pinecone/core-2020-05-10-deduplication huggingface dataset:
Spectral filtering as a method of visualising and removing striped artefacts in digital elevation data

Spectral filtering was compared with traditional mean spatial filters to assess their ability to identify and remove striped artefacts in digital elevation data. The techniques were applied to two datasets: a 100 m contour derived digital elevation model (DEM) of southern Norway and a 2 m LiDAR DSM of the Lake District, UK. Both datasets contained diagonal data artefacts that were found to propagate into subsequent terrain analysis. Spectral filtering used fast Fourier transformation (FFT) frequency data to identify these data artefacts in both datasets. These were removed from the data by applying a cut filter, prior to the inverse transform. Spectral filtering showed considerable advantages over mean spatial filters, when both the absolute and spatial distribution of elevation changes made were examined. Elevation changes from the spectral filtering were restricted to frequencies removed by the cut filter, were small in magnitude and consequently avoided any global smoothing. Spectral filtering was found to avoid the smoothing of kernel based data editing, and provided a more informative measure of data artefacts present in the FFT frequency domain. Artefacts were found to be heterogeneous through the surfaces, a result of their strong correlations with spatially autocorrelated variables: landcover and landsurface geometry. Spectral filtering performed better on the 100 m DEM, where signal and artefact were clearly distinguishable in the frequency data. Spectrally filtered digital elevation datasets were found to provide a superior and more precise representation of the landsurface and be a more appropriate dataset for any subsequent geomorphological applications
GIS-assisted modelling for debris flow hazard assessment based on the events of May 1998 in the area of Sarno, Southern Italy. II: Velocity and Dynamic Pressure

The velocity and dynamic pressure of debris flows are critical determinants of the impact of these natural phenomena on infrastructure. Therefore, the prediction of these parameters is critical for hazard assessment and vulnerability analysis. We present here an approach to predict the velocity of debris flows on the basis of the energy line concept. First, we obtained empirically and field-based estimates of debris flow peak discharge, mean velocity at peak discharge and velocity, at channel bends and within the fans of ten of the debris flow events that occurred in May 1998 in the area of Sarno, Southern Italy. We used this data to calibrate regression models that enable the prediction of velocity as a function of the vertical distance between the energy line and the surface. Despite the complexity in morphology and behaviour of these flows, the statistical fits were good and the debris flow velocities can be predicted with an associated uncertainty of less than 30% and less than 3 m s-1. We wrote code in Visual Basic for Applications (VBA) that runs within ArcGIS® to implement the results of these calibrations and enable the automatic production of velocity and dynamic pressure maps. The collected data and resulting empirical models constitute a realistic basis for more complex numerical modelling. In addition, the GIS implementation constitutes a useful decision-support tool for real-time hazard mitigation. Copyright © 2008 John Wiley & Sons, Ltd
Residual relief separation: digital elevation model enhancement for geomorphological mapping

This article was published in the journal, Earth Surface Processes and Landforms [© John Wiley & Sons, Ltd.] and the definitive version is available at: http://dx.doi.org/10.1002/esp.1659Geomorphologically mapped data form a primary set of observations that can be used to infer former environmental conditions. Thus, objective and consistent mapping of landforms from remotely sensed data (e.g. satellite imagery, digital elevation models (DEMs)) is paramount for reconstructing palaeoenvironments.\ud
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This paper proposes a technique, ‘residual relief separation’, to enhance landforms in DEMs prior to visualization and digital mapping. This is applied to a ∼600 km2 region surrounding Lough Gara, Ireland, where drumlins (∼200 m wide) overlie a regional relief of hills (∼10 km wide). Here, residual relief separation uses this difference in width-scale. Regional relief is approximated by a 1 km wide median filter, then subtracted to leave the drumlins in a ‘residual’ topography. In a second step, the residual relief is normalized to allow for amplitude variations in the drumlins across the area (∼5–40 m high). Finally, visualization uses a simple black-to-white colour scale for height.\ud
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Although not numerically outperforming other visualization techniques, this method performs equally well, and as the data are not ‘illuminated’ there is no azimuthal bias. Additional benefits include the relatively simple calculation, intuitive visual comprehension, no emphasis of noise, and the possibility of using any desired visualization technique after the landscape has been topographically manipulated
Formation mechanisms for ice-stream shear margin moraines.

