costly to the food system.
Site C: already developed land (no farmland or habitat lost) close to existing services. The slope is a hazard only along one edge, so homes can be placed with a setback from the top of the slope, with the strip kept as open space.
Rank: C, then A, then B.

Site C is best if a setback is kept from the slope; Site A is second because it is safe but loses farmland; Site B is worst because of flood risk.

Overlay analysis (A1.4)

Geographic information systems (GIS) stack map layers, such as rivers, floodplains, slopes, soils, roads and land use, so you can see where constraints overlap. You can do the same by tracing each layer on a separate sheet of tracing paper or clear plastic and stacking them over a base map.

Just for fun

Canadians joke that there are only two seasons: winter and construction. Freeze–thaw is the reason: all winter, frozen water cracks the roads open, and all summer, crews fix them.

Hands-on activity

Make your own constraint overlay

You need: a printed or hand-drawn simple map of an area near you (or an imaginary one), 3 sheets of tracing paper or clear sandwich bags cut flat, and markers.

On sheet 1, shade any water and the land within about 30 m of it (a pretend floodplain).
On sheet 2, shade steep slopes (look for hills, ravines or use your imagination).
On sheet 3, shade parks, wetlands or woodlots that you think should be protected.
Stack the sheets on the map. The unshaded areas are possible building sites.
Pick the best site for a new school and write 3 to 4 sentences explaining your choice.

What to look for: layers that are lined up correctly, a site that avoids all shaded areas, and reasons that mention hazards and protecting nature.

Your turn

Explain why building homes in a floodplain is risky.

What lesson did Ontario learn from Hurricane Hazel in 1954 about land use?

What is a setback, and why are setbacks used near eroding shorelines?

Why do buildings on permafrost often sit on piles?

How do wetlands help reduce flood risk?

Name one physical process that damages roads in Canada and explain it.

Why are the Oak Ridges Moraine and the Niagara Escarpment protected by their own provincial plans?

More practice: warm-up

What is permafrost?

Which Canadian region has the highest earthquake risk?

What does a constraint map show?

What kind of Ontario agency regulates development near rivers and wetlands?

Name one natural hazard that northern forest communities plan for.

More practice: on your own

Explain why bedrock near the surface can make building more expensive in parts of the Canadian Shield.

Why might a town keep a floodplain as a park instead of leaving it empty?

Explain how the Lemieux example shows the natural environment shaping land use.

Give two ways a community surrounded by forest can reduce wildfire risk through land-use planning.

Why do building codes in snowy parts of Canada require stronger roofs?

Challenge

A developer argues that modern pumps and walls make floodplain building safe. Give one argument for and two against.

Use the concept of interrelationships to explain how paving over a wetland could affect a neighbourhood downstream.

Why is choosing a site on already-developed land (like an old parking lot) often better for the environment than building on a farm field? Give one possible drawback.

Check your understanding

Quiz

What is the main reason many Toronto ravines are parks rather than housing?

Which land use is most appropriate inside a river floodplain?

Why do builders in the Arctic often raise buildings on piles?

Freeze–thaw damages roads because water:

In GIS, putting a floodplain map, a slope map and a wetlands map on top of each other is called:

Which statement about wetlands is TRUE?

For parents and teachers

This lesson connects physical geography (landforms, soils, water, climate) with where people build. Hurricane Hazel and the Fort McMurray wildfire involved real losses; discuss them calmly and focus on what communities learned. If your child seems worried about hazards where you live, look up your local conservation authority's or municipality's hazard maps together; this usually reassures more than it frightens. Common difficulties: thinking engineering can remove all risk, and forgetting that protecting farmland is also a land-use constraint. The overlay activity works well with clear plastic bags and dry-erase or permanent markers.