MFRE GP Showcase · 21 August 2026

How natural ecosystems reduce flood risk

A spatial analysis of the Lower Fraser

AuthorIsaac Qi Master of Food and Resource Economics
UBC Sustainability Scholar

Project PartnerMetro Vancouver

Faculty SupervisorDr. Matthew Mitchell

1Community view

Following storm runoff downstream

Rain that falls in the headwaters passes through a long sequence of ecosystems before it reaches the communities below. The community view visualizes the above sequence for any community in Metro Vancouver and the Fraser Valley Regional District.

Clicking a community draws every watershed that contributes to it, along with the channels carrying runoff downwards. Darker areas attenuate more of the storm along the way.

Adding a second community shows the ecosystems that contribute to both areas.

2Upstream ecosystems

Seeing what these ecosystems already do

This view visualizes each watershed in four different ways: what it holds back today, what its loss would send downstream, how many communities benefit from its retention, and how far that contribution travels.

Selecting a watershed opens what it retains and where that retention travels. The map's shading updates with each measure.

With ecosystems

The runoff a watershed absorbs during the storm, given its cover, soil type and slope. This view shows existing retention.
Without ecosystems

The extra runoff the same storm would send downstream if the natural landcover in each watershed were cleared.
Communities reached

How many communities benefit from a single watershed's retention. A high count means the benefit reaches multiple communities, sometimes crossing more than one boundary.
Distance downstream

How far a contribution travels before it fades. This measure is focused on orienting the user topologically.

3Supply & demand

Putting it all together

Narrowing to Metro Vancouver and Fraser Valley Regional District communities, this view matches the ecosystem services provided upstream against the dissemination areas most exposed within the floodplain. A weighting tool lets you adjust the model inputs to your own priorities.

Supply is the ecosystem service delivered downstream by each upstream area.

Demand is the built-up land and cropland sitting inside the modelled floodplain, read one dissemination area at a time.

The weighting tool in action. Changing how much each kind of exposure counts re-ranks the watersheds upstream and the neighbourhoods downstream together.

Critical facilities and population are trial features. Neither takes part in the model behind these rankings.

Try it yourself

The interactive map is now accessible on desktop

Opening this same website on a desktop or laptop gives you the live map, where every feature shown above can be explored directly.

qhw-isaac.github.io/lower-fraser-flood-attenuation/

The map is built for a wider screen. It will still run on mobile, though features are limited.

How natural ecosystems reduce flood risk

Following storm runoff downstream

Seeing what these ecosystems already do

With ecosystems

Without ecosystems

Communities reached

Distance downstream

Putting it all together

The interactive map is now accessible on desktop

Flood-Attenuating Ecosystem Services in the Lower Fraser