The lateral shear margins of palaeo-ice stream beds are occasionally marked by large curvilinear moraines, but little work has addressed how they might form. In this paper we review the characteristics of ‘lateral shear margin moraines’ and present two quantitative models for their formation: (i) differential erosion rates related to lateral variations in the stream velocity and (ii) lateral incursion from inter-stream ridges after the thinner stream retreats, where the shear margin moraine is consequently just a terminal moraine of the inter-stream ridge. Other possible mechanisms of formation are addressed qualitatively. Both of our quantitative theories are, in principle, feasible, but the incursion model is less plausible and inconsistent with observations. The differential erosion model can predict moraines tens of metres thick and several kilometres wide, which can be formed in a thousand years. The width of the moraine depends on the competition between a term that varies across the ice stream because it is dependent on ice velocity and that always causes erosion, and a term related to the local accumulation rate, which causes erosion if is positive and deposition if negative. These terms combine to create the possibility of deposition at the shear margins of ice streams in ablation areas. The width of the moraine has a tendency to increase with the width of the stream. The conditions that permit shear margin moraines to form are quite constrained: too much ablation and deposition occurs everywhere rather than just near the lateral margins of the ice streams; too little ablation and there is erosion everywhere. This is consistent with the infrequent observations of lateral shear margin moraines
Superimposition of ribbed moraines on a palaeo-ice-stream bed : implications for ice stream dynamics and shutdown.

The sediments and landforms preserved on palaeo-ice-stream beds can provide important information about their subglacial conditions and flow mechanisms, and the processes accompanying their shutdown. In this paper, detailed observations of an intriguing subglacial landform assemblage of ribbed moraines superimposed on glacial lineations on the Dubawnt Lake Ice Stream bed (north-west Canadian Shield) are presented, including their morphometry, internal structure (from ground penetrating radar (GPR) surveys and from glaciogeological analysis) and sedimentological characteristics (from sediment architecture and lithofacies analysis). The observations suggest an abrupt change in ice dynamics that correlates with two phases of glacial landform development. This hypothesis is based on evidence from a deformed lodgement till, which subsequently underwent brittle deformation and developed prominent thrust (shear) structures and tension fractures. Tension fractures are observed in a sediment exposure and thrust structures are observed in GPR surveys, where they occur most prominently in the ribbed moraine ridge crests. The presence of the fractures, and their association with a population of clasts in the till that are orientated with their a-axes transverse to the inferred ice flow direction, suggests a compressional flow regime. It is therefore inferred that the glacial lineations were formed under an extensional flow regime during ice stream activity, but that at some point patches of till under the ice stream stiffened through dewatering. The subsequent increase in basal shear stress resulted in compressional flow and the development of subglacial thrusting and the building of ribbed moraines. We therefore suggest that ribbed moraines may form in areas of compressional flow under ice streams, i.e. sticky spots, and/or at the transition between slow and fast ice flow along parts of an ice stream. The general absence of ribbed moraines on most other palaeo-ice-stream beds suggests that either these ice streams continued operating during deglaciation or processes other than the development of localized compressional flow (sticky spots) led to their shutdown (e.g. ice depletion)
Stabilization of fine gravels by net-spinning caddisfly larvae

This article was submitted for publication in the journal, Earth Surface Processes and Landforms [© John Wiley & Sons, Ltd.] and the definitive version is available at: http://dx.doi.org/10.1002/esp.1750We examined the impact of Hydropsychidae caddisfly larvae on the incipient motion of two sizes of narrowly graded\ud
fine-gravel (4–6 and 6–8 mm). This impact was assessed relative to the collective impact of other abiotic and biotic processes that\ud
are potentially important conditioning agents of fine-gravels. Trays of gravel were placed in the River Soar, Leicestershire, UK,\ud
where they were colonized to natural densities by caddisfly larvae. Identical trays that were surrounded by a 250 μm mesh were\ud
also deployed, preventing colonization but allowing field conditioning of sediments, including minor reworking of grains and\ud
biofilm development. After 21 days in the river, trays were removed to a laboratory flume where grain entrainment stresses were\ud
established. In addition to the colonized and conditioned treatments, critical shear stresses were measured for identical sediments\ud
that were not placed in the river (laboratory gravels). Gravels that were colonized by Hydropsychidae required significantly\ud
greater shear stresses for entrainment than conditioned trays (p ≤ 0·002), however, there was no significant difference between\ud
conditioned and laboratory gravels. This implies that the presence of caddisfly can be a more important influence on fine-gravel\ud
stability than some conditioning processes. Shields parameter was compared across treatments and across the two gravel size-fractions\ud
using two-way ANOVA. No significant differences or interactions were observed, indicating that 4–6 mm gravel was stabilized to\ud
a similar degree as 6–8 mm gravel by conditioning and colonization processes. Our results extend earlier studies in two important\ud
ways: (1) entrainment stresses were established for fine gravels that were colonized at natural densities, under natural stream\ud
conditions; and (2) the caddisfly effect was measured relative to both field-conditioned and unconditioned laboratory controls.\ud
The temporal and spatial distribution of silk-spinning caddisfly larvae suggests that they have the potential to influence fine-sediment\ud
mobility in many rivers, worldwide
Experimentation at the interface of fluvial geomorphology, stream ecology and hydraulic engineering and the development of an effective, interdisciplinary river science

