Effects of vegetation buffer strips on concentrated flow hydraulics and gully bed erosion based on in situ scouring experiments

Abstract

Vegetation on gully beds could intercept runoff, reduce incision of gully bed, and trap sediment from upstream area. The aim of this study is to evaluate the influences of vegetation buffer strips on concentrated flow hydraulics and gully bed erosion downstream of gully headcuts. Five gully head plots containing different buffer strip widths with similar vegetation density were constructed for in situ scouring experiments. Each plot received 11 tests with 2 discharges (i.e., 7 tests simulating 83.3 L min−1 and 4 tests simulating 166.7 L min−1). Buffer strips clearly decrease flow hydraulics (about 56–70%) and increase flow resistance (1.2 to 1.5 times) according to the selected hydraulic parameters. After 11 tests, total net erosion volume (NEV) and average sediment concentration from each gully bed showed an exponential decreasing relationship with increasing widths of buffer strips. All the selected hydraulic parameters showed a strong correlation with total NEV from the bare soil sections (0.43 < R2 < .61 with significance level reaching .01), whereas the relationship was very weak in the buffer strips. The gross deposition volume in buffer strips showed a linear correlation with upstream NEV (NEVu) and flow velocity (R2 = .91, p < .001). Split flow effects expressed by braid index increased with increasing widths of buffer strips and scouring times. Both bare and vegetated sections suffered from erosion clearly, but the average NEV from buffer strips was about 30.2% of bare soil sections. This indicated the buffer strip effects on reducing erosion were more significant than trapping sediments were in this study.

Assessment of soil shear strength in gully systems: A case‐study in the Wangjiagou (WJG) watershed on the Loess Plateau of China

“…Vegetation growing in the gullies significantly increases soil shear strength. The grasses growing at the bottom/sideslope of gullies can increase soil shear strength up to 70 kPa (with a mean value of 36 kPa) and therefore increases resistance to water erosion in addition to protection of surface soils from detachment, which is reported in other regions as an effective measure as well (Burylo, Rey, Mathys, & Dutoit, 2012; Dabney, Shields, Temple, & Langendoen, 2004; Dong et al, 2018; Gyssels, Poesen, Bochet, & Li, 2005). Likewise, shrubs growing on the sideslopes increase soil shear strength due to the root reinforcement of topsoils (De Baets et al, 2008; Fan & Su, 2008).…”

The effectiveness of selected vegetation communities in regulating runoff and soil loss from regraded gully banks in the Mollisol region of Northeast China

“…The significant correlation between soil loss and vegetation characteristics ( C , AGB, RMD, and LB) indicated that the five vegetation communities could efficiently reinforce erosion resistance of regraded gully banks. Three reasons for this result were mainly as follows: first, vegetation reduced the flow velocity and turbulence, and thus the capacity of sediment transportation and detachment greatly decreased on vegetated gully banks driven by the lower flow energy (Dong et al, 2018; Knapen et al, 2009; Wu, Wu, Feng, & Merkley, 2011). Second, the sediments were trapped and accumulated on the regraded gully bank due to the filtrating effect of flow through vegetation (Rey, 2003).…”

Simulation of the impacts of native vegetation and polyacrylamide on hydraulic properties and heavy metal concentrations at mine dumps

“…Plants reduce soil erosion via the physical and chemical effects of aboveground biomass and roots (Dong et al, 2018;Gyssels & Poesen, 2003). Native grass, through its organs (e.g., stem and roots)…”