LaRiMo - A simple and efficient GIS-based approach for large-scale morphological assessment of large European rivers

Multicomponent assessment of the impact of hydropower cascade on fish metrics

The water sector is one of the priority areas of the European Union; therefore, legislation encourages the development of methods to protect the river ecosystem. The key to this is the characterization of the river's physical features with respect to ecological quality. Rivers are a complex system in which geomorphic conditions, hydrological regime, and ecological indicators interact. The group of hydropower plants (HPPs) that forms a hydropower cascade disturbs the natural continuity of river system components. Analysis of the spatial and temporal alterations in the river environment is important for understanding the potential impact of the hydropower cascade on ecological indicators. In a current study, the multicomponent assessment was used to evaluate the impact of the hydropower cascade of five HPPs on fish metrics as ecological indicators in the case study Varduva River. The research involved field surveys to collect hydrological data in highly affected ungauged river to estimate indicators of hydrologic alterations under HPPs operation, use of Unmanned Aerial Vehicles and digital photogrammetry to map geomorphic units, fish sampling to estimate composition of fish species and guilds, and fish habitat availability modelling based on the collected data and the conditional habitat suitability criteria using the MesoHABSIM modelling approach. Results revealed that the technical characteristics of HPPs determined their individual operation mode, which had a crucial impact on the hydrologic alterations of the river and, together with the distance between the dams, on the variation of fish metrics in the hydropower cascade. The intensive operation of the hydropower cascade created adverse effects for intolerant fish but was advantageous for tolerant fish species. The proposed HPP multimetric correlated with the fish metrics and showed similar tendencies between HPPs as habitat integrity index (IH), derived from MesoHABSIM modelling.

A Comparative Evaluation of Hydromorphological Assessment Methods Applied in Rivers of Greece

The ecological assessment of all surface water bodies in Europe according to the Water Framework Directive involves the monitoring of biological, physicochemical and hydromorphological quality elements. For the hydromorphological assessment in particular, there are numerous methods that have been developed and adopted by EU member countries. With this study, we compared three different methods (River Habitat Survey, Morphological Quality Index and River Hydromorphology Assessment Technique) applied in 122 river reaches that are part of the National Monitoring Network of Greece. The main objectives were (a) to identify whether different assessment systems provide similar classifications of hydromorphological status and (b) to distinguish strengths and weaknesses associated with the implementation of each method. Our results show that the River Hydromorphology Assessment Technique (RHAT) and the Morphological Quality Index (MQI) resulted in the same classification for 58% of the studied reaches, while 34% of the remaining cases differed by only one quality class. Correlations between the two indices per river type (ICT) showed that the two indices were strongly correlated for water courses located at low altitudes. Concerning the HMS index of the River Habitat Survey (RHS), which is an index that reflects the overall hydromorphological pressure, it showed larger differences with the other two indices, mainly because it classified more sites as “Poor” and “Bad” quality classes. Based on our results, we recommend that the two indices, RHAT and MQI, can be implemented complementary to the RHS for providing a rather easy and quick assessment of the overall hydromorphological status, at least until a national hydromorphological database is compiled that will allow for the proper adaptation of the Habitat Quality Assessment (HQA) index.

Hydro-Morphological Assessment of Dittaino River, Eastern Sicily, Italy

The present conditions of the Dittaino River were investigated by using tools addressing different components of the IDRAIM (stream hydro-morphological evaluation, analysis, and monitoring system) procedure. After the segmentation of the river, the Morphological Quality Index (MQI) and the Morphological Dynamic Index (MDI) were assessed to analyze its morphological quality and to classify the degree of channel dynamics related to progressive changes occurring in the relative long-term (i.e., 50–100 years), respectively. The results show that 45% and 22% of the analyzed reaches (mainly located in highest zones of the hydrographic network) were, respectively, of high and good quality. The MQI class decreased to good and then to moderate in the downstream direction, and two reaches were of poor class. The highest MDI classes were also mainly identified in the highest zones of the hydrographic network. Some limitations (i.e., the elevated number of indicators, as well as their simplification) and strengths (i.e., the easy applicability to a large number of reaches) were identified during the application of the MQI method to the Dittaino River.

