Natural vs anthropogenic streams in Europe: History, ecology and implications for restoration, river-rewilding and riverine ecosystem services

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordIn Europe and North America the prevailing model of “natural” lowland streams is incised-meandering channels with silt-clay floodplains, and this is the typical template for stream restoration. Using both published and new unpublished geological and historical data from Europe we critically review this model, show how it is inappropriate for the European context, and examine the implications for carbon sequestration and Riverine Ecosystem Services (RES) including river rewilding. This paper brings together for the first time, all the pertinent strands of evidence we now have on the long-term trajectories of floodplain system from sediment-based dating to sedaDNA. Floodplain chronostratigraphy shows that early Holocene streams were predominantly multi-channel (anabranching) systems, often choked with vegetation and relatively rarely single-channel actively meandering systems. Floodplains were either non-existent or limited to adjacent organic-filled palaeochannels, spring/valley mires and flushes. This applied to many, if not most, small to medium rivers but also major sections of the larger rivers such as the Thames, Seine, Rhône, Lower Rhine, Vistula and Danube. As shown by radiocarbon and optically stimulated luminescence (OSL) dating during the mid-late Holocene c. 4–2 ka BP, overbank silt-clay deposition transformed European floodplains, covering former wetlands and silting-up secondary channels. This was followed by direct intervention in the Medieval period incorporating weir and mill-based systems – part of a deep engagement with rivers and floodplains which is even reflected in river and floodplain settlement place names. The final transformation was the “industrialisation of channels” through hard-engineering – part of the Anthropocene great acceleration. The primary causative factor in transforming pristine floodplains was accelerated soil erosion caused by deforestation and arable farming, but with effective sediment delivery also reflecting climatic fluctuations. Later floodplain modifications built on these transformed floodplain topographies. So, unlike North America where channel-floodplain transformation was rapid, the transformation of European streams occurred over a much longer time-period with considerable spatial diversity regarding timing and kind of modification. This has had implications for the evolution of RES including reduced carbon sequestration over the past millennia. Due to the multi-faceted combination of catchment controls, ecological change and cultural legacy, it is impractical, if not impossible, to identify an originally natural condition and thus restore European rivers to their pre-transformation state (naturalisation). Nevertheless, attempts to restore to historical (pre-industrial) states allowing for natural floodplain processes can have both ecological and carbon offset benefits, as well as additional abiotic benefits such as flood attenuation and water quality improvements. This includes rewilding using beaver reintroduction which has overall positive benefits on river corridor ecology. New developments, particularly biomolecular methods offer the potential of unifying modern ecological monitoring with the reconstruction of past ecosystems and their trajectories. The sustainable restoration of rivers and floodplains designed to maximise desirable RES and natural capital must be predicated on the awareness that Anthropocene rivers are still largely imprisoned in the banks of their history and this requires acceptance of an increased complexity for the achievement and maintenance of desirable restoration goals.OSL dating from the Severn-Wye Basin was undertaken at the Geochronology Laboratories, University of Gloucestershire under grants from the EU Leader+ Programme (administered by English Heritage) and the Leverhulme Flood and Flow Project (RPG-2016-004)

Is riverbank vegetation important for the estimation of flood water levels?

Freshwater plants are one of the main components of the aquatic ecosystem and significantly influence river processes at different scales, and they are also affected by the river flow (Nikora, 2010; Nepf, 2012). Thus, a proper flood risk management requires to include understanding the processes of mutual interactions (flowbiota), which are still challenging (Nikora, 2010; Nepf, 2012). It is essential to know that such vegetation is a crucial component of the environment, which provides important tool for nature-based solutions for river engineering and management. Considering appropriate placement of plants along the stream, various possibilities for using vegetation as a nature-based solution may include facilitate sediment transport in the channel, control to direct overbank flows, and the reduction of scour and river channel erosion processes (Shields Jr. et al., 2017). However, a proper prediction of processes occurring in rivers with vegetated bank? (e.g., vegetationinduced turbulence) needs sufficient studies of vegetation seasonality due to its dynamic nature. Past approach to the subject of river management (e.g., Ree 1949) did not include the ecological meaning (wildlife habitat) of riverine vegetation and thus, all the actions were focused only on reducing the source of flow resistance by cutting the vegetation to reduce flooding (Nepf, 2012). Hence, current methods should be developed in such a way as to comply with the assumptions of finding the balance in predicting the channel resistance in the presence of vegetation between ecological management and flood control (Nilsson et al. 2005; Nepf, 2012). Flow-biota-sediment interactions, due to continuous vegetation development, are vulnerable to extensive knowledge gaps in the investigation linking the fluid mechanics, biomechanics, ecology and transport processes that prevent a full understanding of these phenomena (Nikora, 2010; Łoboda et al., 2018). To expand knowledge in this research field, the aim of this study is to investigate the effect of riverbank vegetation on the flood water levels, considering various riverbank vegetation coverage due to its variation throughout the annual seasons. For that purpose, the hydrodynamic model Delft3D Flexible Mesh will be used to simulate river flow hydrodynamics on the part of the Meuse river as a case study. This study will investigate various static vegetation scenarios considering seasonal changes in vegetation roughness and their life cycle, e.g., due to leaf loss or plant dying. The main focus will be drawn to short periods including before, during and after the flood event (i.e., period of approximately two weeks; starting two days before the flood event). As Nepf (2012) highlighted, vegetation is not distributed uniformly, which plays an important role in the reach-scale flow resistance. Thus, the proposed study will consider the density of plant coverage on the riverbanks as well as species variety

