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Numerical models have not yet systematically been used to predict properties of fluvial terrace records in order to guide fieldwork and sampling. This paper explores the potential of the longitudinal profile model FLUVER2 to predict testable field properties of the relatively well-studied, Late Quaternary Allier system in France. For the Allier terraces an overlapping 14C and U-series chronology as well as a record of 10Be erosion rates exist. The FLUVER2 modelling exercise is focused on the last 50 ka of the upper Allier reach because for this location and period the constraints of the available dating techniques are tightest. A systematic calibration based on terrace occurrence and thicknesses was done using three internal parameters related to (1) the sediment erodibility; (2) the sediment transport distance; and (3) the sediment supply derived from the surrounding landscape. As external model inputs, the best available, reconstructed, tectonic, climatic and base-level data were used. Calibrated model outputs demonstrate a plausible match with the existing fluvial record. Validation of model output was done by comparing the modelled and measured timing of aggradation and incision phases for the three locations. The modelled range of landscape erosion rates showed a reasonably good match with existing erosion rate estimates derived from 10Be measurements of fluvial sands. The quasi-validated model simulation was subsequently used to make new testable predictions about the timing and location of aggradation and erosion phases for three locations along the Allier river. The validated simulations predict that along the Allier, reach-specific dynamics of incision and aggradation, related to the variations in sediment supply by major tributaries, cause relevant differences in the local fluvial terrace stratigraphy. Numerical models have not yet systematically been used to predict properties of fluvial terrace records in order to guide fieldwork and sampling. This paper explores the potential of the longitudinal profile model FLUVER2 to predict testable field properties of the relatively well-studied, Late Quaternary Allier system in France. For the Allier terraces an overlapping 14 C and U-series chronology as well as a record of 10 Be erosion rates exist. The FLUVER2 modelling exercise is focused on the last 50 ka of the upper Allier reach because for this location and period the constraints of the available dating techniques are tightest. A systematic calibration based on terrace occurrence and thicknesses was done using three internal parameters related to (1) the sediment erodibility; (2) the sediment transport distance; and (3) the sediment supply derived from the surrounding landscape. As external model inputs, the best available, reconstructed, tectonic, climatic and base-level data were used. Calibrated model outputs demonstrate a plausible match with the existing fluvial record. Validation of model output was done by comparing the modelled and measured timing of aggradation and incision phases for the three locations. The modelled range of landscape erosion rates showed a reasonably good match with existing erosion rate estimates derived from 10 Be measurements of fluvial sands. The quasi-validated model simulation was subsequently used to make new testable predictions about the timing and location of aggradation and erosion phases for three locations along the Allier river. The validated simulations predict that along the Allier, reach-specific dynamics of incision and aggradation, related to the variations in sediment supply by major tributaries, cause relevant differences in the local fluvial terrace stratigraphy. Copyright © 2016 John Wiley & Sons, Ltd.

This paper presents a first-order HLLC (Harten-Lax-Van Leer with contact discontinuities) scheme to solve the Saint-Venant shallow-water equations, including morphological evolution of the bed by erosion and deposition of sediments. The Exner equation is used to model the morphological evolution of the bed, while a closure equation is needed to evaluate the rate of sediment transport. The system of Saint- Venant–Exner equations is solved in a fully coupled way using a finite-volume technique and a HLLC solver for the fluxes, with a novel wave-speed estimator adapted to the Exner equation. Wave speeds are usually derived by computing the eigenvalues of the full system, which is highly time-consuming when no analytical expression is available. In this paper, an eigenvalue analysis of the full system is conducted, leading to simple but still accurate wave-speed estimators. The new numerical scheme is then tested in three different situations: (1) a circular dam-break flow over movable bed, (2) an one-dimensional bed aggradation problem simulated on a 2D unstructured mesh and (3) the case of a dam-break flow in an erodible channel with a sudden enlargement, for which experimental measurements are available.

The quantitative modelling of fluvial reservoirs, especially in the stages of enhanced oil recovery, requires detailed three-dimensional data at both the scale of the channel belt and within-channel. Although studies from core, analogue outcrop and modern environments may partially meet these needs, they often cannot provide detail on the smaller-scale (i.e. channel-scale) heterogeneity, frequently suffer from limited three-dimensional exposure and cannot be used to examine the influence of different variables on the process–deposit relationship. Physical modelling offers a complementary technique that can address many of these quantitative requirements and holds great future potential for integration with reservoir modelling. Physical modelling provides the potential to upscale results and derive reservoir information on three-dimensional facies geometry, connectivity and permeability. This paper describes the development and use of physical modelling, which employs generic Froude-scaling principles, in an experimental basin that permits aggradation in order to model the morphology and subsurface depositional stratigraphy of coarse-grained braided rivers. An example is presented of a 1:50 scale model based on the braided Ashburton River, Canterbury Plains, New Zealand and the adjacent late Quaternary braided alluvium exposed in the coastal cliffs. Critically, a full, bimodal grain size distribution (20% sand and 80% gravel) was used to replicate the prototype, which allows the realistic reproduction of the surface morphology and importantly permits grain size sorting during deposition. Uncertainties associated with the compression of time, sediment mass balance and the hydrodynamics of the finest particle sizes do not appear to affect the reproducibility of stratigraphy between experimental and natural environments. Sectioning of the preserved sedimentary sequence in the physical model allows quantification of the geometry, shape, spatial distribution and internal sedimentary structure of the coarse- and fine-grained facies. A six-fold facies scheme is proposed for the model braided alluvium and a direct link is established between the grain size distribution and facies type: this allows permeability to be estimated for each facies, which can be mapped onto two-dimensional vertical cross-sections of the preserved stratigraphy. Results demonstrate the dominance of four facies based on permeability that range over three orders of magnitude in hydraulic conductivity. Quantification of such variability, and linkage to both vertical proportion curves for facies distribution and connectivity presents significant advantages over other methodologies and offers great potential for the modelling of heterogeneous braided river sediments at the within channel-belt scale. This paper outlines how physical models may be used to develop high-resolution, geologically-accurate, object-based reservoir simulation models

[The Po River Lowstand Wedge (PRLW) of the central Adriatic Sea is made up of stacked alternated clinothems (Type A, B and C clinothems) that show different amount of aggradation of their topsets (e.g. Pellegrini et al., 2018). In this paper, we present novel sedimentological and paleontological analyses and discuss the processes responsible for the observed successions. We detail the character of the clinoforms deposited at the shelf‐edge, discussing the importance of hyperpycnal and storm‐enhanced sediment‐gravity flows in controlling the lithologic assemblage of the different tracts of the compound clinoforms. More in general, we show that, when the fine details of prograding clinoform units are investigated, the processes that lead to margin outbuilding are more complex than usually envisaged. , Abstract Clinoforms with a range of scales are essential elements of prograding continental margins. Different types of clinoforms develop during margin growth, depending on combined changes in relative sea level, sediment supply and oceanographic processes. In studies of continental margin stratigraphy, trajectories of clinoform ‘rollover’ points are often used as proxies for relative sea‐level variation and as predictors of the character of deposits beyond the shelf‐break. The analysis of clinoform dynamics and rollover trajectory often suffers from the low resolution of geophysical data, the small scale of outcrops with respect to the dimensions of clinoform packages and low chronostratigraphic resolution. Here, through high‐resolution seismic reflection data and sediment cores, we show how compound clinoforms were the most common architectural style of margin progradation of the late Pleistocene lowstand in the Adriatic Sea. During compound clinoform development, the shoreline was located landward of the shelf‐break. It comprised a wave‐dominated delta to the west and a barrier and back‐barrier depositional system in the central and eastern area. Storm‐enhanced hyperpycnal flows were responsible for the deposition of a sandy lobe in the river mouth, whereas a heterolithic succession formed elsewhere on the shelf. The storm‐enhanced hyperpycnal flows built an apron of sand on the slope that interrupted an otherwise homogeneous progradational mudbelt. Locally, the late lowstand compound clinoforms have a flat to falling shelf‐break trajectory. However, the main phase of shelf‐break bypass and basin deposition coincides with a younger steeply rising shelf‐break trajectory. We interpret divergence from standard models, linking shelf‐break trajectory to deep‐sea sand deposition, as resulting from a great efficiency of oceanographic processes in reworking sediment in the shelf, and from a high sediment supply. The slope foresets had a large progradational attitude during the late lowstand sea‐level rise, showing that oceanographic processes can inhibit coastal systems to reach the shelf‐edge. In general, our study suggests that where the shoreline does not coincide with the shelf‐break, trajectory analysis can lead to inaccurate reconstruction of the depositional history of a margin.]

