Numerical modelling of floodplain hydraulics and suspended sediment transport and deposition at the event scale in the middle river Elbe, Germany

Abstract

The objective of this case study was to calibrate and verify a detailed sediment transport model in a 4-kilometre stretch of the middle Elbe floodplains in Germany. The hydraulic RMA-2 model and the SED2d-WES sediment transport model were used. The sediment transport model was verified with a flood event by detailed measurements of surface water levels, flow velocities at six profiles, suspended sediment concentration and sediment deposition (by means of 10 sediment traps). Discharge was modelled for three steady-state conditions. Surface water levels could be calculated to an accuracy of less than 5 cm compared to measurements. The differences between calculated and measured velocities were with one exception smaller than 0.2 m/s (measured range 0.1…1.0 m/s). Simulated average sediment input amount to 35 g/(m 2 d) for the given flood event. The highest calculated sedimentation rates of 700 g/(m 2 d) (dry density 90 kg/m 2 ) took place in backwaters and abandoned channels. Twenty-five percent of the deposited sediment settled in the backwaters (which only account for 13 percent of the area). The most sensitive parameters of the sediment transport model were the settling velocity and critical shear stress. The modelling approach allowed a realistic spatial distributed calculation of sediment inputs into the floodplain of the Elbe River.

Spatial variability in floodplain sedimentation: the use of generalized linear mixed-effects models

“…By coupling hydraulic and sediment deposition models, field-based sedimentation rates and digital elevation models of the floodplain surface were incorporated to numerical modelling in order to reflect the high spatial heterogeneity observed in field-based investigations. Some of these models are based on a discrete-element approach (Stewart et al, 1998;Buttner et al, 2006), and other models on a finite-element approach (Nicholas and Walling, 1997;Nicholas and Walling, 1998;Middelkoop and Van der Perk, 1998). Those techniques advanced the potential to predict sedimentation effects by simple, computationally efficient functions parameterised by distance from the main channel and floodplain elevation.…”

Methods to calculate sedimentation rates of floodplain soils in the middle region of the Elbe River

“…In order to transfer the results to large areas (e. g. in the context of GIS-based extrapolation), it is necessary to identify what proportion of the potential alluvial area is actually flooded. Alternatively the sediment input must be simulated using flux and solid matter transport models [31,32].…”

Sedimentation monitoring including uncertainty analysis in complex floodplains: a case study in the Mekong Delta

“…A number of studies monitoring sedimentation on floodplains have been published, often using mat traps to quantify the accumulative sediment deposition during flood events (Asselmann and Middelkoop, 1995;Steiger et al, 2001Steiger et al, , 2003Middelkoop, 2005;Büttner et al, 2006;Baborowksi et al, 2007;Hung et al, 2013b). But to the knowledge of the authors, these used multiple traps to quantify the deposition at a single point (Asselmann and Middelkoop, 1995;Steiger et al, 2001;Middelkoop, 2005;Baborowksi et al, 2007).…”

“…Sedimentation is mostly monitored by sediment traps, as shown by a number of recent studies (Steiger et al, 2001Middelkoop, 2005;Büttner et al, 2006;Baborowksi et al, 2007;Hung et al, 2013b). Sediment traps can provide cumulative samples for different physical and chemical analyses.…”