The value of lichenometry and historical archives in assessing the incision of submediterranean rivers from the Little Ice Age in the Ardèche and upper Loire (France)

Gob, Frédéric; Jacob, Nicolas; Bravard, Jean‐Paul; Petit, François

doi:10.1016/j.geomorph.2007.05.005

Cited by 25 publications

(25 citation statements)

References 26 publications

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“…In our opinion, these changes might be attributed to the important variations in sediment supply/flow regimes associated with the final period of the Little Ice Age, as tentatively argued in Comiti (2012), matching what was observed in other European regions (see Rumsby and Macklin, 1996;Gob et al, 2008).…”

supporting

confidence: 83%

Channel degradation and restoration of an Alpine river and related morphological changes

et al. 2014

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supporting

confidence: 83%

Channel degradation and restoration of an Alpine river and related morphological changes

et al. 2014

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“…The period from 1845-1850 to the present, was marked by a deepening of the streambeds, by more than 3 m in some areas. This phenomenon, which has also been demonstrated in a nearby area through the analysis of lichens (Gob et al, 2008), results from an incision in the gravelly alluvium, and the gradual scouring out of this material once the sedimentary build-up in the channels had stopped in these catchments. As in most watercourses in the Rhône watershed, the process seems irreversible as from the 1950s.…”

Section: Available Historical Datamentioning

confidence: 61%

Flood frequency analysis using historical data: accounting for random and systematic errors

Neppel

Renard²,

Lang³

et al. 2010

Hydrological Sciences Journal

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2010) Flood frequency analysis using historical data: accounting for random and systematic errors. Hydrol. Sci. J. 55(2), 192-208. Abstract Flood frequency analysis based on a set of systematic data and a set of historical floods is applied to several Mediterranean catchments. After identification and collection of data on historical floods, several hydraulic models were constructed to account for geomorphological changes. Recent and historical rating curves were constructed and applied to reconstruct flood discharge series, together with their uncertainty. This uncertainty stems from two types of error: (a) random errors related to the water-level readings; and (b) systematic errors related to over-or under-estimation of the rating curve. A Bayesian frequency analysis is performed to take both sources of uncertainty into account. It is shown that the uncertainty affecting discharges should be carefully evaluated and taken into account in the flood frequency analysis, as it can increase the quantiles confidence interval. The quantiles are found to be consistent with those obtained with empirical methods, for two out of four of the catchments. Analyse fréquentielle des débits de crues avec des données historiques en prenant en compte les erreurs aléatoires et systématiquesRésumé Ce papier présente une analyse fréquentielle des crues basée sur un échantillon de crues collecté sur une période systématique et sur une période historique. Elle est appliquée sur plusieurs petits bassins versants méditerranéens. Après le recensement et la collecte des données sur les crues historiques, plusieurs modèles hydrauliques ont été construits pour prendre en compte l'évolution géomorphologique des cours d'eau. Des courbes de tarage pour les périodes récentes et historiques ont été construites et utilisées pour estimer les débits de crues avec leurs incertitudes. Ces incertitudes prennent en compte deux types d'erreurs: (a) une erreur aléatoire liée à la lecture de la hauteur d'eau, et (b) une erreur systématique liée à une sur ou sous estimation de la courbe de tarage. Un modèle bayésien d'analyse fréquentielle est développé pour prendre en compte ces deux sources d'incertitudes. Il est montré que les incertitudes affectant les débits doivent être prise en compte dans l'analyse fréquentielle des crues car elles peuvent significativement modifier les intervalles de confiance des quantiles. Les quantiles de crues obtenus semblent concordant avec les estimations de formules empiriques pour deux des quatre bassins étudiés.

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“…In this study, the species Rhizocarpon geographicum was chosen because it is largely found in the Mediterranean region and is the most popular species used in lichenometry. The three growth curves used in this study and the methodology of their construction are detailed in Jacob et al (2002) and Gob et al (2008). The traditional lichenometric technique is based on the measurement of the diameter of the largest or the fi ve largest thalli present on a particle (Innes, 1985).…”

Section: Lichenometrymentioning

confidence: 99%

“…All lichens discussed in this paper were measured in the riverbed. Those from the fl oodplain were not considered here [they were used to date river incision (Gob et al, 2008)]. …”

Section: Lichenometrymentioning

confidence: 99%

The influence of sediment size, relative grain size and channel slope on initiation of sediment motion in boulder bed rivers. A lichenometric study

Gob¹,

Bravard²,

Petit

2010

Earth Surf Processes Landf

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Sediment transport of four boulder bed rivers is studied using lichenometry. The presence of lichens on boulders in the river channel is used to date the last mobilization of the blocks. Using size frequency diagrams and regional growth curves calibrated with dated reference points it is possible to determine the fl ood event responsible for the last mobilization of each boulder with lichens present. The specifi c stream power of fl ood events over the last 60 years is then calculated, and thresholds of sediment transport based on the sediment size are calculated. The results from the four studied rivers are compared to similar relationships in the literature. Sediment motion thresholds appear to be very variable within the same type of river (mountainous boulder bed rivers). The critical specifi c stream power necessary to mobilize a particle of a given diameter may vary by up to 10 times from one river to the next. Bed sediment size and river slope may explain this large range of stream powers. Calculation of the relative size of the transported particles (D i /D 50 ) also shows that both hiding and protrusion effects, as well as channels slope, are important factors in sediment transport.

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The value of lichenometry and historical archives in assessing the incision of submediterranean rivers from the Little Ice Age in the Ardèche and upper Loire (France)

Cited by 25 publications

References 26 publications

Channel degradation and restoration of an Alpine river and related morphological changes

Channel degradation and restoration of an Alpine river and related morphological changes

Flood frequency analysis using historical data: accounting for random and systematic errors

The influence of sediment size, relative grain size and channel slope on initiation of sediment motion in boulder bed rivers. A lichenometric study

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