Lessons from Japan

Water level induced changes of habitat quality determine fish community composition in restored and modified riverbanks of a large alpine river

Urban river restorations focus on restoring aquatic and riparian habitats, increasing flood protection, and enhancing recreational potential. The increased recreational value such newly created urban green spaces is a key benefit of these measures as urban riparian areas are highly valued for recreation. However, high recreational pressure may contribute to the loss of natural vegetation and of biodiversity in restored riparian sites. This study investigates the impact of different recreational intensities and use types on the vegetation structure and vegetation quality by documenting direct (foot-traffic, breaking of branches, stems and roots) and indirect damages (litter and excrements). The major results are fourfold. First, while the proportion of some vegetation types can be correlated to the recreational intensity, neither recreation intensity nor recreation types enhanced the colonization success of invasive species. However, monitoring data showed that human-induced disturbances such as hydro-morphological changes favor alien plant establishment. Second, the study suggests a tipping point for pioneer vegetation at around a density of one user per 10 m river stretch. Already at lower user densities, pressure from trampling can slow down vegetation development. Third, the results indicate that users prefer urban greening and gravel bar elements rather than natural vegetation. Finally, while intensity of direct damages on the vegetation are weakly correlated with the user density, indirect damages increase with the user density. This study concluded that the identification of user hotspots would be helpful in developing a resilient restoration design, which in addition to information about the sensitive vegetation types in relation to recreational users and nature friendly recreational behavior could decrease vegetation damages. In particular, younger recreational users should be targeted by environmental protection campaigns. 

Effects of recreational use on restored urban floodplain vegetation in urban areas

Fließgewässer-Renaturierung heute und morgen

Aim: To give an overview of the hydromorphological aspects of freshwater ecosystems (focusing on running waters), including human activities affecting the physical and hydrological aspects of freshwater ecosystems, ways to measure hydromorphological stressors including biological indicators, management, and policy aspects. Main concepts covered: Hydromorphology links hydrology and geomorphology, with physical characteristics and processes being at the center of management and restoration in freshwaters. Human activities affect the hydromorphology of rivers and lakes in profound and numerous ways, creating a complex web of impacts and multiple feedbacks. Hydrological alterations are caused by activities that change natural run-off and flooding pattern of a catchment, the flow regime of a river or the water circulation and retention in a lake. Humans further cause impact by directly modifying the physical shape and material structure of river and lake morphology. Main methods covered: There are three main components to assess hydromorphological condition of waterbodies: hydrological, physical morphological (including riparian/floodplain), and geomorphological process. Many attempts have been made to find biological indicators that give a useful measure of the degree of hydromorphological impact, but this has proven challenging in both lakes and rivers. A fruitful future direction might be the development of functional and ecosystem process-based indicators for hydromorphological management and restoration. Conclusions: The importance and influence of the physical habitat (hydromorphological condition) on freshwater ecological response is widely recognized and there are a number of conceptual frameworks that have been developed to assess these links. There are several such management guidelines available, but in many instances these are not taken into account, and investments in river restoration and management over the last decades have, overall, failed to halt declines in habitat quality, ecosystem function and biodiversity. Both rivers and lakes need to be managed for a multitude of purposes as they provide many different benefits for humans. As hydromorphological factors and human induced changes have strong impacts on river and lakes, the understanding of these variables and their interactions are crucial in freshwater management and restoration. 

Hydromorphology: Overview and Assessment Methods

The goals of the European Water Framework Directive changed the perspective on rivers from human to ecosystem-based river management. After decades of channelizing and damming rivers, restoration projects are applied with more or less successful outcomes. The anthropogenic influence put on rivers can change their physical parameters and result in a different morphological type of river. Using the Ammer River as an example, a comparison between applied systems of corridor determination based on historical maps and data; calculation of regime width; and the change in parameters and river typology are pointed out. The results showed (a) a change in stream power and morphology (b) great difference between the historical and the predicted river type and (c) that regulated rivers can have a near-natural morphology.

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Martin Guzelj

Papers

The third dimension in river restoration: how anthropogenic disturbance changes boundary conditions for ecological mitigation.