Assessing the Connectivity of Riparian Forests across a Gradient of Human Disturbance: The Potential of Copernicus “Riparian Zones” in Two Hydroregions

The connectivity of riparian forests can be used as a proxy for the capacity of riparian zones to provide ecological functions, goods and services. In this study, we aim to test the potential of the freely available Copernicus “Riparian Zones” dataset to characterize the connectivity of riparian forests located in two European bioclimatic regions—the Mediterranean and the Central Baltic hydroregions—when subject to a gradient of human disturbance characterized by land-use/land-cover and hydromorphological pressures. We extracted riparian patches using the Copernicus “Actual Riparian Zone” (ARZ) layer and calculated connectivity using the Integral Index of Connectivity (IIC). We then compared the results with a “Manual Riparian Zone” (MRZ) layer, produced by manually digitizing riparian vegetation patches over a very high-resolution World Imagery layer. Our research evidenced reduced forest connectivity in both hydroregions, with the exception of Least Disturbed sites in the Central Baltic hydroregion. The ARZ layer exhibited overall suitability to assess the connectivity of riparian forests in the Central Baltic hydroregion, while the Mediterranean hydroregion displayed a consistent pattern of connectivity overestimation in all levels of human disturbance. To address this, we recommend some improvements in the spatial resolution and thematic accuracy of the Copernicus ARZ layer.

Sparing and sharing land for maintaining the multifunctionality of large floodplain rivers

Large floodplain rivers (LFRs) are among the most threatened ecosystems on Earth and their utilization is expected to grow. Therefore, the need to develop more effective spatial prioritization tools to maintain their multifunctionality becomes increasingly important. We present a novel approach to land use design and conservation planning of LFRs and demonstrate its applicability using a case study for the Danube River, Central-Europe. Specifically, we use indicators of habitat naturalness and complexity to define four main land use functions for LFRs: (1) relatively intact areas with high habitat complexity, which are of high priority for conservation (C), (2) degraded and simplified areas, which are not suited for conservation, but for human utilization (HU), (3) relatively natural areas with low habitat complexity, which are suited both for conservation and for sustainable use of goods and services (LS), (4) degraded areas with relatively high habitat complexity potential, which should be used for rehabilitation (R). While C and HU spare land primarily for conservation and for human utilization, respectively, categories LS and R share land both for biodiversity conservation and for human use and well-being. Results of the case study show that the different land use functions did not clearly separate spatially along the evaluated segment, but distributed relatively equally. Area weighted indices highlighted the importance of large floodplains, while non-weighted indices indicated the importance of many smaller segments with narrow floodplain riparian zone, which can still be important for conservation or rehabilitation purposes. Our multiscale analysis revealed how land use categorizations depend on index use, index weightings and spatial resolution of land use function maps, which should be considered by management. The suggested methodology provides a transparent framework to any stakeholder groups on how to plan out management actions in the context of land conservation and ecosystem services delivery of LFRs.

Disentangling the Main Components of Hydromorphological Modifications at Reach Scale in Rivers of Greece

The Water Framework Directive (WFD) requires from member states to monitor hydromorphological features of rivers in order to assess their ecological quality. Thus, numerous hydromorphological assessment methods have been developed with most of them focusing on the dynamics of hydrology, geomorphology and riparian zone extent. Within the scope of this study, we assessed the hydromorphological features of 106 river reaches distributed among thirteen WFD River Basin Districts (RBDs) to identify the main drivers of hydromorphological perturbation at a national scale. The studied reaches reflect a wide range of natural variability as they include various types of watercourses extending from lowlands to mid-altitude and mountainous systems. We employed the River Habitat Survey (RHS), and we recorded hydromorphological features and modifications in both banks and the channel bed along 500 m for each reach. Then, the Habitat Modification Score (HMS) and the individual sub-scores that indicate the extent of specific modifications (e.g., bridges, fords, weirs, bank reprofiling, bank reinforcement, etc.) were calculated in order to a) assess the severity of the total artificial modification and b) to highlight the most common and severe causes of overall alteration. The results showed that alterations such as reprofiling and reinforcement of banks contributed the most to the total HMS followed by the presence of fords and bridges. Particularly, the bank alterations indicate a serious deterioration of the longitudinal profile of the reaches, while the occurrence of many fords and bridges is the main cause for perturbations that affect locally the stream cross-sectional profile. Overall, these results compile a first nationwide assessment of the hydromorphological status of Greek rivers in line with the WFD and set the basis for further research that will focus on the diversity of stream habitat features as a measure for the overall ecological quality.

