The Anthropocene: is there a geomorphological case?

The ‘Anthropocene’, as used to describe the interval of recent Earth history during which humans have had an ‘overwhelming’ effect on the Earth system, is now being formally considered as a possible new geological Epoch. Such a new geological time interval (possibly equivalent to the Pleistocene Epoch) requires both theoretical justification as well as empirical evidence preserved within the geological record. Since the geological record is driven by geomorphological processes that produce terrestrial and near‐shore stratigraphy, geomorphology has to be an integral part of this consideration. For this reason, the British Society for Geomorphology (BSG) has inaugurated a Fixed Term Working Group to consider this issue and advise the Society on how geomorphologists can engage with debates over the Anthropocene. This ESEX Commentary sets out the initial case for the formalisation of the Anthropocene and a priori considerations in the hope that it will stimulate debate amongst, and involvement by, the geomorphological community in what is a crucial issue for the discipline. The Working Group is now considering the practical aspects of such a formalization including the relative magnitude problem, the boundary problem and the spatial diachrony of ‘anthropogenic geomorphology’. Copyright © 2013 John Wiley & Sons, Ltd.     

Analytical model for a geomorphological instantaneous unit hydrograph

The rainfall‐runoff modelling of a river basin can be divided into two processes: the production function and the transfer function. The production function determines the proportion of gross rainfall actually involved in the runoff. The transfer function spreads the net rainfall over time and space in the river basin. Such a transfer function can be modelled using the approach of the geomorphological instantaneous unit hydrograph (GIUH). The effectiveness of geomorphological models is actually revealed in rainfall‐runoff modelling, where hydrologic data are desperately lacking, just as in ungauged basins. These models make it possible to forecast the hydrograph shape and runoff variation versus time at the basin outlet. This article is an introduction to a new GIUH model that proves to be simple and analytical. Its geomorphological parameters are easily available on a map or from a digital elevation model. This model is based on general hypotheses on symmetry that provide it with multiscale versatile characteristics. After having validated the model in river basins of very different nature and size, we present an application of this model for rainfall‐runoff modelling. Since parameters are determined relying on real geomorphological data, no calibration is necessary, and it is then possible to carry out rainfall‐runoff simulations in ungauged river basins. Copyright © 2006 John Wiley & Sons, Ltd.     

Stormy geomorphology: geomorphic contributions in an age of climate extremes

The increasing frequency and/or severity of extreme climate events are becoming increasingly apparent over multi‐decadal timescales at the global scale, albeit with relatively low scientific confidence. At the regional scale, scientific confidence in the future trends of extreme event likelihood is stronger, although the trends are spatially variable. Confidence in these extreme climate risks is muddied by the confounding effects of internal landscape system dynamics and external forcing factors such as changes in land use and river and coastal engineering. Geomorphology is a critical discipline in disentangling climate change impacts from other controlling factors, thereby contributing to debates over societal adaptation to extreme events. We review four main geomorphic contributions to flood and storm science. First, we show how palaeogeomorphological and current process studies can extend the historical flood record while also unraveling the complex interactions between internal geomorphic dynamics, human impacts and changes in climate regimes. A key outcome will be improved quantification of flood probabilities and the hazard dimension of flood risk. Second, we present evidence showing how antecedent geomorphological and climate parameters can alter the risk and magnitude of landscape change caused by extreme events. Third, we show that geomorphic processes can both mediate and increase the geomorphological impacts of extreme events, influencing societal risk. Fourthly, we show the potential of managing flood and storm risk through the geomorphic system, both near‐term (next 50 years) and longer‐term. We recommend that key methods of managing flooding and erosion will be more effective if risk assessments include palaeodata, if geomorphological science is used to underpin nature‐based management approaches, and if land‐use management addresses changes in geomorphic process regimes that extreme events can trigger. We argue that adopting geomorphologically‐grounded adaptation strategies will enable society to develop more resilient, less vulnerable socio‐geomorphological systems fit for an age of climate extremes. © 2016 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

