Background
On Monday 14th November 2016 a magnitude 7.8 earthquake jolted approximately 60km of the Kaikoura coastline triggering numerous large slip events along the Hikurangi subduction zone. Close to one million cubic metres of slip material fell onto the coastal transport corridor, interrupting the economy and isolating many local communities.
Problem
An area identified as Slip 6 had been categorised as Red Zone due to the high risk of rockfall; therefore, physical access within that area is prohibited.
Topsoil, nutrients, and biological networks were removed by the slip events and subsequent debris clearance using aerially applied seawater left the substrate barren, dehydrated, and prone to further erosion.
Solution
Red Tree Environmental Solutions Ltd was engaged and by harnessing the principles of ecological engineering, recommended the Enviroblanket® technology that has been developed over several years of research.
To eliminate the risk to ground staff, an aerial application methodology was developed and costed, then deployed in three phases.
Phase 1: Herbicide application via aerial broadcast and wand spraying techniques to perform site preparation.
Phase 2: Aerial application of a site-specific Enviroblanket® formulae incorporating a tailored mix of locally harvested native seed species to 1 Ha of disturbed slope face.
Phase 3: Aerial application of Vital Bon-Matt HR to secure the Enviroblanket® to the slope.
Benefit
In any restoration process, pioneer species establish more quickly than other species as their physiological adaptations and rate of metabolism are best suited to the environment. The Enviroblanket® uses media and ingredients that facilitate erosion and sediment control while providing the ideal growing conditions for pioneering New Zealand native species.
The use of Vital Bon-Matt HR greatly increased the stabilisation factor on the exposed coastal slope and, during drier periods, will also support increased moisture retention complimenting and enhancing the overall benefits of the site-specific Enviroblanket® application.
As site conditions can vary greatly, each use of this methodology requires a prescriptive approach utilising appropriate species selection, mix proportions, and selective additives along with timings and operational strategies.