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Badass geomorphology
Abstract
The archetypal badass is individualistic, non-conformist, and able to produce disproportionate results. The badass concept is applied here to geomorphology. The individualistic concept of landscape evolution (ICLE) is introduced, based on three propositions: excess evolution space, capacity of all landforms to change, and variable selection pressure from environmental factors within and encompassing landscapes. ICLE indicates that geomorphic systems are idiosyncratic to some extent, and that even where two systems are similar, this is a happenstance of similar environmental selection, not an attractor state. As geomorphic systems are all individualistic, those that are also non-conformist with respect to conventional wisdoms and have amplifier effects are considered badass. Development of meander bends on a section of the Kentucky River illustrates these ideas. The divergence of karst and fluvial forms on the inner and outer bends represents unstable amplifying effects. The divergence is also individualistic, as it can be explained only by combining general laws governing surface and subsurface flow partitioning with a specific geographical and environmental setting and the history of Quaternary downcutting of the Kentucky River. Landscape evolution there does not conform to any conventional theories or conceptual frameworks of geomorphology. The badass traits of many geomorphic systems have implications for the systems themselves, attitudes toward geomorphic practice, and appreciation of landforms. Badass geomorphology and the ICLE reflect a view, and approach to the study of, landforms as the outcome of the interplay of general laws, place-specific controls, and history. Badass geomorphology also implies a research style receptive to contraventional wisdoms. Aesthetically, amplifier effects and individualism guarantee an essentially infinite variety of landforms and landscapes that geoscientists can appreciate both artistically and scientifically. Non-conformity makes the interpretation and understanding of this variety more challenging—and while that increases the degree of difficulty, it also makes for more interesting and compelling professional challenges. This article is protected by copyright. All rights reserved.
... For the landform transitions, positive links were assigned where multiple examples of apparent transitions from one form to another were recognized in the field (Phillips, 2017a), where the "destination" landform did not precede the "origin" landform in the chronosequence (Phillips, 2018a), and where the basic principles of fluviokarst landform development support the transition (Phillips, 2015a(Phillips, , 2017a. Negative links were assigned where no evidence of a transition was observed, and principles suggest that a transition would be extremely unlikely, if not impossible. ...
... The flow partitioning framework apportions excess precipitation among these four pathways, though more detailed partitions could be made among different forms of each flow type. I have used the flow partitioning framework in studies of geomorphic landscape evolution in fluviokarst (Fig. 5.9;Phillips and Walls, 2004;Phillips, 2015a), but the general idea is applicable to any landscape where water fluxes are a significant process. ...
... Such transitions occur, for instance, during fluviokarst landscape evolution as hydrologic systems develop on newly exposed substrates, and in response to climate, land use, and vegetation changes. In the central Kentucky study areas of Phillips and Walls (2004) and (Phillips, 2015a), the flow partitioning is best characterized as competitivedthat is, the two forms of surface flow and the two forms each of concentrated and diffuse flows interact in a zerosum manner whereby fluxes in one form reduce the others (Fig. 5.10A). Multiple alternative relationships exist in other situations; four are shown in Fig. 5.10. ...
History matters. Global (independent of place and time) principles are necessary to explain landscape evolution, as are place factors (geographical and environmental context). But, by themselves, they are not sufficient. To explain landscape evolution—which by definition has important temporal dimensions—history must also be incorporated. Landscape evolution is historically contingent. This chapter outlines several different types of historical contingency, discusses multiple pathways and outcomes in landscape evolution, and evaluates why some imaginable pathways are rare and others common, and some trends are divergent and others convergent. Methods for evaluating path stability of historical trajectories are introduced and applied to several different Earth surface systems. The chapter concludes with a consideration of landscape evolution in the context of convergence, divergence, and equifinality.
... The Kentucky River gorge has strongly incised meanders, with slipoff slopes on the bend interiors, and steep slopes, typically palisadelike cliffs, on the outer bends (the area is sometimes referred to as the Palisades). These meanders have been extending since the Pleistocene incision began, as indicated in some cases by high-level fluvial deposits representing the pre-incision path (Andrews 2004;Phillips 2015b). The bend interior slip-off slopes are occupied by strath terraces. ...
... Thirty-three meander bends, including 22 bends previously studied to compare the degree of fluvial incision vs. surface karstification on inner vs. outer bends (Phillips 2015b) were examined using geographical information system (GIS) data obtained from the Kentucky Geological Survey (KGS). The purpose was to identify the key karst and fluvial landforms on the bend interiors. ...
... The 22 bends analyzed in earlier studies (Phillips 2015b) were expanded to include more of the Inner Bluegrass section of the Kentucky River, as the Outer Bluegrass bends are not fully comparable with respect to karstification, given their more variable lithology. The downstream (northwest) limit was established because farther downstream near Frankfort, several Quaternary cutoffs and an avulsion occurred, such that the lateral channel change dynamics have differed from the studied meanders. ...
