Analysis and evaluation of large‐scale river restoration planning in Germany to better link river research and management

Abstract

In December 2008, the draft programmes of measures (PoM) have been published in the EU member states, which list the measures that will be taken to enhance the ecological status of surface and groundwater bodies, and to reach the environmental objectives of the EU-Water Framework Directive (WFD). We have analysed the German PoM to identify the main pressures and the restoration measures water managers planned to implement in streams and rivers. The objective was to evaluate the PoM and to identify the main, practically relevant knowledge gaps in river management on which applied river research should focus on.In general, the selection of measures in the PoM was reasonable. In accordance with the analysis of pressures and impacts in Germany, the PoM focussed on measures addressing morphological alterations and river continuity, and the results indicated that diffuse source pollution and fine sediment input were additional main pressures in Central European streams and rivers. Although point source pollution was not a main pressure in most rivers, respective point source measures have been selected for many water bodies. Apparently, these were so-called basic measures that have to be taken due to other EU-Directives or national laws. Therefore, although in line with the WFD, it seemed doubtful if the point source measures would help to substantially enhance the ecological status. Furthermore, the results indicated that there was a general lack of knowledge on the effect of restoration measures and a specific knowledge gap in how to enhance the ecological state of heavily modified water bodies (HMWB) in the lowland region with a high land-use pressure, which was reflected by the high share of water bodies for which conceptual measures have been selected (e.g. developing management plans).Based on the analysis of the PoM and a literature review, we identified the following, practically relevant knowledge gaps in river management: (i) the morphodynamics of river reaches where natural channel dynamics have been restored, (ii) the combined effect of measures addressing diffuse nutrient and fine sediment input at different spatial scales (e.g. riparian buffer strips and land-use changes), (iii) methods to identify suitable and efficient measures and to define environmental objectives for HMWB and (iv) the effect of measures on less well-studied biological groups like macrophytes and phytoplankton. There is a strong need to summarize recent research results on these issues, to identify the knowledge gaps and research needs in detail, and to make the results of such a comprehensive literature review or meta-analysis available for the next 6-year management cycle and second WFD management plans.

Effects of vegetation distribution on experimental river channel dynamics

“…Creating a new, more natural channel planform is increasingly used as a restoration measure to improve the hydromorphological state of rivers [e.g., Gurnell et al ., ; Pedersen et al ., ]. Moreover, enhancing natural channel dynamics and creating a more natural channel planform are among the most frequently designated hydromorphological measures in the river management [ Kail and Wolter , ]. The results of this study show that a newly created restored channel potentially increases in channel dynamics and hence, sediment output are high until the river banks and floodplain get vegetated with a more pronounced effect if seeds are dispersed by flow compared to a uniform distribution of seeds (which is comparable to planting on the floodplain).…”

Disentangling the effects of habitat suitability, dispersal, and fragmentation on the distribution of river fishes

“…Restored longitudinal connectivity might not result in quantifiable biotic improvement if the segments up-and downstream of a barrier already contain the species, if no new or essential habitats become available for the species, or if connectivity measures are not accompanied by habitat enhancements (Kail and Wolter 2011). The overall importance of accessible habitats was underlined by the results of the mixed models, indicating that habitat suitability and the dispersal from proximal source populations govern the spatial distribution of freshwater fishes.…”

Performance of bottom ramps to mitigate gravel habitat bottlenecks in a channelized lowland river

“…This study showed that gravel bottom ramps can effectively fulfill multiple management goals in regulated rivers by maintaining river continuity and providing compensatory habitat (Kail & Wolter ). Although a more holistic restoration of the geomorphic processes and hydrology would be desirable to create and maintain gravel bars and riffles (Beechie et al ), the design of the bottom ramps also addressed flood control and water table management objectives.…”