Bay of Plenty estuary projects aims to understand impact of sea-level rise

New equipment has been installed at Ōhiwa Harbour to understand the impact of rising sea-levels. Photo / Supplied

A new project has been installed in two Bay of Plenty estuaries to monitor the impact of rising sea levels.

The equipment was installed in Athenree Estuary and Ōhiwa Harbour last month to understand whether coastal wetlands can survive the inevitable threat.

Bay of Plenty Regional Council contracted NIWA to install 12 Rod Surface Elevation Tables, or RSETs.

Coastal wetlands containing mangrove and saltmarsh habitats must accumulate sediments and gain elevation at the same rate, or more rapidly, than sea-level rise if they are to survive.

Their survival is critical because they function as a long-term sink for stormwater contaminants, support biodiversity and provide nurseries for estuarine and coastal species.

NIWA coastal and estuarine physical processes principal scientist Dr Andrew Swales led the installation project.

"We know the rate of sea-level rise is accelerating around the New Zealand coast at different rates.

"This is an opportunity to work with the Bay of Plenty Regional Council to manage these systems and understand the pressures on them."

Coastal wetlands could migrate landwards as sea levels rose, but this was prevented around the shorelines of many New Zealand estuaries by stop banks, roading and rail infrastructure.

The monitoring sites will provide information to understand the pressures on estuaries from sea-level rise and sediment coming in from the catchment. The epuipment is used globally to monitor sediment surface-elevation trends in coastal wetlands, relative to rates of sea-level rise.

Bay of Plenty was the second location in New Zealand where the devices have been installed for long-term monitoring, with the Firth of Thames being first in 2007, said Dr Swales.

The regional council's environmental scientist Shay Dean said the data would feed into the council's estuarine wetland monitoring programme.

"Over time, this will be used to interpret any changes in vegetation, the health of saltmarsh wetlands, and their responses to changing environmental conditions."

Information from the monitoring sites will also inform coastal wetland research in the NIWA-led Future Coasts Aotearoa research programme.

The five-year study aimed to provide tools and guidance to help rural communities living in coastal lowlands adapt and prosper despite unavoidable sea level rise.

The study could potentially involve installing more RSET sites in key coastal communities over the next year.