Lateral and vertical erosion at meander bends in the Kentucky River gorge area has created a series of strath terraces on the interior of incised meander bends. These represent a chronosequence of fluviokarst landscape evolution from the youngest valley side transition zone near the valley bottom to the oldest upland surface. This five-part chronosequence (not including the active river channel and floodplain) was analyzed in terms of the landforms that occur at each stage or surface. These include dolines, uvalas, karst valleys, pocket valleys, unincised channels, incised channels, and cliffs (smaller features such as swallets and shafts also occur). Landform coincidence analysis shows higher coincidence indices (CI) than would be expected based on an idealized chronosequence. CI values indicate genetic relationships (common causality) among some landforms and unexpected persistence of some features on older surfaces. The idealized and two observed chronosequences were also represented as graphs and analyzed using algebraic graph theory. The two field sites yielded graphs more complex and with less historical contingency than the idealized sequence. Indeed, some of the spectral graph measures for the field sites more closely approximate a purely hypothetical no-historical-contingency benchmark graph. The deviations of observations from the idealized expectations, and the high levels of graph complexity both point to potential transitions among landform types as being the dominant phenomenon, rather than canalization along a particular evolutionary pathway. As the base level of both the fluvial and karst landforms is lowered as the meanders expand, both fluvial and karst denudation are rejuvenated, and landform transitions remain active.
... On this basis, it is a major concern to verify whether the fluvial record reflects, first of all, local to regional dynamic patterns, or whether there may be even interregional dynamic patterns embedded in the local patterns, which in turn might permit to draw conclusions on large-scale control factors. As a critical point, in particular local fluvial dynamics appear to be subject to great complexity including issues such as self-organization (see Phillips, 1999) which makes it difficult to build up relations to certain framework conditions (Marston, 2010;Murray et al., 2014;Phillips, 2015). Thus, a main concern of the following sections will be to comprehensibly demonstrate in which way we attempt to distinguish between regional and interregional patterns of floodplain dynamics with a certain focus on establishing links between stratigraphic findings and environmental indications. ...
... From this it follows that certain aspects of landscape evolution are difficult to understand and assess in detail, which also implies that the prediction of future developments is only possible to a limited extent. As shown by Phillips (2015) these ideas were continued and singularities were described to be linked to non-linear complexity and historical contingency, with contingency referring to geographically and temporally contingent factors that make landscapes unique. Phillips (2015) emphasizes the individualistic behavior of geomorphic systems, and introduces the concept of 'badass geomorphology' that is based on individualism, together with non-conformity of geomorphic systems with conventional wisdom and the existence of amplifiers of climate change effects. ...
... As shown by Phillips (2015) these ideas were continued and singularities were described to be linked to non-linear complexity and historical contingency, with contingency referring to geographically and temporally contingent factors that make landscapes unique. Phillips (2015) emphasizes the individualistic behavior of geomorphic systems, and introduces the concept of 'badass geomorphology' that is based on individualism, together with non-conformity of geomorphic systems with conventional wisdom and the existence of amplifiers of climate change effects. This perspective is undeniably a reasonable counter pole to the constant search for universal rules in the context of geomorphic system dynamics. ...
Fluvial archives, in particular, late glacial to Holocene floodplain records may provide valuable information regarding past environmental conditions and stages of landscape evolution. In view of the high significance of floodplain dynamics for the development of entire landscapes, the number of studies that have been performed on floodplain sediments remains comparatively low, especially regarding the Western Mediterranean region. However, one of the reasons could be seen in the high complexity and diversity of processes and factors that control and influence fluvial activity that often hampers a straightforward interpretation of floodplain dynamics. Therefore, a basic demand on fluvial archive research is to address the complexity of the factors that control the characteristics of fluvial sequences in order to provide a robust basis for their interpretation.
As a starting-point for discussion this paper aims to give an overview of fluvial dynamic patterns in the Western Mediterranean for the last 15 ka in order to examine their relevance for palaeoenvironmental reconstructions. The basis for this is provided by previous investigations on four different river systems in Spain and northern Africa the results of which are herein synthesized in order to propose a regional Late Pleistocene and Holocene fluvial history for the Western Mediterranean realm. Basic results are related to alluvial floodplain deposits and visible features within them such as alluvial soils, incision marks and aggradation phenomena. Since fluvial systems are open systems, we discuss our findings against the background of different influencing factors that could modify fluvial architecture and may restrict palaeoenvironmental reconstructions. A more comprehensive interpretation focuses on signals that are common to each of the studied river systems. In this respect, we critically discuss the customary nature of cumulative probability functions for the identification of regional flooding episodes and point out the benefits of a stratigraphy-supported approach for characterizing regional floodplain dynamics. Finally, three alluvial soil formation periods were found in all settings: a first phase after 15 ka, ending with the Younger-Dryas Event; a second one from 7 to 5 ka with a break between 6.5 and 5.5 ka, and a third phase between 3 and 2 ka. These soil formation periods were interrupted and framed by fluvial dynamic phases accompanied by channel aggradation, floodplain deposition, floodplain erosion and/or river incision. In particular, after 5 ka, around 1.6 and at 1 ka, and during the Little Ice Age (LIA) floodplain aggradation affected river systems in Iberia and northern Africa as well. A cautious assessment of these results and extensive comparisons with secondary archive information prompts us to relate the aggradation periods with climate forcing by means of a supra-regional aridification that effected large areas of the Western Mediterranean. In contrast, the three mentioned soil formation periods can be linked with landscape stability, most probably triggered by favorable climate conditions in the Western Mediterranean.
