Coarse sediment supply sets the slope of bedrock channels in rapidly uplifting terrain: Field and topographic evidence from eastern Taiwan

2021 ◽  
Author(s):  
Larry Syu‐Heng Lai ◽  
Joshua J. Roering ◽  
Noah J. Finnegan ◽  
Rebecca J. Dorsey ◽  
Jiun‐Yee Yen
Keyword(s):  
Sediment Supply ◽  
Coarse Sediment ◽  
Bedrock Channels

Width control on event scale bedload dynamics in bedrock-confined channels

2021 ◽  
Author(s):  
Kristen Cook ◽  
Jens Turowski ◽  
Niels Hovius
Keyword(s):  
Random Sequence ◽  
Bedload Transport ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Channel Width ◽  
Sediment Grain Size ◽  
Event Scale ◽  
Narrow Channels ◽  
Coarse Sediment ◽  
The Impact

<p>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 modeling to address this gap. Observations from two flood events in the Daan River gorge in western Taiwan suggest that coarse sediment evacuation and re-deposition can cause intra-flood changes of up to several meters in channel bed elevation that are distinct from measured before/after bed changes. We hypothesize that this could be related to the abrupt change in width between the 1 km long bedrock gorge and the river upstream and downstream. An analysis of the theoretical relationships between discharge, channel width, and bedload transport capacity shows that for a given slope, narrow channels transport bedload more efficiently than wide ones at low discharges, while 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 modeling 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. Further, the deposition or erosion that takes place within a flood is often not reflected in the before/after changes to the bed, and this disconnect increases with increasing flood size.</p>

scholarly journals Seeking the Shore: Evidence for Active Submarine Canyon Head Incision Due to Coarse Sediment Supply and Focusing of Wave Energy

2018 ◽  
Vol 45 (22) ◽  
pp. 12,403-12,413 ◽  
Author(s):  
M. Elliot Smith ◽  
Samuel H. Werner ◽  
Daniel Buscombe ◽  
Noah J. Finnegan ◽  
Esther J. Sumner ◽  
...  
Keyword(s):  
Wave Energy ◽  
Submarine Canyon ◽  
Sediment Supply ◽  
Coarse Sediment

scholarly journals State of the Art Study of Influence of Bed Roughness and Alluvial Cover on Bedrock Channels and Comparisons of Existing Models with Laboratory Scale Experiments

2020 ◽  
Author(s):  
Jagriti Mishra ◽  
Takuya Inoue
Keyword(s):  
Mathematical Models ◽  
State Of The Art ◽  
Theoretical Models ◽  
Sediment Supply ◽  
Laboratory Scale ◽  
Experimental Results ◽  
Bed Topography ◽  
Bed Roughness ◽  
The Relationship ◽  
Bedrock Channels

Abstract. Several studies have implied towards the importance of bed roughness on alluvial cover, besides, several mathematical models have also been introduced to mimic the effect bed roughness may project on alluvial cover. Here, we provide a state of the art review of research exploring the relationship between alluvial cover, sediment supply and bed topography, thereby, describing various mathematical models used to analyse deposition of alluvium. In the interest of analysing the efficiency of various available mathematical models, we performed laboratory-scale experiments and compared the results with various models. Our experiments show that alluvial cover is not merely governed by increasing sediment supply, and, bed topography is an important controlling factor of alluvial cover. Testing experimental results with various theoretical models suggest a fit of certain models for a particular bed topography and inefficiency in predicting higher roughness topography. Three models efficiently predict the experimental observations, albeit their limitations which we discuss here in detail.

COARSE SEDIMENT SETS THE SLOPE OF BEDROCK CHANNELS IN A FAST UPLIFTING TERRAIN, COASTAL RANGE OF EASTERN TAIWAN

2019 ◽  
Author(s):  
Larry Syu-Heng Lai ◽  
◽  
Joshua J. Roering ◽  
Noah J. Finnegan ◽  
Rebecca J. Dorsey ◽  
...  
Keyword(s):  
Coarse Sediment ◽  
Bedrock Channels ◽  
Coastal Range

scholarly journals Conversion of tectonic and climatic forcings into records of sediment supply and provenance

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Glenn R. Sharman ◽  
Zoltan Sylvester ◽  
Jacob A. Covault
Keyword(s):  
Sediment Load ◽  
Sediment Supply ◽  
Sediment Provenance ◽  
Sediment Sources ◽  
Environmental Forcing ◽  
Stratigraphic Record ◽  
Forcing Mechanisms ◽  
Bedrock Channels ◽  
Geomorphic Processes ◽  
Different Time Scales

Abstract Understanding how environmental forcings (e.g., tectonics, climate) are transformed by erosional landscapes into sedimentary signals is a critical component of inverting the stratigraphic record. Previous research has largely focused on sediment supply (Qs) and grain size as the de facto sedimentary signals of changing forcing mechanisms. We use a numerical model to consider the paired response of sediment provenance (Pv), expressed as fractional sediment load, and Qs to demonstrate that the same change in environmental forcing may have a different expression in the sedimentary record. While Qs reflects integrated denudation across an erosional catchment, Pv is controlled by spatially variable erosion that occurs in transient landscapes. Pv from proximal sediment sources increases during upstream knickpoint migration, whereas Pv from distal sediment sources increases when bedrock channels incise to produce lower gradient profiles. Differences between the Qs and Pv signals relate to distinct geomorphic processes that operate on different time scales and allow for a refined differentiation of the timing and mechanism of forcings than possible via analysis of either signal alone. Future efforts to integrate multiple sedimentary signals may thus yield a richer picture of underlying forcing mechanisms, facilitating efforts to invert the stratigraphic record.

Sign in / Sign up

Export Citation Format

Share Document