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Abstract: A jökulhlaup burst from the head of Grasshopper Glacier in Wyoming''s Wind River Mountains during early September 2003. Five reaches with distinct sedimentation patterns were delineated along the Dinwoody Creek drainage. This paper focuses on a portion of the jökulhlaup route where erosion of the forested banks created 16 large logjams spaced at longitudinal intervals of tens to hundreds of meters. Aggradation within the main channel upstream from each logjam created local sediment wedges, and the jams facilitated overbank deposition during the jökulhlaup. Field surveys during 2004 and 2006 documented logjam characteristics and associated erosional and depositional features, as well as initial modification of the logjams and flood deposits within the normal seasonal high-flow channel. Overbank deposits have not been altered by flows occurring since 2003. Field measurements supported three hypotheses that (i) logjams present along the forested portions of the jökulhlaup route are larger and more closely spaced than those along adjacent, otherwise comparable stream channels that have not recently experienced a jökulhlaup; (ii) logjams are not randomly located along the jökulhlaup route, but instead reflect specific conditions of channel and valley geometry and flood hydraulics; and (iii) the presence of logjams facilitated significant erosional and depositional effects. This paper documents a sequence of events in which outburst floodwaters enhance bank erosion and recruitment of wood into the channel, and thus the formation of large logjams. These logjams sufficiently deflect flow to create substantial overbank deposition in areas of the valley bottom not commonly accessed by normal snowmelt peak discharges, and through this process promote valley-bottom aggradation and sediment storage. Changes in the occurrence of glacier outburst floods thus have the potential to alter the rate and magnitude of valley-bottom dynamics in these environments, which is particularly relevant given predictions of worldwide global warming and glacial retreat. Processes observed at this field site likely occur in other forested catchments with headwater glaciers. [Copyright &y& Elsevier]

Abstract: In recognition of the fundamental control exerted by weathering on landscape evolution and topographic development, the 35th Binghamton Geomorphology Symposium was convened under the theme of Weathering and Landscape Evolution. The papers and posters presented at the conference imparted the state-of-the-art in weathering geomorphology, tackled the issue of scale linkage in geomorphic studies and offered a vehicle for interdisciplinary communication on research into weathering and landscape evolution. The papers included in this special issue are encapsulated here under the general themes of weathering mantles, weathering and relative dating, weathering and denudation, weathering processes and controls and the ‘big picture’. [Copyright &y& Elsevier]

Numerical modeling of landform evolution is the key to understanding the formation of land surfaces. However, landform evolution occurs under certain initial topographic conditions, while existing landform evolution models often use a plane or a randomly produced surface to establish the initial topographic conditions. This misunderstanding of the initial topographic conditions causes the landform evolution results to deviate greatly from the real terrain. Therefore, the initial topographic conditions must be reconstructed and integrated into the current numerical landform evolution model. In this paper, the Loess Plateau of China was selected as a typical sample area. The paleotopography was reconstructed and integrated into the numerical landform evolution model. Based on the evolutionary mechanism of loess landforms, modules of surface erosion, matter diffusion and precipitation were selected to construct a numerical model of loess landform evolution. Moreover, randomly produced terrain was used as the initial conditions during the landform evolution process and compared with the paleotopography-constrained evolution results. In addition, the results of the landform evolution process were evaluated with different terrain factors, and the uncertainty of the model was assessed by comparing different model conditions. The results show that, due to the control of paleotopography, the evolution results can maintain the main morphological structure of valleys in the loess landscape. Without considering the paleotopography, a large difference exists between the evolution results and the true ground terrain. These results show that paleotopography is an important feature of loess landform evolution modeling and is indispensable for reasonably expressing the process of landform evolution. Finally, the numerical modeling of loess landform evolution with the consideration of paleotopography can not only help to achieve a better understanding of the loess landform evolution process but also provide a reference for feature dependent landform evolution modeling in different landform applications. • Paleotopography affects the evolution of loess landform in the Loess Plateau. • We integrate the paleotopography into the numerical loess landform evolution model. • Our results can maintain the main morphological structure of loess landform. • Our research provides a reference for feature-concerned landform evolution modeling. [ABSTRACT FROM AUTHOR]

