The first in a series of new stormwater flood hazard maps for the Upper Clutha has been released by Queenstown Lakes District Council (QLDC).

The maps identify potential flood risk from extreme rainfall events to properties in the Wānaka and Albert Town areas.

They are publicly available online using a GIS map tool.

Residents and property owners can zoom in on any property and identify the potential flood risk.

QLDC strategy and asset planning manager Mark Baker said the maps and similar assessments are being completed for all townships across the district and are due to be released from later this year through to 2024.

“The modelling has been completed to better understand the flood hazard in the district,” he said. 

“The maps will inform our stormwater investment programme and help the community to understand possible flood risk in their area and for their property.”

Modelling has been completed for the area marked here within pink lines. IMAGE: Supplied 

Two maps have been produced based on the same modelling results: One map indicates possible water depth caused by stormwater flooding and the other indicates any potential hazard affecting people, property or vehicles, based on a combination of water depth and velocity.

Mark said the maps were created using a computer model that calculates how, when and where rainwater flows, accounting for climate change, local topography and stormwater drainage such as pipes, basins, creeks, bridges, culverts and soak pits.

Environmental factors such as soil characteristics and where rainwater moves slowly or soaks into the ground are also factored into the model. 

QLDC has sent owners of properties within the flood assessment areas a letter advising them that potential flood information will appear on a Land Information Memorandum (LIM) if one is requested for their property.

“Property owners don’t need to take any specific action as a result of this modelling,” Mark said.

“However, we do recommend they take a look at the maps and understand any potential risk, especially if they have plans to subdivide or build. 

“This new information will be used to inform consent processes and our consent officers will be able to provide advice for each specific situation as it will depend on the property and proposal,” he said.

Mark added that the modelling would further inform QLDC’s stormwater investment programme.