A rapid method for simulating three-dimensional fluvial terrain

A rapid, computer-based method of simulating ‘geomorphologically-sensible’ three-dimensional terrain data by modelling landform morphology is presented. For some engineering applications such an approach, even in a simple form, is preferable to the synthesis of terrain data by purely stochastic methods, and additionally can be useful where real data sets are difficult to obtain. The approach adopted utilizes a computer program which models landscape evolution by establishing a stream network on a tilted surface, with accompanying fluvial downcutting and slope adjustment. This is achieved by an iterative mechanism that combines deterministic and stochastic processes with geomorphological theory. The end-product is a matrix of high-resolution altitude data that has been used as the terrain model for a vehicle simulation exercise.     

Distance,time and scale in soil erosion processes

This commentary brings together, as a virtual Special Issue, a number of recent papers in Earth Surface Processes and Landforms that are all related to issues of scale in soil erosion. Empirical concepts that were developed in the 1940s are now in need of re‐thinking, and papers are increasingly exploring, through modelling and measurement, appropriate ways to recognize the mechanisms that connect processes across time and space scales. Issues include a more nuanced approach to selective transportation, responses to variability in surface and sub‐surface conditions and the need to analyse measurements in ways that can be transferred between sites and storms. Copyright © 2010 John Wiley & Sons, Ltd.     

Reappraising the geomorphology‐ecology link

This thematic Virtual Special Issue highlights a personal selection of 18 recent (2007–2009) contributions to Earth Surface Processes and Landforms. These papers provide a flavour of recent research that is concerned with furthering our understanding of the many ways in which the biosphere interacts with the physical and chemical processes of sediment transfer/transformation. Much of this research has focused on understanding the mechanics by which the biota can modulate sediment transport and the strength of earth surface materials, often with the aim of applying that knowledge to enhance bioremediation methods of erosion control. This work continues to be fundamentally important in enhancing our understanding of earth surface processes, but often treats the biosphere and physical world as uncoupled entities. This selection therefore also provides samples of work that point to an ongoing but significant disciplinary reappraisal in which it is the interactions between ecological and geomorphological realms that are of primary interest. Copyright © 2009 John Wiley & Sons, Ltd.     

Geomorphological control on boulder transport and coastal erosion before,during and after an extreme extra‐tropical cyclone

Extreme wave events in coastal zones are principal drivers of geomorphic change. Evidence of boulder entrainment and erosional impact during storms is increasing. However, there is currently poor time coupling between pre‐ and post‐storm measurements of coastal boulder deposits. Importantly there are no data reporting shore platform erosion, boulder entrainment and/or boulder transport during storm events – rock coast dynamics during storm events are currently unexplored. Here, we use high‐resolution (daily) field data to measure and characterize coastal boulder transport before, during and after the extreme Northeast Atlantic extra‐tropical cyclone Johanna in March 2008. Forty‐eight limestone fine‐medium boulders (n = 46) and coarse cobbles (n = 2) were tracked daily over a 0.1 km² intertidal area during this multi‐day storm. Boulders were repeatedly entrained, transported and deposited, and in some cases broken down (n = 1) or quarried (n = 3), during the most intense days of the storm. Eighty‐one percent (n = 39) of boulders were located at both the start and end of the storm. Of these, 92% were entrained where entrainment patterns were closely aligned to wave parameters. These data firmly demonstrate rock coasts are dynamic and vulnerable under storm conditions. No statistically significant relationship was found between boulder size (mass) and net transport distance. Graphical analyses suggest that boulder size limits the maximum longshore transport distance but that for the majority of boulders lying under this threshold, other factors influence transport distance. Paired analysis of 20 similar sized and shaped boulders in different morphogenic zones demonstrates that geomorphological control affects entrainment and transport distance – where net transport distances were up to 39 times less where geomorphological control was greatest. These results have important implications for understanding and for accurately measuring and modelling boulder entrainment and transport. Coastal managers require these data for assessing erosion risk. © 2016 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

