Abstract
Gullies are sources and reservoirs of sediments and perform as efficient transfers of runoff and sediments. In recent years, several techniques and technologies emerged to facilitate monitoring of gully dynamics at unprecedented spatial and temporal resolutions. Here we present a detailed study of a valley-bottom gully in a Mediterranean rangeland with a savannah-like vegetation cover that was partially restored in 2017. Restoration activities included check dams (gabion weirs and fascines) and livestock exclosure by fencing. The specific objectives of this work were: (1) to analyze the effectiveness of the restoration activities, (2) to study erosion and deposition dynamics before and after the restoration activities using high-resolution digital elevation models (DEMs), (3) to examine the role of micro-morphology on the observed topographic changes, and (4) to compare the current and recent channel dynamics with previous studies conducted in the same study area through different methods and spatio-temporal scales, quantifying medium-term changes. Topographic changes were estimated using multi-temporal, high-resolution DEMs produced using structure-from-motion (SfM) photogrammetry and aerial images acquired by a fixed-wing unmanned aerial vehicle (UAV). The performance of the restoration activities was satisfactory to control gully erosion. Check dams were effective favoring sediment deposition and reducing lateral bank erosion. Livestock exclosure promoted the stabilization of bank headcuts. The implemented restoration measures increased notably sediment deposition.
Highlights
Erosion is a land degradation process that takes place in a wide range of climatic, geomorphological, and pedological conditions [1,2,3]
We considered a spatially variable error estimated using rules implemented through a fuzzy inference system in addition to the georeferencing error calculated for every individual digital elevation models (DEMs) during the photogrammetry processing
We considered the effect of grassland, applying a minimum level of detection based on the height of grasses in the periods analyzed
Summary
Erosion is a land degradation process that takes place in a wide range of climatic, geomorphological, and pedological conditions [1,2,3]. Gullies can be classified as permanent or ephemeral [4]. Gullies are classified, depending on topographic position, as hillslope gullies or valley-bottom gullies [5] and may be the consequence of natural and/or human-induced soil erosion processes [2,6]. Topographical factors, such as drainage area and slope gradient, drive the formation of gullies, showing the importance of surface runoff. Development has been associated to land use changes, management, and exploitation systems [9,10,11,12]
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