Monitoring of gully erosion on the Loess Plateau of China using a global positioning system

With the development of a technique, global positioning system (GPS) has become progressively less expensive, lighter and easier to use. The accuracy of GPS has been improved and it appears applicable to the continuously monitoring morphology changes on the earth surface with small and slow change. The objective of this study is to use GPS to measure the morphology of gullies in a small catchment near Suide, Shaanxi Province, China. There are three main gully types in the study area: bank gullies, floor gullies, and hill slope gullies, and this study mainly focuses on the hill slope gullies. The hill slope gullies in the study area are mainly discontinuous and are developing rapidly. The gully density in the study area is very large. The retreat rate of hill slope gullies is 0.16-2.02 m year− 1. The relationships between the upslope drainage area (A) and the critical slope gradient (S) for hill slope gullies is S = 0.1839A− 0.2385. The values of AS2 range from 41 to 814 m2 for the hill slope gully headcuts, and most of them fell into the range of 100-300 m2. Both of these relationships are suggested as indexes for estimating the location of gully headcuts.