Environmental Reporting, Ministry for the Environment and Statistics New Zealand
"This data records estimated erosion risk for different areas in the North Island.
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. Highly erodible land comprises land at risk of landsliding, gullying, or earthflow erosion if it does not have protective woody vegetation (Dymond et al, 2006). Landsliding occurs on steep slopes where the soils do not have the support of tree roots. Gullying and earthflow erosion can occur on all slopes, irrespective of steepness, but the land is only considered at risk if it does not have woody vegetation. Landslide erosion is the shallow (approximately 1m) and sudden failure of soil slopes during storm rainfall. Gully erosion is massive soil erosion that begins at gully heads and expands up hillsides, over decadal time scales. Earthflow erosion is the slow downward movement (approximately 1m/year) of wet soil slopes towards waterways.
This data set relates to the ""Estimated highly erodible land in the North Island"" measure on the Environmental Indicators, Te taiao Aotearoa website."
Source: Landcare Research Method: Landcare New Zealand calculated erosion risk based on the characteristics, including slope, landcover, etc. of different areas in the Land Cover Database v4.0.