The Vjosa River corridor: a model of natural hydro-morphodynamics and a hotspot of highly threatened ecosystems of European significance

Context: Large near-natural rivers have become rare in Europe, a fact reflected in the high conservation status of many riverine ecosystems. While the Balkan still harbors several intact river corridors, most of these are under pressure from planned hydropower constructions. Unfortunately, there is little information available on the hydromorphodynamics and biota of Balkan rivers under threat. Objectives: We present a synthesis of research on the Vjosa in Southern Albania. Here, longitudinal continuity in water flow, undisturbed sediment transport and intact fluvial dynamics are still maintained, but threatened by two large dams planned in its downstream section. We intend to provide a first multidisciplinary inventory of this river system as an example of the knowledge base required for sound water management decisions in the Balkans. Methods: Based on field work of a multidisciplinary consortium of scientists from Albania and other countries conducted from 2017 onwards, we summarize the most important findings on geomorphology of the riverine landscape, habitat turnover rates, vegetation ecology and selected animal taxa. Results: We found evidence that significant areas (86%) of the river corridor are covered by habitats listed in Annex 1 of the European Union Habitats Directive. These are associated with a high number of threatened biota. Conclusions: Our findings underscore the value of the Vjosa as one of the few remaining reference sites for dynamic floodplains in Europe and as a natural laboratory for interdisciplinary research. We emphasize that such multidisciplinary studies are a prerequisite for informed evaluation of potential impacts caused by hydropower plants

Rekonstruktion ursprünglicher Lebensraumverhältnisse der Fluss-Auen-Biozönose der Donau im Machland auf Basis der morphologischen Entwicklung von 1715 - 1991

Vorliegende Arbeit ist ein Beitrag, die natürliche Charakteristik alluvialer Donau-Flusslandschaften im Sinne eines "visionären Leitbildes" zu erforschen. Die Analysen beruhen auf der Rekonstruktion des flussmorphologischen Zustandes der Donau im östl. Machland (Strom-km 2094,4-2084,0) seit 1715. Dadurch können detaillierte Aussagen zur ehemaligen aquatischen Habitatausstattung sowie zu den dynamischen Umlagerungsprozessen und der Auenvegetation getroffen werden. Vor der Regulierung bestand das Auensystem aus einem komplexen Netzwerk von Flussarmen, zahlreichen Schotterbänken und großflächigen Inseln (anabranched river type). Das Gewässersystem wurde zu mehr als 90 % von durchströmten Flussarmen (Eupotamon) dominiert, wovon primär die rheophile Fischfauna der Donau profitierte. Die Ergebnisse unterstützen die Hypothese, dass trotz der hohen Dynamik annähernd ein Gleichgewicht zwischen Anlandungs- und Erosionsprozessen bestand. Dieser Zustand der Flusslandschaft lässt sich als "shifting-mosaic steady-state" - gekennzeichnet durch einen Gradienten unterschiedlich entwickelter Habitate - charakterisieren. Der Ausgleich von Habitatalterungs- und Verjüngungsprozessen äußerte sich in einer morphologisch "sehr jungen" Flusslandschaft und einer kurzen Dauer des Habitat-Lebenskreislaufes. Regulierungen und Kraftwerkerrichtungen seit dem 19. Jhdt. führten zu einer zunehmenden Stabilisierung der Flusslandschaft, wodurch die durch Dynamik geprägten Habitate eine starke Verringerung erfuhren. Der natürliche Kreislauf von Anlandung und Erosion wurde unterbrochen, weshalb die gegenwärtige Flusslandschaft durch fehlende Habitatregeneration bzw. Überalterung gekennzeichnet ist. Dieser Zustand entspricht daher nicht länger einem "shifting-mosaic steady-state", sondern ist vielmehr als "static-state" zu bezeichnen.The present study contributes to research on river type-specific reference conditions ("visionary Leitbild") and is focused on the natural characteristics of alluvial Danube river landscapes. The analyses are based on river morphological reconstructions of the Danube River in the eastern Machland (Upper/Lower Austria, river-km 2094.4-2084.0) since 1715. These reconstructions yield detailed information on the former habitat composition and fluvial processes. This enables conclusions to be drawn about the original fish fauna of the river-floodplain system and the riparian vegetation. Prior to channelization, the river landscape comprised a complex network of river channels, numerous gravel bars and large islands (anabranched river type). The channel system was dominated (>90 %) by the main channel and lotic side arms (eupotamon) that primarily promoted the rheophilic Danube fish fauna. The results support the central hypothesis of the dissertation that - despite the high degree of hydromorphological turnover - a dynamic equilibrium of aggradation and erosion processes largely existed. This state of the riverine ecosystem can be described as a "shifting-mosaic steady-state", characterized by a gradient of differently developed habitats. The balance of habitat succession and regeneration is reflected by a morphologically very young river landscape with a comparably brief habitat life-time cycle. River channelization and hydropower plant construction since the 19th century increasingly stabilized the river landscape. As a consequence, the former dynamic habitat types have been heavily reduced. The natural cycle of aggradation and erosion became disrupted and the current river landscape is characterized by missing habitat regeneration and prevailing senescence. Altogether, this state no longer constitutes a "shifting-mosaic steady-state system" but rather a "static-state system".verf. u. eingereicht v. Severin HohensinnerAbweichender Titel laut Übersetzung der Verfasserin/des VerfassersWien, Univ. für Bodenkultur, Diss., 2008OeBB(VLID)193045

