Shaping Landscapes – Landslide Analysisfrom Cyclone Gabrielle in Hawke’s Bay, New Zealand
Abstract:
Cyclone Gabrielle severely impacted the Hawke’s Bay region’s natural capital to the extent that it would take many years to recover. Alongside its impacts on built capital, such as bridges, roads, homes and businesses, are the impacts on natural capital, including geology, soil, biodiversity, air and water. The focus of this work is on the impacts on soil and regolith in the form of landslides, which embed the surface geomorphic process dynamics of erosion to runout and deposition. Research has been undertaken by Hawke’s Bay Regional Council (HBRC) to investigate the direct impacts of the cyclone on rural land stability in the region through geospatial analysis and the System Dynamics of landslides. Determinants of failure were assessed such as slope, aspect, antecedent weather, land use, land cover and the influence of any mitigation measures that promote resiliency. It is well documented that vegetation reduces erosion; with management plans stretching back beyond Cyclone Giselle and Bola. The question is, how have these land use changes measured up against the force of Cyclone Gabrielle? An initial farm-scale analysis found that the presence of trees at Awapapa Station in the Wairoa catchment likely influenced a reduction in slips by 67% when adjusting for farm size and slope. Once such information is known, the issue becomes managerial, where future planning to mitigate the impact of such events at the regional scale is critical. Here System Dynamics modelling is a useful tool to investigate how land use interventions can unfold over time and lead to positive outcomes for soil stability and economic output. This research provides a proof of concept of how System Dynamics can be employed to assess interventions ahead of time for rural areas.
