Connectivity has been embraced by the geosciences community as a useful concept to understand and describe hydrological functioning and sediment movement through catchments. Mathematical modelling has been used for decades to quantify and predict erosion and transport of sediments, e.g. in scenarios of land use change or conservation measures. Being intrigued by both models and the connectivity concept, as a group of modellers we aimed at investigating what different models could tell us about connectivity. Therefore, we evaluated the response of contrasted spatially-distributed models to landscape connectivity features and explained the differences based on different model structures. A total of 53 scenarios were built with varying field sizes and orientations, as well as the implementation of soil conservation measures. These scenarios were simulated, for two rainfall intensities, with five event- and process-based water and soil erosion models – EROSION3D, FullSWOF_2D, LandSoil, OpenLISEM and Watersed. Results showed that rainfall amount plays the most important role in determining relative export and connected area of runoff and sediment in all models, indicating that functional aspects of connectivity were more important than structural connectivity. As for the role of structural landscape elements, there was no overall agreement between models regarding the effects of field sizes, crop allocation pattern, and conservation practices; agreement was also low on the spatial patterns of connectivity. This overall disagreement between models was unexpected. The results of this exercise suggest that the correct parameterization of runoff and sediment production and of routing patterns may be an important issue. Thus, incorporating connectivity functions based on routing would help modelling forward. Our results also suggest that structural connectivity indices may not suffice to represent connectivity in this type of catchment (relatively simple and monotonous land cover), and functional connectivity indices should be applied.

中文翻译：

---

关于水和沉积物的连通性，模型告诉我们什么？

地球科学界已将连通性作为一个有用的概念来理解和描述流域中的水文功能和沉积物运动。数十年来，数学模型一直被用于量化和预测沉积物的侵蚀和迁移，例如在土地利用变化或保护措施的情景中。被模型和连通性概念所吸引，作为一组建模者，我们的目标是调查不同的模型可以告诉我们关于连通性的哪些信息。因此，我们评估了对比空间分布模型对景观连通性特征的响应，并解释了基于不同模型结构的差异。总共构建了 53 个场景，具有不同的田地大小和方向，以及土壤保持措施的实施。这些场景针对两种降雨强度进行了模拟，使用五种基于事件和过程的水土流失模型 - EROSION3D、FullSWOF_2D、LandSoil、OpenLISEM 和 Watersed。结果表明，在所有模型中，降雨量在决定径流和泥沙的相对输出和连接面积方面起着最重要的作用，表明连接的功能方面比结构连接更重要。至于结构景观元素的作用，模型之间在田地规模、作物分配模式和保护措施的影响方面没有总体一致；在连通性的空间模式方面的一致性也很低。模型之间的这种整体分歧是出乎意料的。该练习的结果表明，径流和沉积物产生以及路径模式的正确参数化可能是一个重要问题。因此，结合基于路由的连接功能将有助于建模。我们的结果还表明，结构连通性指数可能不足以代表此类流域（相对简单和单调的土地覆盖）中的连通性，应该应用功能连通性指数。