Hydromorphological Processes Research Articles

Fuzzy cognitive mapping for predicting hydromorphological responses to multiple pressures in rivers

Summary Different pressures often co‐occur in rivers and act simultaneously on important processes and variables. This complicates the diagnosis of hydromorphological alterations and hampers the design of effective restoration measures. Here, we present a conceptual meta‐analysis that aims at identifying the most relevant hydromorphological processes and variables controlling ecological degradation and restoration. For that purpose, we used fuzzy cognitive mapping based on conceptual schemes that were created according to 675 scientific peer‐reviewed river hydromorphology studies. A model generated from this approach predicts responses that are consistent with common understanding of the direct interactions between hydromorphological pressures, processes and variables. However, it also leads to new knowledge beyond traditional hydromorphological models by dealing with the complex interactions of hydromorphology, vegetation, water chemistry and thermal regime. Water flow dynamics appeared as the most important of all hydromorphological processes affected by simultaneously interacting pressures. Relevant processes such as vegetation encroachment and sediment entrainment are closely linked to water flow. Synthesis and applications. Our results demonstrate the relevance of natural flow regime rehabilitation for river management. Hence, we suggest focusing primarily on rehabilitating the natural flow regime before carrying out extensive habitat restoration works. This challenging target in river rehabilitation could strongly increase the success of additional habitat restoration.

Assessing restoration effects on hydromorphology in European mid-sized rivers by key hydromorphological parameters

The effects of river restoration on hydromorphological conditions and variability are often documented immediately following the restoration, but rarely properly monitored in the long term. This study assesses outcomes of 20 restoration projects undertaken across central and northern Europe for a comprehensive set of hydromorphological parameters, quantified at both larger and smaller spatial scales. For each project, we compared a restored river section to an upstream degraded section. Ten pairs of large projects were contrasted to ten similar but less extensive projects, to address the importance of restoration extent for the success of each project. Overall, river restoration increased habitat diversity through changes in channel morphology. Our results indicated that restoration particularly improved macro- and mesohabitat diversity, but had a limited effect on microhabitat conditions, including the diversity of substrates. We found no significant difference in effects between large and small restoration projects. Our results reveal the need to assess hydromorphological parameters which reflect processes occurring at different spatial scales, including indicators of larger-scale hydromorphological processes such as bank erosion, to monitor restoration effects effectively and accurately. Additionally, our results demonstrate the importance of developing terrestrial parameters, to assess the lateral dimension of river restoration.

Temporal and Spatial Patterns of Fish Response to Hydromorphological Processes

AbstractThis paper relates life cycle characteristics of fishes, their environmental tolerances, habitat requirements, and resilience against hydromorphological disturbances to a recently developed river typology providing a hierarchy of spatial units. It aims to identify the most relevant spatiotemporal scales for river restoration and environmental assessment.Most fish species, except diadromous and some potamodromous species, can complete their life cycle within a river reach and form sustainable populations within a river segment. They typically move within the spatial scale of river segments and have their home range within the river reach. By comprising heterogeneous patterns of different geomorphic and hydraulic units, the reach provides habitat complexity and heterogeneity that supports river‐type‐specific fish assemblages. The single units are often used temporarily or by specific life stages only underpinning the need for habitat diversity. Further, they might be only temporarily available. River fishes have evolved several life cycle adaptations to improve their resilience against stochastic disturbances, as high fecundity, multiple spawning, batch‐spawning, a protracted annual spawning season, and long life‐time fecundity with multi‐cyclic spawning. Therefore, they are well adapted to environmental variations driven by hydromorphological processes.Considering the home range of most species, representative sampling at the reach scale will cover all functional river elements, hydraulic, and geomorphic units, while accounting for their temporary or sporadic use by fish. Therefore, the reach scale appears as practicable and sufficient scale for fish‐based assessments and as highly relevant planning unit in hydromorphological river restoration practise. Nonetheless, reach‐scale characteristics are largely inherited from large‐scale geomorphic processes and multiple pressures at the catchment scale that may impact aquatic communities and river restoration success at the lower spatial scales. Copyright © 2015 John Wiley & Sons, Ltd.