Apart from these large-scale patterns we discuss the reliability of information emerging from floodplain records against the background of individualistic river behavior and self-organization. Regarding future work we want to emphasize the great potential of yet rarely applied system-oriented approaches that also attach importance to sub-catchment dynamics as a link between catchment slopes and the main river floodplain.
... Likewise, karst-to-fluvial (KF) transformations have also been documented (e.g., Jaillet et al. 2004, Ortega Becerril et al. 2010, Tiria & Vijulie 2013, Lipar & Ferk 2015). The Inner Bluegrass karst region of Kentucky, the study area for this project, is no exception ( Thrailkill et al. 1991, Currens & Graham 1993, Phillips & Walls 2004, Ray & Blair 2005, Phillips 2015, Jerin & Phillips 2017). Previous studies of geomorphic transitions in fluviokarst have generally focused on specific features or phenomena (e.g., karst capture or meander cutoffs in streams; Jennings et al. 1976, Mylroie & Mylroie 1990, Fabel et al. 1996, Jerin & Phillips 2017), or landscape scale transformations (e.g., Sauro 2002, Bocic et al. 2015). ...
... Three study areas were selected within the Inner Bluegrass, based on access, minimal topographic disturbance (by construction, agriculture, mining, etc.), and inclusion of both fluvially incised and unincised areas ( Fig. 7). Sites were selected to also include areas on the inside and outside of Kentucky River meander bends, as these have experienced fundamentally different landscape responses with respect to fluviokarst development ( Phillips 2015). Raven Run is on the outside of a meander bend, and the core of the area is managed as a public park and nature preserve. ...
... Ground slopes are also shown as self-limiting, owing to finite available elevation above base level, and to geomech anical limits on slope stability. In addition to the models of Smart (1988) and Phillips (2015), a number of empirical studies support the feedback links shown in Fig. 8. The discussion of factors determining cave patterns by Audra & Palmer (2015) either explicitly includes or implies feedbacks indicated in Fig. 2, as does Bailly-Comte et al.'s (2009) work on groundwater-surface water interactions on an event (rather than landscape evolution) time scale. ...
Flow diversions and landform transitions between channelized surface (fluvial) and concentrated subsurface (karst conduit) flows may be common in fluviokarst landscapes. Identifying landforms associated with fluvialto- karst or karst-To-fluvial transitions shows this to be the case at three study sites in the Inner Bluegrass karst region of Kentucky. Forms representing the capture or diversion of stream flow to subsurface conduits include sinking streams, dry karst valleys, paleovalleys resulting from karst stream piracy, and alluvial collapse dolines. Features indicating karst-To-fluvial transitions include stream incision into dry karst valleys, doline breaching by surface runoff or stream incision, and formation of karst pocket valleys and karst windows. Many smaller transitional landforms also exist (e.g., stream swallets). The three study sites have about three larger transitional landform features per km2, with karst-To-fluvial features slightly more common. Dissolution in bedrock-controlled stream channels leading to karst piracy is the most common cause of fluvial to karst transitions, while general stream incision driven by Kentucky River downcutting is the main driver of karst-To-fluvial shifts. The landform transitions are examined via a network model based on hydrological probability and flow partitioning. The model is dynamically unstable. Instability indicates that local changes and disturbances that modify moisture fluxes, local relief, conduit or surface channel conveyance capacity, or hydraulic slopes are likely to persist and grow, resulting in hydrogeomorphic transitions. Evolution of the Kentucky fluviokarst is best understood as mutual reinforcement, whereby fluvial dissection can be intensified and accelerated by the presence of karst features, and karstification is enhanced by stream incision. © 2017 Gebr. Borntraeger Verlagsbuchhandlung, Stuttgart, Germany.
... Ebb-tidal deltas are badass morphological features (BAMFs) (c.f. Phillips (2015)). ...
... WHAT MAKES A BADASS "BADASS"? Phillips (2015) defines the archetypal badass as "individualistic, non-conformist, and able to produce disproportionate results", and applies this concept to geomorphology (the study of how landscapes evolve, at the crossroads of geology and physical geography). Ebb-tidal deltas meet these three criteria, which makes them badass morphological features (BAMFs): Gaudiano and Kana, 2001;Ridderinkhof et al., 2016)), and hence individualistic. ...
In an era of rising seas and other challenges posed by climate change, coastal regions like the Netherlands are facing ever graver threats. Strategic sand nourishments could mitigate the threat of coastal erosion and sea level rise on barrier island coasts while limiting ecological impacts. However, insufficient knowledge of sediment transport pathways at tidal inlets and ebb-tidal deltas prevents an informed response in these areas.
