Study on the influence of vegetation change on runoff generation mechanism in the Loess Plateau, China

Abstract

In recent years, the amount of water and sediment in the Yellow River Basin has dropped drastically. This paper selected 125 rainfall and flood data points from 1965 to 2015, combined hydrological methods and mathematical statistics to analyze the hydrological factors and runoff generation mechanism, and combined the underlying surface conditions of the Gushanchuan Basin. The characteristics of change revealed the temporal and spatial variation characteristics and related factors of the runoff generation mechanism in the basin. The results showed that the Gushanchuan Basin is still dominated by HOF runoff, but the runoff generation mechanism has also changed with changes in the underlying surface, which are reflected in increased runoff components, the reduced proportion of HOF runoff, and the increased proportion of saturation-excess overland flow (SOF) runoff and mixed runoff. We analyzed the variation law of underlying surface in the basin, which indicated that the increase in the forest grass area was the main factor affecting changes in the watershed runoff generation mechanism. This research will enable a deeper understanding of the runoff generation mechanism of the main soil erosion areas in the Loess Plateau, and reveal variations in the runoff generation mechanism in the Yellow River.

Revegetation impacts on runoff generation processes in a typical loess catchment

“…This would then lead to the gradual accumulation in the upper soil layers, forming a transient perched water table and, eventually, resulting in Dunne overland flow (Figures 6, 7). Several studies by hierarchical conceptual models also indicated this potential pattern of soil water redistribution (Ghimire et al, 2013; Hong, 2020; Tian et al, 2017; Zwartendijk et al, 2017).…”

“…The spatial resolution of the surface mesh varies gradually from 150 m near the catchment edges to 5 m along the channels and outlet. Given that the active hydrological processes within the vadose zone of the Loess Plateau are mainly within the shallow root zone (e.g., 0–1 m) (Suo et al, 2018), in this work the vertical soil depth was restricted to 10 m, which was sufficient for detecting the shallow hydrological response at short‐duration event scale and to better realize simulation convergence (Hong, 2020; Ran et al, 2019). The top one‐meter soil depth was divided into 10 sublayers with a vertical spacing of 0.1 m. For the soil depth at 1–2 m, the vertical spacing is 0.2 m, with a 1‐m spacing for the lower 2–10 m soil depth. Boundary conditions and initial conditions …”

“…The results indicated that vegetation restoration has substantially altered the underlying surface conditions, including vegetation coverage and soil properties, especially the vertical profiles of Ks (Pan et al, 2023; Wang et al, 2013; Zhu et al, 2022). Several studies suggested that there could be potential changes in runoff generation processes according to the calculation from conceptual models given the combinations of Ks profiles and rainfall intensity (Ghimire et al, 2013; Hong, 2020; Tian et al, 2017; Zwartendijk et al, 2017). Using a numerical approach, Liu et al (2012) found that the run‐on infiltration of overland flow existed in the downstream routing process at the upper Weihe River due to high surface saturated hydraulic conductivity, and this could lead to saturation of soil layers near the channel to form runoff.…”

“…Yet, most of them were mainly based on runoff segmentation analysis without consideration of the change of water distribution in the soil (Gu, 2019;Hu et al, 2020;Mu et al, 2023), and few quantitatively analysed the relationship between the runoff generation mechanism and underlying surface characteristics in the Loess Plateau based on physical mechanism. Besides, hierarchical conceptual models only compared the relative magnitude of saturated hydraulic conductivity and rainfall intensity (Hong, 2020;Tian et al, 2017). A comprehensive analysis of the runoff process under various rainfall and soil conditions is needed.…”

A Laboratory Study of the Role of Nature-Based Solutions in Improving Flash Flooding Resilience in Hilly Terrains

“…Rigid vegetation, being less dense, is only a direct obstruction against rainfall impact on the land's surface, providing limited resistance. In contrast, flexible vegetation has shown more resistance, as surface runoff is continuously facing resistance in its path [27]. The combination of both rigid and flexible vegetation results in a collaborative resistance against surface runoff, making this mixed approach the most efficient.…”