## 1 Introduction  
River ecosystems are influenced by a variety of anthropogenic factors. Their structure and function respond to both abiotic and biotic factors. Abiotic components such as hydrology [1; 2; 3], geomorphology [4; 5], hillslope-riparian interactions [6], groundwater-surface-water interactions [7; 8], nutrient availability [9; 10; 11], light [12], dissolved gases [13], and water chemistry [14], play an important role in the development of biological communities in streams and rivers. These external determinants may be regarded as bottom-up controls of the trophic chain [15]. The interactions in logic ecosystemsare often interrupted by man-made changes in the river channel, including the straightening of naturally meandering bends, embankments, bottom deepening, as well as intensive land use in their catchment areas. Therefore, these activities induce changes in both water quality (WQ) [10], and the type and quantity of energy and food sources (organic matter and nutrients) that reach the ecosystem [13; 16]. River restoration is a process of returning an ecosystem to a pre-disturbance state [16; 17]. To achieve that goal, both the structure and the function of rivers and floodplains should be recreated by re-establishing their original hydrological attributes and the associated physical, chemical, and biological characteristics [18; 19]. River and floodplain restoration requires subsequent monitoring of abiotic and biotic factors, and the identification of ecosystem stressors, that provide design guidance for targeted enhancements [18; 19; 20; 21]. Post-project monitoring supports continued advancements in restoration approaches to biologically impaired rivers. Waters flowing through rural areas have numerous functions and constitute a valuable component of the natural environment [20]. Human efforts aiming to adapt aquatic systems for agricultural and residential purposes have induced both physical and chemical alterations in river channels [10; 13; 21]. River regulation, reinforcement of river banks, decrease in river bed slopes, and the construction of hydraulic systems and buildings inhibit or prevent the migration of flora and fauna. Anthropogenic disturbances alter both geographic features and the natural balance of water reaching the floodplain. Intensive farming is commonly regarded as a non-point source of pollution, which leads to significant deterioration of water quality, as well as significant changes in water runoff dynamics. The associated water quality problems can affect the ecology and economy of riparian areas by decreasing the productivity of fisheries and reducing the recreational appeal of those areas [21; 22]. The growing environmental impacts of nutrient pollution have prompted efforts to track pollution sources and manage nutrient loads in streams and rivers [21; 22]. The loss of nutrients (mainly N and P) from catchments can be effectively minimized on-site through multiple strategies, including reducing fertilizer inputs, fixing leaky sewer systems, and banning the use of phosphates in detergents [21; 22; 23]. However, in many regions, good management practices that aim to reduce pollution sources and loads meet social, political, and economic resistance. In Europe, natural river corridors and floodplains are rare and threatened by human activity. Due to growing levels of awareness that streams fulfil important ecological, societal, and economic functions, scientists, water authorities, NGOs, and political exponents have rendered river restoration a trendy and popular discipline. The restoration of streams, rivers, wetlands, and floodplains has become a pivotal element of catchment management to counteract anthropogenic degradation, depletion of river health and water resources, and to increase overall biodiversity and ecosystem service provisioning.