Ruiz-Villanueva V, Piégay H, Scorpio Vittoria, Bachmann Annette, Brousse Guillaume, Cavalli Marco, Comiti Francesco, Crema Stefano, Fernández Elena, Furdada Glòria, Hajdukiewicz Hanna, Hunzinger Lukas, Lucía Ana, Marchi Lorenzo, Moraru Adina, Piton Guillaume, Rickenmann Dieter, Righini Margherita, Surian Nicola, Yassine Rabab, Wyżga Bartłomiej
University of Lausanne, Institute of Earth Surface Dynamics (IDYST), Geopolis, UNIL-Mouline, CH-1015 Lausanne, Switzerland.
École Normale Supérieure de Lyon, (ENS), France, Environment City Society (EVS) Research unit, UMR 5600, 15 parvis René Descartes, 69342 Lyon, France.
Sci Total Environ. 2023 Dec 10;903:166103. doi: 10.1016/j.scitotenv.2023.166103. Epub 2023 Aug 7.
River widening, defined as a lateral expansion of the channel, is a critical process that maintains fluvial ecosystems and is part of the regular functioning of rivers. However, in areas with high population density, channel widening can cause damage during floods. Therefore, for effective flood risk management it is essential to identify river reaches where abrupt channel widening may occur. Despite numerous efforts to predict channel widening, most studies have been limited to single rivers and single flood events, which may not be representative of other conditions. Moreover, a multi-catchment scale approach that covers various settings and flood magnitudes has been lacking. In this study, we fill this gap by compiling a large database comprising 1564 river reaches in several mountain regions in Europe affected by floods of varying magnitudes in the last six decades. By applying a meta-analysis, we aimed to identify the types of floods responsible for more extensive widening, the river reach types where intense widening is more likely to occur, and the hydraulic and morphological variables that explain widening and can aid in predicting widening. Our analysis revealed seven groups of reaches with significantly different responses to floods regarding width ratios (i.e., the ratio between channel width after and before a flood). Among these groups, the river reaches located in the Mediterranean region and affected by extreme floods triggered by short and intense precipitation events showed significantly larger widening than other river reaches in other regions. Additionally, the meta-analysis confirmed valley confinement as a critical morphological variable that controls channel widening but showed that it is not the only controlling factor. We proposed new statistical models to identify river reaches prone to widening, estimate potential channel width after a flood, and compute upper bound width ratios. These findings can inform flood hazard evaluations and the design of mitigation measures.
河道拓宽，即河道的横向扩张，是维持河流生态系统的关键过程，也是河流正常功能的一部分。然而，在人口密度高的地区，河道拓宽在洪水期间可能会造成破坏。因此，为了进行有效的洪水风险管理，确定可能发生突然河道拓宽的河段至关重要。尽管人们为预测河道拓宽付出了诸多努力，但大多数研究仅限于单一河流和单一洪水事件，可能无法代表其他情况。此外，一直缺乏一种涵盖各种环境和洪水规模的多流域尺度方法。在本研究中，我们通过汇编一个大型数据库填补了这一空白，该数据库包含欧洲几个山区的1564个河段，这些河段在过去六十年中受到了不同规模洪水的影响。通过进行荟萃分析，我们旨在确定导致更广泛拓宽的洪水类型、更可能发生强烈拓宽的河段类型，以及解释拓宽并有助于预测拓宽的水力和形态变量。我们的分析揭示了七组河段，它们在宽度比（即洪水后与洪水前的河道宽度之比）方面对洪水的反应有显著差异。在这些组中，位于地中海地区且受短时间强降水事件引发的极端洪水影响的河段，其拓宽程度明显大于其他地区的其他河段。此外，荟萃分析证实河谷限制是控制河道拓宽的关键形态变量，但表明它不是唯一的控制因素。我们提出了新的统计模型，以识别容易拓宽的河段，估计洪水后的潜在河道宽度，并计算宽度比上限。这些发现可为洪水灾害评估和减灾措施设计提供参考。
