Application of globally available, coarse‐resolution digital elevation models for delineating valley bottom segments of varying length across a catchment

Khan, Sana; Fryirs, Kirstie

doi:10.1002/esp.4930

Cited by 12 publications

(11 citation statements)

References 47 publications

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“…(2019) suggest their method is more effective in U-shaped valleys rather than V-shaped which are more common in fluviallycarved landscapes. Khan and Fryirs (2020) developed a semi-automated GIS tool that delineates valley bottom polygons and calculates valley floor width from valley cross sections. This tool needs manual processing and GIS analysis to extract valley floor widths.…”

Section: Methods For Calculating Valley Floor Widthmentioning

confidence: 99%

Continuous measurements of valley floor width in mountainous landscapes

Clubb

Weir

Mudd

2022

Preprint

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Abstract. Mountainous landscapes often feature alluviated valleys that control both ecosystem diversity and the distribution of human populations. Alluviated, flat valley floors also play a key role in determining flood hazard in these landscapes. Various mechanisms have been proposed to control the spatial distribution and width of valley floors, including climatic, tectonic and lithologic drivers. Attributing one of these drivers to observed valley floor widths has been hindered by a lack of reproducible, automated valley extraction methods that allow continuous measurements of valley floor width at regional scales. Here we present a new method for measuring valley floor width in mountain landscapes from digital elevation models (DEMs). This method first identifies valley floors based on thresholds of slope and elevation compared to the modern channel, and uses these valley floors to extract valley centrelines. It then measures valley floor width orthogonal to the centreline at each pixel along the channel. The result is a continuous measurement of valley floor width at every pixel along the valley, allowing us to constrain how valley floor width changes downstream. We demonstrate the ability of our method to accurately extract valley floor widths by comparing with independent Quaternary fluvial deposit maps from sites in the UK and the USA. We find that our method extracts similar downstream patterns of valley floor width to the independent datasets in each site. The method works best in confined valley settings and will not work in unconfined valleys where the valley walls are not easily distinguished from the valley floor. We then test current models of lateral erosion by exploring the relationship between valley floor width and drainage area in the Appalachian Plateau, USA, selected because of its tectonic quiescence and relatively homogeneous lithology. We find that an exponent relating width and drainage area (cv = 0.3 ± 0.06) is remarkably similar across the region and across spatial scales, suggesting that valley floor width evolution is driven by a combination of both valley wall undercutting and wall erosion in the Appalachian Plateau. Finally, we suggest that, similar to common metrics used to explore vertical incision, our method provides the potential to act as a network-scale metric of lateral fluvial response to external forcing.

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Section: Methods For Calculating Valley Floor Widthmentioning

confidence: 99%

Continuous measurements of valley floor width in mountainous landscapes

Clubb

Weir

Mudd

2022

Preprint

View full text Add to dashboard Cite

show abstract

“…Zhao et al (2019) suggest their method is more effective in U-shaped valleys rather than V-shaped which are more common in fluvially carved landscapes. Khan and Fryirs (2020) developed a semi-automated GIS tool that delineates valley bottom polygons and calculates valley floor width from valley cross sections. This tool needs manual processing and GIS analysis to extract valley floor widths.…”

Section: Methods For Calculating Valley Floor Widthmentioning

confidence: 99%

Continuous measurements of valley floor width in mountainous landscapes

2022

View full text Add to dashboard Cite

Abstract. Mountainous landscapes often feature alluviated valleys that control both ecosystem diversity and the distribution of human populations. Alluviated, flat valley floors also play a key role in determining flood hazard in these landscapes. Various mechanisms have been proposed to control the spatial distribution and width of valley floors, including climatic, tectonic, and lithologic drivers. Attributing one of these drivers to observed valley floor widths has been hindered by a lack of reproducible, automated valley extraction methods that allow continuous measurements of valley floor width at regional scales. Here, we present a new method for measuring valley floor width in mountain landscapes from digital elevation models (DEMs). This method first identifies valley floors based on thresholds of slope and elevation compared to the modern channel and uses these valley floors to extract valley centrelines. It then measures valley floor width orthogonal to the centreline at each pixel along the channel. The result is a continuous measurement of valley floor width at every pixel along the valley, allowing us to constrain how valley floor width changes downstream. We demonstrate the ability of our method to accurately extract valley floor widths by comparing with independent Quaternary fluvial deposit maps from sites in the UK and the US. We find that our method extracts similar downstream patterns of valley floor width to the independent datasets in each site, with a mean width difference of 17–69 m. The method works best in confined valley settings and will not work in unconfined valleys where the valley walls are not easily distinguished from the valley floor. We then test current models of lateral erosion by exploring the relationship between valley floor width and drainage area in the Appalachian Plateau, USA, selected because of its tectonic quiescence and relatively homogeneous lithology. We find that an exponent relating width and drainage area (cv=0.3±0.06) is remarkably similar across the region and across spatial scales, suggesting that valley floor width evolution is driven by a combination of both valley wall undercutting and wall erosion in the Appalachian Plateau. Finally, we suggest that, similar to common metrics used to explore vertical incision, our method provides the potential to act as a network-scale metric of lateral fluvial response to external forcing.

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“…The geomorphic map was then used to identify and map sedimentary buffers across the catchment using the methodology in Fryirs et al (2007b) and Lisenby and Fryirs (2017). The sedimentary buffers were identified as: floodplain, swamp, alluvial fan, levee, trapped tributary fills and lakes (natural and artificial) (Khan & Fryirs, 2020b). The 5 m resolution LiDAR DEM was resampled to 30 m resolution to calculate ECA as a relatively coarse DEM resolution produces more optimum results in similar landscape settings (cf., Fryirs et al, 2007a; Lisenby & Fryirs, 2017).…”

Section: Methodsmentioning

confidence: 99%

Modelling sediment (dis)connectivity across a river network to understand locational‐transmission‐filter sensitivity for identifying hotspots of potential geomorphic adjustment

Khan

Fryirs

Bizzi

2021

Earth Surf Processes Landf

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Rivers act as ‘jerky conveyor belts’ that transmit fluxes of flow and sediment downstream. This transmission of fluxes can be highly variable within a drainage basin resulting in either abrupt or gradational sediment (dis)connectivity patterns and processes. This study assesses sediment (dis)connectivity across a basin as a means to understand the locational, transmission and filter sensitivity properties of a fluvial system. Drawing upon the case study of Richmond River Catchment, New South Wales, Australia we use the concepts of effective catchment area and buffers, along with graph theory and an empirical sediment transport model CASCADE (Catchment Sediment Connectivity and Delivery), to assess (1) the degree to which modelled sediment cascades along the river network are connected or disconnected (2) how the position, pattern and configuration of (dis)connection facilitates or restricts geomorphic adjustment in different parts of a catchment, and (3) use the findings as a basis to explain the locational‐transmission‐filter sensitivity of the catchment. We use this analysis to segregate supply limited and transport limited reaches and identify various controls on sediment dynamics: in‐stream sediment storage units, junctions between different geomorphic river types, tributary confluences and sediment storage units within partly confined floodplain units. Such analysis lays the foundation for network scale identification of potential hotspots of geomorphic adjustment.

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Application of globally available, coarse‐resolution digital elevation models for delineating valley bottom segments of varying length across a catchment

Cited by 12 publications

References 47 publications

Continuous measurements of valley floor width in mountainous landscapes

Continuous measurements of valley floor width in mountainous landscapes

Continuous measurements of valley floor width in mountainous landscapes

Modelling sediment (dis)connectivity across a river network to understand locational‐transmission‐filter sensitivity for identifying hotspots of potential geomorphic adjustment

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