Interdisciplinary research on rivers

Identification and quantification of habitats

Riverscapes are composed of a variety of landforms, which host different habitats for terrestrial, aquatic and amphibian species. A habitat results from particular physical and biotic factors and represents a suitable location that supports the establishment, survival and reproduction of species. One of the 13 subprojects studied the prediction of suitable habitats for the German tamarisk (Myricaria germanica), a species typical of riparian gravel bars and an indicator for near-natural river reaches. In doing so, researchers from VAW and WSL linked a large-scale ecological statistical model with a two-dimensional deterministic hydrodynamic model.

The identification and quantification of habitats is crucial for the management of riverscapes. The amount and variety of habitat are linked to the biodiversity and ecological resilience of a given environment. Habitat analysis has practical applications for river managers, for example for evaluating the consequences of changes in environmental conditions, such as the hydrological regime (e.g. natural floods) or climate variables (e.g. temperature increase), on target plant or animal species.

Flood protection for riverine organisms

In another sub-project, researchers from the VAW of ETH Zurich and Eawag investigated how a specific type of restoration project – dynamic river widening – develops with a reduced supply of bedload. In many rivers in Switzerland, barriers or bank protection structures reduce the input of bedload. What does this mean for the organisms in the watercourses, especially during floods? Riverine organisms are dependent on refugia such as backwaters or side channels to protect themselves from the raging floods. In the joint studies, the researchers found that bedload supply plays a decisive role in determining the extent to which river widening can improve the supply of refugia and thus protect biodiversity.

The response of the river

Lateral diversion structures in rivers are common measures used to divert parts of the discharge during flood events. The lateral overflow reduces discharge and thus bedload transport capacity in the main channel, resulting in sediment deposition. Researchers from VAW studied the interactions between lateral discharge and changes in bed level by numerical 1D and 2D modelling using the software BASEMENT and prepared recommendations for practical model applications.

Fine sediment deposition on floodplains

Rivers extend beyond the channels that are typically associated with this word. Of particular interest are floodplains, where important hydro- and morphodynamic processes occur. Recurrent flooding of floodplains may create specific habitat conditions that support the establishment of many species in need of conservation – processes which are relevant for river restoration projects. Researchers from VAW of ETH Zurich and the Platform of Hydraulic Constructions (PL-LCH) of EPFL investigated the hydro-morphodynamic processes of fine sediment deposition on floodplains. The main findings were implemented in the simulation tool BASEMENT to forecast fluvial responses due to flood events.