Physical hazards affecting coastal margins and the continental shelf

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This programme is about providing improved knowledge of the causes and potential consequences of coastal hazards in New Zealand, and how often they might pose a threat.

The problem

There are many types of coastal hazard, each having different degrees of risk:

  • coastal erosion and shoreline stability
  • coastal flooding (extreme tides, storm surge, rivers)
  • tsunami impacts
  • damaging waves and storms
  • surf zone conditions (rips and undertow)
  • global-warming impacts and sea-level rise
  • maritime activities (navigation hazards, search & rescue)
  • oil or chemical spills.

New Zealanders love their coast. We take pride in our maritime heritage, ocean resources, recreational opportunities, and beach holidays, yet sometimes the sea can be a hazardous place. In recent times, New Zealand has been spared from any major coastal disaster, but we remember the sinking of the inter-island ferry Wahine (1968), the February 1936 storm – the most destructive of the 20th Century – that caused $800M damage across the North Island, and the 3 to 10-m-high tsunami after the 1855 Wairarapa earthquake. In the future, the consequences of coastal hazards will be greater, because there is more real estate and infrastructure “squeezed” along coastal margins. In addition, new threats will arise from sea-level rise and global-warming effects. All these factors mean we can’t be complacent in our long-term planning for coastal margins and ocean activities.

The solution

This programme is about providing improved knowledge of the causes and potential consequences of coastal hazards in New Zealand, and how often they might pose a threat. The initial focus is on attaining a much better understanding of the wide range of coastal hazards, and how, when and where they might occur (we call this the “hazardscape”). This is being achieved by field and numerical model studies, backed up by monitoring networks to measure tides, sea level, tsunami, coastal erosion, waves, winds and surf conditions (surf rips).

The results of the research and expert knowledge gained from the programme are then being amalgamated in predictive computer models, e.g. tidal models, wave models and sediment-transport models (see links below). These models are the foundation for developing operational forecasting models, which are not too dissimilar from a weather forecasting model.

The programme aims to help enhance New Zealand’s ability to respond to and mitigate quickly the consequences of coastal hazards and, better still, plan for their eventuality. Benefits will be through more efficient search and rescue missions, forewarning of approaching tsunami, better wave forecasts for navigation and fisheries, remote monitoring of erosion hotspots during storms, long-term planning for the impacts of sea-level rise on the coast, and improved estimates of coastal sand budgets for managing shoreline stability.

The result

The interlinked projects in this research programme fall into the following groups: Coastal Inundation, Maritime Hazards, Winds & Storms, Waves, Coastal Erosion & Sediment Systems, Surf Zone Processes, and Hazard Planning & Awareness.

Coastal flooding & tides

Coastal flooding by storms usually coincides with large tides, so how often does that occur in a year? Is storm surge affected by the speed of storms passing across New Zealand? What is the rate of sea-level rise around New Zealand? Where are the main areas of New Zealand that are vulnerable to tsunami?

Maritime hazards & support

Can surface currents be measured and predicted accurately? How can they be used in real time for search & rescue and oil-spill response? What is the pattern of tidal currents around NZ?

Winds & storms

What improvements in data input and computer speed are needed to produce timely forecasts of marine winds? How much stronger are ocean/shelf winds compared with winds at the coast?

Waves

Why do southerly fronts cause such quick growth of waves on the east coast? Is there a significant difference in the wave climate between seasons? How can wave forecasts be improved, particularly near the coast?

Coastal erosion & sediment systems

What causes long-period (10 to 40 year) cycles of erosion and accretion? Will sea-level rise cause increased erosion? How much “new” sand is feeding NZ’s beaches? Where does sand go when it erodes from beaches? Why are some beaches built of sand and others of gravel?

Surf zone processes

How much information can be gleaned from remote video-camera monitoring of beaches and entrances? What causes variability in surf rips? Can better estimates of wave run-up be estimated for storm conditions? Why do offshore beach sandbars migrate?

Hazard planning, awareness, and building resilient communities

How can hazard risk assessments be improved? What impacts will global warming have on changing coastal hazard risks? What is the best way to raise awareness of coastal hazards? How would coastal communities cope with a hazardous event, such as a storm or tsunami? How can the preparedness of coastal communities and emergency agencies be improved?

Page last updated: 
10 August 2017