Determining return water levels at ungauged coastal sites: a case study for northern Germany
Determining return water levels at ungauged coastal sites: a case study for northern Germany
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DOI：
10.1007/s10236-015-0814-1
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发表时间：
2015-04-01
期刊：
影响因子：
2.3
通讯作者：
Jensen, Juergen
中科院分区：
文献类型：
--
作者：
Arns, Arne;Wahl, Thomas;Jensen, Juergen
我们估计重现期和极端静止水位的高度脆弱和历史和文化上重要的小沼泽岛屿被称为Halligen，位于瓦登海近海的北方德国的海岸。这是一项具有挑战性的任务，因为该地区只有很少的水位记录，而且它们目前太短，无法应用传统的极值分析方法。因此，我们使用区域频率分析（RFA）方法。这源于水文学，但以前曾在几项海岸研究中使用过，目前也由负责研究区域海岸保护的地方联邦管理部门使用。RFA使我们能够通过将水文信息从测量站点转移到相关的未测量站点来间接估计回报水平。我们的分析强调，这种方法有一些缺点，可能会过度或低估回报水平相比，直接分析使用站数据。为了克服这些问题，我们提出了一种替代方法，结合数值和统计模型。首先，我们制作了一个数值多年代际模型后报的水位为整个北海。根据验潮仪记录的信息，对事后预报的水位进行了偏差校正。因此，模拟水位与实测水位在计量站点吻合良好。偏差校正，然后在空间上插值，以获得在研究区域的每个沿海和岛屿模型网格点的模拟水位的校正函数。使用推荐的程序进行极端值分析，从一个同伴的研究，返回水位适合沿海基础设施设计的估计连续沿着整个海岸线的研究区，包括近海岛屿。类似的方法也可应用于世界上验潮仪观测稀少的其他区域。
We estimate return periods and levels of extreme still water levels for the highly vulnerable and historically and culturally important small marsh islands known as the Halligen, located in the Wadden Sea offshore of the coast of northern Germany. This is a challenging task as only few water level records are available for this region, and they are currently too short to apply traditional extreme value analysis methods. Therefore, we use the Regional Frequency Analysis (RFA) approach. This originates from hydrology but has been used before in several coastal studies and is also currently applied by the local federal administration responsible for coastal protection in the study area. The RFA enables us to indirectly estimate return levels by transferring hydrological information from gauged to related ungauged sites. Our analyses highlight that this methodology has some drawbacks and may over- or underestimate return levels compared to direct analyses using station data. To overcome these issues, we present an alternative approach, combining numerical and statistical models. First, we produced a numerical multidecadal model hindcast of water levels for the entire North Sea. Predicted water levels from the hindcast are bias corrected using the information from the available tide gauge records. Hence, the simulated water levels agree well with the measured water levels at gauged sites. The bias correction is then interpolated spatially to obtain correction functions for the simulated water levels at each coastal and island model grid point in the study area. Using a recommended procedure to conduct extreme value analyses from a companion study, return water levels suitable for coastal infrastructure design are estimated continuously along the entire coastline of the study area, including the offshore islands. A similar methodology can be applied in other regions of the world where tide gauge observations are sparse.