Case studies

A number of dwellings had experienced severe flooding over the last ten years. By taking a catchment approach we identified the causes of flooding and recommended eight actions that the owners could take to reduce flooding.

As well, we recommended fourteen measures that should be carried out by Auckland Council. We have been retained to provide ongoing assistance to oversee the implementation of the mitigation measures.

These properties were affected by the West Auckland floods of August 2021 and the Anniversary Weekend floods of January 2023. We established that flooding was caused by a combination of factors from five catchments.

Our solution included installing flood alarms, flood barriers and identified the flood protection measures that the owners should request from Auckland Council.

About 154 properties were flooded in Anniversary Weekend 2023. We evaluated the catchment-wide causes and found that flooding was mainly caused by a complete lack of stormwater infrastructure.

Our report recommended that Council should implement detention/retention systems in the catchment and inject stormwater into the ground

17 properties were flooded in Anniversary Weekend 2023. We found that flooding was caused by poor planning (previous councils did not set flood levels for the dwellings), limited capacity of an existing detention pond and blocked stormwater infrastructure.

We recommended that the owners request Auckland Council to increase storage capacity and take measures to prevent blockages.

Anniversary Weekend 2023 flooding affected a group of about 30 dwellings. We established that flooding was due to overflow from a stream and blocked overland flowpath.

Our recommendation was that the owners request Auckland Council to improve the flow capacity of the stream and enforce overland flowpath regulations so that water flows freely through them.

This involved a study of one dwelling flooded in Anniversary Weekend. Although the catchment area is small, flooding occurred because the floor level is below the flood level.

Our recommendation was to reshape the ground so that flood water runs away from the dwelling.