The main goal of this project was to describe and quantify the pathways that sediment takes on an ebb-tidal delta. To reach this goal, we focused our analyses on Ameland ebb-tidal delta in the Netherlands. Before we could begin to tackle this challenge, we needed to develop new tools and techniques for analyzing a combination of field measurements and numerical models. These include a method for analyzing the stratigraphy and mapping the morphodynamic evolution of ebb-tidal deltas, a new metric for characterizing suspended sediment composition, and innovative use of sediment tracers. We also established a quantitative approach for looking at and thinking about sediment pathways via the sediment connectivity framework, and developed a Lagrangian model to visualize and predict these pathways efficiently.
The techniques developed here are useful in a wider range of coastal settings beyond Ameland, and are already being applied in practice. We foresee that the main impacts of this project will be to improve nourishment strategies, numerical modelling, and field data analysis. This dissertation also points forward to numerous opportunities for further investigation, including the continued development of the connectivity framework and SedTRAILS. By managing our coastal sediment more effectively, we will set the stage for a more sustainable future, in spite of the challenges that lie ahead.
... The importance of place and history in explaining landscape evolution has been a significant focus for research in recent years as the specificity and unpredictability of geomorphic landscapes necessitates a more-than-theoretical understanding that recognises emergence and contingency (Phillips 2015, Murray et al. 2014, Church 2010, Phillips 2007, 2006a, b, Harrison 2001. Phillips (2007) elegantly explains contingency and emergence thinking in his description of all landscapes as 'Perfect Landscapes', "Recognition of the perfection of landscapes leads away from a worldview holding that landforms and landscapes are the inevitable outcomes of deterministic laws, such that only one outcome is possible for a given set of laws and particular conditions. ...
... which provides an open-ended but structured framework for constructivist interpretation thus allowing 'non-conformist' characteristics (Phillips 2015) to be understood with reference to theory. ...
... It also illustrates a case where the network of interactions is based on observations across part (four levels) of the hierarchy , but speculative with respect to two additional levels. Evolution of fluviokarst landscapes in central Kentucky can be studied in terms of the partitioning of flow among surface, subsurface, concentrated , and diffuse flow paths (Phillips and Walls, 2004; Phillips, 2015 ). Other karst landscapes have also been analyzed or described in these terms (e.g., Albéric, 2008; Ortega Becerril et al., 2010; Ryb et al., 2014; Bocic et al., 2015). ...
... Flow pathways and related geomorphic processes of dissolutional and mechanical erosion, sediment transport, and deposition operate over at least four distinct spatial scales. In the studies underpinning this analysis ( Martin, 2006; Phillips, 2015) the most detailed level observed is that of a runoff plot, a patch-size area that is uniform with respect to factors influencing hydrologic responses to precipitation (the approximate equivalent would be a representative elementary volume in ground water hydrology or a pedon in soil geomorphology ). At this scale flow partitioning is governed largely by precipitation characteristics, soil properties, and processes related to infiltration, soil moisture dynamics, and percolation. ...
Scale linkage problems in geosciences are often associated with a hierarchy of components. Both dynamical systems perspectives and intuition suggest that processes or relationships operating at fundamentally different scales are independent with respect to influences on system dynamics. But how far apart is “fundamentally different”—that is, what is the “vanishing point” at which scales are no longer interdependent? And how do we reconcile that with the idea (again, supported by both theory and intuition) that we can work our way along scale hierarchies from microscale to planetary (and vice-versa)? Graph and network theory are employed here to address these questions. Analysis of two archetypal hierarchical networks shows low algebraic connectivity, indicating low levels of inferential synchronization. This explains the apparent paradox between scale independence and hierarchical linkages. Incorporating more hierarchical levels results in an increase in complexity or entropy of the network as a whole, but at a nonlinear rate. Complexity increases as a power α of the number of levels in the hierarchy, with α and usually ≤ 0.6. However, algebraic connectivity decreases at a more rapid rate. Thus, the ability to infer one part of the hierarchical network from other level decays rapidly as more levels are added. Relatedness among system components decreases with differences in scale or resolution, analogous to distance decay in the spatial domain. These findings suggest a strategy of identifying and focusing on the most important or interesting scale levels, rather than attempting to identify the smallest or largest scale levels and work top-down or bottom-up from there. Examples are given from soil geomorphology and karst flow networks.
... Intriguingly, although removal of indigenous forest was fairly uniform across the region, contrasting channel responses reflect the range and diversity of river types across this relatively small region, often for rivers that share catchment boundaries and land-use histories. Erosion processes such as gully mass movement complexes or 'badass' gullies evident in some of the study catchments do not conform to any existing gully model, generating profoundly disproportionate inputs into sediment cascades (Phillips, 2015;Fuller et al., 2020). Significant bed aggradation and pulsed sediment movement have ensued in the Waiapu and Waipaoa catchments. ...
