Best Practices for Longitudinal Training Walls to mitigate channel bed erosion

Efficacy of Longitudinal Training Walls to Mitigate Riverbed Erosion

The Waal Branch of the Rhine River has eroded over the last 150 years following channel straightening and narrowing. In 2014–2015 a pilot project replaced existing groynes over an 11 km long reach with three longitudinal training walls (LTWs) to mitigate channel bed erosion, among other purposes. Walls are lower than the river bank and split the...

Sediment Nourishments to Mitigate Channel Bed Incision in Engineered Rivers

Engineering modifications of rivers, e.g., dams or groynes, often induce long-term riverbed erosion, which can be mitigated with sediment nourishments. Here, we consider nourishments to mitigate channel bed erosion induced by channel narrowing, as opposed to the more common application downstream of dams. Our objective is to assess and...

Impact of Weir Location on Discharge Partitioning in Longitudinal Training Walls

River Response to Anthropogenic Modification: Channel Steepening and Gravel Front Fading in an Incising River

While most of the world's large rivers are heavily engineered, channel response to engineering measures on decadal to century and several 100 km scales is scarcely documented. We investigate the response of the Lower Rhine River (Germany-Netherlands) to engineering measures, in terms of channel slope and bed surface grain size. Field data...

Degradational response of engineered channels to changes in the upstream controls and channel width: Simplified 1D numerical simulations

In response to changes in the upstream controls (i.e., the water discharge, the sediment supply rate, and the calibre of the load), engineered alluvial channels adjust their bed slope and bed surface texture to establish a new equilibrium state. Here we present and discuss various causes of degradational response of engineered channels to...

A Sand-Gravel Gilbert Delta Subject to Base Level Change

Laboratory experiments were conducted on a sand-gravel Gilbert delta to gain insight on its dynamics under varying base level. Base level rise results in intensified aggradation over the topset, as well as a decrease in topset slope and topset surface coarsening, the signals of which migrate in an upstream direction. Preferential deposition...

Advance, Retreat, and Halt of Abrupt Gravel-Sand Transitions in Alluvial Rivers

Downstream fining of bed sediment in alluvial rivers is usually gradual, but often an abrupt decrease in characteristic grain size occurs from about 10 to 1 mm, i.e., a gravel-sand transition (GST) or gravel front. Here we present an analytical model of GST migration that explicitly accounts for gravel and sand transport and deposition in the...

The equilibrium alluvial river under variable flow and its channel-forming discharge

Mitigation of long-term bed degradation in rivers: set-up of research

Sediment management measures are  becoming increasingly popular as they are  considered sustainable from both economic  and environmental point of view. For example,  aimed at counteracting river bed degradation,  sediment nourishments have been carried out  in the German reaches of the Rhine river while  a...

Causes of long-term bed degradation in rivers: Setup of research

The main objective of this research is to  improve our understanding of the relative  contribution of the causes of long-term bed  degradation in Rhine and other degrading  rivers. That is, the research is intended to  quantify past channel adjustment processes,  mainly bed degradation and bed surface  coarsening...

The graded alluvial river: Profile concavity and downstream fining

There has been quite some debate on the relative importance of particle abrasion and grain size selective transport regarding the river profile form and the associated grain size trends in a graded alluvial stream. Here we present new theoretical equations for the graded alluvial river profile that account for the effects of particle abrasion...

Size stratification in a Gilbert delta due to a varying base level: Flume experiments

Comparison between experimental and numerical stratigraphy emplaced by a prograding delta

A one-dimensional model that is able to store the stratigraphy emplaced by a prograding delta is validated against experimental results. The laboratory experiment describes the migration of a Gilbert delta on a sloping basement into standing water, i.e., a condition in which the stratigraphy emplaced by the delta front is entirely stored in the...

Laboratory experiment of a mixed-sediment Gilbert delta under varying base level (abstract)

Comparison between experimental and numerical stratigraphy emplaced by prograding bedforms with a downstream slip face (abstract)