Title
Modelling the effects of normal faulting on alluvial river meandering
Author
Woolderink, H.A.G.
Weisscher, S.A.H.
Kleinhans, M.G.
Kasse, C.
van Balen, R.T.
Publication year
2022
Abstract
The meandering of alluvial rivers may be forced by normal faulting due to tectonically altered topographic gradients of the river valley and channel at and near the fault zone. Normal faulting can affect river meandering by either instantaneous (e.g. surface-rupturing earthquakes) or gradual displacement. To enhance our under standing of river channel response to tectonic faulting at the fault zone scale we used the physics-based, two-dimensional morphodynamic model Nays2D to simulate the responses of a laboratory-scale alluvial river with vegetated floodplain to various faulting and offset scenarios. The results of a model with normal fault downstepping in the downstream direction show that channel sinuosity and bend radius increase up to a maximum as a result of the faulting-enhanced valley gradient. Hereafter, a chute cutoff reduces channel sinuosity to a new dynamic equilibrium value that is generally higher than the pre-faulting sinuosity. A scenario where a normal fault downsteps in the upstream direction leads to reduced morphological change upstream of the fault due to a backwater effect induced by the faulting. The position within a meander bend at which faulting occurs has a profound influence on the evo lution of sinuosity; fault locations that enhance flow velocities over the point bar dur ing floods result in a faster sinuosity increase and subsequent chute cutoff than locations that enhance flow velocity directed towards the floodplain. This upward causation from the bend scale to the reach and floodplain scale arises from the com plex interactions between meandering and floodplain and the nonlinearities of the sediment transport and chute cutoff processes. Our model results provide a guideline to include process-based reasoning in the interpretation of geomorphological and sedimentological observations of fluvial response to faulting. The combination of these approaches leads to better predictions of possible effects of faulting on alluvial river meandering.
Subject
Alluvial rivers
Faulting
Meandering
Modelling
Morphodynamics
Morphology
Neotectonic
Tectonic
Geological Survey Netherlands
2015 Energy
To reference this document use:
http://resolver.tudelft.nl/uuid:07f750c2-3086-491f-948c-7b0e594046d1
DOI
https://doi.org/10.1002/esp.5315
TNO identifier
967470
Publisher
John Wiley and Sons Ltd
ISSN
0197-9337
Source
Earth Surface Processes and Landforms, 47 (47), 1252-1270
Document type
article