Assessment of Green Infrastructure in Riparian Zones Using Copernicus Programme

This article presents an approach to identify Green Infrastructure (GI), its benefits and condition. This information enables environmental agencies to prioritise conservation, management and restoration strategies accordingly. The study focuses on riparian areas due to their potential to supply Ecosystem Services (ES), such as water quality, biodiversity, soil protection and flood or drought risk reduction. Natural Water Retention Measures (NWRM) related to agriculture and forestry are the type of GI considered specifically within these riparian areas. The approach is based on ES condition indicators, defined by the European Environment Agency (EEA) to support the policy targets of the 2020 Biodiversity Strategy. Indicators that can be assessed through remote sensing techniques are used, namely: capacity to provide ecosystem services, proximity to protected areas, greening response and water stress. Specifically, the approach uses and evaluates the potential of freely available products from the Copernicus Land Monitoring Service (CLMS) to monitor GI. Moreover, vegetation and water indices are calculated using data from the Sentinel-2 MSI Level-2A scenes and integrated in the analysis. The approach has been tested in the Italian Po river basin in 2018. Firstly, agriculture and forest NWRM were identified in the riparian areas of the river network. Secondly, the Riparian Zones products from the CLMS local component and the satellite-based indices were linked to the aforementioned ES condition indicators. This led to the development of a pixel-based model that evaluates the identified GI according to: (i) its disposition to provide riparian regulative ES and (ii) its condition in the analysed year. Finally, the model was used to prioritise GI for conservation or restoration initiatives, based on its potential to deliver ES and current condition.

The Landscape Ecology of Rivers: from Patch-Based to Spatial Network Analyses

Purpose of Review

We synthesize recent methodological and conceptual advances in the field of riverscape ecology, emphasizing areas of synergy with current research in landscape ecology.

Recent Findings

Recent advances in riverscape ecology highlight the need for spatially explicit examinations of how network structure influences ecological pattern and process, instead of the simple linear (upstream-downstream) view. Developments in GIS, remote sensing, and computer technologies already offer powerful tools for the application of patch- and gradient-based models for characterizing abiotic and biotic heterogeneity across a range of spatial and temporal scales. Along with graph-based analyses and spatial statistical stream network models (i.e., geostatistical modelling), these approaches offer improved capabilities for quantifying spatial and temporal heterogeneity and connectivity relationships, thereby allowing for rigorous and high-resolution analyses of pattern, process, and scale relationships.

Summary

Spatially explicit network approaches are able to quantify and predict biogeochemical, hydromorphological, and ecological patterns and processes more precisely than models based on longitudinal or lateral riverine gradients alone. Currently, local habitat characteristics appear to be more important than spatial effects in determining population and community dynamics, but this conclusion may change with direct quantification of the movement of materials, energy, and organisms along channels and across ecosystem boundaries—a key to improving riverscape ecology. Coupling spatially explicit riverscape models with optimization approaches will improve land protection and water management efforts, and help to resolve the land sharing vs. land sparing debate.

Seasonal morphodynamic evolution in a meandering channel of a macrotidal estuary

The spatio-temporal morphodynamics in relation to the fortnightly tidal variations and seasonal river discharge variations in a meandering estuarine channel were investigated. Intensive topographic surveys (longitudinal and transverse) every 3-4 months using a digital sonar system equipped with a differential global positioning system and continuous monitoring of salinity and turbidity with moored instruments were carried out during 2009-2012 in the upstream section of the highly turbid macrotidal Chikugo River estuary, Japan. The results revealed that the tidal flow dominated in the estuary for most of the year except for the rainy season in which river flow dominates. During the low flow season, tidally induced net upward sediment transport dominates and deposition takes place in the upstream section especially in the inner part of the meander. It contributes towards the strengthening of the existing estuarine turbidity maximum (ETM) in the upstream section of the estuary, and the channel capacity reduced gradually during this period. However, large flood events led to the breakdown of this ETM zone in the upstream during the rainy season and exported the sediments to the downstream tidal flat which resulted in the rapid increase of channel capacity. This further exhibited that the ETM zone was migrated to the downstream part of the estuary during the rainy season. There were significant differences in the seasonal trends of morphological evolution in the estuary which further greatly influenced the channel capacity. The drastic changes in channel morphology due to the sediment export by the high river flow during the flood season was approximately recovered through the sediment import by the fortnightly tidal cycle during the dry season over a seasonal basis. The study concludes that the morphological changes in the tide dominated estuaries are strongly influenced by the fortnightly tidal variations as well as the seasonal river discharge variations.