Scale dependency in quantifications of the avulsion frequency of coastal rivers

Colombera, Luca; Mountney, Nigel P.

doi:10.1016/j.earscirev.2022.104043

Cited by 6 publications

(30 citation statements)

References 145 publications

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“…The size of the spots indicates values of normalized avulsion metrics. Spot colors indicate values of mean shoreline progradation rate (see Colombera & Mountney, 2022).…”

Section: Resultsmentioning

confidence: 99%

“…Alternative proxies for channel avulsion frequencies are computed as the number of avulsion events, channel threads, and delta lobes per unit time. Along with metrics defined as raw counts per unit time, additional measures of avulsion “density” in time and space are computed based on the normalization of each of these quantities with respect to the size of the study area over which they are evaluated, that is, the planform extent of the delta plain or of the active part of coastal plain whose evolution was documented during the time of interest (Colombera & Mountney, 2022). For eight case studies documenting coastal plains traversed by rivers that joined intermittently during the Holocene, the same quantities are also normalized by the maximum number of river systems with distinct catchments that had independent drainage to the sea or lake at some point in time.…”

Section: Methodsmentioning

confidence: 99%

“…Q t is obtained by considering tidal flows as having the sediment concentration of river flows, and is proportional to the ratio between tidal water‐discharge amplitude and mean annual river discharge (Nienhuis et al., 2020). Hence, in view of some scaling of avulsion metrics with river size (Colombera & Mountney, 2022), a normalization was applied in this study whereby Q t is expressed relative to the rate of fluvial sediment supply, Q r . Q r is based on the WBMSed 2.0 distributed global‐scale sediment flux model using the BQART approach (Cohen et al., 2013; Kettner & Syvitski, 2008).…”

Section: Methodsmentioning

confidence: 99%

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Downstream Controls on Coastal Plain River Avulsions: A Global Study

Colombera

Mountney

2023

JGR Earth Surface

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The avulsion frequency of coastal‐plain rivers is primarily governed by the rate at which channels become superelevated over neighboring plains, which is itself controlled by multiple factors. Notably, the importance of wave and tidal processes, the rates of relative sea‐level (RSL) change, and the bathymetry of the receiving basin are thought to affect channel morphodynamics and channel‐mouth progradation, thereby controlling streambed aggradation and influencing the avulsion frequency and drainage density of coastal plains and deltas. This work tests the significance of these downstream factors on the avulsion histories of 57 Holocene lowland river systems. A quantitative analysis is performed of relationships between variables that quantify downstream controls and estimations of avulsion frequency, based on the number of avulsion events, active or abandoned channel paths, and delta lobes; measures of spatiotemporal avulsion “density” are also derived by normalizing these metrics by the size of study areas and the number of distinct drainage systems. Relationships between avulsion‐frequency metrics and descriptors of process regime indicate that wave and tidal processes may stabilize coastal channel systems, but also that their influence may be modest. No consistent relationship is seen between avulsion‐frequency proxies and the offshore bathymetric gradient, which in the studied examples does not scale with the rate of shoreline progradation. No evident trend exists between measures of avulsion frequency and estimated rates of either eustatic or RSL fluctuations. Overall, the considered variables do not leave a clear statistical signature in Holocene avulsion histories, suggesting that upstream or intrabasinal factors may represent more important controls.

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“…The size of the spots indicates values of normalized avulsion metrics. Spot colors indicate values of mean shoreline progradation rate (see Colombera & Mountney, 2022).…”

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Downstream Controls on Coastal Plain River Avulsions: A Global Study

Colombera

Mountney

2023

JGR Earth Surface

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“…Konlechner et al, 2019;Thampanya et al, 2006) could certainly enhance or dampen the overall mobility of the coastline (how much the coastline migrates) and the rates at which the coastline moves (how fast the coastline migrates). Nevertheless, DFSs are affected by continuous lateral channel migration or frequent avulsions at a kyr timescale (Colombera & Mountney, 2022;Porritt et al, 2020) depending on grainsize and sediment load (Cazanacli et al, 2022), none of which occurred within the time frame covered by the DEA Coastline dataset. Such avulsions would influence the spatial distribution of wave, tidal, and fluvial processes along the coastline, as well as diverting the sediment supply.…”

Section: The Sedimentary Recordmentioning

confidence: 99%

Use of Remote-Sensing to Quantify the Distribution of Progradation/erosion Along a Forced-Regressive Modern Coastline: Driving Factors and Impact on the Stratigraphic Record

