The main issues to be tackled during the design and construction of hydraulic works in harsher climates are connected to the extreme climatic conditions. Among these, low temperatures and related issues for people, materials, as well as machinery must be considered and solved in advance through detailed planning.
Applying solutions for risk mitigation helps to avoid delays and stops. Natural hazards such as avalanches and winter surges increase the risks for logistics and transportation on site and along site access roads, thus requiring solutions for independency and autarchy of the construction site during limited periods.
Climate change
The relationship between climate change and its impact on both hydrological patterns of alpine catchments as well as natural hazards has been scientifically demonstrated.
Warmer winter temperatures increase the probability of liquid precipitation even at higher elevations and in months where typically only snow was falling in the past, thus influencing the flow regime of alpine catchments. The flood seasonality could also experience a shift with events occurring more often in previously unexpected periods. Another issue related to higher temperature is the rapid melting of the snowpack in spring thus causing larger runoff values as in the past.
So what lessons can be learnt looking to the future?
The spectrum of consequences related to climate change spreads from modification of the precipitation patterns across the year and variation in the hydrology, while other natural hazards can also be influenced by climate change. A consequence of permafrost melting is the increase of rockfalls and rock avalanches with their related risks, as well as modified zones exposed to erosion and an increase in sediment transportation rate.
Worker safety
There also considerations with regards to worker safety within the dam environment when operating in such climates.
In-depth site knowledge and painstaking preparation for the worst-case scenario can help predict which situations one might run into. The creation of an interdisciplinary committee of natural hazards experts can help the construction management team in assessing changes in weather forecasts, snow conditions, and judging the degree of danger to which the site and access routes are exposed. The safety perception of workers can also be significantly increased.
And when working in colder climates, dam designs or working practices can also evolved within the region The choice of reducing the concrete quantity to be poured and especially preparing the formworks on site by prefabrication can help in avoiding complex formwork installation as well as rebars positioning in harsh climate conditions. The chance to reduce the overall construction time is evident. Redundancy in construction site logistics can also play a role.
Gigerwald project
A mild winter played a helping hand in the recent upgrading of the Gigerwald outlet project in Switzerland. Carried out by Axpo and Kraftwerke Sarganserland, it was completed on schedule, on time and without any major incidents. The raising of the inlet structures for the works water and the bottom outlet had become necessary due to increased silting up of the lake bed. It took 50 employees six months to build at the base of the 150m high dam.
The work should have been carried out as early as 2022, but was postponed due to concerns about a potential electricity shortage across Switzerland. In the summer of 2024, high levels of sand recorded in the turbine water were a clear sign sediment in the lakebed had already reached the height of the existing inlet structures. So emptying of the reservoir was carried out earlier than planned.
A mild winter with little snow helped the tight schedule which didn’t really allow for any major delays. Everything had to be ready before the snow started to melt because larger amounts of water would have stopped construction. Thankfully this wasn’t the case due to meticulous planning and intensive preparations on site which began in June 2024.
At the end of March 2025, just in time before the thaw set in, the main work at the foot of the Gigerwald dam was completed ahead of schedule. This was by no means a matter of course, as the unusual construction site presented extraordinary challenges for the project management and employees.
The time invested in the preparation resulted in an overall reduction of the construction time. It was a good example of great teamwork between the owner’s representatives, contractor, site managers and designers helped keep the project on track.
Andrea Balestra is Head of Division and Design Project Manager at Lombardi; Erich Schmid is General Project Manager at Axpo Power
