Extreme flooding in early October in the western and central districts (dzongkhags) of Bhutan led, amongst other things, to significant erosion along river banks and, consequently, to slumps. As a result, the Dagachhu run-of-river power plant suffered considerable damage to its headrace channel and had to be taken out of operation.
The BERNARD Gruppe was immediately asked to provide support with the aim of restoring operations as quickly as possible. An initial on-site analysis showed that priority must be given not only to resuming operations as soon as possible, but also to finding a resilient, future-proof and durable solution. In addition to the necessary immediate measures, this includes the controlled dismantling of the damaged buildings, stabilisation measures for the approx. 50-metre-high slope below the headrace channel, the reconstruction of the headrace channel, and accompanying hydraulic engineering measures. Thanks to the cooperation of an interdisciplinary team comprising experts in the fields of Geotechnical Engineering, Hydraulic Engineering, Hydropower and Structural Engineering, an integrated and comprehensive rehabilitation concept was presented as early as December 2025. This includes hydraulic engineering measures to stabilise the watercourse, safety measures in the area of the damaged slope, and the reconstruction of the headrace. In terms of river engineering, groynes were constructed on the orographic left bank to control the flow. In addition, the river cross-section was widened by removing a spoil tip on the orographic right bank, in order to increase hydraulic capacity and minimise future erosion. For slope stabilisation, the foot of the slope and the riverbank embankment were reinforced with ripraps. The embankment was restored with a slope angle of 30°, supplemented by organic erosion control mats and vegetation appropriate to the site. The new headwater channel was constructed as a flexible steel pipe approximately 220 m long with a diameter of 4 m. The construction also takes into account the possible failure of individual supports as a result of further extreme events. The measures implemented have created a future-proof infrastructure that meets the increasing requirements for climate resilience and operational safety. Thanks to the cooperation of all those involved in the project, the power plant was able to resume operations in less than seven months after the incident.
Markus Türtscher, BERNARD Gruppe