Tectonically controlled landforms develop morphologic features that provide useful markers to investigate crustal deformation and relief growth dynamics. In this paper, we present results of morphotectonic experiments obtained with an innovative approach combining tectonic and surface processes (erosion, transport, and sedimentation), coupled with accurate model monitoring techniques. This approach allows for a qualitative and quantitative analysis of landscape evolution in response to active deformation in the three end-member geological settings: compression, extension, and strike–slip. Experimental results outline first that experimental morphologies evolve significantly at a short time scale. Numerous morphologic markers form continuously, but their lifetime is generally short because erosion and sedimentation processes tend to destroy or bury them. For the compressional setting, the formation of terraces above an active thrust appears mainly controlled by narrowing and incision of the main channel through the uplifting hanging-wall and by avulsion of deposits on fan-like bodies. Terrace formation is irregular even under steady tectonic rates and erosional conditions. Terrace deformation analysis allows retrieving the growth history of the structure and the fault slip rate evolution. For the extensional setting, the dynamics of hanging-wall sedimentary filling appears to control the position of the base level, which in turn controls footwall erosion. Two phases of relief evolution can be evidenced: the first is a phase of relief growth, and the second is a phase of upstream propagation of topographic equilibrium that is reached first in the sedimentary basin. During the phase of relief growth, the formation of triangular facets occurs by degradation of the fault scarp, and their geometry (height) becomes stationary during the phase of upstream propagation of the topographic equilibrium. For the strike–slip setting, the complex morphology of the wrench zone, composed of several interacting fault segments, enhances the interactions with the drainage network. Because of the widening of the main fault zone toward the surface, a significant amount of distributed deformation is observed along the wrench zone. Locally, where two terminations of fault segments interact, less than a quarter of the far field displacement can remain measurable using fault offsets, leading to a systematic underestimation of the real fault slip rate. These different experimental examples illustrate the great potential of the approach coupling deformation mechanisms and erosion–transport–sedimentation processes to investigate qualitatively and quantitatively the morphotectonic evolution of tectonically controlled landscapes. [ABSTRACT FROM AUTHOR]

Abstract: Development of experimental landform with rainfall erosion and uplift is expected to provide some ideas for better understanding how landform evolves through the interaction between uplift and erosion. This paper reports three runs of the rainfall-erosion experiment (runs I, II, and III), in which miniature erosion landform developed with artificial rainfall on a square mound of a mixture of fine sand and kaolinite. The mound is the upper half of a square column (ca. 90×90×24cm) of the material exposed on the ground, and another half is under the ground on the uplift-generating device. All runs lasted for 1759h, and the uplift started from 255h in runs II and III after the mound was eroded to a low-relief surface. While average height decreased exponentially in run I (no uplift), it decreased linearly with 0.041mm/h uplift (run II) and stayed approximately constant with 0.067mm/h uplift (run III). Local relief decreased exponentially after reaching its maximum in the early stage, but the uplift made it stay around a certain height corresponding to its rate. Two prominent types of fluvial erosion, “erosion with knickpoints,” which makes slopes steeper, and “erosion of declining slopes,” which makes slopes gentler, were observed through the experiment. Although the erosion with knickpoints faded with the decrease in relief in run I, it was active even in later stages in runs II and III. The uplift promoted erosion with knickpoints to make local relief and erosion rate higher depending on its rate. The uplift of a higher rate in run III, which was seemingly above a certain threshold, promoted more erosion with knickpoints and helped hills grow until slope failures occurred. In run II, the uplift rate was below the threshold and erosion was exclusively fluvial under the detachment-limited condition, in which local relief (and erosion rate) has a certain limit determined by mound erodibility and rainfall intensity regardless of the uplift rate. The linear decrease in average height indicates that the critical erosion rate exceeded the uplift rate. In run III, on the other hand, increased sediment supply from hill slopes made fluvial erosion transport-limited. Upstream deposition of sediments made channel slopes increase until fluvial erosion matched the sediment supply. Erosion and uplift balanced to keep average height constant (dynamic equilibrium) and similar landforms continued to exist, while hills gradually narrowed through the process of repeated growth and failure (quasi-steady state). [Copyright &y& Elsevier]