Indicators of river system hydromorphological character and dynamics: understanding current conditions and guiding sustainable river management

A set of multi-scale, process-based hydromorphological indicators of river character and dynamics has been developed to support river management and restoration activities. Indicators are selected to represent key hydromorphological processes at each spatial scale, i.e., catchment, landscape unit, river segment, river reach. Their evaluation allows identification of the cascade of these processes through the spatial units and the historical changes in their propagation as a consequence of natural or human induced hydromorphological changes. The approach is deliberately open-ended so that it can be adapted to local environmental conditions and management, and it can make the most effective use of available data sets. The indicators support assessments of the current condition of the river and its catchment; past changes within the catchment and their impacts on river reaches. Therefore, they represent a sound foundation for assessing the way the catchment to reach scale units and the geomorphic units within reaches may respond to future natural changes or human interventions. The procedure is illustrated using the example of the river Frome (UK).

Hydrologo-geomorphological analysis of landscape formation within the selenga river delta

We examine the causes for changes in the delta surface and carry out an analysis of the area characteristics for the last 50 years. It is shown that the dynamicity of the subaerial delta surface, caused by contemporary erosion-accumulation processes, manifests itself most clearly at periods of increased hydraulicity, which promotes restructuring of the relief in elevation and plan, and of the hydrographic network. We investigate the interrelations of particular landscape components with the hypsometric position, the location relative to the main elements of the hydrographic network of the delta, and with the humidification conditions of the territory. Data are provided for the distribution and structural composition of the key vegetation species in accordance with the hydrologo-geomorphological properties of their habitat. It is found that the structural and age characteristics of plant complexes can be used to determine the transformation dynamics of topographic features and, in the future, to indicate the intensity and time intervals of delta surface reconfiguration. Based on observational evidence and remote sensing data, we carried out a landscape-hydrologo-geomorphological regionalization of the delta surface, the principal criterion of which were the intensity and directedness of the leading Hydromorphological processes. A zoning of the subaerial delta surface was instrumental in identifying different (in resistance to erosional changes) tracts of the delta and recommending the most acceptable of them for economic development of the territory.

Climate change and uncertainty assessment over a hydroclimatic transect of Michigan

Predictions of a warmer climate over the Great Lakes region due to global change generally agree on the magnitude of temperature changes, but precipitation projections exhibit dependence on which General Circulation Models and emission scenarios are chosen. To minimize model- and scenario-specific biases, we combined information provided by the 3rd phase of the Coupled Model Intercomparison Project database. Specifically, the results of 12 GCMs for three emission scenarios B1, A1B, and A2 were analyzed for mid- (2046–2065) and end-century (2081–2100) intervals, for six locations of a hydroclimatic transect of Michigan. As a result of Bayesian Weighted Averaging, total annual precipitation averaged over all locations and the three emission scenarios increases by 7 % (mid-)–10 % (end-century), as compared to the control period (1961–1990). The projected changes across seasons are non-uniform and precipitation decreases by 3 % (mid-)–5 % (end-) for the months of August and September are likely. Further, average temperature is very likely to increase by 2.02–2.85 °C by the mid-century and 2.58–4.73 °C by the end-century. Three types of non-additive uncertainty sources due to climate models, anthropogenic forcings, and climate internal variability are addressed. When compared to the emission uncertainty, the relative magnitudes of the uncertainty types for climate model ensemble and internal variability are 149 and 225 % for mean monthly precipitation, and they are respectively 127 and 123 % for mean monthly temperature. A decreasing trend of the frost days and an increasing trend of the growing season length are identified. Also, a significant increase in the magnitude and frequency of heavy rainfall events is projected, with relatively more pronounced changes for heavy hourly rainfall as compared to daily events. Quantifying the inherent natural uncertainty and projecting hourly-based extremes, the study results deliver useful information for water resource stakeholders interested in impacts of climate change on hydro-morphological processes.

