L10 Demo: Risk Assessment & MCE

Multi-Criteria Risk Calculator

Adjust weights and sea level to explore coastal flood risk

MCE Weights (auto-normalised)

Hazard 40%

Exposure 35%

Vulnerability 25%

Weights sum to 100% ✓

Weights don't sum to 100%

Sea Level Scenario

1m sea level rise

Off1m2m3m4m

Map Layers (exposure context)

Coastline

Roads

Economic Impact Estimate

Metric	Value
Flooded area	—
Flooded houses	—
Flooded roads	—
House losses	—
Road losses	—
Total losses	—

Mitigation Comparison

Seawall

12 km × $50M/km base

+$10M/km per m above 2m

—

Managed Retreat

Relocate flooded houses

× 4 people × $264,450

—

What you are looking at: every building in the study area, coloured by its combined MCE risk score. Each building's elevation is sampled from the nearest LINZ contour line; the contours themselves are not drawn. Grey buildings have no contour within 1000 m, so their elevation would be a guess — — of — buildings. The dashed dark-blue line is the flood boundary.

Risk = Hazard × Exposure × Vulnerability. Hazard is the probability/magnitude of the flood event. Exposure is what is in the flood zone (buildings, roads). Vulnerability is the susceptibility of those assets to damage. The three are combined as a weighted product, so any component of zero gives zero risk — with the scenario Off there is no hazard, and therefore no flood risk anywhere, however exposed a building is.

Guided Questions

Look at the risk map. Identify each MCE component for the New Brighton flood scenario. What data layer represents Hazard? Exposure? Vulnerability?

Set weights to Hazard 60%, Exposure 30%, Vulnerability 10%. Then change to equal weights (33/33/33). How does the risk map change? Which weighting is more appropriate for coastal flood planning?

At 2 m sea level rise, what is the estimated total economic loss? Read from the impact panel. Are the $600k/house and $1.5M/km road assumptions reasonable for Christchurch in 2025?

Compare the seawall cost vs relocation cost at your chosen sea level. Which strategy do you recommend and why? Consider both economics and non-monetary factors.

Why is sensitivity analysis essential in MCE? Change one weight by ±20% — does the highest-risk area change location? What does this tell you about result robustness?

ENCN205 — Lecture 10: Risk Assessment & MCE