Experimental alluvial fans: Advances in understanding of fan dynamics and processes

Clarke, Lucy

doi:10.1016/j.geomorph.2015.04.013

Cited by 46 publications

(36 citation statements)

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“…Bryant et al, 1995;Whipple et al, 1998). These scaled physical models have allowed researchers to get around the impracticality of long-term field observation, and to freely manipulate 'environmental' controls (Clarke, 2015). While informative, the utility of experiments is somewhat limited by scaling issues, as well as a high degree of abstraction from reality.…”

Section: Introductionmentioning

confidence: 99%

Tributary‐junction fans as buffers in the sediment cascade: a multi‐decadal study

Leenman

Tunnicliffe

2020

Earth Surf Processes Landf

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Alluvial fans at tributary junctions modulate sediment flux through river networks, by buffering the mainstem channel from disturbance in the tributaries. Buffering occurs through the storage (and release) of sediment in fans. Here, we use an extensive historic dataset to characterise the ways in which fan buffering can change as sediment supply varies. In New Zealand's East Coast region, sediment supply and fluvial transport are prolific by global standards. We reconstruct how tributary‐junction fans in this region have responded to sediment generated by deforestation and extreme storms. The dynamics of five fans along the Tapuaeroa River are examined for the period 1939–2015. In response to major sediment loading, fans aggraded by up to 12 m and prograded by up to 170 m. Net sediment accumulation ranged from near zero to 1.5×106 m3. Fan size, gradient, sediment storage and buffering were influenced by both upstream and downstream controls. Key upstream (tributary) influences were sediment supply and stream power; downstream (mainstem) influences included distal confinement and, importantly, the nature of fan interaction with the mainstem, which aggraded by up to 6 m. The fans' ability to buffer the Tapuaeroa River from change in the tributaries was largely governed by this downstream interaction: as the mainstem aggraded, it increasingly curtailed fan progradation, thus limiting buffering. Previous studies of tributary‐junction fans have related fan morphometry to basin characteristics. However, we find that fan slope and area can vary considerably at decadal, annual or even monthly timescales. Consequently, we suggest that such studies could benefit by examining regional histories of disturbance. © 2019 John Wiley & Sons, Ltd.

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Section: Introductionmentioning

confidence: 99%

Tributary‐junction fans as buffers in the sediment cascade: a multi‐decadal study

Leenman

Tunnicliffe

2020

Earth Surf Processes Landf

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“…Sediment supply from the source to sink largely depends upon the tectonics, climate, base level, lithology, geomorphology, and morphometry of the drainage basin (Bull, 1962;Hook, 1968;Calvache, Viseras, & Ferńandez, 1997;Harvey, 2002;Harvey et al, 2005;Blair & McPherson, 2009;Shukla, 2009;Goswami et al, 2009;Arzani, 2012;Bahrami, 2013;Goswami, 2016; and references therein). The characters of the accommodation space on the other hand are closely related to the tectonic activities along the basin-margin and/or in the basin, climate-induced variations in sediment and water influx into the basin and base-level fluctuations (Bahrami, 2013;Clarke, 2015;Goswami et al, 2009;Viseras, Calvache, Soria, & Fernández, 2003;Weissman, Bennett, & Lansdale, 2005;Weissman, Mount, & Fogg, 2002). Admittedly, a complex interaction of several allogenic and autogenic forces occurs during the alluvial fan evolution (Clarke, 2015).…”

Section: Discussionmentioning

confidence: 99%

“…The characters of the accommodation space on the other hand are closely related to the tectonic activities along the basin-margin and/or in the basin, climate-induced variations in sediment and water influx into the basin and base-level fluctuations (Bahrami, 2013;Clarke, 2015;Goswami et al, 2009;Viseras, Calvache, Soria, & Fernández, 2003;Weissman, Bennett, & Lansdale, 2005;Weissman, Mount, & Fogg, 2002). Admittedly, a complex interaction of several allogenic and autogenic forces occurs during the alluvial fan evolution (Clarke, 2015).…”

