Measurement of soil erosion from river basins can be done by computing runoff from the water level, velocity, and discharge over time from a river. The aim of soil erosion hazard assessment is to identify those areas of land where the maximum sustained productivity from a given land use is threatened by excessive soil loss or the off-site damage arising from erosion is unacceptable. Semi-detailed assessment of soil erosion hazard includes land capability classification, land systems classification and soil erosion survey. Soil erosion surveys are carried out using data from aerial photographs or satellite imageries. Detailed soil erosion surveys which give information on extent and severity of erosion, are conducted at selected sites manually. Macro-scale measurement of soil erosion includes erosion by streams and rivers and the area may vary from a few hundred to a few thousand square kilometers. Soil surveys have long been used to quantitatively estimate erosion hazard over large areas.