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Eye in the sky scans flood-stricken city

Eye in the sky scans flood-stricken city

A break in the weather has allowed flood damage in Tauranga to be captured in the most detailed satellite imagery available to civilians.

Heavy rain last month caused extensive damage in the region, with Tauranga, Mt Maunganui and the township of Matata worst affected.

Landcare Research scientists have organised the United States “QuickBird” satellite to take images of Tauranga, and are making them available to ten agencies, including science organisations, central government agencies, and local and regional councils. Clear satellite images rely on minimal cloud cover, and there has been a considerable wait for an opportunity for a useable image to be taken.

The images look like aerial photos, but are much more detailed, down to a 0.6-metre resolution. As Landcare Research scientist Murray Jessen points out, “that’s close enough to find a lost child!

“They really do provide a snapshot inventory of landslides and sedimentation from floodwaters.

“From them we can extrapolate other information such as slope and type of soil, and look for causal relationships to answer questions about the safety of land that could be developed in the future.”

Unlike aerial photos, satellite images have no “joins” and do not need to be rectified for geographical accuracy. “Also, because of the digital format, computers can immediately run statistical analyses on them,” Mr Jessen says.

“Satellite images can show factors such as the percentage of impervious areas like paths and buildings in the city. This is important, because whenever we modify natural landscapes we have issues with stormwater management.

“The image will be of real use for Tauranga’s town planners and engineers, as it provides a geographically accurate picture of the event, and such resources are essential to wise land-use planning in this fast-growing city. Tauranga clearly has sensitive geological features when even moderate slopes can give way as they have, and agencies such as GNS can use these images to add value to the excellent advice they prepare for local councils.

“Landcare Research staff will be talking with a range of agencies to discuss what other useful analyses we can run from this imagery.”

Mr Jessen says Landcare Research is increasing its research focus on urban design. “Poor urban planning eventually gets ‘found out’ by New Zealand’s climate. No part of the country is safe from receiving the very high intensity rainfalls that are becoming increasingly common.

“We are researching better ways to manage water in and around urban areas, and the capabilities of land, particularly hill sites, to be modified and remain stable. We are also researching smarter technologies for buildings and stormwater management.”

Tauranga is not the first flood-hit site Landcare Research has placed under a satellite’s eagle eye. Last year, staff used the French SPOT5 satellite to map the extent of the February flood damage to rural Manawatu, Wanganui and Rangitikei. The image revealed that nearly 20,000 hectares of land had been lost to pasture production through some 62,000 landslides.


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