Check dam influence on vegetation species diversity in mountain torrents of the Mediterranean environment

ABSTRACTPrevious research has developed a method to assess the impact of check dams on riparian vegetation and related river bed sediment size with vegetation coverage and development. On the basis of this knowledge, this paper aims to investigate the effects on riparian species diversity induced by 32 check dams in four torrent headwaters of Southern Italy. Species richness and composition of riparian vegetation in the active channel were surveyed upstream and downstream of each check dam and in intermediate (less disturbed) sites. Furthermore, links between hydromorphological processes and vegetation diversity were analysed.The identified differences in species diversity seem to be related to the morphological adjustments of the channel after the installation of check dams. These fluvial morphological adjustments introduced variations to the flood depth and frequency of the riparian areas creating new riparian conditions. Higher species richness and evenness were observed upstream of check dams, where alien species prevail over native ones in new habitats on the sedimentation wedge behind the dam. Conversely, downstream of check dams, where the boundary of the inundated area moves down towards the thalweg (due to incision processes after check dam installation), riparian vegetation tends to assume a terrestrial character, losing some herbaceous species of the riparian environment.This research confirms that the discontinuity in the fluvial environment caused by check dams induces morphological adjustments that can be translated in new riparian conditions for the establishment of vegetation, affecting the ecological aspects and species diversity of riparian habitats. Copyright © 2013 John Wiley & Sons, Ltd.

Anthropogenic factor of ice jamming and spring breakup flooding on the Lena River

The analysis of ice jam formation processes of anthropogenic nature in the middle reach of the Lena River in 2001 and 2010 is carried out. Peculiarities of ice jam formation, springflood and inundation of villages in the Republic of Sakha (Yakut Republic) related to preventive actions are demonstrated. Intensity of variation of stages of spring ice jam flooding at the Lena River streamgage sites is considered. The degree of anthropogenic factor effect on ice jams through hydrological and hydromorphological processes is demonstrated.

Adapting and adopting River Habitat Survey: Problems and solutions for fluvial hydromorphological assessment in Portugal

Adapting and adopting River Habitat Survey: Problems and solutions for fluvial hydromorphological assessment in Portugal The Water Framework Directive (WFD), which established the use of hydromorphological quality elements to assess the ecological status of water bodies, has influenced the purpose and content of several European methods for characterizing physical structure and assessing habitat quality in rivers. The River Habitat Survey (RHS) is a WFD compliant method developed in the UK and follows rapid and simple survey procedures using a standardised approach to characterize the physical habitat and evaluate hydromorphological quality. In Portugal, RHS was adopted for WFD purposes due to its successful long term application across the UK and other European countries. Even so, an effort was made to adapt the RHS to Portuguese regional and river characteristics, in order to accurately record habitat features, assess habitat quality and comply with legal requirements. This paper describes the constraints, adaptations, state of the art and way forward for a successful RHS implementation in Portugal. Constraints concerning the application of RHS to Mediterranean rivers are strongly related to natural hydromorphological processes, namely annual and inter-annual flow variability, which is a potential source of covariance with anthropogenic pressures. This leads to difficulties in recognizing and accurately recording some RHS features. Adaptations to RHS were introduced for survey guidelines, recording procedures and improved definitions of habitat features. Additional modifications were prepared in different sections of RHS fi eld form to reflect Portuguese river features and incorporate components required by the WFD.

Complex hydromorphology of meanders can support benthic invertebrate diversity in rivers

