Milldale Ecological Offsetting

WWLA has undertaken a project for Fulton Hogan Land Development Ltd in Milldale, north of Auckland.  This project involved the creation of new wetlands.  These wetlands served as mitigation for the unavoidable removal of an area of pasture that was identified as a potential wetland site under the National Policy Statement for Freshwater Management (NPS-FN).

WWLA designed a series of shallow at-grade contour bunds, which act as small embankments trapping overland flow, to create a terraced topography similar to the visual aspect of rice paddies common in Southeast Asia.  The site has naturally poorly drained soils, hence with this small amount of intervention, the area is set to become a new wetland and, in some cases, expanded wetlands where contour bunds are positioned adjacent to existing degraded farm wetlands, identified by Viridis Ecologists, at either end. 

How it works: the bunds detain surface runoff, sub-soil discharges and any perched water spring discharges, which subsequently seep slowly into the ground, creating a sustained saturated environment emulating the natural wetlands on lower sloped land or at springs in gully heads. 

The first stage of bund construction was undertaken in early May, and native hydrophytic vegetation planting has since taken place.  Rainfall events have filled the bunds, providing a water source to the vegetation.  It is exciting to see our ideas come to fruition.