sediment transport; brown trout habitat; mountain stream; flood risk; climate change
Rickenmann Dieter, Böckli Martin, Heimann Florian U.M., Badoux Alexandre, Turwoski Jens M. (2016), Bedload transport simulation with the model sedFlow: application to mountain rivers in Switzerland, in Koboltschnig Gernot (ed.), International Research Society INTERPRAEVENT, Klagenfurt, Austria, 387-395.
Junker Julian, Heimann FlorianU.M., Hauer Christoph, Turowski JensM., Rickenmann Dieter, Zappa Massimiliano, Peter Armin (2015), Assessing the impact of climate change on brown trout (Salmo trutta fario) recruitment, in Hydrobiologia
, 751(1), 1-21.
Heimann Florian U.M., Rickenmann Dieter, Böckli Martin, Badoux Alexandre, Turowski Jens M., Kirchner James W. (2015), Calculation of bedload transport in Swiss mountain rivers using the model sedFlow: proof of concept, in Earth Surface Dynamics
, 3(1), 35-54.
Junker Julian, Heimann FlorianU.M., Hauer Christoph, Turowski JensM., Rickenmann Dieter, Zappa Massimiliano, Peter Armin (2015), Erratum to: Assessing the impact of climate change on brown trout (Salmo trutta fario) recruitment, in Hydrobiologia
, 751(1), 23-24.
Heimann Florian U.M., Rickenmann Dieter, Turowski Jens M., Kirchner James W. (2015), sedFlow – a tool for simulating fractional bedload transport and longitudinal profile evolution in mountain streams, in Earth Surface Dynamics
, 3(1), 15-34.
Badoux A. Peter A. Rickenmann D. Junker J. Heimann F. Zappa M. Turowski J.M. (2014), Geschiebetransport und Forellenhabitate in Gebirgsflüssen der Schweiz: mögliche Auswirkungen der Klimaänderung
, SWV, Wasser Energie Luft, Baden, Switzerland.
Rickenmann D. Heimann F. Böckli M. Turowski J.M. Bieler C. Badoux A. (2014), Geschiebetransport-Simulationen mit sedFlow in zwei Gebirgsflüssen der Schweiz
, SWV, Wasser Energie Luft, Baden, Switzerland.
Riedl Christina, Peter Armin (2013), Timing of brown trout spawning in Alpine rivers with special consideration of egg burial depth, in Ecology of Freshwater Fish
, 22(3), 384-397.
Badoux Alexandre, Turowski Jens Martin, Mao Luca, Mathys Nicole, Rickenmann Dieter (2012), Rainfall intensity-duration thresholds for bedload transport initiation in small Alpine watersheds, in NATURAL HAZARDS AND EARTH SYSTEM SCIENCES
, 12(10), 3091-3108.
Several studies indicate that climate change will affect flooding and sediment transport in mountain catchments in Switzerland over the coming 40 to 100 years. Sediment yield in a catchment is dependent both on the stream’s capacity to transport and on the availability of loose material. Changing atmospheric circulation will affect the regional distribution and amount of precipitation, and thus possibly the number and frequency of extreme events, and their time of occurrence throughout the year. The extent of glaciation and of permafrost zones, and vegetation patterns will respond to changing temperature, with various effects on sediment availability. The expected resulting increase of the sediment load of a given flood will affect both stream morphology and flood risk assessment. The anticipated hydrological changes will have clear consequences for salmonid survival in mountain streams. Brown trout (Salmo trutta fario) is the most important fish species in Alpine rivers and can be used as an indicator species. The main goal of the proposed project is to study the effect of changing climate conditions on flood and sediment transport behaviour in mountain rivers, and to examine the related impact on trout habitat conditions. The modelling of the sediment transport behaviour for future environmental conditions will be accomplished by adapting an existing, cellular automaton based sediment transport model. The findings of this study will serve to formulate recommendations concerning an ecologically sound river management for the fish habitat both for present and future environmental conditions. The model predictions will also be a basis for the evaluation of future potential sediment hazards at the catchment scale. The main expected outcome of the project can be summarized as follows:•Prediction of the impact of climate change on sediment delivery from Alpine basins•Quantification of relevant components of climate change (snowmelt, glacial melt, vegetation cover) which will have the biggest impact on sediment delivery (which will support flood risk mitigation)•Prediction of the influence of climate driven changes in sediment delivery on fish habitats and related consequences for the survival of brown troutOne of the most highly developed cellular automaton model for fluvial environments cur-rently available is the Cellular Automaton Evolutionary Slope And River (CAESAR) model (Coulthard et al., 2007). This model is appropriate to consider the evolution of coarse and fine sediment transfer in Alpine catchments over longer time periods. It can be operated at two different scales (catchment and reach scale), and has been successfully applied in similar sized UK catchments responding to climate change during the Holocene. Recently, the CAESAR model has been applied to an Alpine