The recent catastrophic events in southeastern Austria, Slovenia and Croatia once again put the growing challenge of flooding and flood damage in the media spotlight. Scientists from the National Hub Biodiversity and Water (BiodiWa) explain the causes of these events. They outline sustainable, nature-based solutions that prevent flooding and also have a positive impact on the climate and biodiversity crisis while reducing land consumption.

Floods are natural events that serve an important function in intact river systems. Given enough space, wetlands and rivers maintain a balance by absorbing water like sponges and releasing it when needed. As a result, flood waves flow off much more flatly and, above all, more slowly. These dynamics are vital for ecosystem functioning, habitat diversity and biodiversity. A deep understanding of the process is essential to develop appropriate protection and prevention strategies for people, settlements and infrastructure.

Human activities aggravate flood risk

The experts of BiodiWa hold four main triggers responsible: River regulation (1), such as river straightening and dams, shorten flowing waters, reduce the width of rivers and wetlands and their connection to each other, and thus cause particularly rapid and high water level rises in downstream areas. Building on flood-prone areas (2) increases the extent of damage and destroys natural water reservoirs. Soil sealing (3) prevents rainwater from draining away. Large-scale deforestation and poor agricultural practices also reduce the soil's natural water-holding capacity. Water runs off faster, causing flooding and soil erosion, and increasing the risk of landslides. Triggered by the climate crisis (4), however, the Alpine region is increasingly experiencing prolonged heavy precipitation over large areas or very heavy local precipitation.

Integrative approach required

Experts call for an integrative approach to meet the challenges on several levels: (1) increased measures for non-structural flood protection, based on nature-based solutions and in line with the European Nature Restoration Law and the EU Water Framework Directive. Healthy river ecosystems with their floodplains and wetlands must be restored or, where they still exist, strictly protected from further development. Natural water ecosystems with high biodiversity also have a positive impact on our climate by storing carbon and regulating the water balance. Nature-based flood protection solutions often also have a mitigating effect on droughts, which are at the other end of the spectrum of extreme hydrological events and are also becoming more frequent as a result of climate change. (2) Ambitious climate protection measures must be demanded from politicians. The sufficiently known, targeted steps to reduce greenhouse gases must finally be implemented consistently. This will also reduce the frequency of extreme weather events.

In addition, (3) land-use planning must be sustainable, responsibilities must be re-evaluated. Soil sealing must be stopped. Abandoned built-up areas must be unsealed, renaturalized, and ecosystems restored. Additional investment in local and rapidly effective (4) structural flood control measures (protective dams, levees, reservoirs, etc.) is also necessary to reduce flood hazards. However, technical measures should be limited to the protection of settlements and essential infrastructure. Upstream or downstream, the focus must be on renaturation and the provision of water retention areas for non-structural flood protection. In addition, investment in advanced early warning systems, including new models of global warming, could provide faster and more detailed information about potential hazards.

About the National Hub Biodiversity and Water

The networking activities of the National Hub Biodiversity and Water, its interdisciplinarity and comprehensive expertise support the cooperation of all stakeholders, namely politics, administration, economy, science and the public. By providing access to expert knowledge and a broad dissemination of information, BiodiWa contributes to the further development of integrative flood management and to the promotion of sustainable solutions for the problem of flooding.

This article was written in collaboration with the following experts of the National Hub BiodiWa: Florian Borgwardt (BOKU Vienna), Prof Thomas Hein (BOKU Vienna), Robert Konecny (Environment Agency Austria), Prof em Roland Psenner (Eurac Bolzano), Gabriele Weigelhofer (WasserCluster Lunz); Prof Helmut Habersack (BOKU Vienna) and Günther Unfer (BOKU Vienna).

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