Les systèmes fluviaux à chenaux anastomosés en milieu périglaciaire : la Léna et ses principaux affluents (Sibérie centrale)

Gautier, Emmanuelle; Costard, F.

doi:10.7202/005647ar

Cited by 20 publications

(17 citation statements)

References 40 publications

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“…Between wet and arid cold-climate conditions, a range of fluvial planforms is seen which is similar to that of warmer climates, with braided rivers predominantly in arid conditions. A study of the Lena basin rivers showed the importance of log jams and ice jams (Gautier and Costard, 2000). With the exception of bank strength, which is influenced by permafrost (see section 'Landforms and Processes'), these have no unique link to periglacial conditions.…”

Section: Morphologymentioning

confidence: 99%

PERMAFROST AND PERIGLACIAL FEATURES | Periglacial Fluvial Sediments and Forms

Huissteden¹,

Vandenberghe²,

Gibbard

et al. 2013

Encyclopedia of Quaternary Science

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Section: Morphologymentioning

confidence: 99%

PERMAFROST AND PERIGLACIAL FEATURES | Periglacial Fluvial Sediments and Forms

Huissteden¹,

Vandenberghe²,

Gibbard

et al. 2013

Encyclopedia of Quaternary Science

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“…The width of the channels varies between several hundred metres and three kilometres. These multiple channels enclose large forested islands from 1 to 5 km long and large sandy bars (Anisimova et al, 1973;Gautier and Costard, 2000).…”

Section: Introductionmentioning

confidence: 99%

“…Thawing of the ice (for any ice content) within a porous medium reduces the strength of the thawed sediments and produces easily removable uncemented ground (Jahn, 1975). During the thawing period, with a relatively high discharge, the thawed sediments are swept away (Gautier and Costard, 2000). In this typical situation, the water flow in permanent contact with frozen river banks induces a combination of thermal and mechanical erosion.…”

Section: Introductionmentioning

confidence: 99%

Fluvial thermal erosion: heat balance integral method

Randriamazaoro

Dupeyrat

Costard

et al. 2007

Earth Surf Processes Landf

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In periglacial regions, frozen river banks are affected by thermal and mechanical erosion. In Siberia, bank retreats of up to 40 m per year are observed. This thermal erosion occurs during a few weeks, at springtime, for high enough water temperatures and river discharges. Until now, models of thermal erosion have been based on the assumption of a constant thermal erosion rate. We have developed a more general model at variable rate, whose solution is calculated using the integral method. Results of this model are compared with experiments, carried out in a cold room. A hydraulic channel allows measurements of the thermal erosion rate of a ground ice sample subjected to a turbulent water flow. Once validated, the model is applied to the periglacial river study case. The model has contributed to better understanding of the roles of each parameter during the thermal erosion process. High water temperature, discharge and ice temperature produce major thermal erosion, whereas the ice content in the soil tends to slow down the thermal erosion process. The effects of water temperature are predominant. An acceleration phase characterized by an increase of the thermal erosion rate occurs at the beginning of the thermal erosion process. The duration of such an acceleration phase is systematically studied. A relatively long acceleration phase is related to a low ablation rate. During the flood season, when the water temperature is increased to 18°C, this acceleration phase lasts only a few minutes. However, for data typical of periglacial rivers, when the water temperature is close to the melting point, the acceleration phase can last a few days. Figure 3. Experimental data. Effects of water temperature, discharge and ice temperature on the location of the moving surface s(t). This figure is available in colour online at www.interscience.wiley.com/journal/espl 1834 R. Randriamazaoro et al.Figure 4. Evolution of the thermal erosion rate for different water temperatures, discharges, ice temperatures and ice contents. The reference case (bold line) corresponds to ice at −7·5°C in contact with a water flow at 5·5°C and a Reynolds number equal to 15 900. corresponds to 90% of the final erosion rate and gives the duration of the acceleration phase (A.P.). This figure is available in colour online atFigure 6. Applications to an arctic river. Effects of water temperature, discharge, ice temperature and ice content on the thermal erosion rate and the duration of the acceleration phase. Bold line, reference case. , duration of the acceleration phase. Synthesis and DiscussionWater temperature and discharge can be represented by the heat flux exchanged by convection at the interface between the water flow and the permafrost (Equation (21) and Figure 7).

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“…A numerical model in combination Figure 1. Water mean temperatures and discharge in the Lena River at Tabaga (Gautier and Costard, 2000). This figure shows the instantaneous discharge against time and suggests that the majority of the discharge occurs during a short breakup period of about one month in June with a laboratory simulation is proposed to understand the strong erosion rates along some river banks.…”

Section: Fluvial Thermal Erosionmentioning

confidence: 99%

“…Their fluvial regime maximizes bed-sediment transport under very low gradient and efficient discharges. Therefore, the sediment load (mainly sandy deposits) does not migrate over long distances downstream and is accumulated on wide bars and long islands (Gautier and Costard, 2000).…”

mentioning

confidence: 99%

Fluvial thermal erosion investigations along a rapidly eroding river bank: application to the Lena River (central Siberia)

Costard

Dupeyrat

Gautier

et al. 2003

Earth Surf Processes Landf

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In Central Yakutia, frozen river banks are affected by a combination of thermal and mechanical erosion. Exceptional bank retreat of up to 40 m per year is observed. This results from ground thawing produced by heat transfer from the flow of water through the frozen ground, followed by mechanical transport of the thawed sediments. A one-dimensional model is proposed to estimate the thermal erosion efficiency. A test of this model is a comparison of results obtained from experiments carried out in a cold room. A hydraulic channel allows measurements of the thaw front propagation, as well as the thermal erosion rate, in simulated ground ice that is subjected to warm water flow. Various laboratory simulations demonstrate the validity of the mathematical model for the range of laboratory conditions. A hierarchy of parameters (Reynolds number, water and ground ice temperatures) is proposed to explain the present efficiency of thermal erosion along the Siberian rivers. From the characteristics of the Lena River (geometry, temperature and discharge) during the flood season, the erosion of banks with different ice content predicted by the model is in agreement with field observations.

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Les systèmes fluviaux à chenaux anastomosés en milieu périglaciaire : la Léna et ses principaux affluents (Sibérie centrale)

Cited by 20 publications

References 40 publications

PERMAFROST AND PERIGLACIAL FEATURES | Periglacial Fluvial Sediments and Forms

PERMAFROST AND PERIGLACIAL FEATURES | Periglacial Fluvial Sediments and Forms

Fluvial thermal erosion: heat balance integral method

Fluvial thermal erosion investigations along a rapidly eroding river bank: application to the Lena River (central Siberia)

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