Numerical modelling of the evolution of a river reach with a complex morphology to help define future sustainable restoration decisions

IF 2.8 2区 地球科学 Q2 GEOGRAPHY, PHYSICAL
Rabab Yassine, Ludovic Cassan, Hélène Roux, Olivier Frysou, François Pérès
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Abstract

Abstract. The prediction of river morphology evolution is very complicated, especially in the case of mountain and Piedmont rivers with complex morphologies, steep slopes, and heterogeneous grain sizes. The Lac des Gaves (LDG) reach, located within the Gave de Pau River in the Hautes-Pyrénées department, France, has precisely the complex morphological characteristics mentioned above. This reach has gone through severe sediment extractions for over 50 years, leading to the construction of two weirs for riverbed stabilisation. Two large floods resulted in changes in the LDG's hydromorphological characteristics as it went from a single channel river section to a braided river reach. In this study, a 2D hydromorphological model is developed with the TELEMAC-MASCARET system to reproduce the evolution of the channel following a flood that occurred in 2018. The model's validity is assessed by comparing the simulated topographic evolution to the observed one. The results reveal the challenge to choose well-fitted sediment transport equations and friction laws that would make it possible to reproduce such complex morphology. Although the exact localisation of the multiple channels forming the braided nature of the LDG was challenging to reproduce, our model was able to provide reliable volumetric predictions as it reproduces the filling of the LDG correctly. The influence of the two weirs on the river's current and future morphology is also studied. The aim is to provide decision-makers with more reliable predictions to design suitable restoration measures for the LDG reach.
具有复杂形态的河段演变的数值模拟,以帮助确定未来的可持续恢复决策
摘要。河流形态演变的预测是非常复杂的,特别是对于形态复杂、坡度陡峭、粒度不均匀的山地和山前河流。Lac des Gaves (LDG)河段位于法国上pyrpyrsamues省的give de Pau河内,具有上述复杂的形态特征。50多年来,这条河段经历了严重的泥沙抽取,导致修建了两座堰来稳定河床。两次大洪水导致了LDG从单通道河段到辫状河段的水文形态特征变化。在本研究中,利用TELEMAC-MASCARET系统开发了一个二维水文形态模型,以重现2018年发生洪水后河道的演变。通过将模拟的地形演变与观测的地形演变进行对比,对模型的有效性进行了评价。结果表明,选择合适的泥沙输运方程和摩擦定律是一项挑战,这将使重现如此复杂的形态成为可能。虽然要精确定位形成LDG编织性质的多个通道具有挑战性,但我们的模型能够提供可靠的体积预测,因为它正确地再现了LDG的填充。研究了这两个堰对河流当前和未来形态的影响。目的是为决策者提供更可靠的预测,以便为LDG河段设计合适的恢复措施。
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来源期刊
Earth Surface Dynamics
Earth Surface Dynamics GEOGRAPHY, PHYSICALGEOSCIENCES, MULTIDISCI-GEOSCIENCES, MULTIDISCIPLINARY
CiteScore
5.40
自引率
5.90%
发文量
56
审稿时长
20 weeks
期刊介绍: Earth Surface Dynamics (ESurf) is an international scientific journal dedicated to the publication and discussion of high-quality research on the physical, chemical, and biological processes shaping Earth''s surface and their interactions on all scales.
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