Comparison of geomorphological field mapping and 2D‐InSAR mapping of periglacial landscape activity at Nordnesfjellet,northern Norway

The ability to continuously monitor the dynamic response of periglacial landforms in a climate change context is of increasing scientific interest. Satellite radar interferometry provides information on surface displacement that can be related to periglacial processes. Here we present a comparison of two‐dimensional (2D) surface displacement rates and geomorphological mapping at periglacial landform and sediment scale from the mountain Nordnesfjellet in northern Norway. Hence, 2D Interferometric Synthetic Aperture Radar (InSAR) results stem from a 2009–2014 TerraSAR‐X dataset from ascending and descending orbits, decomposed into horizontal displacement vectors along an east–west plane, vertical displacement vectors and combined displacement velocity. Geomorphological mapping was carried out on aerial imagery and validated in the field. This detailed landform and sediment type mapping revealed an altitudinal distribution dominated by, weathered bedrock blockfields, surrounded primarily by slightly, to non‐vegetated solifluction landforms at the mountain tops. Below, an active rockslide and associated rockfall deposits are located on the steep east‐facing side of the study area, whereas glacial sediments dominate on the gentler western side. We show that 2D InSAR correctly depicts displacement rates that can be associated with typical deformation patterns for flat‐lying or inclined landforms, within and below the regional permafrost limit, for both wet and dry areas. A net lowering of the entire landscape caused by general denudation of the periglacial landforms and sediments is here quantified for the first time using radar remote sensing. Copyright © 2018 John Wiley & Sons, Ltd.     

Deciphering orogenic evolution

Deciphering orogenic evolution requires the integration of a growing number of geological and geophysical techniques on various spatial and temporal scales. Contrasting visions of mountain building and lithospheric deformation have been proposed in recent years. These models depend on the respective roles assigned to the mantle, the crust or the sediments. This article summarizes the contents of the Special Issue dedicated to ‘Geodynamics and Orogenesis’ following the ‘Réunion des Sciences de la Terre’ 2010 conference held in Bordeaux, France. Further, based on the example of the Western Alps-Mediterranean domain we emphasize the possibility to integrate long and short term, plate- to sample-scale, datasets in order to constrain orogenic evolution.     

The potential of digital filtering of generic topographic data for geomorphological research

High resolution terrain models generated from widely available Interferometric Synthetic Aperture Radar (IfSAR) and digital photogrammetry are an exciting resource for geomorphological research. However, these data contain error, necessitating pre‐processing to improve their quality. We evaluate the ability of digital filters to improve topographic representation, using: (1) a Gaussian noise removal filter; (2) the proprietary filters commonly applied to these datasets; and (3) a terrain sensitive filter, similar to those applied to laser altimetry data. Topographic representation is assessed in terms of both absolute accuracy measured with reference to independent check data and derived geomorphological variables (slope, upslope contributing area, topographic index and landslide failure probability) from a steepland catchment in northern England. Results suggest that proprietary filters often degrade or fail to improve precision. A combination of terrain sensitive and Gaussian filters performs best for both IfSAR and digital photogrammetry datasets, improving the precision of photogrammetry digital elevation models (DEMs) by more than 50 per cent relative to the unfiltered data. High‐frequency noise and high‐magnitude gross errors corrupt geomorphological variables derived from unfiltered photogrammetry DEMs. However, a terrain sensitive filter effectively removes gross errors and noise is minimized using a Gaussian filter. These improvements propagate through derived variables in a landslide prediction model, to reduce the area of predicted instability by up to 29 per cent of the study area. Interferometric Synthetic Aperture Radar is susceptible to removal of topographic detail by oversmoothing and its errors are less sensitive to filtering (maximum improvement in precision of 5 per cent relative to the raw data). Copyright © 2008 John Wiley and Sons, Ltd.     

