In the midst of relentless rainfall, Hesse's flood situation teeters on the edge of urgency. Over Christmas Eve, some river gauges surpassed the reporting level 3 threshold, signaling serious flooding concerns. By morning, an additional 30 gauges surpassed reporting level 1 and 9 exceeded level 2. Various roads became impassable, exacerbating commuting challenges.
North-eastern Hessian districts, including Hersfeld-Rotenburg and Werra-Meißner, were particularly hard-hit. The districts saw road closures due to flooding, with main roads like 29, 3238, 3242, and 3359 all affected. The HLNUG (Hessian State Agency for Nature Conservation, Environment, and Geology) attributed these critical conditions to the anticipation of continuing rainfall, particularly in the Rothaargebirge, Westerwald, and Vogelsberg regions.
Specifically, the rivers Diemel, Eder, Fulda, and the Lahn, along with their western tributaries, were at risk of further flooding. Predictions pointed to increased rainfall, further impeding drainage systems and exacerbating flood concerns. Thankfully, the heavy rainfall had begun to subside in certain regions, with floodwaves flowing downstream, yet this shift resulted in increased flooding in lower-lying areas.
Reporting level 2 was implemented in various northern Hessian areas, including Dalwigksthal/Orke, Schmittlotheim/Eder, Haueda/Diemel, Fulda Bronzell, and Bad Hersfeld 1 gauges, as well as at other locations. Previously, reporting level 3 had even been briefly surpassed in certain locations. Hesse's Werra and Weser gauges saw reporting level 1 exceeded, while the Werra gauge reached reporting level 2 and the Bad Karlshafen/Weser gauge swelled beyond reporting level 3 due to the confluence of incoming floodwaves from Thuringia with Hessian tributaries.
In the Lahn catchment area, reporting level 2 was recognized at the Gießen-Klärwerk/Lahn and Leun/Lahn gauges. Elsewhere, large river basins within and beyond Hesse witnessed raised reporting levels. The 545-centimeter level was still in effect in the Mainz/Rhine gauge on the Hessian Rhine sector, while the Rockenau/Neckar gauge still grappled with level 2 but trending downwards.
Reaching level 1 indicates that a water body has reached capacity, with overflow occurring in some locations. Once level 2 is attained, properties near the banks will see significant flooding, with occasional cellar overflow. Beyond level 2, towns and villages become encased by floodwaters, making roads impassable.
The German Weather Service anticipated an additional 5 to 15 liters of rain for Christmas Eve. Adding to the existing 30 to 50 liters of rain that had already fallen in the northern Hessian mountains, and occasionally exceeding 60 liters, the impending rainfall shall bring about further challenges. Intermittent rainfall is expected through the Christmas night into Monday, with the northern Hessian-border region forecasted to receive 15 to 20 liters of rain per square meter, and up to 25 liters in select areas. A significant concern lies with the Eder River flood peak in Bad Hersfeld, as heavy rain and melting snow threaten to worsen flood conditions in Hesse.
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Continuous rainfall and melting snow play pivotal roles in the emergence of flood conditions in Hesse, and impacts on flood situations are shaped by various factors:
- Precipitation increases: Northern Germany, including Hesse, has observed an increase in winter precipitation, leading to more frequent and intense flooding events. Constrained drainage systems are further burdened as a consequence.
- Lemon's law and floods: The timing and intensity of snowmelt can significantly influence flooding; when the snowmelt occurs earlier, flood peaks may emerge sooner in regions like East Germany and parts of Western Europe, severely testing flood protection measures.
- Compound flooding: The combination of heavy rainfall and snowmelt creates more severe compound flooding situations, wherein both riverine and coastal flooding concurrently challenge traditional flood management frameworks.
- Changes in the water cycle: Climate change is transforming global precipitation patterns and quantities, leading to an increase in extreme weather events and decreasing soil moisture in certain regions, ultimately resulting in more surface runoff.
Though Hesse is not singled out in the news sources as a region with distinct challenges compared to other parts of Northern Germany, increased precipitation and earlier snowmelt trends are widely applicable to various Northern European regions, including Hesse. To mitigate the impacts of climate change on flood situations, there is a growing need for effective long-term coastal development strategies and integrated flood management approaches.
