Abstract
The fluvial transport is the surface process that has a strong impact on the topography changes, especially in mountain areas. Traditional hydrological measurements usually give a good understanding of the river flow, however, the information of the bedload movement in the rivers is still insufficient. In particular, there is limited knowledge about the movement of the largest clasts, i.e. boulders. This investigation addresses mentioned issues by employing Terrestrial Laser Scanning (TLS) to monitor annual changes of the mountain river bed. The vertical changes were estimated based on the Digital Elevation Model (DEM) of difference (DoD) while transported boulders were identified based on the distances between point clouds and RGB-coloured points. Combined RGB point clouds allowed also to measure 3D displacements of boulders. The results showed that the highest dynamic of the fluvial process occurred between years 2012-2013. Obtained DoD clearly indicated alternating zones of erosion and deposition of the sediment finer fractions in the local sedimentary traps. The horizontal displacement of the rock material in the river bed showed high complexity resulting in the displacement of large boulders (major axis about 0.8 m) for the distance up to 2.3 m.
Highlights
The fluvial transport is the surface process that has a strong impact on the topography changes, especially in mountain areas
This resulted in DEM of difference (DoD) that has excluded areas corresponding to occluded areas in any of source Digital Elevation Model (DEM) (Figure 1)
These values are much higher than the accuracy of point clouds and created models proving that fluvial transport in mountain rivers can be detected and quantitatively assessed using Terrestrial Laser Scanning (TLS) data
Summary
The fluvial transport is the surface process that has a strong impact on the topography changes, especially in mountain areas. Advancing the knowledge of this process contributes in the understanding of surface relief formation and allows to predict its future changes. The data acquired using sedimentary traps provide only partial information about the fluvial transport, because it applies only to the finest fraction of the rock material. The knowledge of the fluvial transport of the largest clats, e.g. boulders (size over 256 mm) and cobbles (64-256 mm) (Wenworth, 1922) is limited because the deposition time of this fraction is long and the frequency of the hydrological incidents strong enough for its transport is low. Other techniques that provide reliable information about the movement of boulders and cobbles are desired. The remote sensing techniques can be potentially used in the fluvial transport monitoring studies since they are able to gather data at different scales
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