scholarly journals A segmentation approach for the reproducible extraction and quantification of knickpoints from river long profiles

2019 ◽  
Vol 7 (1) ◽  
pp. 211-230 ◽  
Author(s):  
Boris Gailleton ◽  
Simon M. Mudd ◽  
Fiona J. Clubb ◽  
Daniel Peifer ◽  
Martin D. Hurst
Keyword(s):  
Landscape Evolution ◽  
Channel Length ◽  
Negative Slope ◽  
Erosion Rates ◽  
Quadrilátero Ferrífero ◽  
Extraction Algorithm ◽  
Tectonically Active ◽  
Segmentation Approach ◽  
Reproducible Method ◽  
River Profiles

Abstract. Changes in the steepness of river profiles or abrupt vertical steps (i.e. waterfalls) are thought to be indicative of changes in erosion rates, lithology or other factors that affect landscape evolution. These changes are referred to as knickpoints or knickzones and are pervasive in bedrock river systems. Such features are thought to reveal information about landscape evolution and patterns of erosion, and therefore their locations are often reported in the geomorphic literature. It is imperative that studies reporting knickpoints and knickzones use a reproducible method of quantifying their locations, as their number and spatial distribution play an important role in interpreting tectonically active landscapes. In this contribution we introduce a reproducible knickpoint and knickzone extraction algorithm that uses river profiles transformed by integrating drainage area along channel length (the so-called integral or χ method). The profile is then statistically segmented and the differing slopes and step changes in the elevations of these segments are used to identify knickpoints, knickzones and their relative magnitudes. The output locations of identified knickpoints and knickzones compare favourably with human mapping: we test the method on Santa Cruz Island, CA, using previously reported knickzones and also test the method against a new dataset from the Quadrilátero Ferrífero in Brazil. The algorithm allows for the extraction of varying knickpoint morphologies, including stepped, positive slope-break (concave upward) and negative slope-break knickpoints. We identify parameters that most affect the resulting knickpoint and knickzone locations and provide guidance for both usage and outputs of the method to produce reproducible knickpoint datasets.

scholarly journals A segmentation approach for the reproducible extraction and quantification of knickpoints from river long profiles

2018 ◽  
Author(s):  
Boris Gailleton ◽  
Simon M. Mudd ◽  
Fiona J. Clubb ◽  
Daniel Peifer ◽  
Martin D. Hurst
Keyword(s):  
Landscape Evolution ◽  
Channel Length ◽  
Negative Slope ◽  
Erosion Rates ◽  
Quadrilátero Ferrífero ◽  
Extraction Algorithm ◽  
Tectonically Active ◽  
Segmentation Approach ◽  
Reproducible Method ◽  
River Profiles

Abstract. Changes in the steepness of river profiles or abrupt vertical steps (i.e. waterfalls) are thought to be indicative of changes in erosion rates, lithology, or other factors that affect landscape evolution. These changes are referred to as knickpoints or knickzones and are pervasive in bedrock river systems. Such features are thought to reveal information about landscape evolution and patterns of erosion, and therefore their locations are often reported in the geomorphic literature. It is imperative that studies reporting knickpoints and knickzones use a reproducible method of quantifying their locations, as their number and spatial distribution play an important role in interpreting tectonically active landscapes. In this contribution we introduce a reproducible knickpoint and knickzone extraction algorithm that uses river profiles transformed by integrating drainage area along channel length (the so-called integral or χ method). The profile is then statistically segmented and the differing slopes and step changes in elevations of these segments are used to identify knickpoints and knickzones, and their relative magnitudes. The output locations of identified knickpoints and knickzones compare favourably with human mapping: we test the method on Santa Cruz Island, CA, using previously reported knickzones and also test the method against a new dataset from the Quadrilátero Ferrífero in Brazil. The algorithm allows extraction of varying knickpoint morphologies, including stepped, positive slope-breaks (concave upward) and negative slope-break knickpoints. We identify parameters that most affect the resulting knickpoint and knickzone locations, and provide guidance for both usage and outputs of the method to produce reproducible knickpoint datasets.

Patchy bedrock explained: Tectonic fracture control on landscape evolution patterns in south-Central Chile 

2021 ◽  
Author(s):  
Emma Lodes ◽  
Dirk Scherler ◽  
Hella Wittmann ◽  
Renee Van Dongen
Keyword(s):  
Chemical Weathering ◽  
Landscape Evolution ◽  
Tectonic Deformation ◽  
Fracture Density ◽  
Rock Fracturing ◽  
Central Chile ◽  
Erosion Rates ◽  
Denudation Rates ◽  
South Central

<p>Rock fracturing induced by tectonic deformation is thought to promote faster denudation in more highly fractured areas by lowering grain size and directing the flow of water. That the density and pattern of fractures in a landscape play a role in controlling erosion and landscape evolution has been known for over a century, but not until recently do we have tools, like cosmogenic nuclides, to quantify erosion rates in places with varying fracture densities. In the Nahuelbuta Range in south-central Chile, we observed that >30-m thick regolith exists next to patches of unweathered bedrock. We hypothesize that the density of fractures dictates the pace and patterns of chemical weathering, regolith conversion, and erosion in the Nahuelbuta Range. To test this, we used in situ cosmogenic <sup>10</sup>Be to obtain denudation rates from amalgamated samples of bedrock, corestones and soils, and measured fracture density and orientation, as well as hillslope boulder size in several sites in the Nahuelbuta Range. We found that more highly fractured areas indeed have higher denudation rates than less fractured areas, and that bedrock denudation rates are ~10 m/Myr while soil denudation rates are ~30 m/Myr, suggesting that soil-covered areas may be sites of higher fracture density at depth. Fractures have orientations that match mapped faults across the Nahuelbuta range, and thus are considered to be tectonically-induced. In addition, both fracture and fault orientations match the orientation of streams incising the range, suggesting that fractures control stream channel orientation by weakening bedrock and thus directing flow.</p>

scholarly journals The periglacial engine of mountain erosion – Part 2: Modelling large-scale landscape evolution

