保护高山莱茵河谷免受洪水

Author: Renata Barradas Gutiérrez

The Rhine, one of the main rivers in Europe, sources from the Swiss Alps in the canton of Grisons. The Alpine Rhine Valley extends over 90 km along the Rhine from its source in Switzerland via Liechtenstein to Austria. The Valley has a history of devastating flood events that date back to the 11th century. Today, around 300,000 people live in the lower Rhine Valley and numerous companies, including Leica Geosystems, flourish in this area. Due to the intense population and major economic activities in the Rhine Valley, damage potential from major flood events is estimated at EUR 10 billion.

To protect people, settlements, and as economic activities in the Valley, more room for flood runoff and water retention needs to be given to the Alpine Rhine. Therefore, the flood protection project “Rhein – Erholung und Sicherheit” (“Rhine - Recreation and Safety”) – or shortRhesi- seeks to increase the flow capacity of the Alpine Rhine from 3,100 m³/s to at least 4,300 m³/s on the international stretch between kilometre 65 at the junction of the tributary river Ill and km 91, where the Alpine Rhine discharges into Lake Constance. The project costs, funded equally by Austria and Switzerland, are currently estimated at EUR 1 billion.

“为了达到要求的洪水保护水平，需要更改高山莱茵河的通道几何形状，以增强沿项目周边的防洪。在Rhesi项目中，选择了一种非常现代的方法：而不是增加河水的堤防，以考虑到4,300 m的排放量增加³/s，所需的流程部分将通过将河流宽度从目前的60至70 m增加到将来增加数百米来创建。由于过去150年中各种河流恢复措施，目前的河道河道目前具有非常技术性的形状，它将通过这种情况，以模仿人类干预前模仿河流状态的近天然状态，”explains Florian Hinkelammert-Zens, environmental engineer at the Laboratory of Hydraulics, Hydrology and Glaciology (VAW) at the Swiss Federal Institute of Technology Zurich (ETH).

To evaluate the effects of the projected measures and to check the hydraulic calculations and assumptions of the Rhesi project, VAW of ETH Zurich has been commissioned with hybrid model experiments on behalf of the International Rhine Regulation (IRR) body. These investigations consist of two main parts: 1) experiments in a physical hydraulic model and 2) accompanying numerical simulations.

“Two key project sections are replicated consecutively at a scale of 1:50 in extensive hydraulic models. For each section, a flow length of approximately 5 km is replicated (around 110 m in model scale) with watercourse widths ranging from 250 m to 350 m (around 8 m in model scale),”says Hinkelammert-Zens。“At the same time, numerical computer models of the project were created to provide and evaluate the boundary conditions of the hydraulic models, to validate the results and to carry out sensitivity analyses.”

As a result, these two hydraulics models are among the biggest models of alpine rivers ever built, with average dimensions of 110 x 9 m. Both are located in an old factory building in Dornbirn, Austria, where ETH Zurich designed a water circuit with a discharge of 400 l/s. The system consists of a high-level tank, inlet and outlet basins, a water return line in the basement and a deep tank, from which the water is pumped back into the high-level tank (max. 400 l/s).

洪水建模的3D地形建模

“在洪水事件中，由于水排放和流速较高，河床会发生重大变化。因此，沉积物可以沉积在多个位置，导致水位上升，也可以侵蚀，例如在桥墩或河岸周围。两种情况都可能是危险的，对防洪产生负面影响。为了复制这些形态学变化，液压模型配备了可移动的河床。”Hinkelammert-Zens说。

观察不同沉积物负载的影响and various scenarios, a large number of scientific experiments with varying parameters (e.g. water discharge and sediment load) are conducted. By means of a laser scanner, the model topography is measured before and after every single experiment. The acquired data is then used to create terrain models which serve as a basis for the determination of areas where sedimentation and erosion occur in the riverbed.

从数据捕获到可操作的数据

右：Alpine Rhine的一部分的3D地形模型（在流动方向上查看） /左：实验结束后液压模型中的可移动河床

为了捕获每个实验之前和之后的地形数据，ETH Zurich的研究团队依赖于Leica Scanstation P20，Leica Geosystems目标和Leica TS02总站为了地理参考，激光扫描15个参考点。扫描仪P20安装在移动三脚架上，并部署在四个扫描位置上以捕获整个型号。扫描高度约为2.7 m-如果观看角度太陡并避免死角，则最大程度地减少阴影效果 - 在与设备的径向距离为10 m的径向距离下，分辨率为3 x 3 mm，可以获得具有非常低噪声的高质量数据。

After each experiment, the data is imported intoLeica Cyclone3D点云处理软件以注册数据并合并点云。此时，面积为4000 m²约有约2.5亿点代表。然后使用多边形“修剪”点云，以切断模型边界之外的数据点。然后将其余的数据点转换为网格单元，其细胞大小代表现实生活中的50 cm x 50 cm。最后，将地形数据转换为瑞士国家坐标系。

Right: visualisation of the observed changes in the riverbed in the hydraulic model after evaluating the laser scan (red: erosion on the outside of the curve, blue: sedimentation on the inside of the curve, viewed in flow direction)/ Left: laser scan in the experiment hall (viewed in flow direction)

“The 3D point clouds are used to create grid datasets with approximately 15 million grid cells with a resolution of 0.5 x 0.5 m, each of them representing one distinct point of time during the experiments. This data is then further processed in geo-information systems in order to create surface views as well as longitudinal and lateral profiles of the mobile riverbed. This enables us to compare different points in time of the experiment with each other,”Hinkelammert-Zens解释。

The referenced grid dataset can be used in GIS applications for various evaluations, including:

• Surface views: The grid values of the scan made at the beginning of the experiment are deducted from those made at the end of the experiment. In this way, theETH团队创建一种观点，使模型河床高度的相对差异可见。

• Transverse profiles: The team creates cross profiles at certain positions, extracting grid values to create lateral profiles. Using the scans before and after the tests, the experts can visualise the observed changes and compare them to the project goals.

• 纵向曲线：提取的跨轮廓平均用于纵向轮廓。通过比较实验前后的平均河床高程以及观察自然界的变化，专家团队可以验证液压模型。

Intermediate results and future steps

苏黎世Eth的VAW的调查已经为进一步发展的Rhesi项目提供了重要的投入。首先，通过复制过去的洪水事件对模型进行了校准。在此过程中，将液压模型中获得的水位和河床地形与全面的事件中捕获的数据进行了比较。成功完成此步骤后，液压模型适应了Rhesi预测的河流的未来形状。从那时起，已经模拟了各种长期情景和高洪水事件，以研究Rhesi项目对河流形态和水位的影响。

随着调查仍在进行中，只能引用中间结果。到今天为止，结果表明，瑞典项目的假设和预测是正确的，并且是详细详细阐述未来项目阶段的扎实基础。混合模型实验将持续到2022年夏季，探讨以下技术问题的答案：

• 砾石银行将在哪里定位？
• Where will depressions resp. scours occur and what will be their maximum depth?
• 必须保护河岸的深度，以防止侵蚀和搜查？
• How can bridge piers be secured against erosion and scouring?
• 在洪水事件中，桥梁在桥梁上的浮木数量是多少？对水位有什么影响？

这些科学实验的发现得到了Leica Geosystems的现实捕获技术的支持，是确保可持续的河流规划并确保Rhesi防亚博ag真人规律洪项目在技术上和经济上可行的基础。这种综合的洪水风险管理方法将大大降低洪水风险，并改善国际高山莱茵河的生态和娱乐价值。