In comparison to a local-scale flood risk analysis, modeling flood losses and risks at the river basin scale is challenging. Particularly in mountainous watersheds, extreme precipitation can be distributed spatially and temporally with remarkable variability. Depending on the topography of the river basin and the topological characteristics of the river network, certain rainfall patterns can lead to a synchronization of the flood peaks between tributaries and the main river. Thus, these complex interactions can lead to high variability in flood losses. In addition, flood inundation modeling at the river basin scale is computationally resource-intensive and the simulation of multiple scenarios is not always feasible. In this study, we present an approach for reducing complexity in flood-risk modeling at the river basin scale. We developed a surrogate model for flood loss analysis in the river basin by decomposing the river system into a number of subsystems. A relationship between flood magnitude and flood losses is computed for each floodplain in the river basin by means of a flood inundation and flood loss model at sub-meter resolution. This surrogate model for flood-loss estimation can be coupled with a hydrological-hydraulic model cascade, allowing to compute a high number of flood scenarios for the whole river system. The application of this model to a complex mountain river basin showed that the surrogate model approach leads to a reliable and computationally fast analysis of flood losses in a set of probable maximum precipitation scenarios. Hence, this approach offers new possibilities for stress test analyses and Monte-Carlo simulations in the analysis of system behavior under different system loads.

与局部规模的洪水风险分析相比，在流域范围内对洪水损失和风险进行建模具有挑战性。特别是在山区流域，极端降水可以在空间和时间上以显着的可变性分布。根据流域的地形和河网的拓扑特征，某些降雨模式可能导致支流和主要河流之间的洪峰同步。因此，这些复杂的相互作用会导致洪水损失的高度可变性。此外，流域范围内的洪水泛滥模型在计算上是资源密集型的，并且多种情况的模拟并非总是可行的。在这项研究中，我们提出了一种减少流域规模洪水风险建模复杂性的方法。通过将河流系统分解为许多子系统，我们开发了用于流域洪水损失分析的替代模型。利用亚米级分辨率的洪水淹没和洪水损失模型，为流域中的每个洪泛区计算了洪水幅度与洪水损失之间的关系。该代为的洪水损失估算替代模型可以与水文-水力模型级联结合使用，从而可以为整个河流系统计算大量的洪水情景。该模型在复杂的山区河流流域中的应用表明，替代模型方法可在一组可能的最大降水情景下对洪水损失进行可靠且计算快速的分析。因此，