Fluvial Processes and Contemporary Fluvial Denudation in Different Mountain Landscapes in Western and Central Norway

Abstract

In the mountainous landscapesLandscapes of mainland NorwayMainland Norway, fluvial processesFluvial processes and contemporary fluvial denudationFluvial denudation occur in both non-glacierizedNon-glacierized and glacierizedGlacierized (glacier-connected)Glacier-connected drainage basin systemsDrainage basin system. Fluvial processesFluvial processes in non-glacierizedNon-glacierized cold climate drainage basins are driven by snowmelt or rainfallRainfall, or by combinations of snowmelt and rainfallRainfall, whereas fluvial processesFluvial processes in glacier-connectedGlacier-connected drainage basin systemsDrainage basin system are generated by snowmelt, glacier melt or rainfallRainfall, or by combinations of snowmelt/glacier melt and rainfallRainfall. Contemporary chemical and mechanical fluvialMechanical fluvial denudation denudationFluvial denudation ratesDenudation rate in drainage basins of the partly glacierizedGlacierized and very steep mountainMountain landscape landscapeLandscapes of the inner NordfjordInner Nordfjord in western NorwayWestern Norway and of the non-glacierizedNon-glacierized and less steep mountainMountain landscape landscapeLandscapes located south of the Trondheim fjord in central NorwayCentral Norway are found to be rather low, with mechanical fluvialMechanical fluvial denudation denudationFluvial denudation being significantly higher in the steeper and partly glacierizedGlacierized mountainMountain landscape landscapeLandscapes of the inner NordfjordInner Nordfjord as compared to the studied mountainMountain landscape landscapeLandscapes in central NorwayCentral Norway. In the partly glacierizedGlacierized mountainMountain landscape landscapeLandscapes of the inner NordfjordInner Nordfjord mechanical fluvialMechanical fluvial denudation denudationFluvial denudation clearly dominates over chemical denudationChemical denudation, whereas the non-glacierizedNon-glacierized mountainMountain landscape landscapeLandscapes in central NorwayCentral Norway is characterized by a clear dominance of chemical denudationChemical denudation over mechanical fluvialMechanical fluvial denudation denudationFluvial denudation. In the inner NordfjordInner Nordfjord pluvially triggeredPluvially triggered denudational process eventsDenudational process events and pluvially activated sediment sources in ice-free surface areas as well as pluvially induced fluvial suspended sediment transportSuspended sediment transport are, with respect to their overall contribution to drainage basin-wide annual suspended sedimentSuspended sediment yield yieldsSediment yield, more important than the mostly thermally induced suspended sediment transportSuspended sediment transport during the summer (glacier ablation)Glacier ablation or in spring (snowmelt). However, the highest quantitative share of fluvial bedload transportBedload transport occurs here during thermally generated snowmelt peak runoffPeak runoff in spring which is due to a significantly higher availability of bedload materialBedload material within the mainstream channelsStream channel as compared to time periods later in the hydrological yearHydrological year. Compared to that, in the studied non-glacierizedNon-glacierized mountainMountain landscape landscapeLandscapes in central NorwayCentral Norway, the highest quantitative share of the total fluvial transportFluvial transport occurs during thermally inducedThermally induced runoff snowmelt peak runoffPeak runoff in spring. With respect to the total annual sediment mobilizationSediment mobilization and total annual fluvial sediment transport, the sum of snowmelt-generated peak runoffPeak runoff events occurring over the hydrological yearHydrological year is here altogether more important than the annual sum of purelyRainfall rainfall-generated peak runoffPeak runoff events. While the larger topographic reliefTopographic relief and the partly glacial coverageGlacial coverage in the mountainMountain landscape landscapeLandscapes of the inner NordfjordInner Nordfjord are important factors for the higher mechanical fluvialMechanical fluvial denudation denudationFluvial denudation ratesDenudation rate, the clearly higher importance of extreme pluvial eventsPluvial event with respect to mobilization and transport of sediments within the drainage basins of this mountainMountain landscape landscapeLandscapes as compared to drainage basins in the non-glacierizedNon-glacierized mountainMountain landscape landscapeLandscapes south of the Trondheim fjord in central NorwayCentral Norway must be highlighted. Fluvial transportFluvial transport in the studied fluvial systemsFluvial system in western and central NorwayCentral Norway is clearly supply limitedSupply limited. It is expected that postulated changes of the current wind, air temperature and precipitation regimes will lead to increased chemical and mechanical fluvialMechanical fluvial denudation denudationFluvial denudation ratesDenudation rate in both partly glacierizedGlacierized drainage basin systemsDrainage basin system in western NorwayWestern Norway and non-glacierizedNon-glacierized drainage basin systemsDrainage basin system in central NorwayCentral Norway.