Landscape Erosion Research Articles

The Relationship Between Topography, Bedrock Weathering, and Water Storage Across a Sequence of Ridges and Valleys

AbstractBedrock weathering regulates nutrient mobilization, water storage, and soil production. Relative to the mobile soil layer, little is known about the relationship between topography and bedrock weathering. Here, we identify a common pattern of weathering and water storage across a sequence of three ridges and valleys in the sedimentary Great Valley Sequence in Northern California that share a tectonic and climate history. Deep drilling, downhole logging, and characterization of chemistry and porosity reveal two weathering fronts. The shallower front is ∼7 m deep at the ridge of all three hillslopes, and marks the extent of pervasive fracturing and oxidation of pyrite and organic carbon. A deeper weathering front marks the extent of open fractures and discoloration. This front is 11 m deep under two ridges of similar ridge‐valley spacing, but 17.5 m deep under a ridge with nearly twice the ridge‐valley spacing. Hence, at ridge tops, the fraction of the hillslope relief that is weathered scales with hillslope length. In all three hillslopes, below this second weathering front, closed fractures and unweathered bedrock extend about one‐half the hilltop elevation above the adjacent channels. Neutron probe surveys reveal that seasonally dynamic moisture is stored to approximately the same depth as the shallow weathering front. Under the channels that bound our study hillslopes, the two weathering fronts coincide and occur within centimeters of the ground surface. Our findings provide evidence for feedbacks between erosion and weathering in mountainous landscapes that result in systematic subsurface structuring and water routing.

SRTM DEM based Neotectonics from Non-Linear Analysis: A Paradigm through Fractal Analysis

Neotectonics amend the river base and causes landscape erosion. This study explores the DEM based differentiation of neotectonics in the northern regions of Pakistan. This method involves vertical and non-linear dissection base on digital evaluation method. This study uses Gliding Box Technique (GBM and GBT) and Box Counting method to evaluate Lacunarity (LA), Succolarity (SA) or 3-Fractals, and Fractal Dimensions (FD). 3-fractals are an attribute used for the recognition of spatial patterns, specifically to compute and differentiate natural textures including natural patterns. This study also investigates vertical dissection using DEM SRTM having spatial resolution of 90m. DEM SRTM measures surface area, plane area as well as the surface ratio. The vertical areas are investigated to make dissection maps and to identify the affects of neotectonics on the roughness of surface. Low value of surface roughness indicates flattened drainage basins and inclination of slope. The Raikot Fault shows higher values of surface roughness towards NE- SW. The surface roughness is mapped to recognize relative uplifts, uneven regions, depressions and pits. Analysis through non-linear method identifies the regions affected by neotectonics activity. Tectonics activity causes deformation and instability in drainage networks.

The extent of soil loss across the US Corn Belt

Soil erosion in agricultural landscapes reduces crop yields, leads to loss of ecosystem services, and influences the global carbon cycle. Despite decades of soil erosion research, the magnitude of historical soil loss remains poorly quantified across large agricultural regions because preagricultural soil data are rare, and it is challenging to extrapolate local-scale erosion observations across time and space. Here we focus on the Corn Belt of the midwestern United States and use a remote-sensing method to map areas in agricultural fields that have no remaining organic carbon-rich A-horizon. We use satellite and LiDAR data to develop a relationship between A-horizon loss and topographic curvature and then use topographic data to scale-up soil loss predictions across 3.9 × 105 km2 of the Corn Belt. Our results indicate that 35 ± 11% of the cultivated area has lost A-horizon soil and that prior estimates of soil degradation from soil survey-based methods have significantly underestimated A-horizon soil loss. Convex hilltops throughout the region are often completely denuded of A-horizon soil. The association between soil loss and convex topography indicates that tillage-induced erosion is an important driver of soil loss, yet tillage erosion is not simulated in models used to assess nationwide soil loss trends in the United States. We estimate that A-horizon loss decreases crop yields by 6 ± 2%, causing $2.8 ± $0.9 billion in annual economic losses. Regionally, we estimate 1.4 ± 0.5 Pg of carbon have been removed from hillslopes by erosion of the A-horizon, much of which likely remains buried in depositional areas within the fields.