International audience; The retreat of glaciers in response to climate warming leads to substantial changes in meltwater and sediment yield. Glacial shrinkage also induces the emergence and growth of proglacial margin landforms which strongly affect water and sedimentary transfers from the glacier to the outwash plains. On a decadal-timescale, field observations show that outwash plains of retreating glaciers typically exhibit proximal incision which decreases in magnitude downstream and stops at an inflection point where aggradation begins. Nevertheless, there is a lack of knowledge about the rates and magnitude of this fluvial adjustment and the effects of the proglacial margin configuration on the temperance or the aggravation of this fluvial adjustment to glacier retreat. This paper investigates the proglacial rivers of 14 retreating glaciers in southeast Iceland over a post-Little Ice Age timescale, combining fluvial deposits mapping, lichenometric dating and long-profile measurements of proglacial fluvial terraces. Our results demonstrate that: (1) proximal incision, associated with distal aggradation and downstream migration of the inflection point is the dominant pattern of proglacial river response to post-LIA glacier retreat in Iceland; (2) estimated mean rates of downstream migration of the inflection point range between 5 and 46 m.a-1 ; (3) the downstream migration rate of the inflection point is positively correlated with the proportion of proglacial lakes within the glacier foreland. These findings suggest that proglacial margins dominated by proglacial lakes intensify the rates of proximal incision and inflection point migration

This paper presents the history and cryostratigraphy of the upper permafrost in the High-Arctic Adventdalen Valley, central Svalbard. Nineteen frozen sediment cores, up to 10.7 m long, obtained at five periglacial landforms, were analysed for cryostructures, ice, carbon and solute contents, and grain-size distribution, and were 14C- and OSL-dated. Spatial variability in ice and carbon contents is closely related to the sedimentary history and mode of permafrost aggradation. In the valley bottom, saline epigenetic permafrost with pore ice down to depths of 10.7 m depth formed in deltaic sediments since the mid-Holocene; cryopegs were encountered below 6 m. In the top 1 to 5 m, syngenetic and quasi-syngenetic permafrost with microlenticular, lenticular, suspended and organic-matrix cryostructures developed due to loess and alluvial sedimentation since the colder late Holocene, which resulted in the burial of organic material. At the transition between deltaic sediments and loess, massive ice bodies occurred. A pingo developed where the deltaic sediments reached the surface. On hillslopes, suspended cryostructure on solifluction sheets indicates quasi-syngenetic permafrost aggradation; lobes, in contrast, were ice-poor. Suspended cryostructure in eluvial deposits reflects epigenetic or quasi-syngenetic permafrost formation on a weathered bedrock plateau. Landform-scale spatial variations in ground ice and carbon relate to variations in slope, sedimentation rate, moisture conditions and stratigraphy. Although the study reveals close links between Holocene landscape evolution and permafrost history, our results emphasize a large uncertainty in using terrain surface indicators to infer ground-ice contents and upscale from core to landform scale in mountainous permafrost landscapes.

Along the eastern margin of Australia, hydrological variability reaches a peak in the subtropics of south-east Queensland and many rivers have entrenched characteristics. To address the nature of entrenchment and the relationship with adjacent alluvium, this paper presents the results of detailed chrono-stratigraphic analysis of alluvial units in the partly confined mid-reaches of Lockyer Creek, Australia. Four sites were investigated using topographic, sedimentological and chronological data. Radiocarbon and single grain optically stimulated luminescence dating indicate a large proportion of the valley fill reflects a major phase of aggradation of fine-grained alluvium from ca. 35 ka throughout the Last Glacial Cold Period. Synchronous incision of Pleistocene alluvial fills between 11.5 and 9.3 ka suggests the current entrenched Lockyer Creek formed in response to changes in late Quaternary climate. Holocene floodplains set within the entrenched Pleistocene valley floor have basal ages of ca. 7.5 ka, but whose proximal margins are still actively accreting. This Holocene fill has accreted over the mid- to late Holocene but overlaps with the contemporary hydrological regime. The sedimentary nature of the Holocene fill appears to be related to persistent antecedent controls in the form of bedrock and terrace constriction.

Controls on the characteristics of floodplain wetlands in drylands are diverse and may include extrinsic factors such as tectonic activity, lithology and climate, and intrinsic thresholds of channel change. Correct analysis of the interplay between these controls is important for assessing possible channel-floodplain responses to changing environmental conditions. Using analysis of aerial imagery, geological maps and field data, this paper investigates floodplain wetland characteristics in the Tshwane and Pienaars catchments, northern South Africa, and combines the findings with previous research to develop a new conceptual model highlighting the influence of variations in aridity on flow, sediment transport, and channel-floodplain morphology. The Tshwane-Pienaars floodplain wetlands have formed in response to a complex interplay between climatic, lithological, and intrinsic controls. In this semiarid setting, net aggradation (alluvium >5 m thick) in the wetlands is promoted by marked downstream declines in discharge and stream power that are related to transmission losses and declining downstream gradients. Consideration of the Tshwane-Pienaars wetlands in their broader catchment and regional context highlights the key influence of climate, and demonstrates how floodplain wetland characteristics vary along a subhumid to semiarid climatic gradient. Increasing aridity tends to be associated with a reduction in the ability of rivers to maintain through-going channels and an increase in the propensity for channel breakdown and floodout formation. Understanding the interplay between climate, hydrology and geomorphology may help to anticipate and manage pathways of floodplain wetland development under future drier, more variable climates, both in South African and other drylands. This article is protected by copyright. All rights reserved.

This paper focuses on the late Holocene occupation of hunter-gatherers at the Marazzi 2 site located on the northwestern steppe of Tierra del Fuego, Chile. Our aim is to understand stratigraphy, formation processes, and pedogenesis with respect to human occupation over the last 3000 years. Based on archaeological excavations on a fluvial terrace of the Torcido River, we integrate soil micromorphology, mineralogy, geochemistry, magnetic susceptibility, and geomorphology, as well as the micro- and macrofrequency distributions of archaeological material. A micro-taphonomical perspective is also applied to anthropogenic components recorded in sedimentary thin sections. We discuss various events in the interplay between soil development and human occupation through time. Marazzi 2 was witness to aggradation and pedogenesis with an episode of surface stability coincident with a phase of more intense human occupation at about 860 BC. Taphonomic analysis suggests that there are multiple occupation events mixed together, probably by biomechanical processes, resulting in a palimpsest with poor temporal resolution.

Archaeological investigations of settlement patterns in dynamic landscapes can be strongly biased by the evolution of the Earth's surface. The Kuril Island volcanic arc exemplifies such a dynamic landscape, where landscape-modifying geological forces were active during settlement, including sea-level changes, tectonic emergence, volcanic eruptive processes, coastal aggradation, and dune formation. With all these ongoing processes, in this paper we seek to understand how new landscape formation in the Holocene might bias archaeological interpretations of human settlement in the Kurils. Resolving this issue is fundamental to any interpretation of human settlement history derived from the distribution and age of archaeological sites from the region. On the basis of a comparison of landform ages and earliest archaeological occupation ages on those landforms, we conclude that landform creation did not significantly bias our aggregate archaeological evidence for earliest settlement. Some sections of the archipelago have larger proportions of landform creation dates closer to archaeological evidence of settlement and undoubtedly some archaeological sites have been lost to geomorphic processes. However, comparisons between regions reveal comparable archaeological establishment patterns irrespective of geomorphic antiquity.

In the present paper the effects of rapid, high-amplitude base-level changes during the last glacial-interglacial transition were studied for the Ain River in eastern France. During the Wurm glacial maximum (MIS 2) rapid aggradation by deep-water Gilbert-type deltas and shallow-water fan deltas occurred at the margins of a 20 to 50m deep proglacial lake. A temporal high-amplitude lake-level fall of 60m resulted in gravel deposition by forced-regressive deltas, followed by rapid lake-level rise and fine-grained glaciolacustrine deposition. During the final deglaciation, a rapid base-level fall of 40m resulted in a complex fluvial response. Knickpoint formation and headward incision of the highstand deltas and concomitant deposition of gravel sheets by forced-regressive deltas and braided systems occurred in several depocentres on the former glacial lake floor. Preservation of highstand and falling-stage deposits and terrace formation in the incised valley depended on vertical incision and lateral channel migration. Terraces are well developed in the former lake-floor depressions, whereas vertical incision was dominant in the higher lake-floor areas. The Ain terrace staircase was likely formed by autogenic processes during a single allogenic base-level fall. This case study possibly offers an analogue for the preservation of interglacial highstand coastal deltas during sea-level fall at warm-to-cold climate transitions, although the rates of base-level fall are different. © 2013 Collegium Boreas. Published by John Wiley & Sons Ltd.

This paper presents three maps that summarize current knowledge as to the extent of Past permafrost and Relict permafrost in North America at approximately the time of the Last Glacial Maximum (LGM; c. 25–17 ka BP) and during subsequent deglaciation until c. 10 ka BP. Analysis of the post-1983 literature suggests that the extent of Past permafrost south of the LGM limit was broader in eastern North America and slightly narrower in the Interior Great Plains than previously mapped. The recognition and dating of Relict permafrost in the nonglaciated terrain of the northwestern Arctic suggests that permafrost may be of great antiquity and can persist under changing climatic conditions. The formation of permafrost features during deglaciation suggests that ice-proximal climatic conditions remained cold at least long enough for short-lived permafrost aggradation; a latitudinal gradient is evident in the timing of its development as the Laurentide Ice Sheet retreated.

