Project Overview

The Savinja River, stretching between Ločica ob Savinji and Letuš, is the focus of a critical initiative aimed at enhancing flood safety in its urban areas. Funded by the European Union’s Recovery and Resilience Plan, this project addresses the pressing need to mitigate flood risks through innovative engineering solutions while ensuring environmental sustainability. The initiative is not just about infrastructure; it’s about creating a resilient community prepared for future climatic uncertainties.

Increasing flood safety will be achieved through a series of infrastructure improvements, such as expanding river profiles, rehabilitating existing flood embankments, and constructing new ones. The emphasis is on nature-based solutions to enhance the morphological characteristics of the river without compromising its ecological functions. The national spatial plan (NSP) for this area was adopted a decade ago, but recent floods have increased the demand for safety. Previously, they relied on hundred-year floods, but now, due to changing climate conditions and recent experiences (Terrible floods in Slovenia in 2023), they must plan infrastructure to withstand even five-hundred-year floods.

Image: Aerial shots of floods in the Mozirje area, August 2023. These floods are also why they started planning infrastructure to withstand even five-hundred-year floods.

Source: https://novice.svet24.si/clanek/novice/slovenija/64ce4697ae897/savinja-poskrbela-za-katastrofo-v-ljubnem-vec-druzin-ostalo-popolnoma-brez-vsega

Key Features of AQUATERRA

In the designing of this challenging project, the AQUATERRA program played an important role. The basis for design was a geodetic survey of points within the riverbed and a lidar scan of the area outside the riverbed. Based on this, they created a digital terrain model, which they used for projecting longitudinal axes. Therefore, the AQUATERRA program helped them accurately draw longitudinal profiles and cross-sections and input the necessary levels for building new embankments and riverbed arrangements. They then calculated the quantities of excavation and materials needed for a particular embankment. These data could then be easily transferred from the AQUATERRA program to the MIKE FLOOD program, with which they then conducted hydraulic calculations.

Image: The plan of water management arrangements, created with the AQUATERRA program.

Image: The plan of water management arrangements, created with the AQUATERRA program.

Engineering and Environmental Challenges

The designers were faced with numerous complex engineering and environmental challenges. These challenges not only demanded technical solutions but also required creative thinking and the integration of various areas of expertise.

1. Adapting to Changed Climatic Conditions

One of the greatest challenges is adapting to changed climate conditions. Traditional plans and infrastructure were designed under the assumption that the river flow would behave within the bounds of hundred-year floods. However, the floods in the summer of 2023, exceeding previous expectations, clearly demonstrate the need to adapt infrastructure to more extreme events. This challenge calls for engineering solutions that are resilient to long-term climate changes.

2. Space Limitations and Stakeholder Collaboration: Integrating Opinions and Interests

Space limitations and the necessity for collaboration with various stakeholders pose additional challenges. The area along the Savinja River is already heavily urbanized, limiting space for implementing infrastructural measures. Furthermore, it is essential to take into account the interests of the local community, agricultural sector, environmental advocates, and other relevant parties throughout the project’s planning and execution phases. Collaborating closely with local authorities, non-governmental organizations, and residents is indispensable for ensuring the project’s success.

3. Preserving Ecosystems and Biodiversity

The project’s goal is to improve flood safety while preserving natural habitats and ecological balance. This requires careful planning to enhance river characteristics and support local wildlife. One challenge is preventing the riverbed from drying out during low flows, which would affect fish migration.

The project also aims to use “nature-based solutions” (NBS) for flood safety. NBS involves sustainable methods that mimic natural river flows and ecosystems, helping the environment adapt to climate change.

Implemented NBS measures include:

• Increasing water retention and expanding floodplains: These actions help absorb more water, reducing the risk of flooding in populated areas.
• Widening river profiles: Plans include widening the Savinja Riverbed to create gentler slopes and plant native vegetation, promoting natural processes and stabilizing the riverbed.
• Installing flow control elements: Devices like stone obstacles will be placed in the river to regulate water flow and prevent major flooding. These obstacles create varied flow conditions, which can form features like small pools with deeper water, enhancing the river’s microhabitats.
  
  Image: Schematic representation of the installation of flow disruptors – stone obstacles – in the riverbed.

• Bioengineering measures: Planting trees and installing tree trunks and vegetation along the banks will increase bank stability and provide habitats for aquatic and riparian wildlife.

4. Ensuring safety for all

In planning, attention must be paid to ensuring that even lower areas that no longer extend into the treated area remain safe. This means not increasing peak flows, which could save some settlements while exacerbating conditions for others.

Conclusion

The project for the arrangement of the Savinja River between Ločica ob Savinji and Letuš represents a significant step towards improving flood safety in urbanized areas. By incorporating innovative and nature-based solutions, it not only responds to the urgent need to reduce flood risk but also creates a resilient community prepared for future climate uncertainties. Key focuses of the project include expanding river profiles, renovating existing flood embankments, and constructing new ones, with a special emphasis on maintaining the ecological functions of the river.

Despite the technical and environmental challenges faced by the project designers, the project ensures that “nature-based solutions” are considered to the greatest extent possible. These solutions allow for the preservation of biodiversity and ecosystems and ensure that infrastructure interventions improve the morphological characteristics of the river without adversely affecting local fauna and flora.

The conclusion of the project does not just signify the end of construction work but also marks the beginning of a new phase in which the effects of the implemented measures will be continuously monitored and evaluated. This will allow for the adaptation and optimization of the entire flood protection system, benefiting not only the current but also future generations of residents in the Savinja Valley. The use of advanced software solutions, particularly AQUATERRA by CGS Labs, has been instrumental in achieving precise designing and effective integration with hydraulic models, highlighting the importance of such tools in complex projects.

This project, supported by European Union funds from the Recovery and Resilience Plan, serves as an example of how effective collaboration among various stakeholders and the use of advanced technical solutions can address environmental challenges ahead.

Other interesting projects