Air Temperature Regulates Erodible Landscape, Water, and Sediment Fluxes in the Permafrost‐Dominated Catchment on the Tibetan Plateau

AbstractApproximately 40% of the Tibetan Plateau (TP) is underlain by continuous permafrost, yet its impact on fluvial water and sediment dynamics remains poorly investigated. Here we show that water and sediment dynamics in the permafrost‐dominated Tuotuohe basin on the TP are driven by air temperature and permafrost thaw, based on 33‐year daily in situ observations (1985–2017). Air temperature regulates the seasonal patterns of discharge and suspended sediment concentration (SSC) by controlling the changes in active contributing drainage area (ACDA, the unfrozen erodible landscape that contributes hydrogeomorphic processes within a catchment) and governing multiple thermal processes such as glacier‐snow melt and permafrost thaw. Rainstorms determine the short‐lived fluvial extreme events by intensifying slope processes and channel erosion and likely also by enhancing thaw slumps. Furthermore, the SSCs at equal levels of discharges are lower in autumn (September–October) than in spring (May–June) and summer (July–August). This reduced sediment availability in autumn can possibly be attributed to the increased supra‐permafrost groundwater runoff and the reduced surface runoff and erosion. Due to rapid climate warming, the ACDA has increased significantly from 1985 to 2017, implying expanding erodible landscapes for hydrogeomorphic processes. As a result, the fluvial water and sediment fluxes have substantially increased. In a warmer and wetter future for the TP, the fluvial sediment fluxes of similar permafrost‐underlain basins will continue to increase with expanding erodible landscapes and intensifying thermal and pluvial‐driven geomorphic processes. Thus, permafrost thaw should be considered as an important driver of past and future water and sediment changes for the TP.

Characteristics of soil organic matter within an erosional landscape under agriculture in Northeast China: stock, source, and thermal stability

The characteristics of soil organic matter (SOM) such as stocks, sources and stability, are important for understanding soil functioning and C cycling in an eroding field. In this study we investigated the characteristics of SOM in bulk soil and aggregates collected from three positions (shoulder, back, and foot) on a sloping field in Northeast China using stable and radioactive isotope (13C and 14C) and thermogravimetry (TG) techniques. The field had originally been populated with C3 grassland plants before conversion to C4 corn dominated arable cropping approximately 80 years ago. Soil samples were collected from 0–120 cm soil profiles in 20 cm depth intervals. Erosion rates were estimated by 137Cs analysis to be 0.21 cm yr–1 and 0.08 cm yr–1 at the shoulder and back positions, respectively. A greater proportion of small macroaggregates (2–0.25 mm) and microaggregates (0.25–0.053 mm) were found in the topsoil and subsoil layers at the foot position compared with the shoulder position. The concentration and storage of soil organic C (SOC) in the bulk soil was significantly lower at the shoulder and back positions compared with the foot position. Greater thermal-labile SOM concentration and storage were observed at the foot position compared with the shoulder and back positions. Positive relationships between C4-derived SOC and the proportion of thermal-labile SOM suggested that most thermal-labile SOM was C4-derived from the recent corn (young SOC), while most stable SOM fractions were C3-derived from previous grassland vegetation (old SOC). However, labile SOM from old SOC was also an important part of total thermal-labile SOM, particularly in deep soil horizons (below 40 cm) at all sampling positions. Small macroaggregates had a greater SOC content, δ13C, and thermal-labile SOM proportion, and younger SOC age, compared with microaggregates and silt + clay (<0.053 mm) fractions, except at the 40–60 cm depth at the foot position. As the mass of aggregates accounted for 32–50% of the bulk soil, about half of thermal-labile and total SOC were stored as associations with silt + clay fractions at erosional and depositional points. Our results indicated that: (1) more thermal-labile and total SOM were stored at depositional position, (2) compared with new carbon sources, old SOM contributed to a large proportion of thermal-labile SOM on an eroding slope, particularly in deep soil, and, (3) soil aggregates and silt + clay fractions had equivalent roles in SOC sequestration in both erosional and depositional locations.