In freshwater environments, high biodiversity is commonly associated with habitat heterogeneity. River bends and meanders are particularly complex morphodynamic elements of watercourses. However, the specific spatio-temporal interactions between hydromorphology and the resident biota have scarcely been studied. This article reviews the relationships between hydraulic processes, and morphological units that are typical for meanders, and analyzes the concomitant spatial and temporal dynamics of habitats suitable for aquatic invertebrates. Flow in river bends is characterized by significant cross-stream velocities, which modify primary flow patterns, and create helical flow trajectories. Consequently, boundary shear stresses at the river-bed are altered, so that complex erosion, transport, and accumulation processes characteristically shape bed and bank morphology. The diversity of substrate types and complex bathymetry in meanders provide a large variety of habitat conditions for benthic invertebrates within a relatively small spatial domain, which are connected via hydraulic pathways. Periodic reversal of hydro-morphological processes between low and high flow, and seasonal growth of aquatic macrophytes creates spatio-temporal dynamics at the meso- and microhabitat scales. Such habitat dynamics increases benthic invertebrate diversity to the extent it is consistent with spatio-temporal scales of invertebrate mobility and life cycle. Furthermore, the presence of flow refugia, and hydraulic dead zones in meanders is essential to sustain species richness. This study concludes that meanders are highly complex morphodynamic elements that exhibit several self-regulating principles supporting invertebrate diversity and resilience in fluvial ecosystems.

Overview of flooding damages and its destructions: a case study of Zonguldak-Bartin basin in Turkey

A number of devastating flood events have oc-curred in the various river basins of Turkey in the last decade. Because floods caused deaths, suffering and extensive damages to both public and private properties in the flood areas, the government had to most of the damage in addi-tion to losing significant revenues due to the consequences of costly social and economic disruption. On the other hand, some social structures such as socioeconomic activities, land-use patterns and hydro-morphological processes are destroyed. Whereas flood control structures are considered as one of the basic strategies that can reduce flood damages and in this context flood protection planning should consider the full range of the hazard mitigation activities. In Turkey, between 1945 and 1990, 737 flooding events were occurred and at least 830 people were killed. In 1998, there was a major flooding in Zonguldak-Bartin region located on north of Turkey. Due to this devastated flooding, people lost their life and numbers of engineer-ing structures built on the river and surrounding area were totally destroyed or heavily damaged. Both side of the canal were covered with muddy soil having 0.10-0.15 m thickness. Cleaning up process took sometimes in the region. In this paper, all these subjects have been investigated in the basin and some engineering proposals have been presented.

Microbial activity within a subaqueous dune in a large lowland river (River Elbe, Germany)

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 36:83-97 (2004) - doi:10.3354/ame036083 Microbial activity within a subaqueous dune in a large lowland river (River Elbe, Germany) Sabine Wilczek1, Helmut Fischer1,2, Matthias Brunke1,3, Martin T. Pusch1,* 1Leibniz-Institute of Freshwater Ecology and Fisheries, Müggelseedamm 310, 12587 Berlin, Germany 2Present address: Department of Limnology, University of Uppsala, Norbyvägen 20, 75 236 Uppsala, Sweden 3Present address: Landesamt für Natur und Umwelt Schleswig-Holstein, Hamburger Chaussee 25, 24220 Flintbek, Germany *Corresponding author. Email: pusch@igb-berlin.de ABSTRACT: Microbial processes within subaqueous dunes of large rivers are important for organic matter retention and decomposition but have rarely been examined. We investigated 3 morphodynamically defined zones (stoss side, crestal plateau, and lee side) within a subaqueous dune in the 8th-order River Elbe. Analysis of flow velocity, vertical hydraulic gradient, concentration of mobile fine interstitial particles, and the quantity and biochemical quality of sedimentary organic matter indicated that the stoss and the lee sides of the dune were focal zones of particulate matter retention due to infiltration and sedimentation processes. Bacterial abundance and most measures of microbial activity (sediment community respiration and activities of the extracellular enzymes b-glucosidase, leucine aminopeptidase, b-xylosidase, and exo-1,4-b-glucanase) were significantly higher in these zones than in the plateau. Increases in bacterial abundance and microbial activity were closely correlated with protein, carbohydrates, nitrogen and phaeopigments associated with high-quality particulate organic matter. Our findings showed that the morphodynamic differentiation of the subaqueous dune resulted in the formation of distinct functional zones in the sediment. The underlying mechanisms can be conceptually summarized by a 2-stage regulatory hierarchy. Microbial activities were controlled directly by the input of dissolved oxygen and easily degradable microbial substrates, and indirectly by hydromorphological processes. We conclude that the subaqueous dune functioned as an efficient filter of particulate organic matter, and that the stoss and the lee sides of this river bedform were focal sites of microbial carbon mineralisation in the large river ecosystem. KEY WORDS: Extracellular enzymes · Particulate organic matter · Subaqueous dune · Sediments · River · Bacteria · Hydrodynamics Full article in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 36, No. 1. Online publication date: June 24, 2004 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2004 Inter-Research.