Control of sediment dynamics by vegetation as a key function driving biogeomorphic succession within fluvial corridors

Riparian vegetation responds to hydrogeomorphic disturbances and environmental changes and also controls these changes. Here, we propose that the control of sediment erosion and deposition by riparian vegetation is a key geomorphological and ecological (i.e. biogeomorphic) function within fluvial corridors. In a 3 year study, we investigated the correlations between riparian vegetation and hydrogeomorphic dynamics along a transverse gradient from the main channel to the floodplain of the River Tech, France. Sediment erosion and deposition rates varied significantly along the transverse gradient as a function of the vegetation biovolume intercepting water flow. These effects, combined with the extremely strong mechanical resistance of pioneer woody structures and strong resilience of pioneer labile herbaceous communities, Populus nigra and Salix spp., explain the propensity of biogeomorphic succession (i.e. the synergy between vegetation succession and landform construction) to progress between destructive floods. This geomorphological function newly identified as an ‘ecosystem function’ per se encompasses the coupling of habitat and landform creation, maintenance and change with fundamental ecosystem structural changes in space and in time. Three different biogeomorphic functions, all related to the concept of ecosystem engineering, were identified: (i) the function of pioneer herbaceous communities to retain fine sediment and diaspores in the exposed zones of the active tract near the water resource, facilitating recruitment of further herbaceous and Salicacea species; (ii) the function of woody vegetation to drive the construction of forested islands and floodplains; and (iii) the function of stabilised riparian forests to act as ‘diversity reservoirs’ which can support regeneration after destructive floods. Overall, this study based on empirical data points to the fundamental importance of sediment flow control by pioneer riparian vegetation in defining fluvial ecosystem and landform organisation in time and in space. Copyright © 2009 John Wiley & Sons, Ltd.     

The fractal properties of topography as controlled by the interactions of tectonic,lithological, and geomorphological processes

Landscape topography widely exhibits fractal structure. Because of the complexity of relief geometry this structure is not homogeneous in space, and the study of its spatial characteristics represents a powerful method for investigating the interrelationships between landforms and underlying processes. We explore these interrelationships using the digital elevation model (DEM) of an area located in central Italy, where landscape topography is strongly linked to its geological evolution, being characterized by alternating intermountain basins and mountain ranges trending NW–SE. A modified version of the method based on the standard deviation of relief elevations is used to evaluate the fractal parameters of relief after tiling the DEM in spatial units characterized by homogeneous fractal geometry, and statistical methods in conjunction with spatial analysis techniques are applied to the resulting terrain datasets. Both the lowest and (to a lesser extent) the highest values of fractal dimension are found to follow the ridge‐and‐valley trend. Low fractal dimension is observed in the mountain ranges characterized by massive strata of limestone, and along the fault scarps defining the contact between the intermountain basins and the surrounding slopes, where sediment deposition prevails. High fractal dimension is observed in regions characterized by highly erodible terrigenous lithology, and in areas where tectonic activity favors erosional processes mainly by rivers. The analysis of the (fractal) power law parameters also suggests that each major lithological complex has its own characteristic fractal signature. These results provide new insights into the link between the fractal properties of topography and the tectonic, lithological, and geomorphological features of the area, and show that the analysis approach proposed is useful to depict key aspects about the geomorphological and geological setting of an area, using only a DEM. Copyright © 2017 John Wiley & Sons, Ltd.     

渭河盆地带地貌结构与新构造运动

根据基岩断块山地、波状黄土源（洪积台地），平缓黄土塬（洪积扇裙），阶地等较多实际资料，研究渭河盆地带地貌结构与活动断裂及新构造运动间的关系。研究认为，层状地貌的发育与形成，主要受以盆地带南缘断裂带为主的相关阶状正断层正倾滑活动的控制，盆地带南缘断裂带除产生强烈的垂直差异运动外，还由盆边向盆内扩展，并导致盆地带另一侧向北扩张，此活动格局控制和影响了盆地带地貌的形成与演化，地貌类型及其分布格局可作为研究活动构造及评估地震危险性的标志。     

