River waves · Case studies
Case study Thun: two waves below historic sluices, without a single franc of construction costs
Thun is the special case among the case studies: nobody built a wave here. The Mühlewelle and the Scherzligwelle form as a side effect of two 18th-century regulating weirs of Lake Thun. The case shows what toleration by canton and city means, how a club takes on responsibility without a structure of its own – and how much a wave depends on the control of the weir. Profile and location: Thun in the wave directory.
At a glance
| Watercourse | Aare, Thun: Mühlewelle below the Mühleschleuse (Inner Aare, old town) and Scherzligwelle below the Scherzligschleuse (Outer Aare, near the railway station) |
|---|---|
| Origin | bed drop and boulders below the regulating weirs; no structure built for surfing |
| Discharge | ideally about 120 to 150 m³/s (Schwäbis measuring station, figure given by the scene); depends on level and gate setting |
| Costs | no construction costs; the club funds itself through fees, sponsorship, courses |
| Operating body | Verein Flusssurfen Thun (statutes 2011), over 400 members (2026), member of the Swiss Surfing Association |
| Legal status | the Canton of Bern (Office for Water and Waste) and the City of Thun consent to surfing below the regulating structures |
History
The Mühleschleuse dates from 1723/24, the Scherzligschleuse from 1726, in its present form since 1818; both regulate the outflow of Lake Thun with ten wooden sluice gates each. Surfing below them has taken place since about 2008. The club Flusssurfen Thun adopted statutes in 2011; one reason was to preserve the wave during renovations of the river bed. In 2018 the first "River Surf Jam" took place, in 2022 the fifth edition with the first Swiss Championship in river surfing. In May 2020 the cantonal police closed the surfing for four days because of the pandemic rules; within a few days the club submitted a protection concept (at most ten surfers in the water, one person per wave, time limits), which the authorities approved. In October 2022 a 49-year-old surfer died after a fall at the Scherzligschleuse. In 2026 the club and partners staged the "River Games Thun": rapid surfing at the Mühlewelle, kayak cross and freestyle at the Scherzligwelle, free admission.
Technology and hydraulics
The Scherzligwelle forms through a bed drop – a "hole" in the river bed below the weir. For the Mühlewelle, according to the club, the cause is not fully understood; the water pressure of the sluice and the nature of the bed with its block carpet, boulders and braking basin are suspected. What is decisive is the setting of the gates: the regulating structures are controlled centrally, the gate positions change several times a day, and the smallest changes alter the wave strongly. Normally the main share of the water flows through the Scherzligschleuse. A flood relief tunnel (since 2009, up to 100 m³/s) additionally affects the outflow. The scene names 120 to 150 m³/s as the ideal range; below that rocks become a danger, above it boards with more volume are needed. Surfing is possible all year round; the rear Mühlewelle runs mainly in spring. → Hydraulics
Costs and funding
Nothing was built for the waves, so there are no construction costs. The club funds itself through membership fees (free basic membership, "Member+" 45 francs a year), sponsorship, donations and courses; liability is limited to the club's assets. What the renovations of the sluices cost the canton is a matter of lake regulation, not of surfing.
Legal matters
There is no user agreement but a toleration: canton and city consent to river surfing below the two regulating structures. The regulation itself follows flood protection and the lake level alone; surfing interests play no part in it. The club's president describes the cooperation with the authorities as very good – the protection concept of 2020 is the example of this.
Operation
The waves are public, membership is not required, no equipment is rented out. The club classifies the Mühlewelle as a wave for experienced river surfers only (bridge piers, rocks just below the surface), the Scherzligwelle as a wave for beginners and intermediates, with eddies in front of the gates. Together with the Swiss Surfing Association, the Swiss Council for Accident Prevention and the Swiss Lifesaving Society it has drawn up a safety guide; surfing without a leash is recommended. Basic courses (80 francs, four hours, from 16 years) are mostly fully booked in 2026. The scene grew from a hard core of around 30 surfers (2020) to over 400 club members (2026) – "more than FC Thun", as the club writes.
What Winterbach can learn from it
Thun is the reminder that a wave is always a product of the weir. In Thun the gate setting decides whether the wave exists or not, and the gates are operated according to the lake level and flood protection, not according to surfers. For Winterbach this means: who operates the "Remswehr" and how it is controlled is one of the first questions of feasibility. Secondly, Thun shows that a club can take on responsibility even without a structure of its own – with a protection concept, a safety guide and courses – and that the authorities honour this responsibility. Thirdly, the accident of 2022 is a warning: natural waves with rocks, piers and eddies are more dangerous than built installations with a clear run-out zone; the safety of a planned wave lies in the structure, not in the signage.
Frequently asked questions
Was the wave in Thun built?
No. Both waves form below historic 18th-century regulating weirs of Lake Thun through bed drops and boulders; nothing was altered for surfing.
Do you need a membership in Thun?
No, the waves are public. The club Flusssurfen Thun offers courses, a safety guide and a free basic membership.
When is the wave surfable?
When discharge and gate setting fit – the scene names about 120 to 150 m³/s as ideal. Because the gates are adjusted several times a day, forecasting is difficult even for experienced surfers.
Sources: Verein Flusssurfen Thun, "Mühleschleuse", "Scherzligschleuse", "FAQ", "Statuten", "Basiskurse", "Vorteile der Mitgliedschaft" (flusssurfen.ch) · Canton of Bern, Bau- und Verkehrsdirektion, "Thunersee" (water regulation) · Der Bund, 11.07.2016 · SRF, 28.08.2018 · Plattform J, 11.05.2020, 07.09.2022 and 24.10.2022 · Berner Zeitung, May 2020 (protection concept) · aare.surf · sportguide.ch, River Games Thun 2026
Last updated: 15 October 2026 · Initiative Remswelle