Loss of Epigenetic Information as a Cause of Mammalian Aging

All living things experience entropy, manifested as a loss of inherited genetic and epigenetic information over time. In yeast, epigenetic changes result in a loss of cell identity and sterility, both hallmarks of yeast aging. In mammals, epigenetic information is also lost over time, but what causes it to be lost and whether it is a cause or a consequence of aging is not known. Using a transgenic mouse system called ICE (for Inducible Changes to the Epigenome), we show that the process of repairing non-mutagenic DNA breaks accelerates age-related physiological, cognitive, and molecular changes, including the erosion of the epigenetic landscape, a loss of cellular identity, cellular senescence and advancement of the epigenetic clock. Epigenetic reprogramming through ectopic expression of Oct4, Sox2 and Klf4 (OSK) restores patterns of youthful gene expression. These data support a model in which a loss of epigenetic information is a cause of aging in mammals.

The future of dialects and the dialectology of the future

Abstract The days when dialectology was a quiet island in the (sometimes rough) ocean of modern linguistics seem to be over. Since the so-called social turn and the integration of quantitative methods into the study of urban as well as rural dialects, the barriers between early ‘Labovian’ sociolinguistics and dialectology have gradually been broken down. Of late, the study of dialect variation has become more and more an integral part of mainstream formal theory as ‘micro-variation’. Even more recently, constructivist approaches (such as Usage-based Phonology and Exemplar Theory for phonetics as well as ethnographic perspectives) are entering and enriching the field. Apart from these various developments, at least in the Old World, the object appears to be changing more and more rapidly, giving rise to the erosion of traditional dialect landscapes and the emergence of supra-local koinai as well as dialect/standard continua. This paper addresses some of the main aspects of these tendencies. We will discuss questions such as: how can the new types of language variety be studied; can dialectology be enriched with other than the traditional data and methods; how far-reaching is the innovative impact of the various disciplinary, inter-subdisciplinary and inter-disciplinary cross-fertilisations?

Potential of Road Rainwater Harvesting in Yemen – Its Social, Environmental and Economic Benefits: A Case Study of Sana›a – Hodeida Road, Yemen

Abstract&#x0D; In Yemen, farmers and people living along the roads are suffering from the lack of utilization of rainwater runoff from road surface &amp; surrounding area and road water structures. The objectives of this research is to optimize the benefits of Road Rainwater Harvesting (RRWH) to the beneficiaries during road design, construction and operation &amp; maintenance; to suggest a technical outlines; to induce the awareness of road’s engineers on the importance of Integrated Water Harvesting Management (IWHM), in addition to discussing the Environmental and Social Impact Assessment (ESIA). The research approach focused on conducting field visits and applying a reconnaissance survey to document the current and potential road rainwater structures along the pilot section of 24 km as part of Sana’a – Al-Hodiedah road between Al- Masajed village and Sooq Al-Aman; Designing and applying questionnaires and interviews for farmers &amp; beneficiaries, and road engineers. The SPSS software program was used to analyze the collected data. From the conducted interviews along the road, it was revealed that almost all the stakeholders have land adjacent to the roadside, and their farms are irrigated from rainwater collected from road structures. All inhabitants considered water floods running from/on the road surface and structures as their rights, and it is distributed at the moment according to the field’s water rights which exist before the road construction. The research found that almost all farmers considered the water from roads as contaminated water. The source of contamination comes from residual oil on the road, diesel, oil from oil shops and suspended soil particles. On the other hand, according to the road engineer’s questionnaire, the concept of water harvesting, groundwater recharge and water for irrigation from road surface and road structures were not considered during design. In addition, the results obtained showed that water-harvesting techniques in the pilot road section is in the form of farmers’initiatives implemented by directing water to their farms for irrigation. The study conclude applying RRWH to protect the road sections from erosion and damage; increase the availability and utilization of water in the areas nearby roads; minimize the erosion of landscape especially in mountainous areas as well as in road embankments; improve the stabilization of the road slopes; and maintain esthetic value of landscape nearby roads. It is recommended that road drainage structure should be located in a proper place to avoid conflicts among farmers and fulfill their water rights. To avoid soil and water contamination by oil, grease and fuel from vehicles along the road, the research recommends that oil workshops should be implemented and forced to collect and recycle oil instead of disposing it on the road surface. RRWH is recommended to be applied to mitigate the damage of terraces during the heavy runoff. The study urges the joint efforts from all stakeholders and road engineers to apply the suggested technical outline in this paper by including rainwater harvesting from roads as part of road design, implementation and maintenance.&#x0D; Keywords: rainwater harvesting, road design, culverts, engineers,stakeholders, farmers, ESIA, Yemen, social and economic benefits.

