Background Gullies are defined as the channels that are too deep to cross or to fill with normal tillage operations. Gully erosion, literally, is the soil detachment and transportation that occurs during the development of gullies, and serves as a major source of soil loss at the catchment scale. Accurate and suitable monitoring techniques are required in the quantitative study of gully erosion and therefore in the establishment and improvement of gully erosion models. During recent decades, more and more effort has been made to improve the previous monitoring methods as well as to develop new efficient methods.

Methods The advanced searches provided by the Web of Science were applied to explore the major gully erosion measurement methods employed in the previous studies by the end of 2019. The application trends and characteristics of these methods were analyzed quantitatively, and the primary advantages and disadvantages of each method were discussed.

Results The results manifest 2 classes of gully erosion monitoring methods, which are contact and non-contact methods. Therefore, the class of the contact method includes erosion pins, tape method, volume replacement method, total station and GPS; and the class of the non-contact method consists of laser scanning, stereo-photogrammetry and remote sensing. According to the supporting platform, these methods are further subdivided into 14 specific types, among which the aerial and satellite remote sensing have been so far applied most frequently. The corresponding publications account for 39.6% and 12.8%, respectively, of the total publications directly measuring gullies. Since 1980s, increasing attention has been paid to the quantitative research of gully erosion. Three typical trends in general are identified for the applications of the 14 gully measurement methods, which are rapid increase represented by the airborne structure from motion (SfM) stereo-photogrammetry, slow followed by fast increase represented by the satellite remote sensing, and slow increase represented by the airborne laser scanning. Different methods are applicable for different research objects and purposes. According to the 9 indices used for method evaluation, the tape method possesses rather low accuracy, but it is simple and efficient, and serves as a great tool for rapid gully survey in the field. The real-time kinematic (RTK) GPS is usually the optimal choice for field gully monitoring as it has a rather high accuracy but low time cost. The newly-developed SfM photogrammetry exhibits significant superiority over the traditional stereo-photogrammetry; whereas, the remote sensing is suitable for large-scale research on temporal and spatial distribution of gullies.

Conclusions These findings hold important implications for selecting gully erosion measurement methods. To ensure the consistency and comparability of measurement results, standard procedures need to be established for each method in the future. It remains a challenge to integrate different techniques to realize the comprehensive gully erosion monitoring at multiple spatial and temporal scales.