Long‐term landscape evolution: linking tectonics and surface processes

Research in landscape evolution over millions to tens of millions of years slowed considerably in the mid‐20th century, when Davisian and other approaches to geomorphology were replaced by functional, morphometric and ultimately process‐based approaches. Hack's scheme of dynamic equilibrium in landscape evolution was perhaps the major theoretical contribution to long‐term landscape evolution between the 1950s and about 1990, but it essentially ‘looked back’ to Davis for its springboard to a viewpoint contrary to that of Davis, as did less widely known schemes, such as Crickmay's hypothesis of unequal activity. Since about 1990, the field of long‐term landscape evolution has blossomed again, stimulated by the plate tectonics revolution and its re‐forging of the link between tectonics and topography, and by the development of numerical models that explore the links between tectonic processes and surface processes. This numerical modelling of landscape evolution has been built around formulation of bedrock river processes and slope processes, and has mostly focused on high‐elevation passive continental margins and convergent zones; these models now routinely include flexural and denudational isostasy. Major breakthroughs in analytical and geochronological techniques have been of profound relevance to all of the above. Low‐temperature thermochronology, and in particular apatite fission track analysis and (U–Th)/He analysis in apatite, have enabled rates of rock uplift and denudational exhumation from relatively shallow crustal depths (up to about 4 km) to be determined directly from, in effect, rock hand specimens. In a few situations, (U–Th)/He analysis has been used to determine the antiquity of major, long‐wavelength topography. Cosmogenic isotope analysis has enabled the determination of the ‘ages’ of bedrock and sedimentary surfaces, and/or the rates of denudation of these surfaces. These latter advances represent in some ways a ‘holy grail’ in geomorphology in that they enable determination of ‘dates and rates’ of geomorphological processes directly from rock surfaces. The increasing availability of analytical techniques such as cosmogenic isotope analysis should mean that much larger data sets become possible and lead to more sophisticated analyses, such as probability density functions (PDFs) of cosmogenic ages and even of cosmogenic isotope concentrations (CICs). PDFs of isotope concentrations must be a function of catchment area geomorphology (including tectonics) and it is at least theoretically possible to infer aspects of source area geomorphology and geomorphological processes from PDFs of CICs in sediments (‘detrital CICs’). Thus it may be possible to use PDFs of detrital CICs in basin sediments as a tool to infer aspects of the sediments' source area geomorphology and tectonics, complementing the standard sedimentological textural and compositional approaches to such issues. One of the most stimulating of recent conceptual advances has followed the considerations of the relationships between tectonics, climate and surface processes and especially the recognition of the importance of denudational isostasy in driving rock uplift (i.e. in driving tectonics and crustal processes). Attention has been focused very directly on surface processes and on the ways in which they may ‘drive’ rock uplift and thus even influence sub‐surface crustal conditions, such as pressure and temperature. Consequently, the broader geoscience communities are looking to geomorphologists to provide more detailed information on rates and processes of bedrock channel incision, as well as on catchment responses to such bedrock channel processes. More sophisticated numerical models of processes in bedrock channels and on their flanking hillslopes are required. In current numerical models of long‐term evolution of hillslopes and interfluves, for example, the simple dependency on slope of both the fluvial and hillslope components of these models means that a Davisian‐type of landscape evolution characterized by slope lowering is inevitably ‘confirmed’ by the models. In numerical modelling, the next advances will require better parameterized algorithms for hillslope processes, and more sophisticated formulations of bedrock channel incision processes, incorporating, for example, the effects of sediment shielding of the bed. Such increasing sophistication must be matched by careful assessment and testing of model outputs using pre‐established criteria and tests. Confirmation by these more sophisticated Davisian‐type numerical models of slope lowering under conditions of tectonic stability (no active rock uplift), and of constant slope angle and steady‐state landscape under conditions of ongoing rock uplift, will indicate that the Davis and Hack models are not mutually exclusive. A Hack‐type model (or a variant of it, incorporating slope adjustment to rock strength rather than to regolith strength) will apply to active settings where there is sufficient stream power and/or sediment flux for channels to incise at the rate of rock uplift. Post‐orogenic settings of decreased (or zero) active rock uplift would be characterized by a Davisian scheme of declining slope angles and non‐steady‐state (or transient) landscapes. Such post‐orogenic landscapes deserve much more attention than they have received of late, not least because the intriguing questions they pose about the preservation of ancient landscapes were hinted at in passing in the 1960s and have recently re‐surfaced. As we begin to ask again some of the grand questions that lay at the heart of geomorphology in its earliest days, large‐scale geomorphology is on the threshold of another ‘golden’ era to match that of the first half of the 20th century, when cyclical approaches underpinned virtually all geomorphological work. Copyright © 2007 John Wiley & Sons, Ltd.     

