Abstract
This research is focused on gully erosion mapping and monitoring at multiple spatial scales using multi-source remote sensing data of the Sancha River catchment in Northeast China, where gullies extend over a vast area. A high resolution satellite image (Pleiades 1A, 0.7 m) was used to obtain the spatial distribution of the gullies of the overall basin. Image visual interpretation with field verification was employed to map the geometric gully features and evaluate gully erosion as well as the topographic differentiation characteristics. Unmanned Aerial Vehicle (UAV) remote sensing data and the 3D photo-reconstruction method were employed for detailed gully mapping at a site scale. The results showed that: (1) the sub-meter image showed a strong ability in the recognition of various gully types and obtained satisfactory results, and the topographic factors of elevation, slope and slope aspects exerted significant influence on the gully spatial distribution at the catchment scale; and (2) at a more detailed site scale, UAV imagery combined with 3D photo-reconstruction provided a Digital Surface Model (DSM) and ortho-image at the centimeter level as well as a detailed 3D model. The resulting products revealed the area of agricultural utilization and its shaping by human agricultural activities and water erosion in detail, and also provided the gully volume. The present study indicates that using multi-source remote sensing data, including satellite and UAV imagery simultaneously, results in an effective assessment of gully erosion over multiple spatial scales. The combined approach should be continued to regularly monitor gully erosion to understand the erosion process and its relationship with the environment from a comprehensive perspective.
Highlights
Erosion is the process in which soil is removed according to the concentration of surface water and subsurface water in narrow flow paths, resulting in the formation of incised channels that may grow into gullies deeper than 30 cm over short time periods [1]
Several studies proposed that gully erosion is the major soil erosion type in the black soil region of Northeast China, which suffered from severe soil erosion [3,4,5]
The spatial resolution of satellite images in previous studies was mostly higher than 5 m, which results in omitting a considerable quantity of ephemeral gullies [26] and does not allow for a detailed analysis [27]
Summary
Erosion is the process in which soil is removed according to the concentration of surface water and subsurface water in narrow flow paths, resulting in the formation of incised channels that may grow into gullies deeper than 30 cm over short time periods [1] This causes significant soil loss and soil degradation, and it is generally considered as an indicator of desertification and land degradation [2]. Airborne LiDAR [20,21,22] and terrestrial laser scanner (TLS) [23,24,25] derive high resolution and precision data products for precise modeling of land surface They offer the ability to measure gullies contactless with a high spatial resolution but require significant expertise. Small changes of an individual gully within short time periods are difficult to identify using satellite images [27]
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