
Session 1 · TRACE: Accounts
When the river rose
- 10 minRead 'When the river rose'. Build a timeline of 18–22 June 2015: rain, warnings, rising river, evacuation, flood, clean-up.
- 20 minSource stations: a council river-level graph, a rainfall record, a news report, a resident's account and an aerial photo. Record who made each, when and why, and what it shows.
- 15 minCorroborate: find one fact at least two sources agree on. Which source helps most with 'What happened?' and which with 'What was it like?'
- 5 minKārearea asks one question: 'Which source would a flood engineer trust most, and would a family who were evacuated agree?'
Session 2 · TRACE: Causes & Consequences
Rain, land and runoff
- 10 minWhy did so much water arrive at once? Rain amount, rain duration, wet ground, steep hills, land cover.
- 25 minInfiltration test outside: push a tin can (both ends removed) a few centimetres into lawn, bare soil and gravel. Pour in 250 ml of water and time how long it takes to soak away. Pour the same amount on asphalt and watch where it goes.
- 10 minGraph your results and link them to the town: roofs, roads and car parks are 'impermeable', so rain runs off fast into drains and streams.
- 5 minExit card: slow it, spread it, sink it. Name one way to do each on a school field.
Getting started
Use the flood timeline cards with the dates already printed, and a results table for the infiltration test.
Stretch
Plot rainfall and river level on the same time-series graph. How long was the gap between the heaviest rain and the highest river? Why?
Checkpoint
The group can explain at least three causes of the 2015 flood with evidence, and has infiltration results for three surfaces.
Activities for this week
- Infiltration test: Why do towns flood faster than forests?
- Flood hydrograph: How does a river respond to rain?
Useful this week
- Rivers and Us ↗ How people and rivers affect each other, with NZ case studies.
- Floods ↗ Why New Zealand rivers flood, and big floods including Edgecumbe 2017.
- Natural Hazards and Flood Management ↗ How the Manawatū–Whanganui council manages stopbanks, river gauges and warnings.
- LAWA: Land, Air, Water Aotearoa ↗ River flow and water data for rivers near you.