Abstract: To exploit natural sedimentary archives and geomorphic landforms it is necessary to date them first. Landscape evolution of Alpine areas is often strongly related to the activities of glaciers in the Pleistocene and Holocene. At sites where no organic matter for radiocarbon dating exists and where suitable boulders for surface exposure dating (using in situ produced cosmogenic nuclides) are absent, dating of soils could give information about the timing of landscape evolution. This paper explores the applicability of soil dating using the inventory of meteoric 10Be in Alpine soils. For this purpose, a set of 6 soil profiles in the Swiss and Italian Alps was investigated. The surface at these sites had already been dated (using the radiocarbon technique or the surface exposure determination using in situ produced 10Be). Consequently, a direct comparison of the ages of the soils using meteoric 10Be and other dating techniques was made possible. The estimation of 10Be deposition rates is subject to severe limitations and strongly influences the obtained results. We tested three scenarios using a) the meteoric 10Be deposition rates as a function of the annual precipitation rate, b) a constant 10Be input for the Central Alps, and c) as b) but assuming a pre-exposure of the parent material. The obtained ages that are based on the 10Be inventory in soils and on scenario a) for the 10Be input agreed reasonably well with the age using surface exposure or radiocarbon dating. The ages obtained from soils using scenario b) produced ages that were mostly too old whereas the approach using scenario c) seemed to yield better results than scenario b). Erosion calculations can, in theory, be performed using the 10Be inventory and 10Be deposition rates. An erosion estimation was possible using scenario a) and c), but not using b). The calculated erosion rates using these scenarios seemed to be plausible with values in the range of 0–57mm/ky. The dating of soils using 10Be has several potential error sources. Analytical errors as well as errors from other parameters such as bulk soil density and soil skeleton content have to be taken into account. The error range was from 8 up to 21%. Furthermore, uncertainties in estimating 10Be deposition rates substantially influence the calculated ages. Relative age estimates and, under optimal conditions, absolute dating can be carried out. Age determination of Alpine soils using 10Be gives another possibility to date surfaces when other methods fail or are not possible at all. It is, however, not straightforward, quite laborious and may consequently have some distinct limitations. [Copyright &y& Elsevier]

Abstract: In this paper, we quantitatively demonstrate that dominant erosion processes on different shore platforms can be explained, in part, by geological properties. We selected sites with a considerable history of rock coast geomorphology study, to evaluate whether geological data can improve our understanding of spatial variations in erosion between sites. Schmidt Hammer tests and discontinuity data were collected on Blue Lias limestone shore platforms in Wales, UK, and sandstone platforms in Victoria, Australia. Significant differences in joint spacing, persistence of discontinuities and block size were found between the Australian and Welsh study sites. These data were related to evidence of meso-scale erosion to examine how geological contingency influences the nature and scale of erosion processes and thresholds. This study quantitatively demonstrates that discontinuities play a fundamental role in altering rock resistance. The findings of this research have important implications for the design of rock coast erosion studies concerned with measuring rates of change and determining the relative contributions of different processes to platform development. [Copyright &y& Elsevier]

Abstract: The complex multiple-age badlands at El Cautivo are cut in upper Miocene marls of the uplifted and dissected Tabernas Basin, Almería, in semi-arid SE Spain. Previous work identified six episodes of erosion and subsequent stabilisation, with ages ranging from the late Pleistocene to the present day. This paper uses newly-acquired digital elevation models, orthorectified aerial photographs, and field survey data to illustrate the development sequence of a series of gullies which drain into the Rambla de Tabernas. Changing drainage directions and phases of incision and stabilisation are related to the filling and subsequent dissection of the Tabernas lower lake sediments, differential material strengths, changing process mixes on hillslopes and, in more recent times, land-use changes. We propose that the erosional phases differed considerably in both time-span and depth of incision. A long period of stability during the existence of the lake led to extensive pediment development in the area. Subsequent incision into the lake sediments by the Rambla de Tabernas produced a limited amount of localised pediment incision in the tributary catchment. Subsequent aggradation occurred in the lower reaches of gullies when incision by the Rambla de Tabernas reached the underlying bedrock. Following incision through the lip of the lake the Rambla de Tabernas cut rapidly into the bedrock leading to an altered drainage direction in the tributary catchments and the major phase of badland development visible today. Stabilisation of the pediments and some of the north-facing slopes occurred subsequently. Increased sediment loads, caused by climatic shift, a change in land use, or both, gave rise to a later phase of valley fill in the gullies. The modern channels have reduced this fill to isolated terrace benches and there are also localised remnants of a lower, more recent fill. Whilst supporting the general interpretation of the site''s development by Alexander et al. [Alexander, R.W., Harvey, A.M., Calvo, A., James, P.A., Cerda, A., 1994. Natural stabilisation mechanisms on badlands slopes: Tabernas, Almería, Spain. In: Millington, A.C., Pye, K. (eds.), Environmental Change in Drylands: Biogeographical and Geomorphological Perspectives. Wiley, Chichester, pp 85–111.], this re-analysis highlights the importance of changing drainage direction to the pattern of landform development and attempts to assess the magnitude and overall rate of incision. [Copyright &y& Elsevier]