Zuchuat

Poyatos‐Moré

Nyberg

et al. 2023

The Sedimentary Record

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The long-term development of ancient and modern coastal distributive fluvial systems (DFSs) during periods of relative sea-level highstand or fall usually drives net-progradation of shorelines. Such systems often develop in periods of relative sea-level highstand or fall and typically record annual to millennial-scale deviations in coastal trajectories. A new continental dataset (Digital Earth Australia Coastlines: DEA Coastlines) provides an opportunity to examine such variations in coastal behaviour over annual to decadal scales (1988-2019) at local to continental spatial scales. This dataset is herein applied to the 655 km coastline fronting Australia’s largest amalgamated coastal distributive fluvial systems, which is situated in the epicontinental seaway of the Gulf of Carpentaria in the north of the continent. Despite the overall forced regressive conditions (i.e. progradation during relative sea-level fall), only 54% of this coastlines length net-prograded, whereas 47% was eroded. Though temporal cyclicity in progradation and erosion is evident along segments of this coast, these patterns could not be correlated with either the Southern Oscillation Index (R2 = -0.20) or rainfall (R2 = 0.24). Instead, short-term coastline dynamics appear to be the result of complex interactions between fluvial, wave, longshore current, and tidal processes. The high-resolution DEA Coastlines dataset highlights the diachronous, heterochronous, composite, and amalgamated nature of net-progradational stratigraphic strata that can develop in shallow-marine environments where hinge-points between prograding and retrograding coastal segments are dynamic features that migrate with time. Our conclusions show that shorelines display granular temporal and spatial deviations in coastal trajectory, with contemporaneous progradation and erosion occurring over 1-100 km length scales. This is significantly more heterogeneity than previously envisaged, thereby suggesting the need for updating models of coastal systems.

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“…Thampanya et al, 2006;Konlechner et al, 2019) could certainly enhance or dampen the overall mobility of the coastline (how much the coastline migrates) and the rates at which the coastline moves (how fast the coastline migrates). Nevertheless, DFSs are affected by continuous lateral channel migration or frequent avulsions at a kyr timescale (Porritt et al, 2020;Colombera and Mountney, 2022) depending on grainsize and sediment load (Cazanacli et al, 2022), none of which occurred within the time frame covered by the DEA Coastline dataset. Such avulsions would influence the spatial distribution of wave, tidal, and fluvial processes along the coastline, as well as diverting the sediment supply.…”

Section: Driving Factors and Preservation Of The Signal In The Rock R...mentioning

confidence: 99%

Use of remote-sensing to quantify the distribution of progradation/erosion along a forced-regressive modern coastline: driving factors and impact on the stratigraphic record

Zuchuat¹,

Poyatos‐Moré²,

Nyberg³

et al. 2023

Preprint

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The long-term development of ancient and modern coastal distributary fluvial systems (DFSs) during periods of relative sea-level highstand or fall usually drive net-progradation of shorelines, though such deposits usually also record annual to millennial-scale deviations in coastal trajectories. A new continental dataset (Digital Earth Australia Coastlines: DEA Coastlines) provides an opportunity to examine such variations in coastal behaviour over annual to decadal scales (1988-2019) and over vast spatial scales. This dataset is herein applied to the 654 km coastline fronting Australia’s largest amalgamated coastal distributary fluvial systems, which is situated in the epicontinental seaway of the Gulf of Carpentaria. Despite the overall forced regressive conditions, only 54% of this coastlines length net-prograded, whereas 47% was eroded. Though temporal cyclicity in progradation and erosion is evident along segments of this coast, these patterns could not be correlated with either the Southern Oscillation Index (R2 = -0.20) or rainfall (R2 = 0.24). Instead, short-term coastline dynamics appear to be the result of complex interactions between fluvial, wave, longshore current, and tidal processes. The high-resolution DEA Coastlines dataset highlights the diachronous, heterochronous, composite, and amalgamated nature of net-progradational stratigraphic strata that can develop in shallow-marine environments where hinge-points between progradating and retrograding coastal segments are dynamic features that migrate with time. Understanding more granular temporal and spatial deviations in coastal trajectory will help to improve models of such complex net-progradational coastal systems.

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Scale dependency in quantifications of the avulsion frequency of coastal rivers

Cited by 6 publications

References 145 publications

Downstream Controls on Coastal Plain River Avulsions: A Global Study

Downstream Controls on Coastal Plain River Avulsions: A Global Study

Use of Remote-Sensing to Quantify the Distribution of Progradation/erosion Along a Forced-Regressive Modern Coastline: Driving Factors and Impact on the Stratigraphic Record

Use of remote-sensing to quantify the distribution of progradation/erosion along a forced-regressive modern coastline: driving factors and impact on the stratigraphic record

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