TY  - JOUR
A1  - Cook, Kristen L.
A1  - Turowski, Jens M.
A1  - Hovius, Niels
T1  - Width control on event-scale deposition and evacuation of sediment in bedrock-confined channels
JF  - Earth surface processes and landforms : the journal of the British Geomorphological Research Group
N2  - In mixed bedrock-alluvial rivers, the response of the system to a flood event can be affected by a number of factors, including coarse sediment availability in the channel, sediment supply from the hillslopes and upstream, flood sequencing and coarse sediment grain size distribution. However, the impact of along-stream changes in channel width on bedload transport dynamics remains largely unexplored. We combine field data, theory and numerical modelling to address this gap. First, we present observations from the Daan River gorge in western Taiwan, where the river flows through a 1 km long 20-50 m wide bedrock gorge bounded upstream and downstream by wide braidplains. We documented two flood events during which coarse sediment evacuation and redeposition appear to cause changes of up to several metres in channel bed elevation. Motivated by this case study, we examined the relationships between discharge, channel width and bedload transport capacity, and show that for a given slope narrow channels transport bedload more efficiently than wide ones at low discharges, whereas wider channels are more efficient at high discharges. We used the model sedFlow to explore this effect, running a random sequence of floods through a channel with a narrow gorge section bounded upstream and downstream by wider reaches. Channel response to imposed floods is complex, as high and low discharges drive different spatial patterns of erosion and deposition, and the channel may experience both of these regimes during the peak and recession periods of each flood. Our modelling suggests that width differences alone can drive substantial variations in sediment flux and bed response, without the need for variations in sediment supply or mobility. The fluctuations in sediment transport rates that result from width variations can lead to intermittent bed exposure, driving incision in different segments of the channel during different portions of the hydrograph.
KW  - bedload transport
KW  - discharge variability
KW  - bedrock-alluvial channels
KW  - channel width
KW  - hysteresis
Y1  - 2020
U6  - https://doi.org/10.1002/esp.4993
SN  - 0197-9337
SN  - 1096-9837
VL  - 45
IS  - 14
SP  - 3702
EP  - 3713
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Coch, Caroline
A1  - Lamoureux, Scott F.
A1  - Knoblauch, Christian
A1  - Eischeid, Isabell
A1  - Fritz, Michael
A1  - Obu, Jaroslav
A1  - Lantuit, Hugues
T1  - Summer rainfall dissolved organic carbon, solute, and sediment fluxes in a small Arctic coastal catchment on Herschel Island (Yukon Territory, Canada)
JF  - Artic science
N2  - Coastal ecosystems in the Arctic are affected by climate change. As summer rainfall frequency and intensity are projected to increase in the future, more organic matter, nutrients and sediment could bemobilized and transported into the coastal nearshore zones. However, knowledge of current processes and future changes is limited. We investigated streamflow dynamics and the impacts of summer rainfall on lateral fluxes in a small coastal catchment on Herschel Island in the western Canadian Arctic. For the summer monitoring periods of 2014-2016, mean dissolved organic matter flux over 17 days amounted to 82.7 +/- 30.7 kg km(-2) and mean total dissolved solids flux to 5252 +/- 1224 kg km(-2). Flux of suspended sediment was 7245 kg km(-2) in 2015, and 369 kg km(-2) in 2016. We found that 2.0% of suspended sediment was composed of particulate organic carbon. Data and hysteresis analysis suggest a limited supply of sediments; their interannual variability is most likely caused by short-lived localized disturbances. In contrast, our results imply that dissolved organic carbon is widely available throughout the catchment and exhibits positive linear relationship with runoff. We hypothesize that increased projected rainfall in the future will result in a similar increase of dissolved organic carbon fluxes.
KW  - permafrost
KW  - hydrology
KW  - lateral fluxes
KW  - hysteresis
KW  - climate change
Y1  - 2018
U6  - https://doi.org/10.1139/as-2018-0010
SN  - 2368-7460
VL  - 4
IS  - 4
SP  - 750
EP  - 780
PB  - Canadian science publishing
CY  - Ottawa
ER  -