Abstract: Areas underlain by Plio-Pleistocene marine mudstone in south Italy are severely affected by denudation processes and have been transformed into badlands with two well defined types of landform: biancane and calanchi. In this paper, factors that contributed to the development of the Aliano badlands and particularly to the geneses of biancane and calanchi have been studied, based on aerospace data; field observations on geomorphic processes and geological structure; laboratory measurements of soil and bedrock samples; and morphometric analysis. Several maps and spatial data were prepared to describe factors which are thought to be related with landform formations, such as lineament distribution, elevation, slope, and pipe distribution. Morphometric characteristics of biancane and calanchi (steepness and slope length), dominant active processes, and the dip/orientation of beddings, joints, and fault planes were investigated, and 71 samples of soils and bedrock were taken to characterise their properties. The results of the analyses of the soil/bedrock samples show no significant differences in their properties between biancane and calanchi. Field observations do not support the idea that biancane are the final product of calanchi development, but support the hypothesis that biancane and calanchi are formed under different terrain conditions related to structural patterns and denudation processes of highly erodible materials. The origin of biancane is associated with highly dissected surfaces along a reticular system of small joints. In contrast, calanchi are formed on steep wall-like slopes along larger lineaments where the rate of incision into the slopes surpasses the denudation of the densely vegetated back-slope. [Copyright &y& Elsevier]

Abstract: The paper analyses uphill-facing scarps and associated troughs developed in the oversteepened slopes of two neighbouring glacial valleys in the central Spanish Pyrenees. Previous studies of sackung landforms in the Pyrenees have argued for deglacial unloading as the genetic mechanism, but this causal and temporal relationship has not been proved due to the lack of chronological data. The antislope scarps in the two studied locations, Vallibierna and Estós, are developed in Palaeozoic metasedimentary rocks (parallel to the contour lines and the structural grain), occur in the intermediate sector of the hillslope, and are up to 0.5 km long and several meters high. A trench was excavated in a sackung trough fill in each of the valleys in order to gain information about their chronology and genesis. Charcoal from the lowermost unit in Vallibierna provided an age of 5.9 cal. ka for the sackung and extrapolation of the three dates obtained in Estós indicates that the trough formed ca. 7.6–7.8 cal. ka. Deglaciation of the studied sectors of the valleys occurred between 16 and 13 ka. The time lag of >5 ka suggests that glacial erosion and the subsequent debutressing of the oversteepened valley walls created slopes predisposed to sackung development, but did not initiate the movement. Seismic shaking is proposed as a probable triggering factor. This hypothesis, although supported by the sudden deformation event recorded by a failure plane exposed in Vallibierna trench, and by the seismic and neotectonic activity of the area, cannot be proved due to the lack of chronological information about paleoearthquakes. [Copyright &y& Elsevier]

Abstract: A number of prehistoric landslides and rock avalanches occurred in the folded and faulted section of the Molasse Zone in Vorarlberg, Austria. Some developed into a Sturzstrom, defined as a ‘rapidly moving fluidised mass movement of large volumes of rock, derived from the disintegration of a falling rock mass, that spread under the influence of gravity’. Their impact on the landscape usually is related to obstruction of rivers and valleys. In this paper, we analyse the geomorphology and the failure mechanism of a relative small ‘Sturzstrom’. The failure mechanism can be described as a ‘buckling failure’. The morphological situation indicates that failure took place after local deglaciation by the end of the Upper Würm. The period of failure coincides with glacial and ice-marginal remnants, which developed between 15.000 and 14.600 BP. The lithological sequence and rock structure, as well as the impact of the processes related to the former glacial environment, were major causal conditions. The rock sequence consists of conglomerates, sandstone layers, and marls. Next to glacial scouring, which increased the inclination of the valley slopes, the effect of late-glacial unloading and postglacial processes, such as weathering and fluvial erosion, subsequently weakened the mass rock fabric until failure occurred. Discontinuity orientation measurements, geostructural and geomechanical conditions, and the former hydrological and geomorphological conditions support bucklings failure. In fact, three-hinge buckling may have occurred. The frontal section of the Sturzstrom consists mainly of large conglomerate blocks, averaging 1.5 m3 in volume, although megablocks, reaching of up to 4000 m3, are present as well. The volume of the entire Sturzstrom equals approximately 10×107 m3. Present activity is only restricted to minor rock falls derived from the conglomerates and mudflows originating from the marl layers. [Copyright &y& Elsevier]