Recently uplifted, highly erodible rocks, and recurrent high intensity storms, generate exceedingly high erosion and sedimentation rates in the East Coast Region (Tairāwhiti) of Aotearoa New Zealand. Despite the recent nature of the Anthropocene record in global terms (∼650 years since Māori arrival, 250 years of colonial impacts), human disturbance has profoundly altered evolutionary trajectories of river systems across the region. Here we document catchment-by-catchment variability in anthropogenic signature as geomorphic river stories for five catchments (Waiapu, Hikuwai, Waimatā, Waipaoa, Mōtū). We show how targeted, fit-for-purpose process-based rehabilitation programmes that manage at source and at scale are required to facilitate river recovery in each of these catchments. The largest rivers in the region, Waiapu and Waipaoa, comprise steep, highly dissected terrains that are subject to recurrent hillslope failures, including systemic shallow landslides, occasional deep-seated rotational slumps and earthflows. Localised sediment input from large (>10 ha) gully mass movement complexes overwhelms valley floors. Targeted revegetation programmes are required to reduce extreme sediment inputs from these sources. Although there are fewer gully complexes in the Hikuwai, multiple landslips supply vast volumes of fine-grained sediment that aggrade and are recurrently reworked along channel margins in lowland reaches. Waimatā has no gully complexes and a smaller number of landslips, but large areas are subject to sediment input from earthflows. The terrace-constrained flume-like nature of this system efficiently flushes materials ‘from the mountains to the sea’, recurrently reworking materials along channel banks in a similar manner to the lower Hikuwai. Systematic reforestation in the middle-upper catchment and revegetation of riparian corridors is required to reduce sedimentation rates in these catchments. In contrast, terraces buffer sediment delivery from hillslopes in the upper Mōtū catchment, where a bedrock gorge separates large sediment stores along upper reaches from the lower catchment. As reworking of valley floor sediments in response to bed incision and reworking (expansion) of channel margins is the primary contemporary sediment source in this system, bed control structures and revegetation of riparian corridors are required as part of targeted sediment management plans. We contend that geomorphic river stories provide a coherent platform for Anthropocene rehabilitation strategies that work with the character, behaviour and evolutionary trajectories of river systems. Although this generic lens can be applied anywhere in the world, we highlight particular meanings and implications in Aotearoa New Zealand where such thinking aligns directly with Māori values that respect the mana (authority), mauri (lifeforce) and ora (wellbeing) of each and every river.
... Like many fluviokarst areas, the inner Bluegrass region of central Kentucky features a complex, interconnected mixture of ground and surface water flow, underground conduits and cavities, and surface channels (Fig. 9). The hydrology and Quaternary geomorphic evolution of this landscape has been outlined by White et al. (1970), Thrailkill et al. (1991), Currens and Graham (1993), Ray and Blair (2005), Reed et al. (2010), and Phillips, (2015;2018). ...
Concentrated or preferential flow patterns occur at all scales in hydrologic systems. They shape, and are shaped by, geomorphic and pedologic patterns and structures. Preferential flow patterns in surface channel networks and dual-porosity subsurface flow systems are a way of achieiving maximum efficiency, as predicted by dissipative systems, constructal, network evolution, percolation, and ecohydrological theories. These all converge on the same predictions and interpretations of preferential flow, which satisfactorily answer “why” these patterns form and persist. However, as geomorphic and hydrologic systems have no intentionality or agency, and thus no ability to actively seek improved efficiency, how these systems evolve is an open question. I propose an emergent explanation based on five phenomena. First, concentrated flows form due to principles of gradient and resistance selection. Second, positive feedback reinforces the concentrated preferential flow paths and their relationship to potential moisture storage zones. Third, intersecting flow paths form networks. Fourth, the expansion of concentrated flow paths and networks is limited by thresholds of flow needed for channel, macropore, or conduit growth and maintenance. This results in a “store and pour” flow system that can retain water during dry periods and transport it efficiently during wet periods. These systems survive provided they develop “spillway” and/or secondary storage mechanisms to accommodate excess water inputs. Finally, store-and-pour systems are maintained (selected for) because they are often stable. Store-and-pour structures are advantageous for flow systems, and for vegetation and ecosystems. These entities cannot actively pursue goals, and no laws dictate evolution toward such patterns. Their development is an emergent phenomenon and their persistence a matter of selection, i.e., survival of the most stable.
... Connectivity theory has been applied within models to assess the active contributing area (e.g., Fryirs et al., 2007;Heckmann et al., 2018;Mahoney et al., 2018) representing the spatial extent (i.e., spatial patterns) of connectivity in watersheds. Within the geomorphologic context, connectivity often serves as a tool to estimate the sensitivity of watersheds to disturbances (Phillips, 2015) and elucidates controlling geomorphologic processes at both fine and course scales (Heckmann et al., 2018;Mahoney et al., 2018). For example, resilience of a system to upstream or downstream feedbacks reflects poor connectivity of the system Cavalli et al., 2019). ...
Integrating connectivity theory within watershed modelling is one solution to overcome spatial and temporal shortcomings of sediment transport prediction, and Part I and II of these companion papers advance this overall goal. In Part I of these companion papers, we present the theoretical development of probability of connectivity formula considering connectivity's magnitude, extent, timing and continuity that can be applied to watershed modelling. Model inputs include a high resolution digital elevation model, hydrologic watershed variability, and field connectivity assessments. We use the model to investigate the dependence of the probability of connected timing and spatial connectivity on sediment transport predictors. Results show the spatial patterns of connectivity depend on both structural and functional characteristics of the catchment, such as hillslope gradient, upstream contributing area, soil texture, and stream network configuration (structural) and soil moisture content and runoff generation (functional). Spatial connectivity changes from catchment-to-catchment as a function of soil type and drainage area; and it varies from event-to-event as a function of runoff depth and soil moisture conditions. The most sensitive connected pathways provide the stencil for the probability of connectivity, and pathways connected from smaller hydrologic events are consistently reconnected and built upon during larger hydrologic events. Surprisingly, we find the probability of connected timing only depends on structural characteristics of catchments, which are considered static over the timescales analyzed herein. The timing of connectivity does not statistically depend on functional characteristics, which relaxes the parameterization across events of different magnitudes. This result occurs because the pathway stencil accumulates sediment from adjacent soils as flow intensity increases, but this does not statistically shift the frequency distribution.