The geomorphology of the Anthropocene: emergence,status and implications

The Anthropocene is proposed as a new interval of geological time in which human influence on Earth and its geological record dominates over natural processes. A major challenge in demarcating the Anthropocene is that the balance between human‐influenced and natural processes varies over spatial and temporal scales owing to the inherent variability of both human activities (as associated with culture and modes of development) and natural drivers (e.g. tectonic activity and sea level variation). Against this backdrop, we consider how geomorphology might contribute towards the Anthropocene debate by focusing on human impact on aeolian, fluvial, cryospheric and coastal process domains, and how evidence of this impact is preserved in landforms and sedimentary records. We also consider the evidence for an explicitly anthropogenic geomorphology that includes artificial slopes and other human‐created landforms. This provides the basis for discussing the theoretical and practical contributions that geomorphology can make to defining an Anthropocene stratigraphy. It is clear that the relevance of the Anthropocene concept varies considerably amongst different branches of geomorphology, depending on the history of human actions in different process domains. For example, evidence of human dominance is more widespread in fluvial and coastal records than in aeolian and cryospheric records, so geomorphologically the Anthropocene would inevitably comprise a highly diachronous lower boundary. Even to identify this lower boundary, research would need to focus on the disambiguation of human effects on geomorphological and sedimentological signatures. This would require robust data, derived from a combination of modelling and new empirical work rather than an arbitrary ‘war of possible boundaries' associated with convenient, but disputed, ‘golden’ spikes. Rather than being drawn into stratigraphical debates, the primary concern of geomorphology should be with the investigation of processes and landform development, so providing the underpinning science for the study of this time of critical geological transition. Copyright © 2016 John Wiley & Sons, Ltd.     

River,Coastal and Estuarine Morphodynamics Selected papers from the 10th anniversary of the RCEM Symposium

This Special Issue collects 17 selected contributions from participants to the 10th edition of the RCEM (River, Coastal and Estuarine Morphodynamics) Symposium, organized in Padova-Trento (Italy) in September 2017. The series of biennial RCEM symposia has the key goal of enhancing interaction and promoting integration among the scientific communities focused on the morphological dynamics of river, coastal and estuarine environments, through various combinations of theoretical, observational, experimental and modelling approaches. The 17 contributions to this Special Issue contain four state-of-science reviews and overall offer a broad view of the cross-cutting perspective adopted when addressing morphodynamics. Such a perspective accounts for the mutual interplay between morphology, fluid dynamics and other environmental factors, and has presently become a widespread paradigm to address landscape evolution. © 2020 John Wiley & Sons, Ltd.     

