Flood risk management: Balancing the protection of assets and the environment

Green transition 28 April 2020 Jens Christian Riise

The recent state and outlook 2020 for the European environment (SOER) highlights the growing concern across Europe for the environmental conditions, not least the state of biodiversity and water resources. Biodiversity and water resources are still under a growing pressure, not least due to changing climate conditions.

8 min

In Denmark and other countries, we see a growing pressure on the Natura 2000 designated areas in connection with flood protection planning, highlighting the needs for be better integrating flood risk management with nature concerns. We also experience good examples of successful projects where flood risk management and nature restoration and conservation go hand in hand.

In an urban context, blue-green infrastructure (BGI), notably parks, green paths and lakes, need to be re-invented with a stronger focus on biodiversity and multiple ecosystem services.

Biodiversity and natural habitats

A core element of the biodiversity policy is the implementation of the Habitats and Birds Directives – both key legal instruments dedicated to habitat and species conservation. The overall aim of the Habitats Directive is to promote the maintenance of biodiversity, taking account of economic, social, cultural and regional requirements. The Birds Directive ensures protection for all of Europe's wild birds. Member States are required to designate areas which are critical for the survival of the targeted species and habitats under both directives, amongst them several rare or threatened floodplain and wetland species. These areas together form the EU Natura 2000 network.

Pressure on ecosystem and water resources in Europe

In general, Europe is not on track to meet the objective of achieving good ecological status for all surface waters by 2020, nor on the right track on improving the status of protected species and habitats, and the overall pressures on waters remain high.

There has been mixed progress in the past 6 years with Europe’s surface waters. Only 40 % of the surface waters are in good ecological status. The conservation status of protected habitats and species in freshwater remains low across Europe.

Nature-based flood risk management – less costly and possibly multiple co-benefits

According to EU, spatial planning, including regulation of floodplain development and relocation, should consider more ‘room for rivers’ and this could have beneficial effects for both flood-prevention and water scarcity challenges. Nature based solutions (NBS), which do not involve large structural measures, such as dikes and pumps, are more flexible and sustainable than the hard measures. However, hard flood protection measures are often necessary to handle the effects of rare major floods events.

In Denmark, BGI and NBS on average cost four times less than traditional solutions for rainwater handling in urban areas. The environmental impact of BGI compared with more traditional grey infrastructure was recently studied by researchers at the Danish Technological University (Brudler et al., 2016), showing that BGI is most cases have an overall environmental footprint much smaller than grey infrastructure.

As competition for green space is an issue in all heavily urbanized areas, we need to work on integrating the blue-green infrastructure and nature-based solutions into the urban fabric. The challenge is to find the right balance, building with nature, and safeguarding biodiversity and vulnerable habitats, but also protecting communities against flood in the least costly manner. Finding the best solutions demands a holistic view and a strong stakeholder involvement from planners and environmentalists to local communities, politicians and governmental agencies.

Case study – Ringsted River Restoration

Ringsted River is a beautiful small stream running from lake to lake through meadows, agricultural land and green rolling hills. It has a large natural watershed with relatively few km2 in peri-urban areas around the city of Ringsted. To reduce the effects of flooding in the city, in 2015 it was proposed to use the meadows close to the river to store and clean water in Nature Based Solutions before discharging into the river. A close dialogue between city planners, city environmental managers and the utility company in charge of handling storm water was initiated. The environmental managers and city planners wanted a more accessible riverside for the public and higher biodiversity - and the utility company wanted storm water basins less costly than the traditional underground concrete basins in the city centre.

The results after four years of development, environmental impact assessments and dialogue with multiple users along the river was a multifunctional nature-based system with multiple recreational values, higher biodiversity and a meadow containing more water with a potential carbon-offsetting effect. All in all, a highly successful project, where flood risk reduction, biodiversity and environmental protection went hand in hand.

Flexibility in the city administration, strong political leadership and maybe most importantly an intense citizen dialogue creating win-win situations were among the key to success of the project.

Case study – Tommerup Village Flood Protection

The village of Tommerup originally originated around the small stream Rævedamsløbet. As the village grew, the stream was piped underground making the stream invisible.  The watershed’s natural hydrology became more restricted with a higher risk of flooding of houses and infrastructure. Straight concrete pipes led to deteriorating conditions for fish and fauna in and around the stream.

In 2016, a multidisciplinary project was formulated by the municipality, the water utility and Ramboll with the aim of reopening the stream, and to separate the village rainwater from running directly into the stream water causing environmental harm and increasing the risk of flooding.

By separating Tommerup’s rainwater, it will now be stored and cleaned in three new rainwater basins before being discharged to the stream. The stream water becomes cleaner and the run will be made more natural by meandering for fish and fauna to live and spawn, and ease migration of valuable species such as trout.

Rainwater basins are constructed as shallow lakes with a focus on ecosystem services. Lakes have multipurpose, making them available natural flora and fauna, as well as for the villagers’ recreational activities summer and winter. Finally, the costs involved are much lower than traditional flood risk management and environmental protection measures using grey infrastructure.

The need for balancing flood risk and the environment

In conclusion, there is a growing need for more holistic urban and peri-urban planning under changing climate conditions, where environmental objectives are balanced with flood protection needs, enabling the best solutions for the natural environment and the communities relying on it.

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