Stratification in channel belts is the key to reconstructing formative channel dimensions and palaeoflow conditions; this requires an understanding of the relation between river morphodynamics and set thickness. So far, theories for reconstruction of the original morphology from preserved stratification have not been tested for meandering river channels due to the lack of detailed bathymetry. This paper reports the results of an experiment that reproduced a dynamic meandering gravel-bed river with the objectives to: (i) test the prediction of set thickness as a function of the morphology formed by a meandering river channel; and (ii) explore and explain spatial and temporal set thickness variations in the resulting channel belt. High-resolution measurements of time-dependent surface elevation were used to quantitatively relate the preserved stratification to the meandering river morphology. Mean set thickness agrees well with the theoretical prediction from channel morphology. The mean preserved set thickness was 30% of the mean channel depth. Due to the absence of aggradation during the experiment, this provides a lower limit for the preserved mean set thickness which is also to be expected for aggrading systems, because reworking is some orders of magnitude faster than aggradation. Furthermore, the time required to mature a channel belt and its set thickness distribution was about the same as the time required to develop and propagate bends that fill the channel belt surface. Finally, there was much systematic spatial variation in set thickness related to repetitive point bar growth and chute cut-off. Undisturbed and thick sets occurred close to channel belt margins and more irregular stratification with stacked thinner sets was observed in the centre of the channel belt.

This paper reports the discovery of a rare partial skeleton of a woolly rhinoceros (Coelodonta antiquitatis Blumenbach, 1799) and associated fauna from a low Pleistocene terrace of the River Tame at Whitemoor Haye, Staffordshire, UK. A study of the sedimentary deposits around the rhino skeleton and associated organic-rich clasts containing pollen, plant and arthropod remains suggests that the animal was rapidly buried on a braided river floodplain surrounded by a predominantly treeless, herb-rich grassland. Highlights of the study include the oldest British chironomid record published to date and novel analysis of the palaeoflow regime using caddisfly remains. For the first time, comparative calculations of coleopteran and chironomid palaeotemperatures have been made on the same samples, suggesting a mean July temperature of 8–11 °C and a mean December temperature of between −22 and −16 °C. Radiocarbon age estimates on skeletal material, supported by optically stimulated luminescence ages from surrounding sediments, indicate that the rhino lived around 41–43 k cal a BP. The combined geochronological, stratigraphic and palaeoenvironmental evidence places the assemblage firmly within the Middle Devensian (Marine Oxygen Isotope Stage 3). This would agree with other regional evidence for the timing of aggradation for the lowest terrace of the Trent and its tributary systems. Copyright © 2012 John Wiley & Sons, Ltd.

Floodplain sedimentation is one of the most dynamic geomorphic processes within plain and lowland landscapes. There is generally a good understanding of longer term floodplain evolution, but quantitative information on overbank deposition rates for recent shorter timescales is lacking. This paper describes the application of Chernobyl-derived 137Cs to quantify floodplain aggradation rates for the River Plava (a small river draining a severely contaminated part of the upland region of Central European Russia), based on detailed sampling of four representative floodplain study sites. Two approaches have been employed for estimating post-Chernobyl (1986–2009) floodplain accumulation rates. The first was based simply on locating the Chernobyl fallout-associated 137Cs peak in overbank sediment sections. The second involved quantification of the increase in the total 137Cs inventory at individual sampling points associated with the post-Chernobyl deposition of contaminated suspended sediment. It has been shown that considerable local-scale variability of overbank deposition rates exists, with aggradation rates on the low level floodplain (6 ± 1.2–14 ± 2.8 mm year−1) exceeding by 1.5–3 times the values for the middle level floodplain (2 ± 0.4–9 ± 1.8 mm year−1) and by 3–6 times the values for the upper level floodplain (1 ± 0.2–5 ± 1.0 mm year−1) floodplain levels. Combining these estimates with information on the areas occupied by different floodplain levels within the 54 km long valley section, derived from detailed geomorphic surveys of the selected reaches, it has been estimated that about 9700 ± 1950 t of sediment have been stored on floodplain during the 1986–2009 period. The role of floodplain storage in the overall basin sediment budget and conveyance losses within the main channel system have been evaluated. Copyright © 2012 John Wiley & Sons, Ltd.

The lower Ebro River experiences long-term hydrological and sedimentary adjustments following major regulation. Alterations in water and sediment fluxes have enhanced a massive macrophyte colonization that, in turn, generates a series of ecological and socio-economic problems. Controlled water releases, so-called flushing flows (FFs), have been designed and implemented since 2002 in this part of the river with the objectives of controlling macrophyte populations and maintaining sediment transport in the channel. FFs may produce adverse geomorphic effects, such as bed incision driven by the increased sediment transport capacity and the lack of sediment replacement from upstream. It is thus important to evaluate the potential geomorphic responses to a specific FF design, and redesign FFs regularly to maximize macrophyte removal while minimizing the undesired consequences. Geomorphic responses associated with FFs can be assessed using hydraulic and sediment transport models. In this paper, we use the hydrodynamic model CCHE2D® to evaluate the role of a monitored FF on a river's geomorphology. The designed FF had a duration of 13 h, attaining a maximum discharge of 1350 m3 s−1. A total of 3375 t of fine material were transported during that event. CCHE2D® model performance is evaluated in terms of hydraulics and sediment transport by comparing observed with modelled values (i.e. discharge, water surface elevation, sediment loads). Overall, objective functions indicate that simulations are in agreement with field observations. For instance, the Root Mean Square Error (RMSE) between the observed and modelled FF hydrograph was 93 m3 s−1, whereas the RMSE of the total load was 71 t. The example modelled here shows that the FF design typically implemented in the lower Ebro does not cause severe geomorphic impacts. The model provides visualization of the spatial patterns of erosion and deposition for the first time, allowing identification of critical zones where degradation or aggradation may occur. Copyright © 2012 John Wiley & Sons, Ltd.

The aim of this paper is to study a low energy fluvial system response to natural and anthropogenic forcing during the last two millennia. In contrast with longer timescales (Holocene to Quaternary), historical sedimentary archives are sparse in such systems which are typically characterized by the predominance of erosion compared with aggradation. We studied three main sections in the Moselle valley (northeastern France) by a multi-proxy approach combining morphology, sedimentology, archaeological evidence, historical archives, and dating. The geochronological framework was based on Optically Stimulated Luminescence (OSL) and validated by independent age control. The exposed sediments were allocated to different historical periods from Roman period to present. The first results show that, in contrast with many other fluvial systems, the Moselle and its tributaries did not experience major changes during historical periods. Climatic changes such as the Little Ice Age had a minor influence on floodplain aggradation (e.g. in grain size or sedimentation rates) in the Moselle valley and were only able to affect the fluvial style. This provides evidence that the reworking of sediments is the main fluvial process at short timescales in the valley floors of the Moselle catchment. In contrast, anthropogenic forcing seems important not only during recent centuries but also since Roman times. This is suggested by the case-study of the Metz-Mazelle section where significant headward erosion and sedimentation were recognized, and may be related to human occupation. The results therefore point to a need for increasing geoarchaeological and geochronological research in the Moselle catchment and similar low energy fluvial systems. Such research is actually essential to improve the knowledge of the fluvial response to environmental changes during the historical periods and to recognize the respective influence of natural variability and human forcing. Copyright © 2012 John Wiley & Sons, Ltd.

The late Middle Pleistocene sites in the Ebbsfleet Valley, Kent, UK, have yielded archaeological assemblages critical to understanding the early Middle Palaeolithic of northwestern Europe. Despite a long history of research, the nature and context of these assemblages are still poorly understood. This paper clarifies the stratigraphic, environmental and archaeological records at Ebbsfleet. These reflect a cold–warm–cold sequence of climatic events, preserved within part of the Taplow/Mucking Formation of the Thames (Marine Isotope Stage (MIS) 8/7/6). Levallois artefacts are shown to be restricted to the lower part of the Ebbsfleet Channel sequence (Phases I and II) and are assigned to late MIS 8/early MIS 7. This material is associated with fauna indicative of open environments during both cool and temperate conditions. Handaxe assemblages are recorded from higher up the sequence (Phases III–V), but have been redeposited from higher terrace units nearby. No primary context archaeology is apparent during these later phases of aggradation. This may indicate that humans abandoned the site once available raw material became inaccessible, and may also reflect a decline in human presence in Britain during the latter part of MIS 7. Copyright © 2010 John Wiley & Sons, Ltd.

The late Cenozoic geomorphic features and geochronologic data of the Zhingfang River catchment in the Yuntaishan World Geopark are studied. Several quarternary geochronologic methods, including electron spin resonance (ESR), optically stimulated luminescence (OSL), thermo-luminescence (TL) and U-series are presented in this paper. The results suggest that there are two planation surfaces, named as the Taihang surface which is a peneplain of Taihang stage formed during Oligocene or Oligocene to early-middle Miocene period, and Tang-hien surface which is a mature wide valley of Tang-hien stage formed during late Miocene-Pliocene or Pliocene-early Pleistocene period and probably ended prior to 2.2–2.6 Ma based on ESR dating. After the Tang-hien stage, the incision and aggradation of the river formed six stream terraces with heights of 3–5 m, 8–12 m, 22–24 m, 28–38 m, 50–62 m and 80–85 m above the river bottom, respectively. The dating results of the alluvium sediments suggest that these terraces were formed during Holocene, 20–23 ka B.P., 110–120 ka B.P., 200–240 ka B.P., 840–1200 ka B.P. or ∼450 ka B.P. and 1600–1800 ka B.P. or ∼1100 ka B.P., respectively. These results indicate that episodic incision of the river, which controls the formation of the scenery in the Yuntaishan World Geopark, was mainly influenced by the periodic dry-wet climate change during late Cenozoic mountain uplift.