This article was submitted for publication in the journal, Earth Surface Processes and Landforms [© John Wiley & Sons, Ltd.] and the definitive version is available at: http://dx.doi.org/10.1002/esp.1838One ‘2020 vision’ for fluvial geomorphology is that it sits alongside stream ecology and hydraulic engineering as a key\ud
element of an integrated, interdisciplinary river science. A challenge to this vision is that scientists from these three communities\ud
may approach problems from different perspectives with different questions and have different methodological outlooks. Refining\ud
interdisciplinary methodology is important in this context, but raises a number of issues for geomorphologists, ecologists and\ud
engineers alike. In particular, we believe that it is important that there is greater dialogue about the nature of mutually-valued\ud
questions and the adoption of mutually-acceptable methods. As a contribution to this dialogue we examine the benefits and\ud
challenges of using physical experimentation in flume laboratories to ask interdisciplinary questions. Working in this arena presents\ud
the same challenges that experimental geomorphologists and engineers are familiar with (scaling up results, technical difficulties,\ud
realism) and some new ones including recognizing the importance of biological processes, identifying hydraulically meaningful\ud
biological groups, accommodating the singular behaviour of individuals and species, understanding biological as well as physical\ud
stimuli, and the husbandry and welfare of live organisms. These issues are illustrated using two examples from flume experiments\ud
designed (1) to understand how the movement behaviours of aquatic insects through the near-bed flow field of gravelly river beds\ud
may allow them to survive flood events, and (2) how an understanding of the way in which fish behaviours and swimming\ud
capability are affected by flow conditions around artificial structures can lead to the design of effective fish passages. In each\ud
case, an interdisciplinary approach has been of substantial mutual benefit and led to greater insights than discipline-specific work\ud
would have produced. Looking forward to 2020, several key challenges for experimentalists working on the interface of fluvial\ud
geomorphology, stream ecology and hydraulic engineering are identified
A numerical modelling and experimental study of flow width dynamics on alluvial fans

Alluvial fans are dynamic landforms, the evolution of which is controlled by both external environmental forcing (climate, tectonics and base level change) and internal process-form feedbacks. The latter include changes in flow configuration (between sheetflow and channelized flow states), driven by aggradation and degradation, which may in turn promote changes in sediment transport capacity. Recent numerical modelling indicates that such feedbacks may lead to dramatic and persistent fan entrenchment in the absence of external forcing. However, the parameterization of flow width within such models is untested to date and is subject to considerable uncertainty. This paper presents results from an experimental study of flow width dynamics on an aggrading fan in which spatial and temporal patterns of fan inundation are monitored continuously using analysis of digital vertical photography. Observed flow widths are compared with results from a simple theoretical model developed for non-equilibrium (aggradational) conditions. Results demonstrate that the theoretical model is capable of capturing the first-order characteristics of width adjustment over the course of the experiment, and indicate that flow width is a function of fan aggradation rate. This illustrates that models of alluvial flow width derived for equilibrium conditions may have limited utility in non-equilibrium situations, despite their widespread use to date
Alluvial gully erosion: an example from the Mitchell fluvial megafan, Queensland, Australia

Considerable attention has been focused on the role of gullies as a contributor to contemporary sediment loads of rivers in Australia. In southern Australia rapid acceleration of hillslope gully erosion has been widely documented in the post-European period (sim last 200 years). In the northern Australian tropics, however, gully erosion processes operating along alluvial plains have not been well documented and can differ substantially from those gullies eroding into colluvium on hillslopes. Aerial reconnaissance surveys in 2004 along 13 500 km of the main stem rivers that drain into the Gulf of Carpentaria (GoC), identified extensive areas of alluvial lands that have been impacted by a pervasive form of gully erosion. More detailed remote sensing based mapping within the 31 000 km2 Mitchell River fluvial megafan has identified that active gullying into alluvium occupies sim 0紥 (129 km2) of the lower Mitchell catchment. These alluvial gullies are concentrated along main drainage channels and their scarp heights are highly correlated to the local relief between the floodplain and river thalweg. While river incision into the megafan since the Pleistocene has developed the relief potential for erosion, other factors such as floodplain hydrology, soil dispersibility, and vegetation also influence the distribution of gullies. In this paper we present a conceptual model of alluvial gullies, and contend that they represent a distinct end member in the continuum of gully forms that have been described in the geomorphic literature. An understanding of the processes driving this form of alluvial gullying can only be gained when they are differentiated from widely described colluvial hillslope gully models and theories. We present evidence of type examples of alluvial gullying in the Mitchell, and through analysis of their distribution and morphology at different scales, highlight some of the key mechanisms that are potentially initiating these features and driving their expansion.Griffith Sciences, Griffith School of EnvironmentFull Tex
Using magnetic susceptibility to assess soil degradation in the Eastern Rif, Morocco

