Cook Drive soakage, Whitianga

Metis designed soakage trenches to mitigate stormwater flooding to businesses and homes in Whitianga.

PROJECT BRIEF

They were designed to intercept rainfall runoff in severe storms, mitigating flood risk to nearby homes and businesses. Construction of the trenches was completed in July 2024.

OUR APPROACH

• Investigated flood mechanism and proposed mitigation options using hydraulic modelling
• Engaged with iwi and local business owners to select preferred options
• Commissioned ground investigations to understand topography and locate buried services
• Created design drawings using Cirtex modular soakage units
• Supported TCDC with procurement of a contractor for physical works

PROJECT OUTCOMES

The soakage trenches have helped reduce the impact of stormwater flooding on Cook Drive. Residents have benefitted from:

• Mitigation in large rainfall events: 650m³ of storage provided, accommodating up to the 50-year ARI rainfall event
• Cultural well-being: Reduced flood risk on iwi land owned by Ngāti Hei
• Low-maintenance solution: Modular soakage units are longer lasting and easier to maintain than traditional gravel trenches
• Trafficability: Though the trenches are under the berm, they are designed for traffic loading. This maintains the useability of berms for car and boat parking

Testimonial

A testimonial from our the TCDC project manager (Len Whittaker) for this project is provided below:

“After initial work with other consultancies, Metis were brought in, who quickly grasped the intricacies of the project. They developed sound, workable flood mitigation solutions that TCDC have been able to implement as a three-stage project. I recommend Metis for any future stormwater projects within New Zealand.”