River catchment planning for future climate change

To develop effective management plans for river catchments, policymakers and catchment managers need to account for how climate change might affect soil erosion and river sediment loads. However, there has been no published, quantitative assessment of national-scale changes in erosion or suspended sediment loads anticipated under future climate for Aotearoa New Zealand.

To address this gap, Manaaki Whenua’s Dr Andrew Neverman and colleagues, in collaboration with AgResearch and NIWA and with funding from the Our Land and Water National Science Challenge’s Whitiwhiti Ora programme, have produced AoNZ’s first national assessment of the potential impact of climate change on erosion and suspended sediment loads.

As part of the project, future erosion and sediment loads were estimated for mid-century (2040) and late century (2090) based on projected changes in climate and hydrology. Changes in suspended sediment loads were modelled under four potential future atmospheric CO₂ concentrations, with associated changes in rainfall intensities and amounts.

The results of this modelling, published in the international journal Geomorphology, show that up to 28% of the North Island and 8% of the South Island are estimated to experience a two-fold or greater increase in average annual sediment supplied to the channel network by late century.