What remains today of pre‐industrial Alpine rivers? Census of historical and current channel patterns in the Alps

To date, no survey on the diverse channel patterns existing prior to the major phase of river regulation in the mid‐19th–early 20th century has been elaborated at the scale of the whole European Alps. The present paper fills this knowledge gap. The historical channel forms of the 143 largest Alpine rivers with catchments larger than 500 km$^{2}$ (total length 11,870 km) were reconstructed based on maps dating from the 1750s to 1900. In the early 19th century, one‐third of the large Alpine rivers were multi‐channel rivers. Single‐bed channels oscillating between close valley sides were also frequent in the Alps (28%). Sinuous and even more so meandering channels were much rarer. Historical river patterns generally followed an upstream–downstream gradient according to slope condition, floodplain width and distance from the sources. The local occurrence of certain channel patterns, however, primarily reflected the tectonic/orographic conditions. Multi‐channel reaches were widespread within the whole Alpine area, alternating with confined and oscillating reaches. This demonstrates that most areas were mainly transport‐limited rather than supply limited. Sinuous and meandering reaches were more frequent in the north‐eastern Alps and were characterized by lower denudation rates and less sediment delivery. Channel straightening caused the loss of about 510 km of river course length, equivalent to 4.3% of the historical extent. Multi‐channel stretches are currently a mere 15% of their historical length, and 45% of the larger Alpine rivers are intensively channelized or have been transformed into reservoirs. Channelization measures differed from one country to another. Human pressures directly affected both local channel geometry and the upstream controls (i.e., sediment supply). Accordingly, individual multi‐channel reaches also evolved into single‐thread channels without any local human interventions

How water and its use shaped the spatial development of Vienna

The final publication is available at Springer via https://doi.org/10.1007/s12685-016-0169-7.Telling an environmental history of Vienna’s urban waters, this paper advocates the compound study of the evolution of fluvial and urban form. It traces the structural permanence of diverse types of running waters in a period of massive urban transformation from early modern times to present. The focus on the material effects, side-effects and afterlives of socio-natural processes offers novel perspectives to the reconstruction of city development. The featured cases show that long-term studies are vital in understanding the genesis of urban water bodies and urban form as a product of socio-natural processes. They inform us about the inertia of arrangements and the unforeseen perpetuation of site-specific effects of interventions. Societal interaction with natural elements such as Vienna’s waters, we conclude, reverberates in the material and immaterial realm alike

What remains today of pre-industrial Alpine rivers? Census of historical and current channel patterns in the Alps

International audienceTo date, no survey on the diverse channel patterns existing prior to the major phase of river regulation in the mid-19 th-early 20 th century has been elaborated at the scale of the whole European Alps. The present paper fills this knowledge gap. The historical channel forms of the 143 largest Alpine rivers with catchments larger than 500 km² (total length 11,870 km) were reconstructed based on maps dating from the 1750s to 1900. In the early 19 th century, one third of the large Alpine rivers were multichannel rivers. Single-bed channels oscillating between close valley sides were also frequent in the Alps (28 %). Sinuous and even more so meandering channels were much rarer. Historical river patterns generally followed an upstream-downstream gradient according to slope condition, floodplain width and distance from the sources. The local occurrence of certain channel patterns, however, primarily reflected the tectonic/orographic conditions. Multi-channel reaches were widespread within the whole Alpine area, alternating with confined and oscillating reaches. This demonstrates that most areas were mainly transport-limited rather than supply-limited. Sinuous and meandering reaches were more frequent in the northeast Alps and were characterized by lower denudation rates and less sediment delivery. Channel straightening caused the loss of about 510 km of river course length, equivalent to 4.3 % of the historical extent. Multi-channel stretches are currently a mere 15 % of their historical length, and 45 % of the larger Alpine rivers are intensively channelized or have been transformed into reservoirs. Channelization measures differed from one country to another. Human pressures directly affected both local channel geometry and the upstream controls (i.e. sediment supply). Accordingly, individual multi-channel reaches also evolved into single-thread channels without any local human interventions

Land Use in Flood-Prone Areas and Its Significance for Flood Risk Management—A Case Study of Alpine Regions in Austria

Increasing flood damage has led to a rising importance of land use in flood risk management policies, commonly referred to as the spatial turn in flood risk management. This includes policies aiming at making space for rivers, which, in practice, lead to an increasing demand for land. Although research has been conducted on the variety of policies, the resulting land use conflicts in flood-prone areas have not been paid much attention to. This paper therefore analyses the current land use and its changes in Alpine flood-prone areas in Austria. The results show that space for rivers has been decreasing due to human activities (e.g., river straightening and channel narrowing) since the middle of the 19th century, and settlements have been expanding into flood-prone areas. Furthermore, the share of valuable agricultural land (which is important for food production) located in flood hazard zones is higher in more mountainous areas. Given the limited space for permanent settlement in Alpine regions, these land use changes exert pressure on the availability of land suitable for flood risk management. Therefore, making space for rivers as part of flood risk management policies faces considerable restrictions in Alpine areas