River Response to Anthropogenic Modification

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

Ylla Arbos, C. (TU Delft Rivers, Ports, Waterways and Dredging Engineering)
Blom, A. (TU Delft Rivers, Ports, Waterways and Dredging Engineering)
Viparelli, E. (University of South Carolina)
Reneerkens, M. (Rijkswaterstaat)
Frings, R. M. (Rheinisch-Westfälische Technische Hochschule; Rijkswaterstaat)
Schielen, R.M.J. (TU Delft Rivers, Ports, Waterways and Dredging Engineering; Rijkswaterstaat)

2021

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 show domain-wide incision, primarily associated with extensive channel narrowing. Remarkably, the channel slope has increased in the upstream end, which is uncommon under degradational conditions. We attribute the observed response to two competing mechanisms: bedrock at the upstream boundary increases the channel slope over the upstream part of the alluvial reach to compensate for the reduction of net annual sediment mobility, and extensive channel narrowing reduces the equilibrium slope. Another striking feature is the advance and flattening of the gravel-sand transition, suggesting its gradual fading due to an increasingly reduced slope difference between the gravel and sand reaches.

alluvial rivers
bedrock
channel bed incision
channel slope
gravel-bed rivers
gravel-sand transition

http://resolver.tudelft.nl/uuid:5a9ac0ec-18e5-4789-94c4-058f6f93545a

https://doi.org/10.1029/2020GL091338

0094-8276

Geophysical Research Letters, 48 (4), 1-10

Institutional Repository

journal article

© 2021 C. Ylla Arbos, A. Blom, E. Viparelli, M. Reneerkens, R. M. Frings, R.M.J. Schielen