Aroturuki

Te Teko sits between the Te Teko Fault and the Edgecumbe Fault, about 4 km from the Awakeri Fault. A Te Teko Fault rupture is likely to produce effects like the 1987 Edgecumbe earthquake.

Likelihood: Te Teko Fault: rupture recurrence under 2,000 years. Edgecumbe, Awakeri and Waiōhau faults: 2,000–3,500 years (GNS).

• Two active fault systems meet here: the North Island Fault System and the Taupō Volcanic Zone.
• 1987 Edgecumbe earthquake: a 7 km rift across the plains, fissures up to 3 m wide and 3–4 m deep; land north-west of the fault dropped up to 2.4 m, making it more flood-prone.
• The Waiōhau Fault runs beneath the Matahina Dam (six active fault strands found under the dam in the 1990s).
• The Pacific Plate subducts beneath the North Island at about 47 mm a year along the Hikurangi Trench.

River, beach and swamp sediments with a high water table make the Rangitāiki Plain susceptible. The 1987 earthquake caused liquefaction around Edgecumbe, the Landing Road bridge approach and Awatapu.

Likelihood: Expected under shaking of around MM7 intensity on the plain’s saturated river and swamp sediments.

• Saturated sand and silt behaves like a liquid during strong shaking.
• BOPRC’s regional assessment rates most of the lower plain “liquefaction damage is possible”.

Liquefied ground near riverbanks, drains and road cuttings can slide sideways toward the open face. In Canterbury (2010–11), up to 3 m of spreading hit properties within 200 m of the Avon River.

Likelihood: Expected in liquefiable soils close to the Rangitāiki Awa and open drains during significant shaking.

• In 1987, stopbanks along the Rangitāiki Awa suffered lateral spreading, stretching and slumping.

Eruptions from the Ōkataina Volcanic Centre, and less so Pūtauaki, may affect Te Teko through ashfall and fast-moving mixtures of hot gas and volcanic rock. Four active centres are in the region: Ōkataina, Pūtauaki, Tūhua and Whakaari.

Likelihood: Ōkataina: eruption in the next 50–100 years “possible” (moderate–large eruptions every 700–3,000 years; last 1886). Pūtauaki: 2–5% in the next 50 years (“unlikely to rare”).

• The 1886 Tarawera eruption dropped airborne material directly onto the plain.
• Pūtauaki last erupted 2,300–3,100 years ago.

The 155 km Rangitāiki Awa (catchment 3,005 km²) runs beside the town and marae. The Aniwhenua and Matahina dams moderate peaks but cannot hold large floods; once full they pass floodwater through.

Likelihood: Stopbanks protect to a 1% AEP (1-in-100-year) flood; larger floods will overtop. Te Teko flooded in 1962, 1970, 2004 and 2005.

• Flood protection: Rangitāiki-Tarawera Rivers Scheme and Rangitāiki Drainage Scheme (BOPRC).
• Lake Matahina operating protocol (after the 2017 Cyclone Debbie flood at Edgecumbe): minor floods above 300 m³/s, major floods above 500 m³/s.
• Matahina is the first part of a four-part scheme protecting Edgecumbe and the lower Rangitāiki Plains.

Moist northerly air forced up the high country on three sides of the plain produces widespread heavy rain. Water ponds on the flat land around Te Teko.

Likelihood: Common in heavy rain — the plain is very flat with high groundwater. Tropical cyclones (November–April) frequently bring destructive storms.

• Annual rain ranged from about half the mean (1994) to double it (2023).

An uncontrolled release would flood the Rangitāiki lower catchment extensively: up to 2.0 m of water in Te Teko township, the SH30 bridge submerged, and flooding lasting long enough to need pumping.

Likelihood: Low — Tonkin & Taylor (2009) assessed the societal and individual risk as low and well within international norms. The dam is strengthened for the largest earthquakes conceivable on the Waiōhau Fault.

• 86 m high earth dam, 80 m above Te Mahoe village directly below it. Lake Matahina: 8 km long, 2.5 km², catchment about 2,844 km².
• Damaged in the 1987 earthquake; repaired 1988 and strengthened again in 1997–98 (including the spillway and dewatering tunnel).
• NZSOLD High Potential Impact Category: 195 instruments monitored monthly, with independent review and an emergency action plan.
• The estimated inundation area (1989 Works and Development study) is Figure 8 of the report — it is not digitised on this map.

In 1987 the Edgecumbe substation failed and cut power; the Edgecumbe dairy factory and Kawerau mills closed for repairs; landslides cut road access; rail lines were wrecked; phone, water, wastewater and stormwater were badly damaged.

Likelihood: Floods, storms and high winds regularly damage drainage, water supplies, roads and power.

• Repair costs fall on asset owners and, for public assets, ratepayers and taxpayers — resilience pays.

Te Teko is sheltered and sunny (over 2,200 sunshine hours a year). Climate change raises heat stress, drought, fire risk (10–30% higher by 2070–2090), algal blooms, waterborne disease and new pests.

Likelihood: More frequent, intense and longer heatwaves, droughts, floods and storms; more days above 25 °C and 30 °C (BOPRC Regional Climate Change Risk Assessment 2023; NIWA 2019).

• Health: heat stress (worse with diabetes or heart disease), outdoor-worker heat illness, mental health effects, poorer air quality and longer pollen seasons.
• Toxic algal blooms in rivers and streams affect mahinga kai, drinking water and swimming.
• Drought reduces pasture, maize and kiwifruit yields; warmer winters threaten kiwifruit chilling.
• Māori, kaumātua, disabled people, people with chronic illness and low-income whānau are particularly vulnerable.