A goal-oriented climate adaptation plan in Silkeborg
- Käyttötapaukset
Silkeborg Municipality is well underway with developing a stronger strategy for the role of water across the municipality. As part of this work, a comprehensive analysis process has been launched, which will result in a green climate adaptation plan.
In this context, the municipality needed to take a closer look at the previous flood analyses that form the basis of the municipality' s strategic development (Kommuneplan in Danish). Flooding had been assessed using bluespot maps and static analyses. Ulrikke Vibe Jensen, engineer at Silkeborg Municipality, together with her colleagues, has carried out detailed work to establish a stronger data foundation for the new climate adaptation plan.
"We spoke with our consultants and agreed to create test cases to examine whether dynamic analyses could provide a more nuanced understanding of how water moves during a rainfall event."
Ulrikke Vibe Jensen, Silkeborg Municipality
“We needed more reliable data and a better way to prioritise our efforts,” Ulrikke explains. “That is why we have been working with hydrodynamic analyses to assess whether they can support a more goal-oriented strategy for the municipality’s climate adaptation work.”
From bluespot maps to dynamic analyses
In the municipality’s earlier climate adaptation work, focus areas had been identified based on terrain depressions where water could accumulate. A key part of the new process has been to reassess these areas.
Ulrikke explains:
“We spoke with our consultants and agreed to create test cases to examine whether dynamic analyses could provide a more nuanced understanding of how water moves during a rainfall event.”
Two test cases were carried out in different parts of the municipality, where the results of dynamic flood analyses were evaluated.
“The DynamicFlood analyses made it possible to see both when depressions fill up during an event and how long water remains at specific levels.”
Ulrikke Vibe Jensen, Silkeborg Municipality
In the first test area, Kjellerup, a static flood analysis for a 100-year event was compared with a dynamic analysis. The results showed that the flood extent was smaller in the dynamic analysis.
Results from the test case Kjellerup.
“Flooding in Kjellerup turned out not to be quite as severe as we initially thought,” Ulrikke describes. “At the same time, the dynamic analyses gave us much better insight into how water moves and spreads along flow paths.”
In the second test area, Laven, where the terrain is more undulating, the bluespot maps indicated relatively limited challenges. However, the dynamic analyses told a different story. Using DynamicFlood, water levels were mapped more precisely, and in several locations significant volumes of water were shown to accumulate on the surface, including along flow paths.
"We concluded that there is significant value in carrying out dynamic analyses.”
Ulrikke Vibe Jensen, Silkeborg Municipality
Results from the test case Laven.
Ulrikke explains:
“The DynamicFlood analyses made it possible to see both when depressions fill up during an event and how long water remains at specific levels.”
Important discussions about rainfall and flooding
The work with DynamicFlood has triggered a number of professional discussions within the municipality. Ulrikke explains that the analyses have, for example, made it necessary to distinguish more clearly between maximum water levels and the duration of high water levels.
“There is the question of when water on the surface actually becomes a problem,” she says. “For instance, is it a problem if 10 cm of water stands for 10 seconds?”
The two test cases showed that the DynamicFlood analyses have several advantages. They made it possible to visualise the extent of flow paths, account for when depressions fill during a rainfall event, and assess how long water remains at a given level.
“We concluded that there is significant value in carrying out dynamic analyses,” Ulrikke says, reflecting on the test cases. “That is why it was decided to run simulations for the entire municipality.”
A municipality-wide analysis
The municipality has now been divided into 32 model catchments based on natural drainage basins. This division ensures that the model catchments are topographically independent.
“It is a major task to carry out analyses for all our catchments,” Ulrikke explains, “but fortunately we have received support from consultants to run the simulations.”
The result is a large amount of new data that municipal planners need to be able to use effectively.
“It is important for us to review the data ourselves and take ownership of it,” Ulrikke says.
The analyses have therefore been integrated into the municipality’s GIS tools so that the results can be used actively in the ongoing planning process.
One experience that slightly surprised the municipality is how well the analyses function as a dialogue tool.
“The analyses give us something concrete to discuss” says Ulrikke. ” That makes it easier to make better decisions together and create a shared understanding of the role of water.”
More than data – creating meaningful information
Ulrikke emphasises that the work does not stop at running the simulations. The results must be presented and interpreted in a way that provides the right information and can be used in a targeted way in the municipality’s long-term planning.
Example of visualisation of flow paths for the municipal plan.
“We need to think carefully about how we interpret the analyses,” Ulrikke concludes. “For example, we are now discussing how to include the dynamic flow paths as part of the municipal plan. We need to be clear about what we want to achieve with the analyses, and that is something we are currently discussing both internally and externally.”