25 pag., 4 Tabl., 7 Fig.\ud
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The definitive version is available at:\ud
http://www3.interscience.wiley.com/journal/2388/homeThe soil in the Rif, Morocco, is at serious risk because increasing anthropogenic pressures are gradually transforming large natural areas into farmland. The distribution of magnetic minerals within the soil profile can be used to assess soil development and degradation. The soils in the study area are severely eroded because of a combination of highly erodible soils, intense rainstorms and scarce vegetation cover. To sample of representative soil profiles, lithology, slope gradient and land use were considered. The ranges of magnetic susceptibility in the soil profiles distinguished between two primary soil groups. Magnetic susceptibility varied in the soil profile and along the soil toposequence, and the variations were related to the differences in the original magnetic composition and the influence of main erosion factors. Lithology is the main factor contributing to the variation in magnetic susceptibility. The magnetic susceptibility values in soils on Tertiary marls ( = 13·5 × 10-8 m3 kg-1) differed significantly from those on Quaternary terraces ( = 122·1 × 10-8 m3 kg-1). Slope affected the distribution of magnetic susceptibility because of the continuous loss of topsoil in some parts of the slope and the deposition of eroded soil in others. Elimination of the natural vegetation cover and a shift to cultivated land for cereals has had a negative impact on soil development and, on similar slopes and substrates, magnetic susceptibility decreased significantly in cultivated soils. The soils on steep slopes that had natural vegetation cover retained the magnetic minerals better than did those on gentler slopes that were under cultivation. Grazing, clearing and, especially, tilling has weakened the soil and made it much more vulnerable to erosion. An analysis of the main factors causing erosion will help to promote rational use of the land and to establish conservation strategies in such fragile agroecosystems.This work was funded by the bilateral projects 2004MA-1005 and 18304-RM from the Agencia de Cooperación Interuniversitaria and the CICYT projects REM (CGL2005-02009/BTE) and MEDEROCAR (CGL2008-00831).Peer reviewe
Restoring earth surface processes through\ud
landform design. A 13-year monitoring\ud
of a geomorphic reclamation model for\ud
quarries on slopes

The application of geomorphic principles to land reclamation after surface mining has been reported in the literature\ud
since the mid-1990s, mostly from Australia, Canada and the USA. This paper discusses the reclamation problems of contour\ud
mining and quarries on slopes, where steep gradients are prone to both mass movement and water erosion. To address these\ud
problems simultaneously, a geomorphic model for reclaiming surface mined slopes is described. Called the ‘highwall–trench–\ud
concave slope’ model, it was fi rst applied in the 1995 reclamation of a quarry on a slope (La Revilla) in Central Spain.\ud
The geomorphic model does not reproduce the original topography, but has two very different sectors and objectives: (i) the\ud
highwall–trench sector allows the former quarry face to evolve naturally by erosion, accommodating fallen debris by means of a\ud
trench constructed at the toe of the highwall; (ii) the concave-slope base sector, mimicking the landforms of the surrounding\ud
undisturbed landscape, promotes soil formation and the establishment of self-sustaining, functional ecosystems in the area\ud
protected from sedimentation by the trench. The model improves upon simple topographic reconstruction, because it rebuilds\ud
the surfi cial geology architecture and facilitates re-establishment of equilibrium slopes through the management and control of\ud
geomorphic processes.\ud
Thirteen years of monitoring of the geomorphic and edaphic evolution of La Revilla reclaimed quarry confi rms that the area is\ud
functioning as intended: the highwall is backwasting and material is accumulating at the trench, permitting the recovery of soils\ud
and vegetation on the concave slope. However, the trench is fi lling faster than planned, which may lead to run-off and sedimentation\ud
on the concave slope once the trench is full. The lesson learned for other scenarios is that the model works well in a twodimensional\ud
scheme, but requires a three-dimensional drainage management, breaking the reclaimed area into several watersheds\ud
with stream channels
Bridging the gap between field data and global models: current strategies in aeolian research

This is the pre-peer-reviewed version of an article submitted for publication in the journal, Earth Surface Processes and Landforms [© Wiley], which has been published in its final form at: http://dx.doi.org/10.1002/esp.1958Modern global models of earth-atmosphere-ocean processes are becoming increasingly sophisticated but still require\ud
validation against empirical data and observations. This commentary reports on international initiatives amongst aeolian researchers\ud
that seek to combine fi eld-based data sets and geomorphological frameworks for improving the quality of data available to\ud
constrain and validate global models. These include a second iteration of the Dust Indicators and Records from Terrestrial Marine\ud
Palaeoenvironments (DIRTMAP2) database, the Digital Atlas of Sand Seas and Dunefi elds of the World and a new geomorphologybased\ud
land surface map produced by the QUEST (Quantifying Uncertainties in the Earth System) Working Group on Dust