New mapping highlights city’s vulnerable areas

Parts of Gisborne coloured blue that would face an extreme flood risk at a sea level rise of 2m. Picture by NIWA Coastal Flood Layers Viewer

A huge swathe of Gisborne, including the airport, would be inundated by extreme coastal flooding if sea levels rise, new research shows.

New maps from NIWA and the Deep South National Science Challenge show areas across New Zealand that could be inundated by extreme coastal flooding. They show a large storm-tide with the sea-level rise that the country is likely to see with climate change.

The map shows at an extreme sea-level rise of 2m, an area from Waikanae Stream to Taurau Valley Road would be inundated, comprising the whole of Awapuni Rd, Centennial Marine Drive, TUAraki Rd and Wharerata Rd to just before Manutuke.

Niwa’s Dr Scott Stephens, chief scientist for coasts and estuaries says that these maps will help shape decisions on how New Zealand adapts to sea-level rise.

“Coastal flooding is a global hazard that impacts New Zealand, with rising sea levels already causing more frequent and intense flooding along many coasts. We have created maps that help identify the changing risk to land, property, and infrastructure from rising seas, at a regional and national scale.

“By 2065, there could be 0.4m of sea-level rise, based on the current trajectory, or sooner where the landmass is subsiding,”  Dr Stephens said.

At a rise of 0.5m the whole of MacDonald and Dunstan Roads, along with Centennial Marine Drive, would be washed away in Gisborne, the maps show.

“We hope this information will raise awareness and help councils and government to know where to conduct detailed investigations when developing adaptation strategies to protect our coastal communities,” Dr Stephens said.

The maps were used in new research that examined New Zealand’s increasing exposure to coastal flooding with sea-level rise.

The research found that small amounts of sea-level rise will drive a rapid increase in cumulative flooding from increasingly frequent coastal-flood events nationally, and 30 percent more land area would be regularly flooded after a 0.3m relative sea-level rise.