Maschänserrüfe: protecting infrastructure and settlements

The Maschänserrüfe in Trimmis in the canton of Graubünden is a formidable debris flow channel, where one to two mudslides per summer are not unusual. These events represent a threat to the railway line, the motorway and the cantonal road in the Rhine Valley and risk damming up the Rhine. During repair work on the A13 motorway, therefore, the opportunity was taken to enlarge the channel and adapt it in line with the latest protection requirements. An extensive alarm concept was developed for the two-year construction period.

Expertise involved

Hydraulic engineering


Federal Roads Office (FEDRO)

Enlarging the channel

Shortly before joining the Rhine, the Maschänserrüfe crosses the north and south lanes of the A13 motorway and the railway lines of the SBB and the Rhaetian Railway. Basler & Hofmann was responsible for planning the enlargement of the debris flow channel in close collaboration with the repair project for the motorway section. The measures included, for example, lowering the bed and underpinning the existing retaining walls, securing the bed with block sleepers and cobbling, and using stone blocks to wall the banks.  


Alarm system for the construction phase

As the mudflow is highly active, a multistage alarm concept was devised specifically for the construction phase. If rain is forecast, the site management is warned in advance and makes the corresponding adjustments to building operations. The emergency system provides additional safety, with radar and ultrasonic level meters measuring the flow depth in the channel around two kilometres above the construction site. From a predefined value, they trigger an alarm that enables the site to be evacuated in a timely manner.

Our services

Option analyses for the sealing structure,  detailed design, invitations to tender, construction documents , commissioning and conclusion.

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