Event-Based Response to Groundwater Contamination from Severe Surface Flooding (Book Chapter)

In mid-February 2023, Cyclone Gabrielle caused unprecedented flooding, landslides, and infrastructure damage across large parts of New Zealand’s North Island. Following the event, significant public safety concerns were raised regarding the safety of untreated drinking water sourced by groundwater. In the weeks following the event, the first coordinated event response between five organizations (local to national) to assess the impact of widespread flooding on groundwater quality in NZ was initiated. The response consisted in an initial rapid, low-cost sampling for screening a large number of wells for indicator parameters of potential contamination. This was followed by subsequent sampling for a more comprehensive suite of contaminants of wells located in areas where anomalous measurements were identified. This approach provided valuable insights on: fieldwork efficiency, sampling site suitability screening, collection of floodwater or baseline data, the suite of analytes to use, inter-organization involvement and communication, and event-response cost. As current climate predictions for NZ suggest more frequent and more severe storm events, we provide recommendations on pre-event preparedness, event response design, and response activities to inform future similar surveys.