Riverine floods cause increasingly severe damages to human settlements and infrastructure. Ecosystems have a natural capacity to decrease both severity and frequency of floods. Natural flood regulation processes along freshwaters can be attributed to two different mechanisms: flood prevention that takes place in the whole catchment and flood mitigation once the water has accumulated in the stream. These flood regulating mechanisms are not consistently recognized in major ecosystem service (ES) classifications. For a balanced landscape management, it is important to assess the ES flood regulation so that it can account for the different processes at the relevant sites. We reviewed literature, classified them according to these mechanisms, and analysed the influencing ecosystem characteristics. For prevention, vegetation biomass and forest extent were predominant, while for mitigation, the available space for water was decisive. We add some aspects on assessing flood regulation as ES, and suggest also to include flood hazard into calculations.

The contamination of waters with nutrients, especially nitrogen and phosphorus originating from various diffuse and point sources, has become a worldwide issue in recent decades. Due to the complexity of the processes involved, watershed models are gaining an increasing role in their analysis. The goal set by the EU Water Framework Directive (to reach “good status” of all water bodies) requires spatially detailed information on the fate of contaminants. In this study, the watershed nutrient model MONERIS was applied to the Hungarian part of the Danube River Basin. The spatial resolution was 1078 water bodies (mean area of 86 km²); two subsequent 4 year periods (2009–2012 and 2013–2016) were modeled. Various elements/parameters of the model were adjusted and tested against surface and subsurface water quality measurements conducted all over the country, namely (i) the water balance equations (surface and subsurface runoff), (ii) the nitrogen retention parameters of the subsurface pathways (excluding tile drainage), (iii) the shallow groundwater phosphorus concentrations, and (iv) the surface water retention parameters. The study revealed that (i) digital-filter-based separation of surface and subsurface runoff yielded different values of these components, but this change did not influence nutrient loads significantly; (ii) shallow groundwater phosphorus concentrations in the sandy soils of Hungary differ from those of the MONERIS default values; (iii) a significant change of the phosphorus in-stream retention parameters was needed to approach measured in-stream phosphorus load values. Local emissions and pathways were analyzed and compared with previous model results.

This study aimed to investigate the occurrence and concentration patterns of three groups of trace contaminants—potentially toxic elements (PTEs), polycyclic aromatic hydrocarbons (PAHs), and per‐ and polyfluoroalkyl substances (PFASs)—in river catchments with contrasting land use and landscape characteristics. A second objective was to relate the concentrations in suspended particulate matter (SPM) to those in soils and to catchment attributes in order to identify dominant transport processes and contaminant sources. A spatially explicit monitoring campaign was conducted in three river catchments of the central Danube River Basin: Zagyva and Koppány in Hungary and Wulka in Austria. Composite soil samples (∼10 per catchment, totaling ∼200 subsamples) were collected from forest, pasture, and cropland areas. SPM was collected using both passive and active samplers under base‐flow and high‐flow conditions. The results revealed strong spatial variability in concentrations for five of seven PTEs, all PAHs, and eight of 10 PFASs. Substances predominantly deposited atmospherically—such as PAHs and several PFASs—were more concentrated in forest soils compared to pasture and cropland. Base‐flow SPM samples were often more contaminated than high‐flow samples, especially for PAHs and some PTEs. Concentrations in SPM were generally correlated with soil concentrations, suggesting that erosion‐related transport of these chemicals may be significant in rural catchments. However, enrichment patterns and correlation strength varied by substance group and land use type. These findings support the use of parallel SPM and soil sampling for improving empirical emission modeling and source identification in catchments with mixed land use.