The effects of Vegetation properties on supercritical Air-Water FLOWs (V-A-W-Flow)

洪水，如2002年的易北河洪水，可能造成高昂的金钱损失和人身损失或损害，特别是如果技术防洪措施失效，洪水蔓延到腹地的话。滞洪区有助于影响洪水过程线，降低洪峰流量。为此，部分高流量的水通过溢流段被重新引导到自然或人造保留区，在那里它被临时储存。溢流段通常被建造为混凝土结构或由灰色护岸保护的土结构。随着环境意识的提高和老化基础设施维护成本的上升，基于自然的解决方案，如植被(溢流)堤坝，近年来受到了更多的重视。溢流堤和溢洪道必须以这样的方式建造，即设计溢流率可以在结构中传递而不会造成破坏。与结构设计相关的水流参数、水流曝气量、水流耗能和水流阻力，包括摩擦系数，都受到表面特性的影响。对于典型的溢洪道结构，如光滑溢洪道、阶梯式溢洪道和岩石溜槽，人们已经进行了广泛的研究。此外，植被对非掺气水流中水流速度和水流阻力的影响已经在几个研究中进行了研究，尽管主要是针对亚临界水流。然而，在设计参数不确定的情况下，植被特性对超临界空气-水流经植物覆盖的溜槽(如溢流堤)中的流动和曝气的影响几乎没有被探讨过。因此，该方案旨在更好地了解植被覆盖的溜槽上的流动和曝气过程，并在考虑水流曝气的情况下将设计参数(如能量耗散和水流阻力)作为植被特性的函数进行量化。为了了解植被覆盖的溜槽上的流动和曝气过程，并根据溜槽表面的植被特性来量化能量耗散和水流阻力，对溜槽模型进行了溢流模拟。在这些试验研究中，水力边界条件和植被特性都发生了系统的变化。为此，对不同植被高度和植被密度的碾压草皮形式的天然滑槽覆盖进行了测试。植物学分析允许对测试的植被进行参数设置。在实验测试过程中，流量和曝气数据是用双头电导探头测量的。在收集数据的基础上，结合理论考虑，分析了植被特性对超临界空气-水流动中水流参数、水流曝气、能量耗散和水流阻力的影响，建立了水流、曝气和植被参数之间的关系。

Flooding, such as the Elbe flood in 2002, can cause high monetary costs and bodily loss or damage, especially if the technical flood protection measures fail and the flooding extends into the hinterland. Flood retention areas help to influence the flood hydrograph and to reduce the peak flow rate. For this, part of the high water flow is redirected via overflow sections into natural or man-made retention areas where it is temporarily stored. Overflow sections are often constructed as concrete structures or as earthen structures protected by grey revetments. With increasing environmental awareness and rising costs for maintenance of aging infrastructure, nature-based solutions such as vegetated (overflow) dikes have received greater emphasis in recent years. Overflow dikes and spillways have to be constructed in such a way that the design overflow rate can be transferred across the structure without inducing damage. The flow parameters, flow aeration, energy dissipation and flow resistance, including friction factors, relevant for the structural design are influenced by the characteristics of the surface. Extensive research has been conducted for typical spillway structures, such as smooth spillways, stepped spillways and rock chutes. Further, the effects of vegetation on flow velocity and flow resistance in nonaerated flows have been investigated in several studies, though primarily for subcritical flows. Yet, the effects of vegetation properties on flow and aeration in supercritical air‐water flows down vegetated chutes such as overflow dikes are barely explored affecting the design process with uncertainties in the design parameters. Therefore, the proposal at hand aims at an improved understanding of flow and aeration processes on vegetated chutes and the quantification of design parameters, such as energy dissipation and flow resistance, as function of vegetation properties under consideration of flow aeration.In order to understand the flow and aeration processes on vegetated chutes and to quantify energy dissipation and flow resistance depending on the vegetation properties of the chute surface, overflow simulations on a chute model are performed. The hydraulic boundary conditions and vegetation properties are systematically varied during these experimental investigations. For this, natural chute covers in the form of rolled turf with different vegetation heights and vegetation densities are tested. Botanical analyses allow for parameterization of the tested vegetation. During the experimental tests, flow and aeration data is measured with double-tip conductivity probes. With the data gathered and under consideration of theoretical considerations, the effects of vegetation properties on flow parameters, flow aeration, energy dissipation and flow resistance in supercritical air‐water flows down vegetated chutes are analyzed and the relation of flow, aeration and vegetation parameters is established.