Potential of Road Rainwater Harvesting in Yemen – Its Social, Environmental and Economic Benefits: A Case Study of Sana›a – Hodeida Road, Yemen

Abstract&#x0D; In Yemen, farmers and people living along the roads are suffering from the lack of utilization of rainwater runoff from road surface &amp; surrounding area and road water structures. The objectives of this research is to optimize the benefits of Road Rainwater Harvesting (RRWH) to the beneficiaries during road design, construction and operation &amp; maintenance; to suggest a technical outlines; to induce the awareness of road’s engineers on the importance of Integrated Water Harvesting Management (IWHM), in addition to discussing the Environmental and Social Impact Assessment (ESIA). The research approach focused on conducting field visits and applying a reconnaissance survey to document the current and potential road rainwater structures along the pilot section of 24 km as part of Sana’a – Al-Hodiedah road between Al- Masajed village and Sooq Al-Aman; Designing and applying questionnaires and interviews for farmers &amp; beneficiaries, and road engineers. The SPSS software program was used to analyze the collected data. From the conducted interviews along the road, it was revealed that almost all the stakeholders have land adjacent to the roadside, and their farms are irrigated from rainwater collected from road structures. All inhabitants considered water floods running from/on the road surface and structures as their rights, and it is distributed at the moment according to the field’s water rights which exist before the road construction. The research found that almost all farmers considered the water from roads as contaminated water. The source of contamination comes from residual oil on the road, diesel, oil from oil shops and suspended soil particles. On the other hand, according to the road engineer’s questionnaire, the concept of water harvesting, groundwater recharge and water for irrigation from road surface and road structures were not considered during design. In addition, the results obtained showed that water-harvesting techniques in the pilot road section is in the form of farmers’initiatives implemented by directing water to their farms for irrigation. The study conclude applying RRWH to protect the road sections from erosion and damage; increase the availability and utilization of water in the areas nearby roads; minimize the erosion of landscape especially in mountainous areas as well as in road embankments; improve the stabilization of the road slopes; and maintain esthetic value of landscape nearby roads. It is recommended that road drainage structure should be located in a proper place to avoid conflicts among farmers and fulfill their water rights. To avoid soil and water contamination by oil, grease and fuel from vehicles along the road, the research recommends that oil workshops should be implemented and forced to collect and recycle oil instead of disposing it on the road surface. RRWH is recommended to be applied to mitigate the damage of terraces during the heavy runoff. The study urges the joint efforts from all stakeholders and road engineers to apply the suggested technical outline in this paper by including rainwater harvesting from roads as part of road design, implementation and maintenance.&#x0D; Keywords: rainwater harvesting, road design, culverts, engineers,stakeholders, farmers, ESIA, Yemen, social and economic benefits.