The Spey Bay geomorphological study

The Spey Bay coastline and the estuary of the River Spey exhibit a rapidly evolving planform. They provide an opportunity to study geomorphological changes in a coupled coastal/estuarine system which can be measured over hours and days rather than the years and decades associated with more slowly evolving landscape features. Attempting to understand coastal and estuarine geomorphology provides engineers and earth scientists with an exciting intellectual challenge. This is not, however, simply an academic challenge because the successful management of coastal and estuarine environments depends on improving this understanding. The impetus behind our work in this area is the protection of land-use interests. It is in this context that Babtie Dobbie Limited have been employed in studying the River Spey since 1962. This paper is based on a practical case study performed for coastal and river engineering purposes between 1990 and 1992. The case study was formulated using the results and conclusions of earlier geomorphological studies of the area undertaken over the past 32 years. Knowledge gained from previous studies was crucial in designing the detailed methods and techniques employed in the 1990–1992 geomorphological study. Methods used included historical analyses, photogrammetry, numerical modelling, geographic information systems (GIS) and interpretation of the complex processes which drive landform changes in the estuary and along the adjacent shoreline. The improved understanding of geomorphological processes that has been achieved has enabled engineers to formulate a new management strategy. Central to this strategy are engineering solutions to river and coastal stability and flooding problems which are in sympathy with the environment and which take maximum advantage of our understanding of geomorphological processes.     

Biogeomorphology,quo vadis? On processes,time, and space in biogeomorphology

Biogeomorphology has been expanding as a discipline, due to increased recognition of the role that biology can play in geomorphic processes, as well as due to our increasing capacity to measure and quantify feedback between biological and geomorphological systems. Here, we provide an overview of the growth and status of biogeomorphology. This overview also provides the context for introducing this special issue on biogeomorphology, and specifically examines the thematic domains of biogeomorphological research, methods used, open questions and conundrums, problems encountered, future research directions, and practical applications in management and policy (e.g. nature-based solutions). We find that whilst biogeomorphological studies have a long history, there remain many new and surprising biogeomorphic processes and feedbacks that are only now being identified and quantified. Based on the current state of knowledge, we suggest that linking ecological and geomorphic processes across different spatio-temporal scales emerges as the main research challenge in biogeomorphology, as well as the translation of biogeomorphic knowledge into management approaches to environmental systems. We recommend that future biogeomorphic studies should help to contextualize environmental feedbacks by including the spatio-temporal scales relevant to the organism(s) under investigation, using knowledge of their ecology and size (or metabolic rate). Furthermore, in order to sufficiently understand the ‘engineering’ capacity of organisms, we recommend studying at least the time period bounded by two disturbance events, and recommend to also investigate the geomorphic work done during disturbance events, in order to put estimates of engineering capacity of biota into a wider perspective. Finally, the future seems bright, as increasingly inter-disciplinary and longer-term monitoring are coming to fruition, and we can expect important advances in process understanding across scales and better-informed modelling efforts. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd     

Hyperscale terrain modelling of braided rivers: fusing mobile terrestrial laser scanning and optical bathymetric mapping

Quantifying the morphology of braided rivers is a key task for understanding braided river behaviour. In the last decade, developments in geomatics technologies and associated data processing methods have transformed the production of precise, reach‐scale topographic datasets. Nevertheless, generating accurate Digital Elevation Models (DEMs) remains a demanding task, particularly in fluvial systems. This paper identifies a threefold set of challenges associated with surveying these dynamic landforms: complex relief, inundated shallow channels and high rates of sediment transport, and terms these challenges the ‘morphological’, ‘wetted channel’ and ‘mobility’ problems, respectively. In an attempt to confront these issues directly, this paper presents a novel survey methodology that combines mobile terrestrial laser scanning and non‐metric aerial photography with data reduction and surface modelling techniques to render DEMs from the resulting very high resolution datasets. The approach is used to generate and model a precise, dense topographic dataset for a 2.5 km reach of the braided Rees River, New Zealand. Data were acquired rapidly between high flow events and incorporate over 5 x 10⁹ raw survey observations with point densities of 1600 pts m^‐2 on exposed bar and channel surfaces. A detailed error analysis of the resulting sub‐metre resolution is described to quantify DEM quality across the entire surface model. This reveals unparalleled low vertical errors for such a large and complex surface model; between 0.03 and 0.12 m in exposed and inundated areas of the model, respectively. Copyright © 2013 John Wiley & Sons, Ltd.