Natural Environments
Domain 2 tests how physical processes operating at different rates and scales produce the landscapes and spatial patterns of Aotearoa New Zealand - fluvial, coastal, glacial, tectonic and climatic systems.
Process first, form second
- Every landform is the visible output of an energy–material balance: available energy (gradient, wave height, ice flow), material (sediment size, supply, lithology) and time.
- Location on the Pacific–Australian plate boundary sets the template: rapid uplift, high sediment yields, short steep rivers and frequent disturbance.
- Climate modulates process. The Southern Alps rain shadow delivers very high rainfall and erosion west of the divide, and drier catchments feeding braided rivers to the east.
- Timescale matters: storm, decadal and millennial records can support opposite conclusions about the same coast.
- Feedbacks are Scholarship-level material: glacial retreat exposes fresh rock, paraglacial sediment supply rises, and aggradation follows downstream.
Worked example
Three sites down one river:
- Site 1: gradient 12 m/km, discharge 4 m³/s, bed median 120 mm.
- Site 2: gradient 3 m/km, discharge 45 m³/s, bed median 25 mm.
- Site 3: gradient 0.4 m/km, discharge 150 m³/s, bed median 0.3 mm.
Reasoning: stream power per unit length scales with discharge × gradient. Site 1 has the steepest slope but little water, so it is erosion-dominated with coarse bedload. Site 2 multiplies discharge elevenfold at a quarter of the gradient, giving the greatest total power and transport. Site 3 carries the most water but loses power through a very low gradient, so fine sediment settles - deposition. Downstream fining and the erosion-to-deposition transition are therefore explained jointly by slope and discharge, not by discharge alone. Limits: no sediment-supply or flood data, either of which can override the trend.
Traps
- Naming landform and process without the mechanism linking them.
- Confusing weathering with erosion.
- Assuming equilibrium in a disturbance-driven system.
- Ignoring sediment supply, which can outweigh transport energy.
- Using "climate change" as an all-purpose cause with no stated mechanism.