Urban flooding is no longer a periodic inconvenience that communities can engineer their way around with bigger drains and taller stop banks — it is an accelerating structural challenge driven by climate change, sea level rise, and rainfall events of increasing severity that are rendering historical flood frequency data obsolete.

The most insidious and least well-understood dimension of this challenge is the role of the subsurface water table: when groundwater is already elevated — from prior rainfall, geological proximity to sea level, or tidal intrusion through porous coastal substrates — storm rainfall has nowhere to drain and minor events produce major flooding outcomes. This white paper examines two of New Zealand's most significant cases of groundwater-driven urban flooding. 

This white paper proposes a three-component integrated flood resilience strategy for South Dunedin — and a simpler two-component strategy for Flockton Basin — that addresses the flooding problem from all sides simultaneously, at a fraction of the cost of the traditional engineering responses.