Suchergebnisse

Abstract
Background
Floods, especially flash floods, are the major transporting agent for fluvial sediments, whose pollution is a global concern. As floods result in the dispersion of and exposure to these sediments, a profound understanding of sedimentary dynamics during flood events and the related pollutant dispersion is of relevance. However, the characteristics of extreme flood events concerning pollutant dynamics are insufficiently known so far.

Results
In a Central European catchment impacted by intense industrial activities and former mining, over the course of five years, we surveyed six high-discharge events, five of them approx. bankfull discharge and one major flash flood event, supplemented by sampling of bank sediments. Fluvial sediments were analyzed for elemental composition by X-Ray fluorescence and for grain size distribution of the fine faction by laser diffraction. By applying a local enrichment factor, trace metal(loid) signatures in these sample sets were compared. Furthermore, Positive Matrix Factorization was used to investigate the trace metal(loid)s' sources.
The sediments deposited by minor flooding had continual trace metal(loid) signatures. However, for the extreme event, significant divergencies arose and persisted for the following years: The enrichment of anthropogenically influenced elements increased, with a slowly decreasing trend in the subsequent two years. Naturally dominated metal(oid)s decrease in enrichment without indicating a return to original levels. In contrast, other elements were insensitive to the extreme event. Positive Matrix Factorization identified anthropogenic influences in elements originating from copper and lead processing and mining activities. Furthermore, bed sediments and a natural background factor were found to dominate the non-anthropogenically influenced metal(loid)s.

Conclusions
In between extreme events, winnowing processes slowly alter the elemental composition of bed sediments. The depletion of such sediments due to the flash flood proves catchment-wide flushing, which induces a natural resetting of the geochemical signals. This ability to renew is an integral part of resilience in fluvial systems. This mechanism is disturbed by industrial activities in floodplains. The exceptional flooding reaches infrastructure that is assumed to be safe and, therefore, unprotected. These additional sources can shift flood sediments' trace metal(loid) signature, which has a long-lasting impact on the catchment sediments. However, the modifications depend on the flooding extent, possible emitters, and protection measures.

AbstractClimate, geology, geomorphology, soil, vegetation, geomorphology, hydrology, and human impact affect river–floodplain systems, especially their sediment load and channel morphology. Since the beginning of the Holocene, human activity is present at different scales from the catchment to the channel and has had an increasing influence on fluvial systems. Today, many river–floodplain systems are transformed in course of river restorations to "natural" hydrodynamic and morphodynamic conditions without human impacts. Information is missing for the historical or rather "natural" as well as for the present-day situation. Changes of the "natural" sediment fluxes in the last centuries result in changes of the fluvial morphology. The success of river restorations depends on substantial knowledge about historical as well as present-day fluvial morphodynamics. Therefore, it is necessary to analyze the consequences of historical impacts on fluvial morphodynamics and additionally the future implications of present-day human impacts in course of river restorations. The objective of this review is to summarize catchment impacts and river channel impacts since the beginning of the Holocene in Europe on the fluvial morphodynamics, to critically investigate their consequences on the environment, and to evaluate the possibility to return to a "natural" morphological river state.

AbstractBackgroundOver the last 200 years, the courses of most European rivers have experienced significant irreversible changes. These changes are connected to different kinds of anthropogenic river use and exploitation, which have varied from running water mills and rafting to large-scale hydroelectric power plants, industrial water withdrawal and flood protection measures. Today, in most developed countries, water quality and ecological river development are important factors in water management. The aim of this study is to evaluate the specific impacts of different time periods during the last 200 years on river courses and their effects on current river management using the example of the 165-km-long German Rur River (North Rhine-Westphalia). The Rur River is a typical central European upland-to-lowland river whose catchment has been affected by various phases of industrial development.MethodsIn this study, a range of morphological changes over the last 200 years are determined based on historic maps and up-to-date orthophotos. River length, sinuosity, oxbow structures, sidearms and the number of islands are used to investigate human impact. The results are correlated with historic time periods.ResultsThis analysis shows that river straightening increases, especially during the Industrial Revolution, even without direct hydraulic channelization. The period and grade of river straightening have a direct morphodynamic impact on today's river restorations. Since the Rur River is a typical upland-to-lowland river, the results show an additional impact by geofactors, such as landform configurations.ConclusionsMorphodynamic development is correlated with five historic periods of industrial development between 1801 and 2019 up to the introduction of the EU—Water Framework Directive (EU-WFD). Each period shows a different influence on the watercourse, which is connected with human intervention. Even if worldwide comparisons show that the five historical phases differ slightly in their timing between regions, they are applicable to other study areas.

Abstract
Background
This study explores morphologic changes in the Ahr River, Germany, caused by the high-energy flood in mid-July 2021. This study aims to assess the flood's significance as a morphological driver using the Lateral Mobility Index (LMI), as well as the impact of infrastructure on morphodynamics in terms of the formation of mud deposits and stagnant water pools, considering three focus areas of about 1 to 5 km river length. The three focus areas cover differences in the valley morphology as well as near natural and anthropogenically affected sections.