Topographic Thresholds and Soil Preservation along the Southern High Plains Eastern Escarpment, Northwest Texas, USA

The eastern escarpment of the Southern High Plains (USA) is today a semi-arid erosional landscape delineated by canyon breaks and topographic relief. A series of buried soils were identified, described, and sampled at 19 soil profile localities exposed along terraces of the South Fork of the Double Mountain Fork of the Brazos River (South Fork) and two associated tributaries (Spring Creek and Macy 285 drainage). Radiocarbon dating revealed late-Pleistocene to early Holocene (~12,580–9100 14C B.P.), middle-Holocene (~6025–4600 14C B.P.), and late-Holocene (~2000–800 14C B.P.) buried soils. The late-Pleistocene to middle-Holocene soils were preserved only at higher elevations within the upper section of the South Fork and Spring Creek. A topographic position analysis was conducted using GIS to identify and examine the impacts of a soil topographic threshold on the preservation and distribution of buried soils within this geomorphic system. Above the identified ~810 m threshold, lateral migration of channels was constrained. Extensive channel migration below the threshold removed older terraces that were replaced with late-Holocene terraces and associated buried soils. Landscape topography constraints on geomorphic processes and soil formation impacted the preservation of archaeological sites in this semi-arid region.

The Impact of Large Erosional Events and Transient Normal Stress Changes on the Seismicity of Faults

AbstractThe long‐term erosion of steep landscapes is punctuated by dramatic erosional events that can remove significant amount of sediments within a timescale shorter than a seismic cycle. However, the role of such large erosional events on seismicity is poorly understood. We use QDYN, a quasi‐dynamic numerical model of earthquake cycles to investigate the effect of a large erosional event on seismicity. The progressive evacuation of landslide sediments is modeled by a transient normal stress decrease. We show that erosional events with a shorter duration compared with the duration of a seismic cycle can significantly increase the seismicity rate, even for small stress changes. Moreover, large erosional events with a shorter period compared with the earthquake nucleation timescale can change earthquake size distribution by triggering more small events. Those results suggest that large erosional events can significantly affect seismicity, illustrating in turn the short‐term impact of surface processes on tectonics.

Contrasting responses of soil C-acquiring enzyme activities to soil erosion and deposition

Soil C-acquiring enzymes are good indicators for the biological mechanism of soil nutrients and organic matter cycles. However, they have been used less frequently to assess the ecological stability and soil C cycle in eroding landscapes due to a lack of knowledge of the responses of C-acquiring enzyme activities to soil erosion and deposition. In the present study, a 3-year field simulation experiment was conducted to examine the variations in the activities of C-acquiring enzymes (β-1,4-xylosidase (βX), β-1,4-glucosidase (βG) and β-D-cellobiohydrolase (CBH)) from erosion-deposition plots with different slope gradients (5°, 10° and 20°) on the Loess Plateau in China (2016–2018). The activities of βX, βG and CBH were higher in the depositional plots than in the erosional plots, and those differences were enlarged with increasing slope gradients. Compared to the 5°-erosional plot, the activities of βX, βG and CBH respectively declined by 3.2–4.5%, 14.3–37.5% and 12.7–29.1% in the 10°-and 20°-erosional plots. The βX, βG and CBH activities were 2.2–18.1%, 17.3–32.1% and 14.8–86.2% higher in the 10°- and 20°-depositional plots than in the 5°-depositional plot. Moreover, the total soil CO2 emissions from the whole erosion-deposition plots decreased as slopes steepened. The displaced runoff and sediment depleted soil moisture, SOC, clay and microbial biomass in the erosional plots but enhanced these resources in the depositional plots, which can account for the changes in C-acquiring enzyme activities. The spatial distribution of enzyme activities affected soil CO2 emissions in a positive linear function. The sensitive responses of the C-acquiring enzyme activities and the controlling effects of C-acquiring enzyme activities on soil CO2 emissions during erosion and deposition processes, should be properly considered in assessing the biological mechanism for nutrition cycling in regions predominated with fragmented eroding landscapes.

