Modelling basin-scale sediment dynamics in the Petit lac d'Annecy catchment, France
Welsh, Katharine Elizabeth
PublisherUniversity of Liverpool
MetadataShow full item record
This research describes the testing, development and application of an established hydro-geomorphic numerical model (CAESAR) over different time scales (170-2000 years) to simulate at hourly time resolution, the changes in the hydrological and sediment regime of the Petit lac d’Annecy catchment in response to changes in system drivers. Two thousand year long model runs in five different morphological settings were simulated, the results suggest that intrinsic system behaviour such as storage-release, hillslope-channel coupling and supply-capacity relationships may well exert larger controls on sediment discharge patterns over this timescale than climate or land use drivers. Hypothetical scenarios to investigate the geomorphic implications of a snow-free pre-alpine region over the last 2000 years show that there would be around 1.4 times more sediment discharge, with the annual hydrological regime radically altered with increased flooding throughout the year, particularly in winter months and a lack of a sustained discharge peak in the ‘melt’ months. This has implications for the projected environmental changes over the coming decades. The simulated effects of increased precipitation, reduced forest cover and snow-free conditions, in combination, point to increased amounts of coarse sediment discharge within the channels. Broad estimations show that a 20% reduction in forest cover or snow-free conditions can result in an additional 1m of sediment moving through the system and accumulating in the lake with potentially large impacts on flooding, in-channel fauna, benthic-dwelling lake fauna, aquatic macrophysics and water quality and water availability for storage and local power generation.