Along‐Stream Variations in Valley Flank Erosion Rates Measured Using 10 Be Concentrations in Colluvial Deposits From Canyons in the Atacama Desert

2021 ◽  
Vol 48 (5) ◽  
Author(s):  
Valeria Zavala ◽  
Sébastien Carretier ◽  
Vincent Regard ◽  
Stéphane Bonnet ◽  
Rodrigo Riquelme ◽  
...  
Keyword(s):  
Atacama Desert ◽  
Erosion Rates ◽  
Valley Flank

Along-stream variations in valley flank erosion rates measured using 10Be concentrations in colluvial deposits from Atacama canyons: implications for valley widening

2020 ◽  
Author(s):  
Valeria Zavala ◽  
Sebastien Carretier ◽  
Vincent Regard ◽  
Stephane Bonnet ◽  
Rodrigo Riquelme ◽  
...  
Keyword(s):  
Erosion Rate ◽  
Landscape Evolution ◽  
Sediment Flux ◽  
Lower Probability ◽  
Upward Migration ◽  
Channel Mobility ◽  
Erosion Rates ◽  
Valley Flank ◽  
Lateral Erosion ◽  
Bed Slope

<p>The downstream increase in valley width is an important feature of fluvial landscapes that may be evident to anyone: even if local exceptions exist, wide fluvial valleys in plains are distinctive of narrow upstream mountainous ones. Yet, the processes and rates governing along-stream valley widening over timescales characteristic of landscape development (>1-10 ka) are largely unknown. No suitable law exists in landscape evolution models, thus models imperfectly reproduce the landscape evolution at geological timescales, their rates of erosion and probably their response to tectonics and climate. Here, we study two 1 km-deep canyons in northern Chile with diachronous incision initiation, thus representing two time-stage evolutions of a similar geomorphic system characterized by valley widening following the upward migration of a major knickzone. We use 10Be cosmogenic isotope concentrations measured in colluvial deposits at the foot of hillslopes to quantify along-stream valley flank erosion rates. We observe that valley flank erosion rate increases quasi-linearly with valley-bed slope and decreases non-linearly with valley width. This relation suggests that lateral erosion increases with sediment flux due to higher channel mobility. In turn, valley width exerts a negative feedback on lateral valley flank erosion since channels in wide valleys have a lower probability of eroding the valley sides. This implies a major control of river divagation on valley flank erosion rate and valley widening. Our study provides the first data for understanding the long-term processes and rates governing valley widening in landscapes.</p>

scholarly journals Erosion after an extreme storm event in an arid fluvial system of the southern Atacama Desert: an assessment of the magnitude, return time, and conditioning factors of erosion and debris flow generation

2020 ◽  
Vol 20 (5) ◽  
pp. 1247-1265 ◽  
Author(s):  
Germán Aguilar ◽  
Albert Cabré ◽  
Victor Fredes ◽  
Bruno Villela
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Atacama Desert ◽  
Storm Event ◽  
Alluvial Fans ◽  
Sediment Discharge ◽  
Stream Networks ◽  
Erosion Rates ◽  
Extreme Storm ◽  
High Sediment

Abstract. The contribution of an individual extreme storm event to long-term erosion rates has been estimated for the first time in the Atacama Desert. A mean erosion of 1.3 mm has been calculated for the March 2015 event that impacted the southernmost part of the Atacama Desert. The estimated erosion is consistent with millennial erosion rates and the previously reported return times of high-sediment-discharge events in the study area. This is significant because erosion rates, related to events of high sediment discharge in arid fluvial systems, are difficult to measure with sediment loading due to destruction of gauges by devastating flash floods and therefore have not been directly measured yet. During the March 2015 storm, debris flows were reported as the main sediment transport process, while gullies and channels erosion were the main source of sediments that generated debris flows reaching the tributary junctions and the trunk valleys. Sediment yield at tributary outlets is highly dependent on the ability of catchments to store sediments in stream networks between storms. The largest tributary catchments, the high hydrological hierarchy, the low topographic gradient and the gentle slopes are the most determining factors in generating debris flows capable of reaching alluvial fans in any storm event from large sediment volumes stored in the stream networks. Our findings better assess the susceptibility to debris flow of arid catchments, which is significant for the southernmost valleys of the Atacama Desert because human settlements and industries are mostly established in alluvial fans.

scholarly journals Erosion after an extreme storm event in an arid fluvial system of the southern Atacama Desert: an assessment of magnitude, return time, and conditioning factors of erosion caused by debris flows

2019 ◽  
Author(s):  
Germán Aguilar ◽  
Albert Cabré ◽  
Victor Fredes ◽  
Bruno Villela
Keyword(s):  
Debris Flows ◽  
Atacama Desert ◽  
Return Time ◽  
Storm Event ◽  
Drainage Network ◽  
Alluvial Fans ◽  
Sediment Discharge ◽  
Erosion Rates ◽  
Extreme Storm ◽  
High Sediment

Abstract. We have calculated a mean erosion of 1.3 mm caused by an individual storm event in March 2015 that impacted a large mountainous area of the southernmost Atacama Desert. The calculated erosion agrees with millennial erosion rates and with return time of high sediment discharge events previously reported in the study area. Here, we quantify for the first time the contribution of an individual extreme storm event to long-term erosion rates in the Atacama Desert. This is significant because erosion rates, related to high sediment discharge events in arid fluvial systems, are hard to measure with sediment load due the destruction of gauges by devastating flashfloods and thus have not been directly measured yet. During the March 2015 storm, debris flows were reported as the main sediment transport process. Erosion of gullies and channels are the main source of sediments that finally generate debris flows that reach the tributary junctions and the trunk valleys. The sediment yield to the tributary outlets strongly depends on the hydraulic capacity of catchments to store sediments in the drainage network between storms. Larger tributary catchments, high hydrological hierarchy, low topographic gradient and gentle slopes are the most susceptible catchments to generate debris flows that reach alluvial fans at any storm event from large debris volumes stored in the drainage network. Our findings better assess debris flow susceptibility of arid catchments, which is significant for the southernmost Atacama Desert valleys because human settlements and industries are mostly established in alluvial fans.

MUDFLOW ALLUVIAL FANS OF THE ATACAMA DESERT IN CHILE

2016 ◽  
Author(s):  
Alan D. Howard ◽  
◽  
William E. Dietrich ◽  
Rebecca M.E. Williams ◽  
Alex M. Morgan ◽  
...  
Keyword(s):  
Atacama Desert ◽  
Alluvial Fans

CONFOUNDINGLY COMPLEX EXPOSURE HISTORIES REVEALED BY 21NE AND 10BE ABUNDANCES IN ALLUVIAL DEPOSITS OF THE ATACAMA DESERT, NORTHERN CHILE

2017 ◽  
Author(s):  
Matthew Cross Jungers ◽  
◽  
Arjun M. Heimsath ◽  
Ronald Amundson ◽  
Greg Balco ◽  
...  
Keyword(s):  
Atacama Desert ◽  
Northern Chile ◽  
Alluvial Deposits
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