Hey there, fellow nature enthusiasts!

In my previous blogs, I have been writing about diverse topics related to the conservation of precious freshwater ecosystems. I started from the diversity of tiny aquatic life forms that live in the sediments of rivers and floodplains; some even can fit within a drop of water! I then moved on to a way bigger scale, discussing the importance of removing barriers from our rivers and letting them flow. Today, I want to write about how my experience during my training at University of Vienna has brought up the vital role of floods in restoring rivers.

Floods are key agents of ecological exchange. Active floodplains teeming with life eagerly await the rush of water that brings renewal and sustenance. These dynamic areas flooded intermittently or seasonally, are vital for countless species that have evolved to depend on these natural rhythms.

Floods also are responsible for the evolution of riverine landscapes. Depending on the time scales, channels of braided rivers can change their position and orientation.

Yet, the story of our rivers isn’t without its challenges. Take the Danube, for example. Once a dynamic, braided river coursing through the landscape, it changed and altered in a large-scale regulation in the 19th century. The construction of dams and engineering structures disrupted its natural flow, gradually disconnected vital floodplains, and created more uniform conditions for navigation.

 

 

Source: austria-forum.org. Grafik: © apa/B. Lager & S. Hohensinner

After the public opposition to a large hydropower project, the largest remnant of alluvial landscape in Central Europe was declared a National Park in 1996 (https://www.donauauen.at/en/facts/history/the-path-to-becoming-a-national-park).

After establishing the National Park, restoration efforts in 1997 and 1998, aimed to regenerate the river’s natural vitality and more dynamic connectivity conditions. Yet, despite initial success, there is still a gradual loss of connectivity in the long term (https://www.viadonau.org/en/company/project-database/dynamic-life-lines-danube/overview-of-aims-and-measures/side-arm-re-connection-haslau-regelsbrunn).

Inflow structure in the region of Haslau-Regelsbrunn in the National Park. Source: © viadonau

Fast forward to today, new restorations are on the horizon, and new plans are underway to reduce the dry fall of these floodplains. The new restoration has plans to create more generous openings so water can flow through unrestricted and fish can have a year-long possibility to pass. Although these measures have not been implemented yet.

In my secondment work at the University of Vienna, alongside my esteemed colleagues John Perez (ESR-8) and Ronnald Poeppl, we’re diving deep into the world of flood modeling. Our goal? To understand how restoration efforts impact flood dynamics and ecosystem connectivity.

We are testing if the pioneer restoration measures (in the late 90s) allowed a bigger area to get inundated during floods. Soon, we’ll be back crunching the numbers, simulating everything from mild floods to once-in-a-century events. Moreover, we’re eager to explore another aspect: investigate the potential outcomes of implementing measures currently in the planning phase. This question has great significance as it could shed light on the management planning process for this protected area.

At this stage of my secondment, we are conducting the first tests and adjusting our model. As a curious fact, we found in our historical database a 200-year flood event! This is the highest intensity since the creation of the national park and we will certainly recreate this event in our models.

The techniques I’ve been exploring give me the flexibility to calculate how connectivity would change if I consider different management settings (before and after the implementation of restoration measures) or flood intensities (i.e., 30-year flood vs. 100-year flood). This helps me better understand the complex conditions that shape life in floodplains and how restoration efforts can more effectively conserve these vital ecosystems.

Acknowledgments: I would like to thank viadonau for providing historical databases that help us define and calibrate our models. I would also like to thank John and Ronny for their teaching, patience, and time during this secondment. Gracias totales!