Classes of land in New Zealand at risk of erosion: high landslide risk - delivery to stream, high landslide risk - non-delivery to steam, moderate earthflow risk, severe earthflow risk, gully risk.
Landslide erosion: the shallow (approximately 1m) and sudden failure of soil slopes during storm rainfall.
Earthflow erosion: the slow downward movement (approximately 1m/year) of wet soil slopes towards waterways.
Gully erosion: massive soil erosion that begins at gully heads and expands up hillsides over decadal time scales.
New Zealand experiences high rates of soil erosion. In the North Island, this is mostly due to the historical clearance of forest for agriculture (see also Estimated long-term soil erosion). In contrast, erosion in the South Island is mostly due to natural processes, primarily high rainfall and steep mountain slopes.
It is important to identify areas of land at risk of severe erosion to inform land-use decisions and help prioritise regional soil conservation work.
Method of collection/Data provider
The data used to estimate the risk of soil erosion accounts for all types of erosion, and generally the amount of sediment delivered to waterways reflects how much an area is at risk of soil erosion. The spatial patterns of highly erodible land are driving patterns of sediment delivered into rivers. The map of soil erosion is modelled from three factors: slope, land cover (from satellite imagery Land Cover Database (LCDB) version 4.0, nominal date 2012/13), rock type.