... There is, of course, more than one way to obtain velocity in a river (acoustic instruments, laser instruments, particle tracking, models, equations), but the choice of method is often limited by the availability and cost of instruments, the physical setting (e.g., methods involving lasers work in the laboratory but are challenging to use in the field), and the expertise of the researcher. Nevertheless, many scientific inquiries can be improved by searching for creative problem-solving techniques and experimenting with nontraditional methods ( Phillips 2015). This is especially true for research involving unique objectives, difficult-to-observe phenomena, and research that crosses disciplines ( Murray et al. 2009;Church 2010). ...
Volunteered geographic information and citizen science have advanced academic and public understanding of geographical and ecological processes. Videos hosted online represent a large data source that could potentially provide meaningful results for studies in physical geography—a concept we term volunteered geographic videos (VGV). Technological advances in image-capturing devices, computing, and image processing have resulted in increasingly sophisticated methods that treat imagery as raw data, such as resolving high-resolution topography with structure from motion or the calculation of surface flow velocity in rivers with particle image velocimetry. The ubiquitous nature of recording devices and citizens who share imagery online have resulted in a vast archive of potentially useful online videos. This article analyzes the potential for using YouTube videos for research in physical geography. We discuss the combination of suitability and availability that has made this possible and emphasize the distinction between moderately suitable imagery that can directly answer research questions and lower suitability imagery that can indirectly support a study. We present example case studies that address (1) initial considerations of using VGV, (2) topographic data extraction from a video taken after a landslide, and (3) data extraction from a video of a flash flood that could support a study of extreme floods and wood transport. Finally, we discuss both the benefits and complicating factors associated with VGV. The results indicate that VGV could be used to support certain studies in physical geography and that this large repository of raw data has been underutilized.
... While our study identified general associations of sediment deposition and soil nutrients with flood frequency and geomorphic setting, it also pointed toward the importance of local contingencies in shaping fluvial geomorphic processes (Phillips, 2007) and supported ideas associated with the individualistic concept of landscape evolution and 'badass geomorphology' (sensu Phillips, 2015). These ideas reflect a view and approach to the study of landforms as the outcome of the interplay of general laws, place-specific controls, and history. ...
The floodplains of large Coastal Plain rivers in the southeastern U.S. are important long-term storage sites for alluvial sediment and nutrients. Yet considerable uncertainty surrounds sediment dynamics on many large river floodplains and, in particular, the local scale factors that affect the flux of sediment and nutrients from rivers onto their floodplains and their subsequent deposition. This research quantifies short-term rates of sediment deposition from 2012 to 2014 on floodplain sites at Congaree National Park using feldspar pads. Sediment deposition rates ranged from 0.1 to 15.6 cm (median = 1.46 cm) and were closely associated with inundation frequency and geomorphic position. Cross-floodplain distributary channels served as particularly important conduits for moving sediment onto the floodplain. Physical and chemical analyses of soil samples demonstrated that the most flood-exposed sites had higher major nutrient and micronutrient levels (especially of phosphorus) and more diverse nutrient compositions. This research advances current understandings of lateral floodplain connectivity by demonstrating the complex effects of regional hydrology and local floodplain environmental characteristics on the supply of sediment and nutrients.
... Experimental flume studies have made significant contributions to our knowledge of river channel dynamics by demonstrating that new river morphologies — or states — emerge when sediment, water, and vegetation fluxes are adjusted (e.g., Friedkin, 1945; Schumm and Khan, 1972; Ashmore, 1991; Paola, 2007, 2010 ). Flume experiments , however, cannot simulate the place-based contingencies that influence river channel evolution following a disturbance (Schumm, 1991Schumm, , 2005 Brierley and Fryirs, 2005; Phillips, 2007 Phillips, , 2015 Beven, 2015). Relatively few studies (e.g., Nevins, 1969; Erskine, 1992; Korpak, 2007 ), have controlled biohydrogeomorphic variables in natural settings to encourage particular forms of channel adjustment. ...