Section: Discussionmentioning

confidence: 99%

Controls of basin margin tectonics on the morphology of alluvial fans in the western Ganga foreland basin's piedmont zone, India

Goswami

2017

Geological Journal

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Six distinct alluvial fans have developed in the western Ganga basin's piedmont zone between the Ganga (aka Ganges) River in the west and the Sarda River in the east. The basin margin is demarked by the active Himalayan Frontal Thrust along which the Siwalik ranges are uplifted and placed over the alluvia of the Ganga basin. The 6 alluvial fans show marked morphological variances, but their morphometric parameters exhibit proportionality relationships with the “mountain‐front sinuosity index (Smf),” “stream‐gradient index (SL),” and “valley‐floor width to height ratio (Vf)” of the adjoining mountain‐front segments. Correlation and regression analyses reveal that these relationships are statistically significant. The size of the fan is directly proportional to the magnitude of Smf and inversely proportional to the magnitude of SL, whereas the fan gradient is inversely proportional to Smf. The higher the Smf and the lower the SL values, the larger and gentler is the alluvial fan. Given that the studied alluvial fans have developed in the same climatic zone and their drainage basins have similar physiographic, geologic, and climatic conditions, the morphological diversities among the alluvial fans are attributed to the tectonics of the basin margin. Moreover, statistical analyses further rule out any significant relationships of the fan size with area, or drainage density of the drainage basin. The lower values of Smf and Vf and higher values of SL indicate a more active nature and, thus, greater/faster uplift of the mountain‐front and expected deepening of the accommodation space in the adjoining basin, which favoured vertical aggradation and development of smaller and steeper alluvial fans. Conversely, the higher values of Smf and Vf and lower values of SL indicate a less active nature and, thus, relatively lower/slower uplift of the mountain‐front and thus creation of shallower accommodation space in the adjoining basin, favouring the development of larger and gentler alluvial fans.

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“…Producing experimental alluvial fans has become common in geomorphology (Schumm et al, 1987;Bryant et al, 1995;Whipple et al, 1998;Ashworth et al, 2004;Van Dijk et al, 2009;Clarke et al, 2010;Powell et al, 2012;Reitz and Jerolmack, 2012;Clarke, 2015). Here, we use a setup similar to that of, for example, Whipple et al (1998) to generate a radially symmetric fan over a horizontal basal surface (Fig.…”

Section: Methodsmentioning

confidence: 99%

“…One way around this problem is to use laboratory experiments, where small alluvial fans can be easily produced under wellcontrolled conditions (Schumm et al, 1987;Parker, 1999;Paola et al, 2009;Clarke, 2015). When water and sediment are injected onto the bottom of a tank, a deposit spontaneously forms around its inlet.…”

Section: Introductionmentioning

confidence: 99%

Self-similar growth of a bimodal laboratory fan

et al. 2017

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Abstract.Using laboratory experiments, we investigate the growth of an alluvial fan fed with two distinct granular materials. Throughout the growth of the fan, its surface maintains a radial segregation, with the less mobile sediment concentrated near the apex. Scanning the fan surface with a laser, we find that the transition between the proximal and distal deposits coincides with a distinct slope break. A radial cross section reveals that the stratigraphy records the signal of this segregation. To interpret these observations, we conceptualize the fan as a radially symmetric structure that maintains its geometry as it grows. When combined with slope measurements, this model proves consistent with the sediment mass balance and successfully predicts the slope of the proximal-distal transition as preserved in the fan stratigraphy. While the threshold-channel theory provides an order-of-magnitude estimate of the fan slopes, driven by the relatively high sediment discharge in our experimental system, the actual observed slopes are 3-5 times higher than those predicted by this theory.

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Experimental alluvial fans: Advances in understanding of fan dynamics and processes

Cited by 46 publications

References 50 publications

Tributary‐junction fans as buffers in the sediment cascade: a multi‐decadal study

Tributary‐junction fans as buffers in the sediment cascade: a multi‐decadal study

Controls of basin margin tectonics on the morphology of alluvial fans in the western Ganga foreland basin's piedmont zone, India

Self-similar growth of a bimodal laboratory fan

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