Detailed chronology of mid-altitude fluvial system response to changing climate and societies at the end of the Little Ice Age (Southwestern Alps and Cévennes, France)

Astrade, Laurent; Jacob-Rousseau, Nicolas; Bravard, Jean‐Paul; Allignol, Françoise; Simac, L.

doi:10.1016/j.geomorph.2011.06.028

Cited by 30 publications

(18 citation statements)

References 41 publications

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“…This tendency was attributed to climatic reasons (i.e. warmer and drier period following the peak of the LIA, with less flood events and reduced sediment supply from glaciers), in agreement with previous studies in larger rivers (Rumsby and Macklin, ; Arnaud‐Fassetta, ; Gob et al ., ; Astrade et al ., ). Forest cover expansion – and thus a reduced sediment supply from hillslopes – probably had a minor or no role at all in the Adige River (Marchese et al ., ), given its limited magnitude (14% from 1855 to 1970, and thus surely less until 1920s, Comiti, ), much lower compared with other Alpine catchments in Italy and France (Descroix and Gautier, ; Liébault and Piégay, ; Comiti et al ., ).…”

Section: Discussionmentioning

confidence: 97%

Channelization of a large Alpine river: what is left of its original morphodynamics?

Scorpio

Zen

Bertoldi

et al. 2018

Earth Surf Processes Landf

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The Adige River drains 12 200 km2 of the Eastern Alps and flows for 213 km within this mountain range. Similar to other large rivers in Central Europe, the Adige River was subject to massive channelization works during the 19th century. Thanks to the availability of several historical maps, this river represents a very valuable case study to document the extent to which the morphology of the river changed due to channelization and to understand how much is left of its original morphodynamics. The study was based on the analysis of seven sets of historical maps dating from 1803–1805 to 1915–1927, on geomorphological analysis, on the application of mathematical morphodynamic theories and on the application of bar and channel pattern prediction models. The study concerns 115 km of the main stem and 29 km of its tributaries. In the pre‐channelization conditions, the Adige River presented a prevalence of single‐thread channel planforms. Multi‐thread patterns developed only immediately downstream of the main confluences. During the 19th century, the Adige underwent considerable channel adjustment, consisting of channel narrowing, straightening, and reduction of bars and islands. Multi‐thread and single‐thread reaches evolved through different evolutionary trajectories, considering both the channel width and the bar/vegetation interaction. Bar and channel pattern predictors showed good correspondence with the observed patterns, including the development of multi‐thread morphologies downstream of the confluences. Application of the free‐bar predictor helped to interpret the strong reduction – almost complete loss – of exposed sediment bars after the channelization works, quantifying the riverbed inclination to form alternate bars. This morphological evolution can be observed in other Alpine rivers of similar size and similar massive channelization, therefore, a simplified conceptual model for large rivers subjected to channelization is proposed, showing that a relatively small difference in the engineered channel width may have a strong impact on the river dynamics, specifically on bar formation. Copyright © 2017 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 97%

Channelization of a large Alpine river: what is left of its original morphodynamics?

Scorpio

Zen

Bertoldi

et al. 2018

Earth Surf Processes Landf

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“…This is not surprising, given the recent history of alpine braided rivers. These have been affected by the cumulative impact of gravel mining, channel embankment, dam, catchment reforestation and climate change following the end of the Little Ice Age (Bravard and Peiry, ; Liébault et al ., ; Piégay et al ., ; Astrade et al ., ). It is generally recognized that the most impacting driving factor is gravel mining, but given the bias towards smaller catchments in our sample, it is likely that reforestation and torrent‐control works play an important role in the observed long profile evolutions.…”

Section: Discussionmentioning

confidence: 98%

Long Profile Responses of Alpine Braided Rivers in Se France

Liébault¹,

Lallias-Tacon²,

Cassel³

et al. 2012

River Research & Apps

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Channel elevation change since the early 20th century was characterized for 31 alpine braided river reaches (total length of 129 km), representing about 20% of the braided river network length in SE France. Present‐day long profiles were surveyed in the field and compared with historical profiles measured between 1894 and 1930. Forty‐four cross sections of active channels including terrace boundaries were also surveyed to study morphological signatures of braided channels characterized by different channel responses (aggradation or degradation). Results show that 56% of the sampling river length is characterized by degradation, 24% by stability and 20% by aggradation. Gravel mining is recognized as the main factor explaining degradation of braided channels. It is also demonstrated that aggrading braided channels are those where sediment supply from active torrents and bank erosion have been best preserved. The comparison of morphological signatures associated with aggrading and degrading channels reveals significant differences in cross‐section morphometry. A normalized bed relief index is proposed as a reliable indicator of the channel response. Field observations show that long‐term aggraded braided channels have a lower bed relief index than degraded channels, as already established by some laboratory experiments. This index can be used to determine the position of the braided channel in the cycle of degradation‐recovery following the cessation of gravel mining. It is also established that aggraded channels develops wider active channels than degraded channels for a same drainage area. This study provides new insights for the assessment of spontaneous recovery potential of braided channels impacted by gravel mining. Copyright © 2012 John Wiley & Sons, Ltd.

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“…In southern France, the LIA resulted in an increase in peak floods and droughts (Grove, 2001), in erosion in the high headwaters in the crystalline massifs (Arnaud et al, 2012) and in human pressure on the landscape which resulted in the establishment of braided rivers in the Rhone catchment (e.g., Bravard, 2010;Astrade et al, 2011). Likewise, previous research has shown how braided rivers developed in the French (Pre-)Alps due to deforestation, increased sediment production because of climatic change, or a combination of both (e.g., Liébault and Piégay, 2001;Bravard, 2010).…”

Section: Relation To Climate and Land Use [Insert Fig 9 Somewhere Inmentioning

confidence: 99%

Characterization and quantification of Holocene colluvial and alluvial sediments in the Valdaine Region (southern France)

2014

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Detailed chronology of mid-altitude fluvial system response to changing climate and societies at the end of the Little Ice Age (Southwestern Alps and Cévennes, France)

Cited by 30 publications

References 41 publications

Channelization of a large Alpine river: what is left of its original morphodynamics?

Channelization of a large Alpine river: what is left of its original morphodynamics?

Long Profile Responses of Alpine Braided Rivers in Se France

Characterization and quantification of Holocene colluvial and alluvial sediments in the Valdaine Region (southern France)

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