This report presents a detailed assessment of large woody debris deposited across Hawke’s Bay following Cyclone Gabrielle – one of the most intense storms in New Zealand’s recorded history.
This report presents a detailed assessment of large woody debris deposited across Hawke’s Bay following Cyclone Gabrielle – one of the most intense storms in New Zealand’s recorded history.
Commissioned by Ministry for the Environment and Ministry for Primary Industries under the supervision of Scion Research, the study expands on earlier work to include northern coastal areas that were previously inaccessible.
Using a scientifically robust line intersect sampling method, the report quantifies the volume, species composition, and likely origin of woody debris across 255 hectares of mapped debris fields. Results showed that:
- only 8% of debris showed signs of harvest residue (commonly referred to as "slash")
- 51% originated from pine plantation forests, with 31% from flood-protection willow and poplar plantings
- a significant portion of debris was linked to erosion-prone landscapes, exacerbated by saturated soils and extreme rainfall.
The findings provide solid evidence for discussions around the role of forestry slash in infrastructure damage, and highlight the complex interplay of land use, vegetation type, and storm intensity. This report provides insights to inform future land management and erosion mitigation strategies in vulnerable regions.