Results
The LMI is derived from orthophotos from 1998 to 2022, and based on the surface area of the old and the new channel. It describes the sum of new and abandoned channel area in relation to the previous channel area. For the 2021 high-energy event, an increased LMI suggests an increasing change in river course and morphology. Post-flood, the LMI in focus areas 1 (furthest upstream, LMI of 1.5) and 3 (at the Rhine confluence, LMI of 3.2) surpasses the historic LMI by a factor of about 3. Focus area 3 exhibits the highest activity, while focus area 2 (LMI between 0.25 and 0.70) the lowest. The area of mud deposits and stagnant water pools increased immediately after the flood, especially in focus area 3. Over the following months, initial post-flood mud deposits not only washed away but also rebuilt to some degree later on.

Conclusions
The LMI enabled to quantitatively identify a rare and significant morphological disruption in the Ahr River's lateral development in three focus areas, and thus, serves as additional proof that the flood of mid-July 2021 was a high-energy event impacting the local river geomorphology. Infrastructure impacted the formation of mud deposits and stagnant water zones during and after the flood, with additional influence from factors such as driftwood and valley width. The data suggested a phase of resuspension of sediments after the flood, likely due to cleanup and ad hoc river management, highlighting the need for continued river monitoring.

Abstract
Background
Archaeological sites are increasingly threatened by climate-related hazards. In response, heritage management authorities initiated projects to document damage and plan risk assessment measures. We present a project initiated after the heavy rainfall and subsequent flood event of July 2021, which involved extensive fieldwork to document the damage to archaeological sites in the Rhineland. We use this database to characterise and assess the damage and investigate site-specific and geospatial factors to identify potential predictive parameters for site damage.

Results
During fieldwork, we found that the flood damaged 19% of the 538 archaeological sites surveyed. The majority of damaged sites are relatively recent, dating from the medieval or modern periods, and are associated with the use of water power. Damage was mainly caused by erosion, floating debris and washout, e.g. mortar. In a case study, we tested the option of comparing pre- and post-disaster Airborne Laser Scanning elevation data to identify damages. It showed that not only the damage detected during fieldwork was found but also additional areas of loss. In general, however, and quantified based on the entire dataset, the ordnance survey Airborne Laser Scanning data were of limited use for monitoring flood-related damage and could not replace fieldwork. Our statistical analysis of possible risk factors, including both site characteristics and geospatial parameters, using Naïve Bayes Modelling and chi-squared tests, showed that no set of parameters could consistently predict the preservation or damage of archaeological sites across all catchments. In contrast, some external geospatial factors correlated with the occurrence of damage.

Conclusions
The study highlights both the strengths and limitations of the approaches used to assess and predict the damage to the archaeological heritage in the 2021 flood zones of the Rhineland. It also demonstrates the complexity of the data and spatial processes involved, which limits generalisation but can still inform decision-making for archaeological site management and on-site protection measures in flood-prone areas. With the prospect of more frequent heavy rainfall due to climate change, the specific needs of the archaeological heritage should be integrated into broader prevention and disaster management plans.

AbstractThe flood event in July 2021 in the uplands of the Eifel-Ardennes mountains in Germany, Belgium and The Netherlands and their foreland was caused by heavy rainfall and resulted in one of the largest flood disasters in Western Europe for decades. Due to climate change, it can be assumed that such events will become more frequent in future. Even though such extreme flood can happen at any time, the consequences and impacts can be significantly reduced by appropriate technical and non-technical measures. However, such measures always require a comprehensive understanding and knowledge of previous events and comparable processes. Therefore, this special issue aims at collecting the scientific evaluation and its implications of the 2021 extreme summer flood. This editorial serves as an introduction for an article collection published in the journal Environmental Sciences Europe, providing an overview of the current state of integrative assessment of the 2021 summer flood in Central Europe.

Abstract
Background
The flood in July 2021 is considered one of the largest flood disasters in Western Europe in decades, with massive socio-economic consequences. The potential emission and remobilization of anthropogenic pollutants can lead to additional environmental consequences, which need to be addressed in long-term mitigation strategies. The Inde River and its tributary, the Vichtbach River, form a catchment located at the transition from the low mountain ranges of the Eifel to the lowlands of the Lower Rhine Embayment in Germany. The area has been an industrial and mining hotspot for centuries, making it a high-risk area for flood sediment pollution. The present study provides an ecotoxicological screening of flood sediments of the Vicht–Inde catchment to gain an impression of the degree of contamination by organic pollutants by means of in vitro effect-based method. Sediment samples were collected within days after the flood and fractionated prior to biotesting, and supportive instrumental geochemical analysis was performed.