The Late Quaternary Evolution of the Upper Reaches of Fluvial Systems in the Southern East European Plain

Networks of dry valleys (or balkas) and hollows in the upper reaches of fluvial basins in extraglacial areas in the Penultimate Glaciation (Marine Isotope Stage 6—MIS 6) regions of the East European Plain demonstrate clear incision/aggradation rhythms corresponding to global glacial/interglacial climate cycles. The first phase of each incision/aggradation rhythm began after the global glacial maximum and was characterized by a cool and humid climate, permafrost and sparse vegetation, when high surface runoff and active linear erosion formed a dense network of gullies. The second phase occurred at the glacial–interglacial transition and the subsequent interglacial period with its warm and humid climate and dense vegetation. This phase was distinguished by the partial filling of fluvial forms with slopewash deposits, the transformation of gullies into dry valleys (balkas) and the subsequent stabilization of fluvial forms marked by the formation of mature soils on the sides and bottoms of balkas. The third phase of the rapid accumulation of balkas developed during the cold and dry part of the next glacial epoch, resulting in the balkas becoming shallow hollows filled in with sediments. The last full incision/aggradation rhythm occurred in the late MIS 6 to mid-MIS 2. The erosion network formed during the late MIS 6 was almost completely filled by mid-MIS 2, and its manifestation in the modern topography is limited to a network of shallow hollows in the upper parts of the fluvial systems. The modern (incomplete) incision/aggradation rhythm began in the late MIS 2 and caused the formation of the modern erosion landscape in the upper reaches of fluvial systems. This rhythm is now in the stabilization phase, and the main accumulation phase of this rhythm is still far in the future.

Complexity and asynchrony of climatic drivers and environmental responses during the Last Glacial-Interglacial Transition (LGIT) in north-west Europe

The Last Glacial-Interglacial Transition (ca 16–8 ka BP) in north-west Europe is an important period of climatic change where millennial-scale climatic evolution led to environmental reorganisation. Imprinted upon these long-term changes are a series of short-lived, centennial-scale events that appear to be spatially and temporally complex across Europe. The complexity of environmental change in response to these climatic events is poorly understood because of a paucity of paired investigations that provide evidence of both driver and response variables. We present a high-resolution palynological, charcoal and stable isotopic record alongside chironomid-inferred temperature data from Tirinie, south-east Grampian Highlands, Scotland. The record is stratigraphically and chronologically constrained using tephra and radiocarbon dating. The isotopic and chironomid data reveal centennial-scale climatic deteriorations at ca 14.0; 13.2 and 11.4 cal ka BP. In response to these cooling events, vegetation became more open, fire frequency increased and landscape erosion was common. The reconstruction of both climate and environment reveals asynchrony in the phasing of annual and summer temperature variability, vegetation change and fire for each climatic event. Whilst responses appear strongest following the convergence of annual and summer temperature variability across all events, the ca 13.2 ka BP event reveals a two-stage environmental and fire response to climatic change, and the ca 11.4 ka BP event exhibits environmental change in the absence of summer temperature variability. The data further suggests that fire is an integral component of abrupt climatic change in this part of north-west Europe.

Correction to: Constructing a spatial analysis model in assessing the sensitivity of landscape erosion in mountainous regions of Vietnam

There was an error in the map in Fig. 1 (Study area of Ngu Chi Son, Vietnam). It is replaced with Fig 1S in the electronic supplementary material.

