Assessing the influence of geo-environmental factors on discontinuous gully erosion at regional scales: A case study of spoon gullies on the loess plateau of China.

Despite being an essential component of gully systems, discontinuous gullies have received less attention for their complex formation mechanisms and often overlooked sediment yield processes. Factorial analysis helps elucidate gullying processes, but relevant studies on discontinuous gullies are currently lacking, especially at large scales. Spoon gullies, characterized by fat heads and thin tails, are a typical type of discontinuous hillslope gully found extensively on the Loess Plateau of China. Based on an inventory of 4077 spoon gullies and 13 geo-environmental factors, variations in factor dominance influencing the gully erosion were explored within a global-local framework, using Geodetector, geographically weighted regression, and spatially constrained multivariate clustering. Among individual factors, continuous gully density explained 41.6% of the spatial distribution of spoon gullies, followed by normalized difference vegetation index (NDVI), soil characteristics, and precipitation, ranging from 12.0% to 18.6%, while land use and topography exerted a negligible effect. The interaction of two factors showed a nonlinear enhancement in explanatory power, reaching 77.1%, 71.8%, and 69.7% when combining continuous gully density with loess thickness, precipitation, and NDVI, respectively. Moreover, except for generally negative regression coefficients of NDVI, other factors showed positive and negative values, indicating significant spatial variability in their effects on spoon gullies. Seven spoon gully clusters were thereby identified, each dominated by an evident factor among continuous gully density, precipitation, loess thickness, and soil texture. A spoon gully susceptibility map comprising five levels was further produced under a model accuracy of 85.8%, suggesting reliable performance in predicting gully occurrence. Overall, the influence of factors on spoon gully development exhibit remarkable complexities, mainly depending on spatial variation in the intricate interactions among factors and their scale-dependent behaviors. This study provides new insights into the spatial heterogeneity of discontinuous gullies at a regional scale and offers implications for developing targeted strategies against gully erosion.