Harnessing cross-disciplinary methods to improve the way we manage rivers

In my previous blog post, I discussed the crucial role of allowing our rivers to flow freely to rehabilitate them. These highly dynamic ecosystems are vital for us and for a vast range of biodiversity.

Since very early on in our history, people had been fascinated on rivers. We had built our settlements near their floodplains, relying on them for basic functions such as drinking water, irrigation for agriculture, transportation, generation of electricity through hydropower and for our own leisure and wellbeing. However, riverine landscapes had been submitted to long-term anthropogenic pressures which had led to a rapid decline in freshwater biodiversity. The mismanagement of rivers caused the fragmentation, degradation and drying of aquatic habitats, pollution and increased sedimentation in channels.

In recent decades, there has been a transformation in the way how we take decisions on how to protect these ecosystems. We’ve come to realise connectivity as a central issue for river management. Today, contemporary management measures include the reconnection of rivers by removing damns or reducing connectivity challenges at the sources of pollution or high sedimentation.

To measure connectivity, landscapes can be represented as spatial networks, with their specific network structure varying depending on the ecosystem type and scale of the study. In this blog post, I want to share part the insights gained from the iCONN advanced courses and workshops, where I’ve had the opportunity to hear about connectivity approaches from other disciplines. I’ll also discuss how these approaches have the potential to transform the way how we make decisions when it comes to restoring riverine ecosystems.

 

Connectivity related issues in fluvial systems

At our Vienna workshop, we dived into the concept of connectivity in fluvial landscapes, considering different spatial scales. During this occasion, John (ESR 10) and I had the chance to organise an advanced course with a focus on social-ecological and geomorphological systems. Throughout this course, Ronald Pöppl, Thomas Hein and Andrea Funk introduced the theoretical background of water-mediated (hydrological) connectivity, emphasizing its integration with physical, social and ecological systems. John and I provided as case studies our own study areas located in Austria, the Donau-Auen National Park and Fugnitz catchment.

In the case study of the Donau-Auen National Park, a pilot restoration project was implemented in the mid-90’s, where floodplain wetlands were reconnected with the main Danube channel. In this example, by increasing connectivity with the river channel, this restoration project aimed to enhance aquatic habitats for freshwater biodiversity, increase flood storage and enhance spatial and temporal dynamics of ecological processes in floodplains. In this case study, I am interested in assessing the changes that restoration induced on the aquatic habitat connectivity for freshwater ornganisms that serve as indicator groups.

In contrast, in the second case study, John presented the panorama at the Fugnitz catchment. Here we could observe a very different connectivity issue, the increase of in-channel soil inputs caused by land use and agricultural practices. In his case study, John focuses on locating hotspots and moments of increased sediment transport. The assessment of sediment connectivity can then be used to inform management about what are the best agricultural practices to reduce the sediment inputs in the channel (e.g. direction of tillage).

These case studies provide a complementary picture to the management of connectivity related issues in fluvial landscapes. Both landscapes, whether a hillslope or river-floodplain scales, can be represented as spatial networks. In this context, structural connectivity refers to the physical connections and surface roughness between elements of the landscape (nodes). Meanwhile, functional connections account for dynamical ecological and geomorphological transport processes (dispersal of animals and transport of sediments).

During the Vienna workshop, ESRs explore possible ways to abstract the hillslope and river-floodplain landscapes as social and ecological systems. They also explored possible network science tools for calculating connectivity.

 

Novel approaches for collecting high resolution data in connectivity science

Fast forward to Cyprus, where we finally had the opportunity to be in Nicosia for the advanced course in collecting high resolution data. During our initial workshop, Rebecca Hodge introduced us to different sources of high-resolution data to analyse geomorphologic connectivity. We started the workshop with a field trip to the astonishing Choirokoitia site.

We gathered information on the surface terrain of a hillslope using a terrestrial laser scanner.

In the following days, we gained the hands-on experience of calculating surface roughness using the surface terrain information that we collected in the field, along with remote sensing information from aerial lidar as additional high-resolution data source.

In the second part of our workshop, our focus shifted to brain connectivity. We covered diverse topics and techniques to measure it including an introduction on magnetoencephalography and collection of brain activity data with EEG. Brain networks are yet another example of spatial networks, but at a very small spatial scale (few millimetres) and at temporal scales that go from milliseconds till hours. During this workshop, we also gained insights into the importance of such techniques in the treatment of patients.

 

But how can connectivity approaches developed in other disciplines assist the management of river system?

This question brings me back to Marseille, were the Datathon took place more than one year apart from the workshops I just mentioned. This was our first try in finding cross-disciplinary applications of connectivity methods and it didn’t come without challenges. And even if it was early on in our iCONN journey, a couple of ESRs, Mel and Chris, had a creative way to answer this question. By building on the ideas developed in their team project during the Datathon, Mel and Chris applied the concepts of time delayed connectivity and the mutual information method, which are methods previously applied in neuroscience, to understanding the transport of geomorphic fluxes in rivers (see the post https://iconn.network/journal/datathon-the-brain-stream-buoys-group/ ).The dynamics of sediments, for example, is highly relevant for the management of fluvial systems since it drives the form of the channel and the heterogeneity of freshwater habitats. Cross-disciplinary application like this one can also be used to enhance our understanding on ecological and physical processes that shape river ecosystems. We could then use these learnings to transform the way we manage and plan the restoration of riverine ecosystems.