Rainfall simulation to identify the storm-scale mechanisms of gully bank retreat

Abstract

a b s t r a c tGully erosion is one of the main causes of soil loss in drylands. Understanding the dominant mechanisms of erosion is important to achieve effective erosion control, thus in this study our main objective was to quantify the mechanisms involved in gully bank retreat as a result of three processes, falling of entire soil aggregates, transport of soil material by splash and by water running along gully banks (runoff), during rainfall events. The study was conducted in the sloping lands of the KwaZulu-Natal province, a region that is highly affected by gully erosion. Artificial rain was applied at 60 mm h −1 for 45 min at the vertical wall of a gully bank typical to the area. The splash material was collected by using a network of 0.045 m 2 buckets. The sediments in the running water were assessed by sampling the runoff collected from a microplot inserted within the base of the bank, and collecting the fallen aggregates after the rainfall simulation was complete. Results indicated that the overall erosion for the simulation was 721 g m −2 h −1 . Runoff erosion proved to be the dominant mechanism and amounted to 450 g m −2 h −1 , followed by splash and fall down of aggregates (about 170 g m −2 h −1 ). Gully bank retreat occurred at a rate of 0.55 mm h −1 and assuming that the soil bulk density is 1.3 g cm −3 , this corresponds to a retreat of 8.8 mm y −1 . Extrapolations to the watershed level, where about 500 m 2 of gully bank are observed per hectare, would lead to an erosion rate of 4.8 t ha −1 y −1 . These limited results based on a simulated storm show that the three main mechanisms (runoff, splash and fall down of aggregates) are responsible for the retreat of gully banks and that to mitigate gully erosion, appropriate measures are required to control all three mechanisms. Further research studies are needed to confirm and to scale up, both in time and space, as these data are obtained at one location and from a single artificial storm.

Assessing the sources of sediment transported in gully systems using a fingerprinting approach: An example from South-east China

“…The gully bank usually retreat as a result of three processes; falling soil, transport of soil material by splashes, or water running along gully banks (Chaplot et al, 2011). The active gully extended upstream as a result of waterfall undercutting and gravitational slumping of the gully head (Derose et al, 1998).…”

Splash erosion: A review with unanswered questions

“…These articles complement and develop research areas started in previous years, and the study of splash erosion becomes fully fledged for scientific applications in a number of fields. The topics studied include disdrometers (Beguería et al, 2015;Fernández-Raga et al, 2010;Meshesha et al, 2016;Sanchez-Moreno et al, 2012;Van Dijk et al, 2002), modelization (Erpul et al, 2013;López-Vicente et al, 2015;Ma et al, 2008;Marzen et al, 2015), stability of aggregates (Arthur et al, 2011;Jomaa et al, 2012;Le Bissonnais, 2016;Mahmoodabadi and Sajjadi, 2016;Mataix-Solera et al, 2011;Wakiyama et al, 2010), rainfall simulations (Chaplot et al, 2011;Fox and Bryan, 2000;Katuwal et al, 2013;Mahmoodabadi and Sajjadi, 2016;Wei et al, 2015), infiltration (Lei et al, 2006;Nanko et al, 2010), interception by vegetation (Geißler et al, 2012a, b;Hoffman et al, 2013;Negishi et al, 2006;Van Dijk et al, 2003a), runoff (García-Díaz et al, 2017;Rodrigo Comino et al, 2017;Dong et al, 2013;Ghahramani et al, 2011a;Van Dijk and Bruijnzeel, 2003;Van Dijk et al, 2003b). Some of the new topics are soil protection by mulching (Bhattacharyya et al, 2010;Gholami et al, 2012a;Smets et al, 2008;Van Dijk and Bruijnzeel, 2004;…”

Evaluación de la estabilidad de taludes en cárcavas, Huasca de Ocampo, Hidalgo, México.

“…Comúnmente, el crecimiento lateral de las cárcavas se ha estimado como un incremento de su área o longitud a través del tiempo, mediante clavos de erosión, fotografías aéreas, imágenes LIDAR y reconstrucción de fotografías -3D (Castillo y Gómez, 2016;Rahmati et al, 2017), con especial atención en la cabecera de la cárcava. Sin embargo, la erosión en los taludes de cárcavas es la fuente principal de sedimento durante la etapa f inal del desarrollo de la cárcava (Qin et al, 2018) y el proceso principal de su evolución (Chaplot et al, 2011).…”