Alluvial connectivity in multi-channel networks in rivers and estuaries
| Autor: | Wout M. Dijk, Willem Sonke, M. R. Hiatt, Maarten G. Kleinhans, Bettina Speckmann |
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| Přispěvatelé: | Applied Geometric Algorithms, Biogeomorphology of Rivers and Estuaries, Coastal dynamics, Fluvial systems and Global change |
| Jazyk: | angličtina |
| Rok vydání: | 2022 |
| Předmět: |
010504 meteorology & atmospheric sciences
Geography Planning and Development 0207 environmental engineering 02 engineering and technology algorithms 01 natural sciences estuary Physics::Geophysics Earth and Planetary Sciences (miscellaneous) 14. Life underwater 020701 environmental engineering Multi channel 0105 earth and related environmental sciences Earth-Surface Processes Hydrology Planning and Development geography geography.geographical_feature_category Geography Estuary connectivity bifurcation network Alluvium Geology |
| Zdroj: | Earth Surface Processes and Landforms, 47(2), 477-490. Wiley Earth Surface Processes and Landforms, 47(2), 477. Wiley Online Library |
| ISSN: | 0197-9337 |
| Popis: | Channels in rivers and estuaries are the main paths of fluvial and tidal currents that transport sediment through the system. While network representations of multi-channel systems and their connectivity are quite useful for characterisation of braiding patterns and dynamics, the recognition of channels and their properties is complicated because of the large bed elevation variations, such as shallow shoals and bed steps that render channels visually disconnected. We present and analyse two mathematically rigorous methods to identify channel networks from a terrain model of the river bed. Both methods construct a dense network of locally steepest-descent channels from saddle points on the terrain, and select a subset of channels with a certain minimum sediment volume between them. This is closely linked to the main mechanism of channel formation and change by displacement of sediment volume. The two methods differ in how they compute these sediment volumes: either globally through the entire length of the river, or locally. We compare the methods for the measured bathymetry of the Western Scheldt estuary, The Netherlands, over the past decades. The global method is overly sensitive to small changes elsewhere in the network compared to the local method. We conclude that the local method works best conceptually and for stability reasons. The associated concept of alluvial connectivity between channels in a network is thus the inverse of the volume of sediment that must be displaced to merge the channels. Our method opens up possibilities for new analyses as shown in two examples. First, it shows a clear pattern of scale dependence on volume of the total network length and of the number of nodes by a power law relation, showing that the smaller channels are relatively much shorter. Second, channel bifurcations were found to be predominantly mildly asymmetrical, which is unexpected from fluvial bifurcation theory. |
| Databáze: | OpenAIRE |
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