Degradation of reef keeps coasts at risk

·2-min read

The size and impact of Pacific Ocean tsunami waves on the Australian coastline are significantly reduced by healthy coral structures in the Great Barrier Reef, research shows.

A study undertaken by researches at the University of Sydney has found Queensland's coasts face increased damage from tsunamis if coral was dead or dying and had lost its structural complexity.

The research, which has been published in the Natural Hazards journal, indicates the impact of tsunamis are dampened when rough coral cover is present.

Using simulated models, researchers were able to quantify that if the coral cover was removed completely, there would be a 31 per cent increase in offshore wave amplitude for a tsunami.

Whereas when the coral structure was present its 'rough' structure aided in dampening the effect of the waves.

Dr Mandi Thran, a senior research associate at the University of Sydney, says the team ran various computer simulations, finding that with more coral present the damage caused by tsunamis was reduced.

"Being able to monitor the reef's health and being able to quantify how rough it is, that will better equip us with the ability to anticipate what the tsunami hazard will be," Dr Thran said.

"We can have a better gauge on how much more hazard there is for a particular area of the coastline if the health of the reef is declining or deteriorating."

As tsunami waves approach the reef they bend inwards, with the energy focused towards the reef platform and potentially causing the waves to grow bigger and more powerful.

However, when healthy 'rough' coral structures are present on the reef, there is a frictional force that counteracts the effect and dampens down the waves.

Co-author of the paper Professor Dale Dominey-Howes said while there were other aspects of damage to the reef to consider, it was vital to address the damage being done by the effects of climate change.

"The most significant finding is to demonstrate clearly, in a quantifiable way, the protective effects that healthy marine reefs can provide to adjacent low-lying coastal landscapes that are at risk from flooding and from tsunami events," Prof Dominey-Howes said.

"Healthy coral reef acts as a buffer, mitigating the effects of tsunami waves, although it doesn't reduce it to zero.

"But it can slow the wave down, which reduces the power of the wave to do damage to buildings and infrastructure in the adjacent coastal plain.

"Changing climate can damage coral reef ecosystems, potentially killing them. And if we do that, we're actually amplifying the risk associated with tsunamis by killing a natural protective barrier.

"This adds weight to the argument that we need to think about protecting coral reefs from the worst impacts of climate change, which means we need to take action on human-induced climate change."