Assessment of alluvial trends toward dynamic equilibrium under chronic climatic forcing

Tranmer, Andrew W.; Goodwin, Peter; Caamaño, Diego

doi:10.1016/j.advwatres.2017.11.015

Cited by 14 publications

(8 citation statements)

References 106 publications

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“…2 to develop regime equations for how B and h change downstream under conditions of increasing discharge. The present study does not make either limiting assumption and addresses a separate question of how a pristine alluvial channel evolves from a non-equilibrium multi-thread condition to a dynamic equilibrium, single-thread channel under the constraints of constant bank-full discharge and no sediment supply limitations (Tranmer et al, 2018).…”

Section: Discussionmentioning

confidence: 99%

“…A 16 km river segment located along the periphery of the Northern Patagonian Icefield in Chile was divided into five unique geomorphic reaches (Figure 1). Hydraulic, topographic, and grain-size data (Table 2) were collected for 27 cross sections within the study site in order to analyze the downstream progression of the extremal hypotheses toward and away from dynamic equilibrium (Tranmer et al, 2018). Each cross section was evaluated according to its full cross-sectional dimensions and active cross-sectional dimensions.…”

Section: Methodsmentioning

confidence: 99%

“…In fact, Bracken and Wainwright (2006) specifically address the question of attainment of dynamic equilibrium in natural systems and deem it impossible to measure. To address this difficulty, Tranmer et al (2018) used a LFTS approach and presented a longitudinal gradient of alluvial channel evolution in an undeveloped gravel-bed river in Chilean Patagonia. As a spatial sequence, the spectrum of channel evolution in the downstream direction illustrates how a broad braid plain devoid of vegetation evolves toward an active single-thread channel with fully vegetated streambanks.…”

Section: Review Criticisms and Limitations Of Extremal Hypothesesmentioning

confidence: 99%

“…As a spatial sequence, the spectrum of channel evolution in the downstream direction illustrates how a broad braid plain devoid of vegetation evolves toward an active single-thread channel with fully vegetated streambanks. Using the arguments of flood magnitude, inter-annual energy expenditure, variation in channel dimensions, and sediment transport capacity, the resultant morphodynamic changes in the downstream direction indicate a convergence toward dynamic equilibrium near the end of the study site (Tranmer et al, 2018). A recent channel perturbation in the form of a chute cutoff in the most downstream reach provides a turning point with which to illustrate how the channel departs from dynamic equilibrium.…”

Section: Review Criticisms and Limitations Of Extremal Hypothesesmentioning

confidence: 99%

“…To evaluate the performance of extremal hypotheses, this study uses the results from Tranmer et al (2018) that considered a location-for-time-substitution (LFTS) approach to successfully identify an evolutionary trend toward and away from dynamic equilibrium on an undeveloped, proglacial stream in Chilean Patagonia. Analysis of bank-full field measurements found certain extremal hypotheses to successfully identify the general evolutionary trend; however, there were no direct means of analysis to determine which one was most appropriate (Tranmer, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of extremal hypotheses in an undeveloped alluvial river

Tranmer

Caamaño

Goodwin

2019

Progress in Physical Geography: Earth and Environment

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Recent work in the undeveloped Rio Murta Basin, located in Chilean Patagonia, identified an evolutionary trend in the fluvial system as it progresses toward and away from dynamic equilibrium. A location-for-time-substitution model employed over the longitudinal extent of a 16 km study site assessed the performance of extremal hypotheses in identifying dynamic equilibrium conditions. Numerous extremal hypotheses were successful in identifying the spatial trend, but no means were available to discern differences between them. Thus, this study uses field measurements within the evolutionary trend to propose a new metric for evaluating extremal hypotheses. A thorough review and synthesis of the extremal approach are additionally presented. The new method compares theoretical predictions against field-measured values to determine which extremal hypothesis is most effective in identifying the condition of dynamic equilibrium in a gravel-bed river. Channel width and depth are identified as the dependent stream variables that uniquely differentiate most extremal hypotheses from one another. The results indicate that extremal hypotheses based on energy metrics of the flow are most successful, with the strongest support for minimum kinetic energy and minimum specific stream power.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Review Criticisms and Limitations Of Extremal Hypothesesmentioning

confidence: 99%

Section: Review Criticisms and Limitations Of Extremal Hypothesesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evaluation of extremal hypotheses in an undeveloped alluvial river

Tranmer

Caamaño

Goodwin

2019

Progress in Physical Geography: Earth and Environment

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Synergistic process interactions and morphological change in a river reach subject to multiple disturbances, the Laja River, Chile

Barahona,

Alcayaga,

Caamaño

et al. 2024

Earth Surf Processes Landf

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This work studies the multiple sources of impacts and disturbances in the Laja River (Central Chile) and evaluates the changes in water and sediment flows and planimetric geomorphic changes.The disturbances sources correspond to hydroelectric plants, water withdrawals for irrigation and the sustained decrease trend in rainfall in the basin. The changes in the plan‐view shape of the river reach were quantified using remote sensing techniques, through a supervised classification of Landsat 5 TM and 8 OLI satellite images, identified Water (W), Islands and Riverine Vegetation (IRV) and Bars and Banks Without Vegetation (BBWV), obtained a Kappa index>0,83 for a period of 15 years (2006–2021).Compared with historical records, the period of analysis shows a decrease in annual rainfall by 17.5%. In addition, water withdrawals for irrigation have contributed to a 64% decrease in monthly stream discharge during the dry season. As a consequence of the decrease in annual rainfall and water withdrawals for irrigation, the sediment transport capacity has also decreased by 10.5%.The changes in morphological driving variables (stream flows and sediment transport regimes) have manifested themselves in morphological changes, where it was possible to establish that a change in the channel form occurred in the last 15 years, going from a river with a single channel to a braided one. An important vegetation establishment has accompanied this morphological change on both riverbanks and the central bars. The colonizing vegetation corresponds to fast‐growing non‐native species (Salix spp., Populus spp. and Alnus spp). A stabilization of the channel form is expected, consolidating itself as a braided section with alternating vegetated bars.

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