Assessment Methods and Strategies for the Restoration of Streams in Switzerland

More than 10 years ago Switzerland developed the modular stepwise procedure for the assessment of streams and rivers. Different  standardized methods are used with abiotic and biotic approaches. The abiotic assessment methods focus for example on morphology, hydrology or chemistry while biotic methods assess fish, macrobenthos or diatoms. The application of the available methods give an overview on the ecological status on streams in Switzerland and implicate the need for river restoration. The morphological analysis were carried out for the most part of Swiss running waters and showed the restoration needs in different geographical areas in the country. In the Swiss Plateau where the human population density is high 38 % of the streams should be restored while in the Alps only 15 % of the rivers need morphological restoration. Beside morphological deficits longitudinal connectivity (artificial barriers) and modified hydrological regimes are additional key issues. The use of different assessment modules makes is possible to detect where riverine habitats have clear deficits and where restoration activities are mostly needed. 

In the year 2011 the federal and local governments started with a substantial sponsorship and will invest billions to support the recovery of streams in the near future. However, a strategy of prioritization is urgently needed: Monitoring studies showed that many restoration projects are not successful in restoring biological communities.  Although many projects are effective in the restoration of habitat heterogeneity, a biological successful response is more difficult to achieve. Due to the existing lack of fundamental ecosystem processes and severe connectivity problems the biological community and mainly fish populations remain unchanged compared to the conditions before restoration.
In order to carry out an effective monitoring we formulated indicators and methods for the outcome evaluation of restoration projects. Monitoring results will be discussed and the reaction of the fish fauna to restoration measures will be analyzed. The results will help to formulate basic principles of prioritization measures for future restoration activities. This prioritization is highly needed because of the limited financial resources.