Man‐made secondary channels along the River Rhine (The Netherlands); results of post‐project monitoring

AbstractOwing to river regulations in the past and intensive farming, the ecological value of the floodplains of the River Rhine in The Netherlands has decreased dramatically. One way to restore riverine biotopes is to create permanently flowing channels in the floodplain. Along the River Waal, the main branch of the Lower River Rhine, two such secondary channels have been created since 1994. A post‐project monitoring programme of 5 years was set up, which included hydrological, morphological and ecological parameters. This article focuses on the monitoring of aquatic macrophytes, aquatic macroinvertebrates, fish and wading‐birds.The results show that man‐made, excavated secondary channels function as a biotope for riverine species including the more demanding rheophilic species. The demands for shipping and protection against flooding on the River Waal cause constraints on secondary channels. Despite these constraints there is still enough space for hydromorphological processes to create new habitats in secondary channel 1, near Opijnen. The space for hydromorphological processes is less in secondary channel 2, near Beneden‐Leeuwen. The density and the number of (rheophilic) species are for a large part influenced by the water level and frequent inundation caused by the high hydrological connectivity. Man‐made secondary channels seem to provide suitable habitat that is currently lacking for a broad range of rheophilic macroinvertebrate and fish species in the Lower River Rhine in The Netherlands. Owing to the lack of suitable habitats for rheophilic macroinvertebrate and fish species before the creation of the secondary channels, the importance of longitudinal and transversal migration could be illustrated by the drift of macroinvertebrates during floods and the seasonal migration of Age‐0 and Age‐1+ fish species. Copyright © 2001 John Wiley & Sons, Ltd.

Marginal Lands and Erosion in Terraced Fields in the Mediterranean Mountains

Abstract Since the 1950s, the Spanish Mediterranean mountains have become a marginal territory, with few inhabitants and limited economic activity. As a consequence, significant land use changes (farmland abandonment, development of extensive cattle rearing, and reforestation) have taken place, resulting in landscape degradation and new hydromorphological processes. In this article, the process and impact of farmland abandonment in the Camero Viejo (northwestern Iberian System) are described. The authors also studied the geomorphological evolution of terraced fields after cultivation was given up. Runoff rates and sediment yield in abandoned and grazed terraces were measured using a rainfall simulator. Results show that the speed and intensity of the hydrological and erosional response increased if plots were grazed intensively. The study demonstrates that new land management systems in the Camero Viejo, in particular extensive cattle grazing, have generated additional source areas of sediments.

The declining but non‐rejuvenating base level—The Lisan lake, the Dead Sea area, Israel

AbstractLaboratory experiments investigating the effects of a lowering base level do not simulate natural eustatic lowering along concave river profiles. The field data on this issue are also quite limited. In evaluating the control exercised by lowering base level on a drainage network, distinction must be made between its influence and those of other hydromorphological processes operating within the basin. Field data on morphological relations, based on photogrammetric mapping and longitudinal profiling, have been gathered in the Dead Sea area, Israel, where a rapid fall in base level has occurred during the Holocene. The study area is an entrenched fan delta with a sequence of 14 unpaired fan terraces which die out at intersection points within an alluvial fan system.The results suggest that the intersection points did not function as base levels. The receding base level played only a passive role, allowing entrenchment without transmitting a head‐cutting feedback basinwards. The arid environment caused a delay in transmission of information through the system. The results support the model of short, episodic, and discontinuous erosional events, inherent in the evolution of drainage basins. It is suggested that base level effects in temperate and humid regions are not transferrable to arid zones.