Alluvial sequences constitute a recognised source of information on past environmental change, but one that has scarcely been tapped in central Mexico. This paper reviews what is currently known about the Holocene alluvial stratigraphy of the region, focusing on the interplay between climate and the pace and style of sedimentation in the incised headwater reaches of stream networks. The records obtained in five different drainage basins – four in the state of Tlaxcala and one in Guanajuato – are presented and compared to published reconstructions of climate change. A near-synchronous incision of all stream networks occurred close to 10 200 14C a BP in response to an increase in precipitation and stream discharge. A spell of very humid but markedly seasonal conditions ensued, resulting in the formation of wet meadows along streams and the accumulation of thick fine-textured valley fills dominated by cumulic soil A horizons. After 9100 14C a BP a transition to a warmer and more arid climate provoked the thinning of vegetation cover on slopes, accelerated runoff and increased sediment delivery to streams. The aggradation of coarser-textured valley fills poor in organic matter set in. It ceased or slowed down significantly after a few millennia as the studied stream reaches achieved a near-graded condition adjusted to the relatively stable climate. Arid mid Holocene conditions are also reflected in the abundant precipitation of secondary carbonates in Guanajuato. At 3100 14C a BP higher precipitation caused more frequent flooding and a resumption of aggradation. Shortly after that date sedentary farmers colonised Tlaxcala. Agriculture altered runoff and sediment delivery to streams and accelerated cut-and-fill cycles on a scale that masked the impact of any climatic fluctuations. Guanajuato was colonised later and its alluvial record suggests the persistence of a humid climate at least until 1000 14C a BP. Copyright © 2009 John Wiley & Sons, Ltd.

Current high-resolution palaeoenvironmental records reveal short-term Holocene cool- ings. One of these major Holocene rapid climate changes occurred between 3.2 and 2.7 cal. ka BP. The sensitivity of river systems vis-a `-vis slight and short-term Holocene climatic variations is a subject of controversy in the scientific community. In this paper, we present a 4.0 to 1.4 cal ka BP palaeoflood record from the Lower Moulouya River (northeastern Morocco) to demonstrate the high sensitivity of semiarid rivers in the southwestern Mediterranean towards Holocene environmental changes. The Lower Moulouya flood deposits are characterised by thick, well-stratified, predominantly clayey to silty overbank fine sediments. These cohesive sediments show evidence of excellent preservation conditions against fluvial erosion and contain a continuous record of mid to late Holocene flood sequences. The Moulouya palaeoflood record can be interpreted in the context of regional and global high-resolution proxy data, revealing a strong coupling with Holocene rapid climate changes. The centennial-scale Moulouya palaeohydrological history will be discussed with palaeoenvironmental data from the same record (palaeomagnetics, sedimentary charcoal record, anthracological analyses, snail analyses) to generate new ideas about the mid to late Holocene hydrological cycle in the southwestern Mediterranean. The deduced features of pronounced Lower Moulouya flooding and the decreased fire recurrence during Holocene cooling remain somewhat inconsistent with the interpret- ation of other palaeohydrological and paleaoecological records from the southwestern Mediterranean. However, enhanced Lower Moulouya flood frequencies between 3.2 and 2.7 cal. ka BP agree with increased floodplain aggradation in other major river systems of Mediterranean North Africa. Copyright # 2009 John Wiley & Sons, Ltd.

Although modern wave-dominated shorelines exhibit complex geomorphologies, their ancient counterparts are typically described in terms of shoreface-shelf parasequences with a simple internal architecture. This discrepancy can lead to poor discrimination between, and incorrect identification of, different types of wave-dominated shoreline in the stratigraphic record. Documented in this paper are the variability in facies characteristics, high-resolution stratigraphic architecture and interpreted palaeo-geomorphology within a single parasequence that is interpreted to record the advance of an ancient asymmetrical wave-dominated delta. The Standardville (Ab1) parasequence of the Aberdeen Member, Blackhawk Formation is exposed in the Book Cliffs of central Utah, USA. This parasequence, and four others in the Aberdeen Member, record the eastward progradation of north/south-trending, wave-dominated shorelines. Within the Standardville (Ab1) parasequence, distal wave-dominated shoreface-shelf deposits in the eastern part of the study area are overlain across a downlap surface by southward prograding fluvial-dominated delta-front deposits, which have previously been assigned to a separate ‘stranded lowstand parasequence’ formed by a significant, allogenic change in relative sea-level. High-resolution stratigraphic analysis of these deposits reveals that they are instead more likely to record a single episode of shoreline progradation characterized by alternating periods of normal regressive and forced regressive shoreline trajectory because of minor cyclical fluctuations in relative sea-level. Interpreted normal regressive shoreline trajectories within the wave-dominated shoreface-shelf deposits are marked by aggradational stacking of bedsets bounded by non-depositional discontinuity surfaces. Interpreted forced regressive shoreline trajectories in the same deposits are characterized by shallow incision of fluvial distributary channels and strongly progradational stacking of bedsets bounded by erosional discontinuity surfaces that record enhanced wave-base scour. Fluvial-dominated delta-front deposits most probably record the regression of a lobate delta parallel to the regional shoreline into an embayment that was sheltered from wave influence. Wave-dominated shoreface-shelf and fluvial-dominated delta-front deposits occur within the same parasequence, and their interpretation as the respective updrift and downdrift flanks of a single asymmetrical wave-dominated delta that periodically shifted its position provides the most straightforward explanation of the distribution and relative orientation of these two deposit types.

This paper presents a detailed analysis of the high-resolution facies architecture of the Middle Pleistocene Porta subaqueous ice-contact fan and delta complex, deposited on the northern margin of glacial Lake Weser (Northwest Germany). A total of 10 sand and gravel pits and more than 100 wells were examined to document the complex facies architecture. The field study was supplemented with a ground-penetrating radar survey and a shear-wave seismic survey. All collected sedimentological and geophysical data were integrated into a high-resolution three-dimensional geological model for reconstructing the spatial distribution of facies associations. The Porta subaqueous fan and delta complex consist of three fan bodies deposited on a flat lake-bottom surface at the margin of a retreating ice lobe. The northernmost fan complex is up to 55 m thick, 6AE2 km wide and 6AE5 km long. The incipient fan deposition is characterized by high-energy flows of a plane-wall jet. Very coarse-grained, highly scoured jet-efflux deposits with an elongate plan shape indicate a high Froude number, probably >5. These jet-efflux sediments are deposited in front of a large 3AE2 km long, up to 1AE2 km wide, and up to 25 m deep flute-like scour, indicating the most proximal erosion and bypass area of the jet that widens and deepens with distance downstream to the region of maximum turbulence (approximately five times the conduit diameter). Evidence for subsequent flow splitting is given by the presence of two marginal gravel fan lobes, deposited in front of 1AE 3t o 2AE5 km long flute-like scours, that are 0AE8 to 1 km wide and 7 to 20 m deep. In response to continued aggradation, small jets developed at the periphery of these bar-like deposits and filled in the low areas adjacent to the original superelevated regions, locally raising the depositional surface and characterized by large-scale trough cross-stratified sand and pebbly sand. The incision of an up to 1AE2 km wide and up to 35 m deep channel into the evolving fan is attributed to a catastrophic drainage event, probably related to a lake outburst and lake-level fall in the range of 40 to 60 m. At the mouth of this channel, highly scoured jet-efflux deposits formed under hydraulic-jump conditions during flow expansion. Subsequently, Gilbert-type deltas formed on the truncated fan margin, recording a second lake-level drop in the range of 30 to 40 m. These catastrophic lake-level falls were probably caused by rapid ice-lobe retreat controlled by the convex-up bottom topography of the ice valley.

This paper investigates the impact of a 1000-year flood in August 2002 on floodplains and valley morphology of an Austrian mixed alluvial bed rock river. Discharges with a recurrence interval between 500 and 2000 years caused distinctive overbank scouring and material deposition in the floodplains. After the 1000-year flood, those morphologically affected areas were at random intervals documented over the whole longitudinal profile. In addition to overbank erosion in curved sections (cut-offs), the river bed locally widened, floodplain stripping occurred and local overbank scours were documented along straight parts of the river. A hydrodynamic-numerical model, combined with field measurements, was used to analyse the cause of these erosional landforms. Based on the modelled hydraulic conditions for a one-year flood (30–78 m3 s–1) and the catastrophic 2002 event (700–800 m3 s–1), the numerical results allowed a cause-effect study with 19 parameters. Deterministic and statistical analysis (ANOVA, discriminant analysis) showed that the morphodynamic effects of the 2002 flood were influenced by the variability of valley morphology of the Kamp River, which led partially to supercritical flow during flood constriction. These processes were in some cases also anthropogenically influenced. Lateral constriction and expansion of the valley geometry over short distances led to scouring and aggradation within the inundated areas during the event. These morphological features were therefore responsible for the elongated scour holes in the floodplains. Copyright © 2009 John Wiley & Sons, Ltd.

