Interactive: Before-and-after imagery shows Gabrielle’s impacts in Hawke’s Bay

Scientists have captured extraordinary new imagery showing the devastation that Gabrielle wrought on Hawke’s Bay.

The before-and-after images come from a Scion-led project to digitally map New Zealand’s productive forests, and which has now been turned to analysing the impacts of last month’s weather disaster.

Before the ex-tropical cyclone swept in, the project team already had a bank of aerial imagery of the region’s forests, from pictures taken by aircraft over 2021 and 2022.

As it happened, Gisborne and Hawke’s Bay happened to be the first areas they began mapping to create their “SmartForest” AI model, which used remote sensing to build a high-resolution picture of forest locations and the resources within them, like carbon and timber.

Scion’s Claire Stewart explained that this model could detect planted forests using only aerial imagery – and in Gabrielle’s aftermath, it had become even more important.

When the project team compared those pre-cyclone aerial pictures - made public by Land Information NZ but largely sourced from council-funded aerial surveys - with satellite imagery collected in the weeks after the event, the contrast was dramatically clear.

Riverside land can be seen covered in flood debris, hills are scarred with numerous slips and gale-force winds have cut swathes through pine plantations.

“Vegetation, ranging from productive forest, native trees and shrubs, and riparian species, in many areas has been swept downstream along with large amounts of silt from landslides,” Stewart said.

“The force of the floodwater and the debris caught within it has had a devastating impact on homes and infrastructure downstream.”

Stewart said the re-purposed model was now helping scientists quantify forest loss and windthrow damage, ultimately enabling a “dynamic and detailed” understanding of the pre- and post-cyclone environment.

“This will enable valuable insights on where forest was standing pre-cyclone, what species it was, what forest is now lost,” she said.

“This tracking of information is critical to determining what has happened in the wake of the cyclone and helping to understand why it might have happened.”

The imagery adds to a wealth of satellite data researchers are using to assess how our extreme summer transformed North Island landscapes.

Elsewhere, it’s revealed how many of New Zealand’s famous northern beaches have been left markedly eroded, with changes in the order of five to 10m at some sites.

As of last week, Gabrielle had already led to half a billion dollars of insurance claims in Hawke’s Bay alone.

Minister for Cyclone Recovery Grant Robertson said the Government’s Cyclone Taskforce, led by Sir Brian Roche, was working with local government and insurance companies to assess the impact on high-risk areas and what that means for rebuilding.

“We are making good progress, with the insurance sector agreeing to provide the taskforce with a consolidated view of the areas they have identified as high-risk within the next week. This will then be overlaid with the risk assessments that local councils are carrying out.”

Ministers are due to discuss the next steps for the recovery early next month.