Results
Flood sediments did not reveal estrogenic potential, which was included in the testing strategy as a relevant endpoint for industrial chemicals and untreated wastewater. In contrast, moderate-to-high dioxin-like activity was observed in 70% of the sediment samples with a peak dioxin-like potential at the restored section of the Inde. Overall, four hotspot samples were identified as at risk, which aligned mostly with the high concentration of organic pollutants including PAHs and PCBs. The fractionation allowed the identification of PAHs and their derivates as the most likely toxicity drivers for dioxin-like activity in the sediments of the Vicht–Inde catchment.

Conclusion
The results provide first information on the prioritization of hotspot locations at risk for a detailed ecotoxicological profiling and a post-flood monitoring of organic contamination. The identified sinks of contamination in the floodplain areas can be considered a source for remobilization of pollution in future flood events, which is highly relevant for the receiving Rur River.

Abstract
Background
Because of global climate change, extreme flood events are expected to increase in quantity and intensity in the upcoming decades. In catchments affected by ore mining, flooding leads to the deposition of fine sediments enriched in trace metal(loid)s. Depending on their concentration, trace metal(loid)s can be a health hazard. Therefore, exposure of the local population to flood sediments, either by ingestion (covering direct ingestion and consuming food grown on these sediments) or via inhalation of dried sediments contributing to atmospheric particulate matter, is of concern.

Results
The extreme flood of July 2021 deposited large amounts of sediment across the town of Eschweiler (western Germany), with the inundation area exceeding previously mapped extreme flood limits (HQextreme). These sediments are rich in fine material (with the < 63 µm fraction making up 32% to 96%), which either can stick to the skin and be ingested or inhaled. They are moderately to heavily enriched in Zn > Cu > Pb > Cd > Sn compared to local background concentrations. The concentrations of Zn, Pb, Cd, Cu, and As in flood sediments exceed international trigger action values. A simple assessment of inhalation and ingestion by humans reveals that the tolerable daily intake is exceeded for Pb. Despite the enrichment of other trace elements like Zn, Cu, Cd, and Sn, they presumably do not pose a risk to human well-being. However, exposure to high dust concentrations may be a health risk.

Conclusions
In conclusion, flood sediments, especially in catchments impacted by mining, may pose a risk to the affected public. Hence, we propose to (I) improve the flood mapping by incorporating potential pollution sources; (II) extend warning messages to incorporate specific guidance; (III) use appropriate clean-up strategies in the aftermath of such flooding events; (IV) provide medical support, and (V) clue the public and medical professionals in on this topic accordingly.

Graphical Abstract

Abstract
Background
The decision of the German federal government to cease lignite mining until 2038 or—if possible—already earlier until 2030, will cause manifold transition processes in the remaining lignite mining districts of Germany. The two largest districts are located in geographically opposite regions: The Rhineland in the western part and Lusatia in the east of Germany. As particularly these two mining districts will experience severe changes in their socioeconomic as well environmental conditions, the federal government has adopted comprehensive economic support measures. However, the environmental changes will also cause altered ecosystem functions and services to be provided by the future post-mining landscapes.

Results
In this paper, the two main lignite-producing regions of Germany are compared with regard to their natural and cultural settings. The economic situation and its history are reflected and differences are outlined. Part of the disparities in the cultural development can be explained by very different natural conditions, especially edaphic factors and climatic situation. Because of dissimilar geological settings, different mining technologies were developed and are in use in the two regions with distinct effects on the resulting post-mining landscapes.

Conclusion
The long-standing and manifold lignite mining activities have radically restructured the landscapes in Lusatia and the Rhineland. With the ongoing decline of the mining industry and its complete cessation, presumably within the next decade, both regions will alter their faces significantly. These changes offer both challenges but also opportunities with respect to the post-mining landscapes and their ecosystem services they are going to provide. The prerequisites for a positive socioeconomic development and for sustainable land-use concepts that also consider ecological aspects are different for both regions. However, or especially because of these differences, the knowledge exchange and experience transfer between both mining regions are pivotal for the success of this extensive transformation process.

Supraregional (palaeo)geoecological studies require detailed knowledge of the distribution of aeolian sediments and their sources. Such spatial data can be visualised and shared in maps, but often these are constrained in their resolution or extent. This is the case for the Carpathian Basin, where cross-border maps are not detailed enough to answer many research questions. Problems occur especially along political borders due to different geological mapping standards and varying lithological definitions. Using a Geographic Information System (GIS), we compiled a map showing the distribution of loess and related Quaternary sediments in the Carpathian Basin, with unprecedented detail. We vectorised and analysed existing data (mainly from geological maps) and combined and transferred these into a common (loess) sediment classification system. This cross-border map shows the distribution of aeolian sediments in the Carpathian Basin at a scale of 1:1,500,000. For the northwestern and the southern Carpathian Basin, we added maps that clarify the extent of late Pleistocene and Holocene terrace and floodplain deposits, which were merged in the to highlight the predominant dust source areas for this region.