Changes in channel morphology that occurred along the Macdonald River between 1949 and 1955 are often cited as an example of catastrophic channel change. However, the question of whether these changes represented one component of a cyclical evolutionary pattern, or a systematic and persistent shift to a new morphologic state remains to be clearly defined, as does the significance of these dramatic channel changes when viewed against the river's longer-term Holocene history. In this paper, new measurements of the Macdonald River's channel morphology are used to resolve the river's evolution in the ∼50 years since these major channel-altering floods. By 2002, the Macdonald River's bed had narrowed considerably from its 1955 post-flood maximum due to the construction of a new floodplain surface within the widened channel. In some locations, the 2002 bed width is comparable to that of the pre-1949 channel. This aspect of the river's evolution follows models of cyclical channel evolution proposed for the region. However, in light of recent research into the river's longer term Holocene evolution, it is clear that other channel changes that occurred in response to the 1949–1955 floods, particularly the 2 metres of river bed aggradation and 7 kilometres down-valley shift in the thalweg's intersection with mean sea level, are less cyclic in nature. The capacity of coastal rivers to prograde into estuaries, which in turn induces river bed aggradation, can be seen in this case to counteract the incisional tendencies associated with post-flood channel contraction, such that persistent river bed aggradation occurs.

Geophysical techniques can be used to examine the spatial distribution of subsurface geophysical properties to delineate horizontally and vertically the active layer, permafrost and taliks. Spatial and temporal changes in subsurface geophysical properties due to permafrost cooling, warming, aggradation or degradation can also be assessed through geophysical monitoring. This paper reviews the geophysical methods most frequently applied in mountain and arctic/subarctic lowland permafrost investigations. Key results and recommendations based on the analysis of the applicability and reliability of different geophysical techniques for permafrost studies are summarised. Emphasis is put on the tomographic capabilities of geophysical methods. Recent advances in application and data interpretation are shown in relation to five case studies, and future perspectives are highlighted. Copyright # 2008 John Wiley & Sons, Ltd.

Geomorphological observations, geoelectrical soundings and photogrammetric measurements of surface movement on the Muragl glacier forefield were used to obtain an integrative analysis of a highly complex glacial and periglacial landform consisting of a push moraine, creeping permafrost and permafrost-free glacial till in close proximity. Electrical resistivity tomography is considered as an important multifunctional geophysical method for research in periglacial permafrost related environments. Joint application with measurements of surface displacements offers a promising tool for investigating periglacial landforms related to ice-rich permafrost for a more comprehensive characterization of permafrost characteristics and geomorphological interpretation of periglacial morphodynamics. The patchy permafrost distribution pattern described in this paper is determined by several factors, including the sediment characteristics, the snow cover distribution and duration, the aspect and the former glacier distribution and thermal regime. Recent and modern permafrost dynamics within the glacier forefield comprise aggradation, degradation and permafrost creep. Copyright © 2007 John Wiley & Sons, Ltd.

This paper uses numerical simulation of flood inundation based on a coupled one-dimensional-two-dimensional treatment to explore the impacts upon flood extent of both long-term climate changes, predicted to the 2050s and 2080s, and short-term river channel changes in response to sediment delivery, for a temperate upland gravel-bed river. Results show that 16 months of measured in-channel sedimentation in an upland gravel-bed river cause about half of the increase in inundation extent that was simulated to arise from climate change. Consideration of the joint impacts of climate change and sedimentation emphasized the non-linear nature of system response, and the possibly severe and synergistic effects that come from combined direct effects of climate change and sediment delivery. Such effects are likely to be exacerbated further as a result of the impacts of climate change upon coarse sediment delivery. In generic terms, these processes are commonly overlooked in flood risk mapping exercises and are likely to be important in any river system where there are high rates of sediment delivery and long-term transfer of sediment to floodplain storage (i.e. alluviation involving active channel aggradation and migration). Similarly, attempts to reduce channel migration through river bank stabilization are likely to exacerbate this process as without bank erosion, channel capacity cannot be maintained. Finally, many flood risk mapping studies rely upon calibration based upon combining contemporary bed surveys with historical flood outlines, and this will lead to underestimation of the magnitude and frequency of floodplain inundation in an aggrading system for a flood of a given magnitude.

This paper outlines evidence from Pakefield (northern Suffolk), eastern England, for sea-level changes, river activity, soil development and glaciation during the late Early and early Mid- dle Pleistocene (MIS 20-12) within the western margins of the southern North Sea Basin. During this time period, the area consisted of a low-lying coastal plain and a shallow offshore shelf. The area was drained by major river systems including the Thames and Bytham. Changes in sea-level caused sev- eral major transgressive-regressive cycles across this low-relief region, and these changes are identi- fied by the stratigraphic relationship between shallow marine (Wroxham Crag Formation), fluvial (Cromer Forest-bed and Bytham formations) and glacial (Happisburgh and Lowestoft formations) sediments. Two separate glaciations are recognised—the Happisburgh (MIS 16) and Anglian (MIS 12) glaciations, and these are separated by a high sea level represented by a new member of the Wroxham Crag Formation, and several phases of river aggradation and incision. The principal driving mechanism behind sea-level changes and river terrace development within the region during this time period is solar insolation operating over 100-kyr eccentricity cycles. This effect is achieved by the impact of cold climate processes upon coastal, river and glacial systems and these climatically forced processes obscure the neotectonic drivers that operated over this period of time. British Geological Survey/Natural Environment Research Council copyright 2005. Reproduced with the permission of BGS/NERC. Published by John Wiley & Sons, Ltd.

An extensive literature about fluvial sediment waves, slugs or pulses has emerged in the past 20 years. The concept has been useful in many respects, but has been applied to diverse phenomena using a variety of definitions. Moreover, inferred linkages between channel-bed changes and sediment loads are often not justifiable. This paper reviews concepts of large fluvial sediment waves at scales extending to several tens of kilometres. It points out constraints on the inferences that can be made about sediment loads based on changes in channel-bed elevation at this scale where channel sediment interacts with storage in floodplain and terrace deposits. The type area of G. K. Gilbert's initial sediment-wave concept is re-examined to show that neither wave translation nor dispersion occurred in the simple manner commonly assumed. Channel aggradation and return to graded conditions provide an alternative theory explaining Gilbert's observed bed-elevation changes. Recognizing the evidence and implications of the former passage of a large-scale bed wave is essential to the accurate diagnosis of catchment conditions and the adoption of appropriate river restoration goals or methods. Sediment loads, water quality, channel morphologic stability and aquatic ecosystems often reflect changes in sediment storage long after the channel bed has returned to grade. Copyright © 2006 John Wiley & Sons, Ltd.

Substrate and flow velocity are two key physical factors influencing the distribution of aquatic plants. These two controls are closely related and reflect interactions between flow regime, quantity and calibre of sediment supplied to and bounding river channels, and channel dimensions. Seasonal growth of aquatic plants has important impacts upon flow resistance, flow velocities and sediment dynamics. This paper focuses upon the reach scale and the aggregate impact of the seasonal growth of aquatic plants on the meso-habitat characteristics of chalk rivers. It provides a contribution to the broader literature by illustrating how submerged and emergent macrophytes interact with one another at the reach scale to control flow patterns and the retention of fine sediment. The research was conducted within the River Frome, Dorset, UK. Four sets of observations from 2004 of the seasonal growth of aquatic plants, flow velocity behaviour and the storage of fine sediment are presented. Aggregate velocity behaviour over the four observation periods is classified using agglomerative, hierarchical cluster analysis. The spatial arrangement of patches exhibiting different aggregate velocity behaviour are explored and the degree to which velocity behaviour can be attributed to physical characteristics of patches and the growth of aquatic plants is discussed. Conclusions include: (i) patterns of aggregate velocity behaviour within reaches are strongly influenced by macrophyte growth; (ii) average fine sediment deposition is higher around emergents such as Sparganium erectum than submerged plants such as Ranunculus penicillatus subsp. pseudofluitans; (iii) complementary flow patterns evolve across the river channel as aquatic macrophytes grow and it appears that this allows marginal emergents to scavenge fine sediment from faster flow velocity threads that become diverted towards the channel edges. (iv) These processes are important for mesohabitat evolution and maintenance, and they also contribute to patterns of bank erosion and aggradation. Copyright © 2006 John Wiley & Sons, Ltd.