environment in eastern France, and the simulated sediment transport successfully compared with the sediment record over the period from 1825 to 2005.The project will be organized in four main tasks, namely “CAESAR model adaptation” (T1), “Investigation of the brown trout life cycle” (T2), “Assessing climate change effects on sediment transport and brown trout habitat” (T3), and “Implementation activities” (T4). An important input to the modelling are the expected climatologic conditions (e.g. rainfall, temperature) for the next 40 years. For this purpose we will coordinate our project with related studies which will provide information on climate change effects on flood scenarios, including glacier retreat and forest cover changes. The task T1 “CAESAR model adaptation” aims to quantify the sediment supply and transfer in typical Swiss mountain catchments, including calibration with past flood events. We will identify dominant hillslope processes and methods for sediment delivery, based on previous studies in Alpine headwater catchments. The elements to be modified in the CAESAR model intend to better represent some important processes in the study catchments and include: snowmelt module, glacial meltwater module, hillslope processes component including quantification of hillslope sediment supply, component to account for changing sediment availability, bedload transport equations tested for mountain rivers and torrents. It is then essential to test and calibrate the modified CAESAR model with past flood events including substantial sediment transport. During the last 10 to 15 years, several large flood events occurred in Switzerland that suit this purpose.In task T2 “Brown trout life cycle” we will study the preferred habitat conditions for brown trout with field investigations in 4-5 prealpine and alpine rivers, and model these conditions with CAESAR. The key environmental variables to describe habitat requirements of brown trout in the model PHABSIM and CASiMiR are streamflow velocity, water depth and substrate properties. Brown trout spawning behaviour will be observed and documented, considering variables used in the habitat models, and new variables will be added (burial depth). Trout spawning sites will be characterized and furthermore, eggs will be artificially incubated in the stream bed and the survival will be monitored at different times, until the time of emergence. In addition wild fry survival will be studied. Using the CAESAR model, we will simulate discharge, flow depth, velocity and substrate variables in two dimensions at a high spatial and temporal resolution. The planned observations at the study river reaches will be used to establish habitat preference curves. Hydraulic and ecological observations will be used to assess the suitability of the CAESAR model predictions to predict the key variables that are essential to characterize the trout habitat conditions.In task T3 “Climate change effects” we will model the effects of expected changes in precipitation, flood occurrence and sediment availability/supply to stream channels due to climate change over the next 40 years. Modelling of sediment transport processes with the modified CAESAR version will be made, accounting for the expected climate change effects on rainfall/flood evolution and sediment supply at the catchment scale and at the reach scale. Model runs will be carried out on relatively coarse spatial scale, using a 25 m grid. The model simulations will show how sediment transfer along the channel system will change for different scenarios of flood occurrence and hillslope sediment delivery. The simulation results (catchment scale) at the upstream point of the selected river reaches will form the input condition for the simulations at a finer spatial scale, with a 2-5 m grid. The focus will be on river reaches of several km lengths which are also part of the field investigations on trout habitat conditions. In task T4 “Implementation activities” we will regularly discuss our findings with stakeholders and we will focus on know-how transfer and software tools to practicing engineers and decision makers. We plan to inform the target audience, i.e. the stakeholders at BAFU and cantonal authorities as well as the practitioners in river engineering and ecological consulting companies, of the findings of our project by the following means: reports summarizing best-practice guidelines for integrated river management; publications in applied journals; workshops with stakeholders at FOEN, cantonal authorities, engineering consultants; a symposium to inform the target audience; and a software tool to predict sediment transport and trout habit conditions.With this project we intend to improve the understanding of the effects of climate change on sediment transporting flood flows, the evolution of river morphology and associated flood hazards in mountain catchments. The project will also contribute to a better understanding of disturbances on the salmonid spawning and rearing habitat, which is basic for future salmonid management and spawning habitat remediation.