Protecting the Alpine Rhine Valley from flooding

作者：Renata BarradasGutiérrez

莱茵河是欧洲的主要河流之一，来自格里斯森广州瑞士阿尔卑斯山的来源。高山莱茵河谷（Alpine Rhine Valley）沿着莱茵河（Rhine）从瑞士的来源延伸到90公里，并通过列支敦士登（Liechtenstein）到奥地利。山谷有毁灭性洪水事件的历史，可以追溯到11世纪。如今，大约30万人居住在莱茵河下部和许多公司，包括Leica Geosystems，在该地区蓬勃发展。由于莱茵河谷的强烈人口和重大经济活动，重大洪水事件的破坏潜力估计为100亿欧元。

为了保护人们，定居点和作为山谷中的经济活动，需要给高山莱茵河的洪水径流和保留水。因此，洪水保护项目“莱茵 - erholung und sicherheit”（“莱茵河 - 娱乐与安全”）或简短Rhesi- 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.

“To achieve the requested level of flood protection, the channel geometry of the Alpine Rhine needs to be altered to enhance flood protection along the project perimeter. In the Rhesi project, a very modern approach has been chosen: instead of raising the river’s levees to take account of the elevated discharge of 4,300 m³/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).

为了评估预计措施的效果，并检查了恒河部项目的液压计算和假设，苏黎世Eth的VAW已代表国际莱茵河调节（IRR）机构进行了混合模型实验。这些研究由两个主要部分组成：1）在物理液压模型中进行实验和2）伴随的数值模拟。

“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),”Hinkelammert-Zens说。“同时，创建了项目的数值计算机模型，以提供和评估液压模型的边界条件，以验证结果并进行灵敏度分析。”

结果，这两种液压模型是有史以来最大的高山河流模型之一，平均尺寸为110 x 9 m。两者都位于奥地利Dornbirn的一栋古老的工厂建筑中，苏黎世Eth设计了一个排放400 l/s的水路。该系统由一个高级水箱，入口和出口盆地，地下室中的水流线和一个深水箱组成，从中，水从中泵回高级水箱（最多400 L/s）。

3D terrain modelling for flood modelling

“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。

为了观察不同的沉积物负荷和各种情况的影响，进行了大量具有不同参数（例如水排出和沉积物负荷）的科学实验。通过激光扫描仪，在每个实验之前和之后都测量模型地形。然后，获得的数据用于创建地形模型，以确定河床中沉积和侵蚀的区域的基础。

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

To capture the topographical data before and after each experiment, the research team of ETH Zurich relies on aLeica ScanStation P20, Leica Geosystems targets and a Leica TS02total station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 into狮子旋风3D point cloud processing software to register the data and merge the point clouds. At this point, an area of 4000 m²is represented with approximately 250 million points. The point cloud is then ‘trimmed’ using polygons to cut-off the data points outside of the model boundaries. The remaining data points are then transformed into grid cells with a cell size representing 50 cm x 50 cm in real life. Finally, the topographical data is converted into the Swiss National Coordinate System.

右：评估激光扫描后，液压模型中观察到的变化的可视化（红色：曲线外部侵蚀，蓝色：曲线内部的沉积物，在流动方向上观察）/左：激光扫描在实验大厅（以流向查看）

“三维点云是用于创建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,”explains Hinkelammert-Zens。

引用的网格数据集可以在GIS应用程序中用于各种评估，包括：

• 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 teamcreates a view where the relative differences in the height of the model riverbed are visible.

• 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.

• Longitudinal profiles: The extracted cross profiles are averaged for the longitudinal profile. By comparing the averaged riverbed elevations before and after the experiments and by observing the changes in nature, the team of experts can validate the hydraulic model.

中级结果和未来步骤

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？
• 抑郁症将在哪里分解。发生冲突，它们的最大深度将是多少？
• 必须r多深iver banks be protected against erosion and scouring?
• 如何保护桥梁免受侵蚀和冲洗的侵害？
• What is the amount of driftwood clocked at bridges during flood events? What will be the effect on the water levels?

The findings of these scientific experiments, supported by reality capture technology from Leica Geosystems, are the basis to ensure sustainable river planning and assure that the Rhesi flood protection project is technically and economically viable. This integrated flood risk management approach will significantly reduce flood risks and improve the ecological and recreational value of the Alpine Rhine in the international stretch.