The shaping of erosional landscapes by internal dynamics

Erosional landscapes transport sediment downstream, host natural hazards and are geologically active. While perturbations in external forcing, particularly climate and tectonics, sculpt erosional landscapes, similar landforms can be created by internal dynamics, that is, feedbacks between topography, erosion and sediment transport that occur independent of external perturbations. Internal system responses, termed autogenic dynamics, can remain active as landscapes adjust to perturbations in forcing, allowing for complex responses to external perturbations that potentially obscure links between external forcing, topographic form and sedimentary archives. Autogenic dynamics are being increasingly recognized in depositional systems, yet understanding of autogenic dynamics in erosional landscapes is nascent. In this Review, we discuss the mechanisms that contribute to internal dynamics in erosional landscapes. We use examples of autogenic terrace formation, knickpoint formation and river-basin reorganization to show how autogenic dynamics that occur over spatial scales of metres and temporal scales of hours can influence the evolution of mountain ranges over Myr periods. Unravelling the mechanics of autogenic processes allows the interplay of internal dynamics and external forcing to be explored and provides a framework to assess the influence of erosional processes in the geologic record. The morphology of erosional landscapes is often considered to be set by climate and/or tectonics; however, similar topographic features can arise through internal processes and feedbacks. This Review considers how the internal and external processes drive landscapes evolution, and how such processes can be differentiated in topographic and stratigraphic records.

Constructing a spatial analysis model in assessing the sensitivity of landscape erosion in mountainous regions of Vietnam

This study demonstrates the steps of building a spatial analysis model that is applicable in synthetically assessing the sensitivity of landscape erosion in mountainous regions. Field testing was carried out at Ngu Chi Son commune, Sa Pa district, Lao Cai Province, Vietnam. The primary basis is the application of the GIS spatial analysis model in mapping the landscape structure. Subsequently, depending on the landscape structure map, the analysis model of erosion levels due to erosion factors (rainfall, terrain, the thickness of soil layers, mechanical compositions, vegetation cover, and cultivation measures of human beings) was constructed. The employed algorithms included spatial overlay, spatial interpolation, attribute reclassification, and average indexes. The results of this study have indicated the erosion sensitivity of every landscape unit, which is categorized into five levels: very low, low, medium, high, and very high. Obtained appraisals and sensitivity categorization are important fundaments to issue exploitation orientations and reasonable usages of resources within the researched region. This proves to be a new direction of research with overall potentials in assessing mountainous landscapes.

Preservation of the last aggradation phase in climate‐driven terraces: Evidence from Late Quaternary reach‐specific fluvial dynamics of the Allier River (France)

AbstractThere is limited knowledge about the preservation of aggradation phases in Quaternary fluvial records. Previous numerical modelling of erosion and deposition in Late Quaternary Allier River (France) generated the prediction that this river has reach‐specific fluvial dynamics related to climate‐driven tributary sediment‐flux dynamics. To test this prediction, new optically stimulated luminescence (OSL) samples were collected of the Late Quaternary Fx terrace at five locations along a stretch of 60 km. OSL dates of both quartz and feldspar sand grains indicate that all relatively basalt‐poor sediments display significantly different ages for each reach (ranging from 36.3 ± 2.0 to 21.1 ± 2.3 ka). The more basalt‐rich terrace body consistently yields ages in the range 21.1 ± 1.7 to 16.1 ± 1.5 ka, suggesting contemporaneous aggradation along the whole studied Allier reach during this interval. Our own new OSL date of a Tartaret eruption around 16.8 ± 2.5 ka also fits this time window, suggesting a direct link with volcanic activity. However, there are many more dated volcanic events that coincide with the older basalt‐poor units, making it less likely that a direct link between terrace‐sediment basalt content and volcanic activity exists. The timings of the dated depositional events in MIS 3 and 2 all match with simulated climate drivers and published landscape erosion rates. Counterintuitively, the volcanic Chaîne des Puys area supplied more sediment during the cold and dry Last Glacial Maximum. Basalt content in the Allier terrace sediments reflects climate‐related sediment‐flux dynamics upstream. The scarcity of older basalt‐poor sediment bodies from MIS 4 and 3 in the Fx terrace suggests that less sediment was supplied and/or the intermittent erosional phases in the Allier were very effective at removing them. We hypothesize that this observation of predominant preservation of the last aggradation phase could be a common phenomenon in most climate‐driven terraces. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley &amp; Sons Ltd

