Abstract
Sediment transport is a key evolution process of rivers and water basins. This process can pose flood hazards to nearby areas. The Eulerian and Lagrangian methods are usually employed to describe sediment transport in mountain rivers. The application of different methods was proposed by scientists to analyze specific aspects of solid transport, however a complete understanding still alludes us. After a brief review of the most common methods, the coupling of three different methods is proposed and tested in order to study sediment dynamics, and its spatial and temporal variability, in mountain rivers. Tracers, painted bed patches, and digital elevation model (DEM) comparisons are used to characterize sediment transport at both a micro-scale short-term and a macro-scale long-term level on a test reach on Caldone River, Italy. Information about travel distance, critical diameters, active width, and morphological evolution was sought. We focused on how water discharge is changing the relationships between different measurement techniques. High discharge events force the channel to behave in a unique way, while low discharge events generate more intrinsic variability. Only measurement technique coupling can overcome this issue. Results are encouraging and show the potential of a mixed Eulerian-Lagrangian approach.
Highlights
Sediment transport is a key evolution process of rivers and watersheds
We propose an integration of the Lagrangian and Eulerian methods to create a new dataset to improve our understanding of the problem
The final aim of much research on sediment dynamics in a mountain river is to find a value for solid discharge at the basin outlet
Summary
Sediment transport is a key evolution process of rivers and watersheds. In addition to floods, sediments represent a hazard that can cause major damage to infrastructure and settlements near riparian zones [1,2,3,4]. A deeper knowledge of the sediment sources [5,6,7,8,9,10] is needed to, forecast and control the hazard, understand the underlying physics, and reduce the associated risk This condition is common to both mountain and low-gradient streams, but they are different both in sediment and water flow features, due to high variability in sediment size and sediment sources [11]. The application of classic methods, such as sediment traps or turbidity sampling, to estimate sediment transport in slow current, low gradient rivers, provide reliable results These techniques cannot be extended to steep mountainous rivers due to the variation of hydraulic processes in time and space. The complex condition of the river channel, influenced by boulders, debris, wood, and bedrock [12], causes highly variable bed-load transport rates [13]
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