At the geological time scale, the way in which the erosion of drainage catchments responds to tectonic uplift and climate changes depends on boundary conditions. In particular, sediment accumulation and erosion occurring at the edge of mountain ranges should influence the base level of mountain catchments, as well as sediment and water discharges. In this paper, we use a landform evolution model (LEM) to investigate how the presence of alluvial sedimentation at range fronts affects catchment responses to climatic or tectonic changes. This approach is applied to a 25 km × 50 km domain, in which the central part is uplifted progressively to simulate the growth of a small mountain range. The LEM includes different slope and river processes that can compete with each other. This competition leads to ‘transport-limited’, ‘detachment-limited’ or ‘mixed’ transport conditions in mountains at dynamic equilibrium. In addition, two end-member algorithms (the channellized-flow and the sheet-flow regimes) have been included for the alluvial fan-flow regime. The three transport conditions and the two flow algorithms represent six different models for which the responses to increase of rock uplift rate and/or cyclic variation of the precipitation rate are investigated. Our results indicate that addition of an alluvial apron increases the long-term mountain denudation. In response to uplift, mountain rivers adapt their profile in two successive stages; first by propagation of an erosion wave and then by slowly increasing their channel gradients. During the second stage, the erosion rate is almost uniform across the catchment area at any one time, which suggests that dynamic equilibrium has been reached, although the balance between erosion and rock uplift rates has not yet been achieved. This second stage is initiated by the uplift of the mountain river outlets because of sedimentation aggradation at the mountain front. The response time depends on the type of water flow imposed on the alluvial fans domains (× by 1.5 for channelized flow regime and by 10 for the sheet flow one). Cyclic variations of precipitation rate generate cyclic incisions in the alluvial apron. These incision pulses create knick-points in the river profile in the case of ‘detachment-limited’ and ‘mixed’ river conditions, which could be mistaken for tectonically induced knick-points. ‘Transport-limited’ conditions do not create such knick-points, but nevertheless trigger erosion in catchments. The feedbacks linked to sedimentation and erosion at range front can therefore control catchment incision or aggradation. In addition, random river captures in the range front trigger auto-cyclic erosion pulses in the catchment, capable of generating incision–aggradation cycles.

The chronology and pattern of Holocene landscape development in the Nebrodi Mountains of north-central Sicily, seen in valley alluviation and the pedological record, has been investigated in the Fiume di Sotto di Troina valley. Intensive geomorphological survey has revealed three phases of alluvial aggradation reflecting increased hillslope disturbance during the late Pleistocene and Holocene. The results of sediment analyses, archaeological survey, and literary evidence were combined in a Geographical Information System (GIS) in order to model the potential erosion caused by different land-use practices throughout history. This paper presents the erosion model used to investigate possible Roman land-use practices and their effects on landscape change as documented in the catchment basin. The results of the model support a correlation between intensive pastoralism and the erosional phases documented in the sedimentary record. © 2005 Wiley Periodicals, Inc.

The channel of the lower Tordera River (Catalan Coastal Ranges) was intensively mined between 1956 and 1987, at an extraction rate 14 times higher than the replenishment rates. Mining caused incision of up to 2 m over the whole reach, leading to damage of infrastructures and affecting the groundwater system. In this paper we analyse the response of the river sediment budget by means of sediment transport measurements (both in suspension and as bedload) and topographic surveys. Historical data on mining activities was used to verify current values of sediment transport and to locate the main extraction areas in the long profile of the river. This has led to an integrated methodology that can be useful for assessing and managing current and future sediment deficits in heavily mined rivers. In the lower Tordera, a minimum of 3 million cubic metres of sand and gravel were extracted, especially from two gravel pits still visible as concavities in the river's longitudinal profile. Nowadays, 15 yr after mining ceased, the river shows during dry periods a general tendency towards aggradation (3.6 mm yr−1 on average and up to 12 mm yr−1 in central sections where mining took place), but a slight long-term tendency to erode the riverbed. Sediment yield at the entrance of the study reach attains 552 000 t yr−1, while net sediment deposition reaches 16 400 t yr−1 (78% as bedload), mostly during small floods in dry periods. Estimated time for the river to recover pre-extraction bed-level is of the order of 420 yr. Copyright © 2005 John Wiley & Sons, Ltd.

Growth faulting is a common feature of many deltaic environments and is vital in determining local sediment dispersal and accumulation, and hence in controlling the resultant sedimentary facies distribution and architecture. Growth faults occur on a range of scales, from a few centimetres to hundreds of metres, with the largest growth faults frequently being under-represented in outcrops that are often smaller than the scale of feature under investigation. This paper presents data from the exceptionally large outcrops of the Cliffs of Moher, western Ireland, where a growth-fault complex affects strata up to 60 m in thickness and extends laterally for 3 km. Study of this Namurian (Upper Carboniferous) growth-fault system enables the relationship between growth faulting and sedimentation to be detailed and permits reconstruction of the kinematic history of faulting. Growth faulting was initiated with the onset of sandstone deposition on a succession of silty mudstones that overlie a thin, marine shale. The decollement horizon developed at the top of the marine shale contact for the first nine faults, by which time aggradation in the hangingwall exceeded 60 m in thickness. After this time, failure planes developed at higher stratigraphic levels and were associated with smaller scale faults. The fault complex shows a dominantly landward retrogressive movement, in which only one fault was largely active at any one time. There is no evidence of compressional features at the base of the growth faults, thus suggesting open-ended slides, and the faults display both disintegrative and non-disintegrative structure. Thin-bedded, distal mouth bar facies dominate the hangingwall stratigraphy and, in the final stages of growth-fault movement, erosion of the crests of rollover structures resulted in the highest strata being restricted to the proximity of the fault. These upper erosion surfaces on the fault scarp developed erosive chutes that were cut parallel to flow and are downlapped by the distal hangingwall strata of younger growth faults.

This paper examines recurrent spatial patterns of prehistoric sites in relation to landforms, alluvial fills, and soil development in the uplands and valleys of the Madaba and Dhiban Plateaus of Jordan. Mousterian lithics (Middle Paleolithic) are largely found on high strath terraces plateaus, where they are associated with red Mediterranean soils. In valleys, Upper Paleolithic sites are often associated with reworked loess deposits of the Dalala allostratigraphic unit. Epipaleolithic occupations are found stratified in deposits of the Thamad Terrace, and Pre-Pottery Neolithic and Pottery Neolithic occupations are associated with colluvium mantling the Thamad Terrace. The Tur al-Abyad Terrace and the Iskanderite alluvial inset are the remnants of middle Holocene floodplains, which were attractive areas for Chalcolithic and Early Bronze Age settlements. Sometime around 4000 B.C., stream incision and further lateral erosion destroyed these floodplains. These historic terraces are underlain by alluvial deposits ranging in age from Roman to Early Islamic periods. The sequence of allostratigraphic units, paleosols, and terraces are the basis for reconstructing phases of fluvial aggradation and stream incision during the past 20,000 years. © 2005 Wiley Periodicals, Inc.

Over the last 30 years, understanding of how river channel morphology adjusts to upstream impoundment has been improved considerably with clearwater erosion close to the dam and aggradation downstream of unregulated tributary confluences being identified. In a UK context our understanding of channel response to impoundment has been based principally on analysis of a number of regulated rivers using a time–space substitution approach but the temporal pattern of channel change was not fully observed. This paper details channel change over almost six decades following impoundment of the River Spey, Scotland, primarily via the use of cartographic and aerial photographic evidence. Channel change initially involved the formation of tributary confluence bars followed by bench development and vegetation colonization and development on the benches and gravel bars. Sixty years after impoundment, the channel is still adjusting its form at distance from the dam to be in quasi- equilibrium with its regulated flow regime; indeed adjustment was most rapid between 1989 to 1995. This accelerated adjustment is due to the occurrence of a greater number of large and geomorphologically significant flood events in this period. Sediment supply limitation from unregulated tributaries will have stemmed the rate of narrowing and bench development prior to 1989. This spatial and temporal pattern of adjustment supports, for the most part, the model advocated by Petts (Progress in Physical Geography, 1979, Vol. 3, pp. 329–362). The wider implications of the channel change for river conservation and management are addressed. Copyright © 2003 John Wiley & Sons, Ltd.

After a short review of present-day surficial sediments on the sea-floor of the English Channel and its Western Approaches, this paper summarises recent results on the Present-Quaternary sandy accumulations (tidal bank systems), based on sea-floor imaging, very high-resolution seismic surveys and a few piston cores. The English Channel, a typical funnel-shaped tidal shelf, is presently starved of terrigenous sediments. Most of mobile sediments at the sea-floor are autochthonous, either skeletal carbonates or siliciclastic sands reworked from old littoral deposits or incised valley fills. Three zones are considered: 1 the Central (and western Central) Channel, which is a bedload parting zone characterised by a pebbly lag making up the sole of the Quaternary sediments throughout the shelf area; 2 the Eastern Channel, a flood-dominated area characterised by medium to fine siliciclastic sands, mainly of aeolian periglacial origin; 3 the Western Approaches, an ebb-dominated area with a polygenic sediment cover characterised by coarse, carbonate-rich, gravelly to muddy sands of marine to glaciomarine origin, with a diachronous faunal content. These sediments are sourced by reworking of a former littoral barrier or incised valley fills. The seismic stratigraphy of Quaternary sediment accumulations (10-50 m) points to the predominant control of tidal dynamics, together with the general interplay between the Channel morphology and the sea-level story. The thickest deposits in the Eastern Channel and Western Approaches are built up into bank systems. Whereas the interpretation of the active Eastern Channel banks finds a general agreement, the 'moribund' banks in the Western Approaches (i.e. the southern Celtic Banks) remains under debate, owing to the lack of long cores. In our hypothesis, both systems were built up during the last post-glacial sea-level rise. The Celtic Banks would represent the tidal transgressive systems tract whereas the Eastern Channel banks correspond to the highstand systems tract. The architecture of both bank systems is studied from two examples, the Bassure de Baas bank in the Eastern Channel and the Kaiser Bank in the Western Approaches. Both examples show transgressive features. The Bassure de Baas exhibits from base to top: an estuarine mouth barrier, a wave erosion surface, a shoreface bank and finally a 'classic' tidal bank. By contrast, the Kaiser Bank consists of the offshore reworking of fully marine deposits. Its base would correspond to the amalgamation of the last glacial sea-level fall with a strong tidal ravinement surface. From base to top, the bank underwent: tidal-bar accretion, very large dune-field aggradation, perched-channels incision, storm erosion and deposition.