Alluvial fans on volcanic islands: A morphometric perspective (São Vicente, Cape Verde)

The distribution, morphology and development of volcanic island alluvial fans are investigated using São Vicente from the Cape Verde volcanic chain (east-central Atlantic Ocean). This is a tectonically and volcanically inactive dryland setting, comprising an eroded Plio-Pleistocene composite volcano overlying a submarine shield volcano. We mapped 228 alluvial fans, quantifying fan (F) and catchment (C) morphological properties (area [A], gradient [G], relief [R], length [L]). Fans and catchments of varying size and gradient are distributed around the island coastal margins (6%) and along interior valley sides (94%). Regression results (i.e. +ve/−ve slopes of best fit lines) conformed to broader fan research but with weak correlations, and coefficient-exponent values outside, or at the lower end of values reported from non-volcanic settings. Analysis of fan area and gradient vs catchment area regression residuals revealed fans were dominated by small-steep gradient (28%) and large-low gradient forms (39%). Fan building space is a fundamental control, specifically linked to volcano structure, but with interplay between rock strength, base level, and climate. Fans around the volcanic edifice flanks are uncommon due to steep flank slopes. Where flank margin fans occur they are typically small and steep forms due to marine erosion. Fans along flank incised valleys are common. Large low gradient fans are associated with a major volcanic rift-aligned valley structure, with extensive erosion into altered and weathered edifice-core lithologies. Small-steep gradient fans are associated with edifice flank valleys. Steeper and narrower valley forms reflect incision into stronger lithologies of the composite volcano flanks, restricting fan building space. Fans located within the volcano central depression are amongst the largest and lowest gradient types, building into the eroded and unconfined edifice core space. Coalescence, apex-toe incision, toe erosion and catchment stream channel backfilling displayed by most fans suggest landscape erosion dominates during more arid periods (e.g. interglacials), with the dryland setting generating limited sediment and insufficient flood runoff for transport and fan deposition. Fan building likely occurs during wetter periods linked to Quaternary climate variability. Quaternary eustatic variations are relevant for the volcano edifice margins where sea level changes control fan building space and erosion.

Late Cenozoic climate change paces landscape adjustments to Yukon River capture

Late Cenozoic cooling and changes in glacial–interglacial cycle tempo are thought to increase global rates of erosion starting ~3 million years ago (Ma). Bedrock rivers set rates and patterns of erosion in most landscapes, but constraints on river response to late Cenozoic climate change remain elusive. Here, we determine cosmogenic isotope and luminescence ages of well-preserved bedrock terraces along the Fortymile River (Yukon River basin) to reconstruct an ~5 Myr history of fluvial adjustment to late Cenozoic climate and Yukon River headwater capture at 2.6 Ma. Post-capture Yukon River downcutting lowered the Fortymile River outlet, forcing subsequent bedrock incision throughout the Fortymile basin in two pulses, from 2.4 to 1.8 Ma and at ~1 Ma. These pulses of incision disrupted longer intervals of slow river channel sedimentation under near-consistent climate forcing from 4.8 to 2.4 Ma and from 1.8 to ~1 Ma. The Fortymile River delivers sediment to the Bering Sea, where provenance and accumulation rate changes since 4.3 Ma match observed variations in incision. Our results link alluviation and incision to late Cenozoic climate steadiness and change, respectively, and support the hypothesis that climate-forced changes in precipitation and runoff fundamentally control the pace of river incision and landscape erosion. Increased river incision and landscape erosion can be attributed to late Cenozoic cooling/changes in hydroclimate, according to cosmogenic isotope and luminescence ages of a sequence of bedrock terraces in the Yukon River basin.