Birs in Sorvilier and Court: Flood protection and ecology

Since 2023, the BKW Ökofonds has been supporting an ecologically particularly ambitious hydraulic engineering project on the Birs in the municipalities of Sorvilier and Court. The Birs is one of the most important brown trout waters in the canton of Bern and is also of great importance as a habitat for numerous other aquatic organisms. For several decades, however, a marked decline in brown trout and grayling stocks has been observed in Switzerland. The causes are varied: watercourse engineering, structurally poor channels, migration barriers, altered flow regimes and rising water temperatures are putting pressure on the populations.

Against this backdrop, the hydraulic engineering project on the Birs has a special role to play. The project is part of the regional drainage plan (REP) Birs, section 53. It combines flood protection with the comprehensive ecological enhancement of a roughly three-kilometre-long stretch of watercourse.

Safety and nature in balance

The aim of the project is to protect the building zones of Sorvilier and Court against flooding while at the same time significantly enhancing the river corridor ecologically. The protective measures are designed for a one-in-100-year flood event with a discharge of 55 m³/s. In these sections, the focus is not on protecting infrastructure, but on creating a diverse aquatic and floodplain habitat. This combination of safety and ecological revitalisation reflects a modern, integrated approach to hydraulic engineering.

A core element of the project is the upper section in Sorvilier. Over a length of around 800 metres, the Birs will be given a new, near-natural river course. Former meanders of the historic watercourse will be reactivated and integrated into the present-day river landscape. The newly created valley meanders provide varied flow conditions, shallow bank areas, pools and gravel banks. This creates spawning grounds for brown trout and grayling, as well as valuable refuges and nursery areas for juvenile fish. At the same time, amphibians, insects and floodplain plant species benefit from the newly created structural diversity.

Collaboration and impact

The revitalisation in Sorvilier shows how hydraulic engineering requirements can be combined with ambitious ecological objectives. Without coordinated implementation with the neighbouring project section in Court, the reactivation of the meanders in this form would not have been feasible in particular. The project therefore also stands for successful cross-municipal collaboration.

The cantonal fisheries inspectorate is supporting the project from planning through to construction acceptance. This ensures that the requirements relating to aquatic ecology are consistently taken into account. Wherever possible, obstacles to fish migration are removed or replaced by suitable measures. The continuity of the watercourse is a key prerequisite for stable fish populations, as it enables genetic exchange between subpopulations and ensures access to spawning and feeding areas.

From an ecological perspective, the project is extremely ambitious. It goes far beyond merely compensating for construction interventions and aims to substantially restore diverse aquatic and floodplain habitats. The enhancements, in conjunction with the section in Court, will lead to a large-scale improvement in the ecological functionality of the Birs. At the same time, the municipalities’ maintenance obligation under the Water Engineering Act ensures the long-term safeguarding of the values created.

The river engineering project in Sorvilier and Court is creating an ecologically valuable, structurally diverse stretch of water with high biodiversity and improved resilience to climate change. The newly created habitats will help to stabilise populations of brown trout and grayling in the long term and preserve the Birs’ character as an important trout river. Support from the BKW Ökofonds is not only financial in nature. With a contribution totalling CHF 270,000 to the two project sections in Sorvilier and Court, the fund is making a substantial contribution to implementing the ecological enhancement measures. It is also a clear commitment to the sustained promotion of watercourse development in the canton of Bern. Projects such as the one on the Birs show that ecological added value, flood protection and regional development do not have to be mutually exclusive, but can reinforce each other.

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