The Killpecker Dunes in southwestern Wyoming have long been known to contain evidence for Paleoindian occupation. This paper presents the results of geoarchaeological investigations in the western, dormant portion of the Killpecker Dunes. Five localities, including the Krmpotich Folsom and Finley Cody Complex sites, were examined in order to better understand the Paleoindian geochronology of the dune field, and to facilitate a late Quaternary paleoenvironmental reconstruction. Age control is provided by radiocarbon, optical, and artifact ages. Four late Quaternary eolian units, designated as strata 1–4, were recognized; strata 1 and 2 are relevant to the Paleoindian record. Aggradation of stratum 1 began by at least 14,690 cal yr (∼12,550 14C yr B.P.), probably in the form of a sand sheet under cool, dry conditions. Redoximorphic features are ubiquitous in stratum 1, indicating a rise in the water table during the latest Pleistocene. A buried soil (Calcid) at the top of this unit indicates a period of stability between ca. 12,000 and 11,000 14C yr B.P. and has the potential to yield Clovis (11,200–10,900 14C yr B.P.) artifacts. Unconformably overlying stratum 1 is stratum 2, a latest Pleistocene to early Holocene sand containing Folsom (10,900–10,200 14C yr B.P.) through Cody Complex (9000–8500 14C yr B.P.) occupations. A buried soil characterized by the accumulation of illuvial clay and sodium (Natrargid) occurs at the top of stratum 2 and probably formed in and around interdunal ponds. The association of Paleoindian material with the stratum 2 soil suggests the use of interdunal areas as natural traps for hunting extinct bison. The accumulation of soluble salts indicates increased rates of evaporation during the early Holocene, probably from an increase in summer insolation. Although conditions in the dune field during the early Holocene became increasingly dry, they were probably moister than at present. © 2003 Wiley Periodicals, Inc.

River avulsions are commonly considered to be driven by the aggradation and growth of alluvial ridges, and the associated increase in cross-valley slope relative to either the down-channel slope or the down-valley slope (the latter is termed the slope ratio in the present paper). Therefore, spatial patterns of overbank aggradation rate over stratigraphically relevant time scales are critical in avulsion-dominated models of alluvial architecture. Detailed evidence on centennial- to millennial-scale floodplain deposition has, to date, been largely unavailable. New data on such long-term overbank aggradation rates from the Rhine–Meuse and Mississippi deltas demonstrate that the rate of decrease of overbank deposition away from the channel belt is much larger than has been supposed hitherto, and can be similar to observations for single overbank floods. This leads to more rapid growth of alluvial ridges and more rapid increase in slope ratios, potentially resulting in increased avulsion frequencies. A revised input parameter for overbank aggradation rate was used in a three-dimensional model of alluvial architecture to study its effect on avulsion frequency. Realistic patterns of avulsion and interavulsion periods (� 1000 years) were simulated with input data from the Holocene Rhine River, with avulsions occurring when the slope ratio is in the range 3–5. However, caution should be practised with respect to uncritical use of these numbers in different settings. Evidence from the two study areas suggests that the avulsion threshold cannot be represented by one single value, irrespective of whether critical slope ratios are used, as in the present study, or superelevation as has been proposed by other investigators.

Recent research in fluvial geomorphology has emphasized the direct monitoring of channel topography as a useful tool to better understand the interrelationship between river form and process, and in particular to estimate bedload transport rates and reach-scale sediment budgets. Until recently, however, this morphometric approach has been limited to comparison of repeatedly surveyed cross-sections with the associated problems of low frequency sampling and an emphasis on cross-stream as opposed to downstream morphological dynamics. Recent advances in analytical photogrammetry have, however, permitted the acquisition of data at sufficient resolutions to represent macroform (101 m) and microform (10° m) channel geometry, in fully three dimensions. While inherently spatially distributed, the photogrammetric approach to land-surveying is, however, restricted to observable areas of the channel and is thus of limited use in the subaqueous zone, especially if flows are turbid or highly coloured. This paper presents an alternative approach to the study of three-dimensional morphological dynamics of a divided reach of the gravelly River Feshie, Scotland, in which topographic survey of both exposed and submerged areas of the reach was undertaken using the Global Positioning System (GPS). Survey results from two field programmes in 1998 and 1999 are presented in which a Geotronics Geotracer 2000, real-time kinematic GPS receiving unit was used to survey a 200 × 80 m reach. Rapid radial survey methods were employed permitting the collection of 2000 + survey points per day, giving a mean density over the 13 ha reach of 1·1 points per square metre. A detailed assessment of survey errors and DEM quality is presented and a limit of detection of c. 10 cm proposed as an upper threshold for the identification of significant change between DEMs. Preliminary interpretation of channel dynamics in 1998–99 reveals relatively little change to the overall macroscale reach structure. DEM differencing techniques, however, highlight important local changes including the progradation of submerged bar fronts, bar head aggradation and scour along major channel thalwegs and the erosion of fines from sloughs. Copyright © 2000 John Wiley & Sons, Ltd.

Late Pleistocene travertines up to 40 m thick near Rapolano Terme in Tuscany, central Italy, were precipitated by hot water issuing from springs on hillsides and flowing into adjacent depressions to mix with rainwater. Proximal light-coloured slope and terrace travertines pass distally into darker reed mound and depression-fill travertines. Lithotypes include crystalline crust, shrub, pisoid, paper-thin raft, coated bubble, reed, and lithoclast-breccia. High precipitation rates resulted in rapid slope aggradation and progradation. Dilution by rainwater likely lowered precipitation rates in depressions, but deposition was augmented by allochthonous material eroded from upslope travertines. Slope Depositional Systems consist of Smooth and Terrace Slope facies characterized by white crystalline crusts, with diverse additional lithotypes in terrace pools. Depression Depositional Systems have mixed light and dark travertines with horizontal to gently concave stratification. Extensive light-coloured Shrub Flat travertine is dominant; darker Marsh-Pool Facies composed of fine lithoclast and reed travertine is localized. Reed Mounds composed of mixed light and dark travertines localized by abundant reed growth, formed where spring water emerged near the bases of low angle slopes. Distal reduction in accretion rate was the major influence on sequence development. Light-coloured slope travertines interdigitate with darker depression deposits. Vertical aggradation of slope deposits, mound progradation, and filling of topographic depressions is expressed by advance and retreat of facies. Evolution from depression to slope or mound sequences is termed ‘steepening up’. Up-sequence change from slope or mound to depression facies is termed ‘levelling up’. Exposure surfaces associated with palaeosols are common in all facies and often constitute sequence boundaries. They are more closely spaced in depression sequences, reflecting slower and possibly also more discontinuous accumulation at sites furthest from hot springs.

Holocene deposits of the Hawkesbury River estuary, located immediately north of Sydney on the New South Wales coast, record the complex interplay between sediment supply and relative sea-level rise within a deeply incised bedrock-confined valley system. The present day Hawkesbury River is interpreted as a wave-dominated estuarine complex, divisible into two broad facies zones: (i) an outer marine-dominated zone extending 6 km upstream from the estuary mouth that is characterized by a large, subtidal sandy flood-tidal delta. Ocean wave energy is partially dissipated by this flood-tidal delta, so that tidal level fluctuations are the predominant marine mechanism operating further landward; (ii) a river-dominated zone that is 103 km long and characterized by a well developed progradational bayhead delta that includes distributary channels, levees, and overbank deposits. This reach of the Hawkesbury River undergoes minor tidal level fluctuations and low fluvial runoff during baseflow conditions, but experiences strong flood flows during major runoff events. Fluvial deposits of the Hawkesbury River occur upstream of this zone. The focus of this paper is the Hawkesbury River bayhead delta. History of deposition within this delta over the last c. 12 ka is interpreted from six continuous cores located along the upper reaches of the Hawkesbury River. Detailed sedimentological analysis of facies, whole-core X-ray analysis of burrow traces and a chronostratigraphic framework derived from 10 C-14 dates reveal four stages of incised-valley infilling in the study area: (1) before 17 ka BP, a 0–1 m thick deposit of coarse-grained fluvial sand and silt was laid down under falling-to-lowstand sea level conditions; (2) from 17 to 6·5 ka BP, a 5–10 m thick deposit composed of fine-grained fluvial sand and silt, muddy bayhead delta and muddy central-basin deposits developed as the incised valley was flooded during eustatic sea-level rise; (3) during early highstand, between 6·5 and 3 ka BP, a 3–8 m thick bed of interbedded muddy central-basin deposits and sandy river flood deposits, formed in association with maximum flooding and progradation of sandy distributary mouth-bar deposits commenced; (4) since 3 ka BP, fluvial deposits have prograded toward the estuary mouth in distributary mouth-bar, interdistributary-bay and bayhead-delta plain environments to produce a 5–15 m thick progradational to aggradational bayhead-delta deposit. At the mouth of the Hawkesbury estuary subaqueous fluvial sands interfinger with and overlie marine sands. The Hawkesbury River bayhead-delta depositional succession provides an example of the potential for significant variation of facies within the estuarine to fluvial segment of incised-valley systems.