Environmentally-sensitive river management : assessment and mitigation of impacts on urban rivers

Includes bibliographies.Urban development and engineering works have resulted in the majority of rivers that drain urban areas being severely degraded, both ecologically and in terms of their potential amenity value. This dissertation explores the reasons for this "spiral of degradation" and it describes the ecological and social impacts on rivers caused by urban development, channelisation and canalisation. It then suggests possible measures to mitigate the impacts at the levels of the catchment, floodplain and river channel. The present cycle of degradation of urban rivers in the Cape Metropolitan Area (and elsewhere) can be halted. In addition, where degradation has already occurred, mitigation and rehabilitation are possible and could restore some of the lost conservation and ecological values, as well as the potential amenity, recreation and education functions. Early colonisation of Cape Town by Europeans inflicted severe impacts on the rivers surrounding and passing through the city. These included: catchment degradation, water abstraction, the disposal of unpurified sewage and industrial effluents, removal of riparian forests, clearing of instream vegetation and the draining of wetlands. During the 20111 century, many urban rivers have been "improved" by straightening or confining within rectangular concrete-lined canals in order to protect urban development in flood-prone areas. The unquestioning faith in technology during this period and the attitude that human ingenuity could "improve nature" are now regarded by the scientific community, together with some local and regional authorities and informed members of the public, as mistakes that resulted in ecological and environmental degradation. These technical solutions merely treated the symptoms of the problem without recognising, let alone attempting to treat, the causes, that is poor catchment and floodplain management. However, there is still a public demand for canalisation of the remaining "natural" rivers in the greater Cape Town area and beyond. At the same time, there has been an increase in environmental awareness, as well as a growing appreciation of the value of holistic and multi-objective planning in the engineering and planning professions. This dissertation aims to assess the impacts of urbanisation, channelisation and canalisation on the aquatic ecosystem and socio-economic environment of urban rivers, and to develop possible measures to mitigate these impacts

Review of Published Climate Change Adaptation and Mitigation Measures Related with Water

Stronger manifestation of climate change impact on global water cycle, water resources, and aquatic ecosystems has given a strong impetus to the development of adaptation measures in water management. The present report gives an insight to potential and planned water related measures tackling climate change causes and consequences, which have been included in the Member States River Basin Management Plans, published in various reports and scientific literature mostly within the last decade. The database of about 450 measures analysed in this report and given in a separate Annex as an Excel spreadsheet, constitutes the most important part of this deliverable. In the context of this report, measures are defined as practical steps or actions taken to (i) reduce the sources or enhance the sinks of greenhouse gases, (ii) to decrease the vulnerability of water resources and aquatic ecosystems to climate change, or (iii) enhance the knowledge base on climate-water relationships and increase the societal capacity to take right decisions on this matter. By strategic approach, the measures belong either to planned adaptation, which specifically focuses on climate change and variability, and autonomous adaptation, which goals are not specifically climate related, but have an added value in improving resilience to climate change. Separate chapters are dedicated to each of the five specific adaptation strategies addressed in the REFRESH Project. The present report is of relevance to the 7th EU Framework Programme, Theme 6 (Environment including Climate Change) project REFRESH (Adaptive strategies to Mitigate the Impacts of Climate Change on European Freshwater Ecosystems, Contract No.: 244121), to JRC Thematic Area 3 (Sustainable management of natural resources) foci on CC, to the European Clearing House mechanism on CC, and to the EC Blueprint on Water.JRC.DDG.H.5-Rural, water and ecosystem resource

Chalk rivers: nature conservation and management

This is a handbook about Chalk Rivers Nature Conservation and Management from March 1999 by the Water Research Centre and commissioned by English Nature and the Environment Agency, primarly provides an objective basis for formulating conservation strategies for relevant Site of Special Scientific Interest (SSSIs) and Special Areas of Conservation (SACs). It was also seen as being applicable to chalk rivers more generally and has increasingly been regarded as important to the work of the Biodiversity Action Plan Steering Group on chalk rivers, which is led by the Environment Agency. This report contains information on characteristic wildlife communities, their habitat requirements and the ecological impact of activities that are relevant to the chalk river environment. It provides guidance on setting management objectives, options for mitigating impacts, and measures for the maintaining and enhancing the river channel, riparian and floodplain areas associated. The term `chalk river’ is used to describe watercourses dominated by groundwater discharge from chalk geology, including those that flow over a range of non-chalk surface geologies at various points along their length. England contains numerous examples of this river type, located in and downstream of areas of outcropping chalk in the south, East Anglia and up into Lincolnshire and Yorkshire. Indeed, England has the major part of the chalk river resource of Europe. A number of chalk rivers have been designated as Sites of Special Scientific Interest (SSSIs) and English Nature and Environment Agency work drawing up joint conservation strategies