The evolution of riverbeds is greatly impacted by changes in the water-sediment relationship resulting from the movement of debris flows. However, little is known about the influence of management in chronic sediment source areas on the evolution of main-stem riverbed morphology. In this study, we used multi-source remote sensing images covering the past 50 years along with water-sediment and topo-graphic data from a river basin, and sediment transport data from debris flows, to analyze the evolutionary processes of the middle and lower reaches of the Daying River (DYR) at the China-Myanmar border. Our results showed that (1) management of the sediment source area shifted the riverbed morphology from aggradation to erosion, transforming the river surface from wide and shallow to narrow and deep, and the channel from multi-threaded to single-threaded; (2) the active alluvial area, marginal bar area, and average river width exhibited an inverted V-shaped trend, increasing by at least 23% and then decreasing by more than 59%; and (3) the evolution of riverbed morphology contributed to the stability of downstream riverbeds, improved flood control, and enhanced utilization of the floodplains. K E Y W O R D S Daying River, debris control, gully sediment yield, river aggradation, riverbed evolution, water-sediment relationship
This chapter addresses controls on the stratigraphic record: the mechanisms, processes, and contingencies affecting sediment supply and accommodation and the resulting stratal surfaces and units. Although it is not necessary to know the forcing mechanisms of sequence formation to construct a sequence-stratigraphic framework and map the distribution of rock properties, it is commonly useful to incorporate one’s understanding of key processes to provide predictive capabilities away from sample control.
Many factors influence the development and expression of parasequences and depositional sequences. These factors can be grouped usefully into two main categories: processes (sediment supply and accommodation) and contingencies (inherited and coeval factors that condition the effects of those processes). The main components of sediment supply include detrital, biogenic, and authigenic processes as well as lateral and temporal changes thereof; the components of accommodation include those processes that affect the upper and lower boundaries of sediment accumulation. Contingencies exert a significant influence on the expression of sequence-stratigraphic surfaces and units because they affect when, where, and how the processes of sediment supply and accommodation operate. Four main contingencies affect all depositional settings and generally do not change significantly during a depositional sequence: (1) geological age, (2) plate-tectonic setting, (3) paleolatitude, and (4) paleogeography at the continental and basinal scale. Other contingencies tend to be specific to particular types of depositional settings or change significantly during accumulation; these include (1) inherited and evolving bathymetry, (2) climate mode, and (3) ocean chemistry.
Ultimately, it is difficult to uniquely identify causal mechanisms because of the many influences on accommodation and sediment supply and the commonly convergent effects of those influences (i.e., similar stratal patterns can result from various combinations of influences). Knowledge of mechanisms is not, however, an essential part of the sequence-stratigraphic approach (and is potentially not possible in many circumstances—especially not from the stratal patterns alone). Sequence stratigraphy allows construction of a comprehensive and useful stratigraphic framework based on a single criterion—the physical relations of the strata themselves—that reveals genetically related rocks.
The Coastal Dune Model, used to examine controls on dune development and evolution, includes negative feedback between the wind and the evolving topography that results in a scale‐invariant beach‐dune profile. While a limited number of reference profiles appear to support the Coastal Dune Model assumption of scale‐invariance, previously published studies and conceptual models suggest that the beach‐dune profile is not scale‐invariant. Using a combination of journal articles, textbooks, and remotely sensed data from Prince Edward Island, Washington state, and Texas, this short communication finds that there is no evidence for a scale‐invariant beach‐dune profile within and between field sites. Variability in the beach‐dune profile is due to site‐specific and scale‐dependent controls on the beach and the dune that are often highlighted in the conceptual models that authors use to depict the controls on sediment supply and transport from the beach to the dune. Results highlight a need to critically evaluate the assumptions and applications of models such as the Coastal Dune Model, and to explore how and when sites can be considered representative and in support of model results .
Students new to geomorphology need to observe and interpret complex landscapes and features being acted upon in space and over widely-varying time periods. These observational complexities are generally communicated via textbooks as much as fieldwork. This paper presents an explanatory schema by linking materials (M), process-mechanisms (P) to the visual aspects and geometry (G) of the landscape. This MPG schema can be viewed within the 'Critical Zone' where the processes, linkages and feedbacks at the Earth's surface are studied. The linkages extend beyond geomorphology to wider aspects of physical geography: geology, soils, biogeography, climate and environment.
Land-cover change attributed to human activity in Australia and New Zealand has had a transformational effect on landscapes over the past ~ 200 years. Initial effects attributed to indigenous populations were insignificant (Australia) or modest (New Zealand). European colonization represented a far more significant disturbance of land cover in both countries and has resulted in complete regime change in some geomorphic systems. This article reviews a selection of geomorphic responses to anthropogenic land-cover change and contrasts system behavior and response between Australia and New Zealand.
Darwinian natural selection acting on individuals is one of only several types of selection influencing landscape evolution. Ecological filtering and abiotic selection (including the least action principle and preferential flows) apply. The overarching principle is one of efficiency selection, whereby more efficient, stable, and durable forms, structures, patterns, networks, and flux pathways are more likely to occur, grow, and persist than less efficient ones. Particularly important forms are gradient selection, favoring steeper and faster flow paths; resistance selection, whereby more resistant features are preferentially preserved; biogeochemical selection, which favors more rapid elemental cycling; network selection, which makes more efficient flux and interaction networks more likely; and thermodynamic selection, reflecting the advantages of energy use efficiency. Efficiency selection is highly local, however, one of several reasons that landscapes and environmental systems are not always inevitably becoming more efficient overall. A case study illustrating selection principles is given.