The historical trend of aggradation in stream beds of Europe';s mountain and piedmont areas has been reversed since the beginning of the twentieth century to a general tendency towards narrowing and incision. After an overview of some causes and geomorphological effects of river bed incision, and a description of some case studies in alpine rivers, this paper aims to assess how the phenomenon affects the ecosystems of alluvial plains. The questions addressed are, in particular, the effect of river bed incision on sediment redistribution during floods, habitat diversity and the water table; and the consequences of these changes for the distribution and diversity of biological communities. The effect of incision on floodplain vegetation, instream invertebrate communities, groundwater and former channel ecosystems and fish communities are considered. It has been found that incision rarely affects the biocoenoses directly, but indirect changes in habitat conditions are significant. At the scale of the whole hydrosystem, the predicted impact of incision is a decrease in habitat heterogeneity, and, thereby, in biodiversity. At the ecosystem scale, the negative effect on biodiversity is higher in habitats that are less connected to the running water of the river. ©1997 by John Wiley & Sons, Ltd.

The mountain fluvial systems of southeast Spain involve sediment supply from steep mountain slopes into headwater channels. Alluvial fans often occur where these headwater channels emerge from the mountain areas, and may influence the connectivity of the sediment transport system from the mountain source areas to the main lowland drainages. Critical in this role is whether the alluvial fans are aggrading or dissecting, and whether there is a break or continuity in the channel through the fan environment. Previous work has identified some of the factors influencing the behaviour of the alluvial fans in southeast Spain. This paper deals with the mountain front alluvial fans in the semi-arid areas of Murcia and Almeria provinces. It attempts, by mapping the location of alluvial fans, then their classification into aggrading or dissecting fans, to identify the extent to which the mountain fluvial systems are buffered by aggrading alluvial fans or exhibit channel continuity through the mountain front environment. It further considers the implications of climatically induced changes between aggradational and dissectional behaviour on alluvial fans.

The objective of this paper is to analyse the short-term effects of restoration on river morphology, flow field, substrate and biota. One of the aims of the restoration measures is to arrest the degradation of the river Drau, which has caused technical (instability of bank protection measures) and ecological (loss of dynamic river reaches with alternate bars) problems. The restoration programme consists of several measures such as digging a new side channel on the right side, leaving an island and erection of groins on the left side of the main channel. These were made to keep the entrance open. After a two year monitoring programme the results of the analysis show that with respect to the river morphology, flow field and substrate, positive and negative effects were recorded, whereas for the ecology, positive effects were in general documented. Repeated morphological surveys using an echosounder showed that within a year without major flood events the main channel aggraded on average about 16 cm and the upper parts of the island degraded by up to 1 m. The groin pools became partially filled due to their function as sediment traps for finer material during low flows. Subsequent, measurements performed after several floods showed that degradation reduced the amount of aggradation by 50%. Flow velocity measurements demonstrated the effects of groins and their inability to force the main flow path to the side channel. In contrast with the main channel, the side channel was characterized by highly variable sediment grain sizes and dynamic morphological changes. The lower shear stresses and higher growth of algae in the side channel were associated with higher numbers of species of macroinvertebrates. Population studies showed significantly higher densities of fish species in this reach with a side channel than in any other river reach. Forty species of birds were observed, seven of which were typical water-related species, and the number of plant species increased from 48 to 118.

This paper examines the timing, nature and magnitude of river response in upland, piedmont and lowland reaches of the Tyne basin, northern England, to high-frequency (20–30 year) changes in climate and flood regime since 1700 AD. Over this period fluvial activity has been characterized by alternating phases of river-bed incision and stability coinciding with non-random, decadal-scale fluctuations in flood frequency and hydroclimate that appear to be linked to changes in large-scale upper atmospheric circulation patterns. Episodes of widespread channel bed incision (1760–1799, 1875–1894, 1955–1969) result from a higher frequency of large floods (> 20 year return period) and cool, wet climate under meridional circulation regimes. Phases of more moderate floods (5–20 year return period), corresponding to zonal circulation types (1820–1874, 1920–1954), are characterized by enhanced lateral reworking and sediment transfer in upper reaches of the catchment, and channel narrowing and infilling downstream. Rates of fluvial activity are reduced in intermediate periods (1800–1819, 1895–1919) with no dominant circulation regime associated with lower flood frequency and magnitude. The results of this study provide a valuable guide for forecasting probable drainage basin and channel response to future climate change.

This paper investigates variability in bedload transport and channel morphology for 11 replicate experimental runs in an approximately 1:50 braided river model. The experiments, each of 90 h duration, were carried out in a 20 × 3m tilting flume. All the experiments started with the same initial conditions. Bedload transport was measured at 5 min intervals in a collection drum at the exit from the flume. The model showed reasonable hydraulic similarity when compared to prototype rivers. Results show that mean bedload transport rates for the 11 runs vary in the range 0·98 to 1·49gs−1 (mean + 1·21, coefficient of variation 11 per cent). Within-run transport rates commonly vary from close to zero, to two and occasionally three or four times the mean rate. Within the bedload series, several irregular phases of transport intensity can be observed, but time series analysis of the data show little underlying serial structure (an AR(2) autoregressive model is appropriate). Channel patterns are narrow/braided, are established quickly and remain relatively stable throughout the runs, although channel widths increase between 20 and 103 per cent over the 11 runs. Channel behaviour varies from aggradational to transitional between aggradation and degradation. Time-averaged bedload transport rate is weakly correlated with braiding intensity. In general, these results demonstrate that for a given set of controlling variables, bedload transport and channel morphology can be approximately replicated.

This paper presents data on the sedimentation processes and basin-fill architecture in an incipient submarine intrabasinal graben, the Strava graben. The Strava graben is a relatively small intrabasinal structure about 15 km long and 3 km wide formed some time during the late Pleistocene. It connects the Alkyonidhes basin to the Corinth basin, in the Aegean back arc, which is characterized by fast rates of extension and intensive seismicity. Analysis and interpretation of high-resolution 3.5-kHz and sparker profiles together with sonar imagery have shown that gravity-driven sediment transport, triggered by earthquakes, is the dominant sedimentation process and that this sediment forms the vast bulk of the basin-fill. The sediment deposited in the Strava graben is derived from the uplifted footwall blocks bounding the graben and is transported to the basin initially as liquefied flows, some of which may progressively evolve to turbidity flows. The deposits of the liquefied flows have accumulated in the graben floor as aggradational stacks, consisting of sheet-like, low-relief lobes, forming base of slope aprons that are fed by multiple sediment sources along active faults. In addition to the lateral (footwall-derived) sediment transport there is also a gravity-controlled axial transport. The axial transport has formed a depositional system in the down-dip termination of the Strava graben, where it enters the Corinth basin. The axial depositional system grows outwards and upwards and consists of liquefied flow depositional lobes which are separated by turbidites. The sedimentation transport processes and basin infilling style described for the Strava graben can be used as a predictive model for the early synrift stage of ancient submarine intrabasinal structures, in which the major sediment source area is the bounding fault scarps and not drainage basins in the hinterland.

Hundreds of kilometres of West Tennessee streams have been channelized since the turn of the century. After a stream is straightened, dredged, or cleared, basin- wide ecologic, hydrologic, and geomorphic processes bring about an integrated, character- istic recovery sequence. The rapid pace of channel responses to channelization provides an opportunity to document and interpret vegetation recovery patterns relative to otherwise long-term, concomitant evolution of river geomorphology. Nearly 150 sites along 15 streams were studied in the Obion, Forked Deer, Hatchie, and Wolf River basins. Channels of these streams, except that of the Hatchie River main stem, have undergone major modi- fications along all or parts of their courses. This paper presents the eco-geomorphic analyses and interpretation of a large multidisciplinary study, with special reference to the inter- related hydrogeomorphic aspects of channel recovery. Quantitative plant ecological anal- yses were conducted to infer relative bank stability, to identify indicator recovery species, and to determine patterns of vegetation development through the course of accelerated channel evolution. Binary-discriminant and ordination analyses show that distinctive ri- parian-species patterns reflect a six-stage model of channel evolution and can be used to infer channel stability and hydrogeomorphic conditions. Woody vegetation initially estab- lishes on low- and mid-bank surfaces at the same location and time that bank accretion begins, and corresponds to the site of initial geomorphic restabilization. The linkage of channel bed aggradation, woody vegetation establishment, and bank accretion all lead to recovery of the channel. Pioneer species are hardy and fast growing, and can tolerate moderate amounts of slope instability and sediment deposition; these species include river birch (Betula nigra), black willow (Salix nigra), boxelder (Acer negundo), and silver maple (Acer saccharinum). High stem densities and root-mass development appear to enhance bank stability. Tree-ring analyses suggest that on average 6 5 yr may be required for recovery after channelization.