2015 ◽  
Vol 3 (4) ◽  
pp. 463-482 ◽  
Author(s):  
D. L. Egholm ◽  
J. L. Andersen ◽  
M. F. Knudsen ◽  
J. D. Jansen ◽  
S. B. Nielsen
Keyword(s):  
Large Scale ◽  
Landscape Evolution ◽  
Computational Experiments ◽  
Frost Action ◽  
Erosion Rates ◽  
Bedrock Erosion ◽  
Simple Scaling ◽  
Sediment Cover ◽  
Mechanical Weathering ◽  
High Elevations

Abstract. There is growing recognition of strong periglacial control on bedrock erosion in mountain landscapes, including the shaping of low-relief surfaces at high elevations (summit flats). But, as yet, the hypothesis that frost action was crucial to the assumed Late Cenozoic rise in erosion rates remains compelling and untested. Here we present a landscape evolution model incorporating two key periglacial processes – regolith production via frost cracking and sediment transport via frost creep – which together are harnessed to variations in temperature and the evolving thickness of sediment cover. Our computational experiments time-integrate the contribution of frost action to shaping mountain topography over million-year timescales, with the primary and highly reproducible outcome being the development of flattish or gently convex summit flats. A simple scaling of temperature to marine δ18O records spanning the past 14 Myr indicates that the highest summit flats in mid- to high-latitude mountains may have formed via frost action prior to the Quaternary. We suggest that deep cooling in the Quaternary accelerated mechanical weathering globally by significantly expanding the area subject to frost. Further, the inclusion of subglacial erosion alongside periglacial processes in our computational experiments points to alpine glaciers increasing the long-term efficiency of frost-driven erosion by steepening hillslopes.

scholarly journals Climate controls on erosion in tectonically active landscapes

2020 ◽  
Vol 6 (42) ◽  
pp. eaaz3166 ◽  
Author(s):  
B. A. Adams ◽  
K. X. Whipple ◽  
A. M. Forte ◽  
A. M. Heimsath ◽  
K. V. Hodges
Keyword(s):  
Tectonic Evolution ◽  
Predictive Power ◽  
Annual Rainfall ◽  
Potential Influence ◽  
Ongoing Debate ◽  
Mountain Ranges ◽  
Erosion Rates ◽  
Tectonically Active ◽  
Climate Controls ◽  
The Himalaya

The ongoing debate about the nature of coupling between climate and tectonics in mountain ranges derives, in part, from an imperfect understanding of how topography, climate, erosion, and rock uplift are interrelated. Here, we demonstrate that erosion rate is nonlinearly related to fluvial relief with a proportionality set by mean annual rainfall. These relationships can be quantified for tectonically active landscapes, and calculations based on them enable estimation of erosion where observations are lacking. Tests of the predictive power of this relationship in the Himalaya, where erosion is well constrained, affirm the value of our approach. Our model allows estimation of erosion rates in fluvial landscapes using readily available datasets, and the underlying relationship between erosion and rainfall offers the promise of a deeper understanding of how climate and tectonic evolution affect erosion and topography in space and time and of the potential influence of climate on tectonics.

Quaternary landscape evolution and erosion rates for an intramontane Neogene basin (Guadix–Baza basin, SE Spain)

Geomorphology ◽  
2009 ◽  
Vol 106 (3-4) ◽  
pp. 206-218 ◽  
Author(s):  
José Vicente Pérez-Peña ◽  
José Miguel Azañón ◽  
Antonio Azor ◽  
Paola Tuccimei ◽  
Marta Della Seta ◽  
...  
Keyword(s):  
Landscape Evolution ◽  
Se Spain ◽  
Erosion Rates

Modelling the effects of permeability, groundwater flow and water table depth on landscape evolution

2020 ◽  
Author(s):  
Elco Luijendijk
Keyword(s):  
Groundwater Flow ◽  
Overland Flow ◽  
Landscape Evolution ◽  
Drainage Density ◽  
Stream Channels ◽  
Erosion Rates ◽  
Landscape Models ◽  
Storage Term ◽  
Stream Erosion

<p>The role of groundwater flow in determining overland flow, drainage density and landscape evolution has long been debated. Landscape models often only address groundwater as a simplified storage term and do not explicitly include lateral groundwater flow, although recently some model codes have started to include lateral flow. However, the role of groundwater flow on landscape evolution has not been explored systematically to my knowledge. Here I present a new numerical and analytical model that combines groundwater flow, saturation overland flow, hillslope diffusion and stream erosion. A number of model experiments were run with different values of transmissivity and groundwater recharge. The model results demonstrate that transmissivity, groundwater flow and the depth of the watertable strongly govern overland flow, the incision of stream channels and erosion rates. The results imply that the permeability and transmissivity of the subsurface are important parameters for explaining and modelling landscape evolution.  </p>

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>

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