Hydromorphologie des lônes : suivi scientifique du programme de restauration hydraulique et écologique du Rhône : un observatoire dynamique de l'état écologique du fleuve

Rapport d'étape 2010. in Olivier J.-M. et Lamouroux N. (Coord.

Hydromorphologie des lônes : suivi scientifique du programme de restauration hydraulique et écologique du Rhône : un observatoire dynamique de l'état écologique du fleuve

Rapport d'étape 2010. in Olivier J.-M. et Lamouroux N. (Coord.

Hydrological and hydraulic characterisation of floodplain and its former channels from LiDAR imagery and GIS

International audienc

Sediment deposition in Rhone River dike fields: patterns and control

International audienc

Multi-scale assessment of overflow-driven lateral connectivity in floodplain and backwater channels using LiDAR imagery

International audienceOverflow-driven lateral connectivity significantly influences the spatial distribution and diversity of floodplain habitats and biota. Proper understanding of lateral connectivity in floodplain and backwater channels is therefore critical for assessment of river quality and for targeting management or restoration actions. In this study, we present a methodological framework for spatial and temporal assessments of overflow-driven lateral connectivity at two spatial scales: bypass reach and backwater channel. Firstly, we compute the relative elevations, as well as overflow discharge, duration, and frequency using a simple, raster-based method that uses a LiDAR digital elevation model (DEM), rating curves, and streamflow time series. Subsequently, we analyse the accuracy of this approach with respect to the accuracy of a DEM and evaluate its further applications. Altogether, four 10-km-long bypass reaches and 11 backwater channels are analysed, located along the Rhone River corridor in France. The results proved the precision of the method to be affected by the LiDAR DEM accuracy, which was on average more precise in a typically homogeneous floodplain setting rather than for backwater channel plugs with pronounced topographic complexity and usually riparian forest canopy. Amongst the four studied reaches, Bregnier Cordon proved to have the greatest flooding dynamics, followed by Belley and Chautagne. The hydrological connectivity pattern of Pierre Benite differed significantly. Three longitudinal patterns of hydrological connectivity of backwater channels displayed stepwise advancement of the water. The presented results can be used to assess ecological potential of floodplain habitats and their historic and prospective evolution through time. Copyright (c) 2014 John Wiley & Sons, Ltd

Facteurs contrôlant la sédimentation contemporaine des casiers Girardon. Exemple de 3 tronçons court-circuités sur le Rhône

International audienc

Facteurs contrôlant la sédimentation contemporaine des casiers Girardon. Exemple de 3 tronçons court-circuités sur le Rhône

International audienc

Hydrological and hydraulic characterisation of floodplain and its former channels from LiDAR imagery and GIS

International audienc

Environmental heterogeneity promotes spatial resilience of phototrophic biofilms in streambeds

The loss of environmental heterogeneity threatens biodiversity and ecosystem functioning. It is therefore important to understand the relationship between environmental heterogeneity and spatial resilience as the capacity of ecological communities embedded in a landscape matrix to reorganize following disturbance. We experimented with phototrophic biofilms colonizing streambed landscapes differing in spatial heterogeneity and exposed to flow-induced disturbance. We show how streambed roughness and related features promote growth-related trait diversity and the recovery of biofilms towards carrying capacity (CC) and spatial resilience. At the scale of streambed landscapes, roughness and exposure to water flow promoted biofilm CC and growth trait diversity. Structural equation modelling identified roughness, post-disturbance biomass and a 'neighbourhood effect' to drive biofilm CC. Our findings suggest that the environment selecting for adaptive capacities prior to disturbance (that is, memory effects) and biofilm connectivity into spatial networks (that is, mobile links) contribute to the spatial resilience of biofilms in streambed landscapes. These findings are critical given the key functions biofilms fulfil in streams, now increasingly experiencing shifts in sedimentary and hydrological regimes

Impact of climate change on floodplain inundation and hydrological connectivity between wetlands and rivers in a tropical river catchment

Surface water connectivity between waterbodies in a river–floodplain system is considered one of the key determinants of habitat quality, biodiversity and ecological integrity. This manuscript presents results from an investigation into the potential changes in floodplain inundation and connectivity between wetlands and rivers under projected future climates, in a large river catchment in Western Australia. The study was conducted using a two-dimensional hydrodynamic model (MIKE 21), and the modelling domain included the floodplain reaches encompassing the ecologically important wetlands. A lumped rainfall–runoff model (SIMHYD) was used to estimate local runoff and inflows from ungauged catchments. A SRTM derived 30-m elevation data was used to parameterize land topography and stream networks in the hydrodynamic model. Hydraulic roughness parameters were estimated using a land cover map, which was developed using a combination of aerial photography, topographic maps and Google Earth imagery. The hydrodynamic model was calibrated using stream gauge data and flood inundation maps derived from Moderate Resolution Imaging Spectroradiometer imagery. Model simulated stage heights were combined with land topography to identify floodplain pathways that connect wetlands with rivers.\ud \ud The connectivity of 30 off-stream wetlands was evaluated under present and future climates. The duration of connection of the individual wetlands to the main river channel varied from 1 to 40 days depending on flood magnitude and duration. Topographic relief, location on the floodplain and magnitude and duration of the flood were found to be key factors governing the level of connectivity, and the relationship between return period of flood and inundated area was found to be non-linear. Modelling under a drier future climate indicated that the duration of connectivity of wetlands could be up to 20% less than under the current climate, whilst under a wetter climate the connectivity could be 5% longer. The results of this study provide potential use for future studies on movement and recruitment patterns of aquatic biota, wetland habitat characteristics and water quality and wetland biodiversity assessment