"Long-term soil erosion is the average mass of soil lost per square kilometre per year (tonnes/km2/year) over a period of approximately 10 years. It is extrapolated from long-term measurements of sediment load in rivers. Extrapolation is based on mean annual rainfall, rock type, and land cover. The total sediment in rivers (tonnes/year) for a particular region is the sum of all soil erosion over the entire region (Dymond et al, 2010). Soil-erosion rates were calculated to 2012.
This data set relates to the "Estimated long-term soil erosion" measure on the Environmental Indicators, Te taiao Aotearoa website."