The Perfect Landscape is a broad, but formally expressed, conceptual model incorporating the law-place-history explanatory triad, explicitly dealing with contingency, and recognizing the interplay of individuality and idiosyncrasies in Earth surface system with shared characteristics and regularities. It holds that individual landscapes reflect a combination of general laws and geographically and historically contingent controls that are highly improbable in terms of duplication elsewhere. The Perfect Landscape concept also indicates that landscape individuality and idiosyncrasy can only increase as more variables are considered. An approach to analyzing and understanding perfect landscapes is based on nine axioms for landscape interpretation. The evolution of perfect landscapes requires creativity in the form of the appearance of new features that are selected for. Several lines of evidence that such creativity occurs in abiotic as well as biotic aspects of landscapes are presented.
Large (>0.1 km2) gully–mass movement complexes (badass gullies) are significant contributors to the sediment cascade in New Zealand's steepland East Coast Region catchments. The scale of change taking place in these gully systems allows significant evolution in morphology and sediment dynamics to be tracked at annual to decadal timescales. Here we document changes in two adjacent badass gullies in Waipaoa catchment (Tarndale and Mangatu) to infer sediment generation processes and connectivity using a morphological budgeting approach. A baseline dataset for this study is provided by a LiDAR‐derived digital elevation model (DEM) in 2005. We produced new DEMs and orthophoto mosaics using photogrammetry in 2017, 2018, and 2019 to quantify gully morphodynamics and associated volumes of sediment erosion and deposition in both systems as they co‐evolved. Results indicate ongoing rapid development of both gully complexes. Severe erosion took place at the gully heads with lowering and migration (up to 25 m vertically and laterally) of the topographic divide separating the two gullies between 2005 and 2019. Over the same period, net lowering of each gully system was ~250 mm year−1. Key sediment‐generating processes included surface erosion, deep‐seated landslides, and debris flows. Longer term, the overall contribution of sediment from both badass gullies to the Waipaoa catchment has been declining. In the mid‐20th century, both gullies yielded in excess of 300 kt year−1. From 2005 to 2019, 80 kt year−1 was yielded from Tarndale and 110 kt year−1 from Mangatu. Our most recent surveys demonstrated considerable variability in sediment yield, ranging from 76 kt year−1 (2017–2018) to 291 kt year−1 (2018–2019). The annual variability observed reflects the complex morphodynamics of discrete hillslopes and tributary fans in these badass gully systems and underlines the importance of integrating decadal and annual surveys when assessing system trajectory. © 2020 John Wiley & Sons, Ltd. We use SfM photogrammetry and LiDAR datasets to quantify the dynamics of two head‐to‐head badass gullies. Tarndale cannibalizes Mangatu, shifting the divide by ~25 m between 2005 and 2019, which drops >20 m in this period. Significant sediment generated is stored in the fan apexes in both systems, notably Tarndale, with the remainder exported to the Waipaoa drainage network: reduced storage capacity means Mangatu is the more efficient conveyor of sediment, yielding ~1.5 Mt compared with Tarndale's ~1 Mt.
In biological evolution, creativity occurs in the appearance of new entities by evolutionary dynamics. This is linked to mutations and genetic drift, which cannot occur in geophysical phenomena. Biota can exhibit evolutionary creativity that influences landforms, but how does creativity (defined here as the capacity for emergence of new entities that increase the adjustedness of the landscape to environmental conditions) occur in landforms and landscapes as entities independent of biota? Creativity in geomorphic evolution does not require any sort of goal functions or purposeful innovation‐‐just that geomorphic development is capable of producing novelties that may be better adapted (more efficient or durable) than predecessors. Independently of biota, evidence exists that landforms may develop to become more or less "fit" in terms of efficiency and/or durability. Thus emergence of novel features may lead to their persistence. Emergence of novel forms is illustrated for the case of karst sinkholes (dolines), which indicates increasing geomorphic diversity over Ma and Ga timescales. A case study of fluviokarst chronosequences in Kentucky demonstrates emergence and elimination of landforms as landscapes evolve. Some of these may represent generally (as opposed to locally) novel landforms. While this paper is more suggestive than demonstrative, results strongly suggest evolutionary creativity in geomorphology both tied to, and independent of, biological evolution. This occurs due to emergence of geomorphic entities that are subject to selection that tends to increase efficiency and durability.
We examined the channel-evolution process in a 19.5 km course in the Mangaoporo River (catchment area: 72.6 km²) in the East Coast region of North Island, New Zealand over 70 years using aerial photographs and cross-sectional survey records. The catchment experienced expansive deforestation during the late 19th and early 20th centuries, which accelerated the growth of the gully complexes. The manner of the evolution was controlled largely by the underlying lithology that determined the valley configuration. In the upstream confined section, where hillslope and channel processes were closely coupled, continuous sediment supply from gully complexes gradually converted the channel course from a narrow single-thread to wide braided reaches, or from sediment transfer to storage zones. This change was accompanied by a decrease in unit stream power (USP). In 1939, the USP was above 200 W/m² in most of the upstream section, while 40% of the USP values were near or below 50 W/m² in 2012/2013. Because a narrow reach situated at the end of the storage zone limited the amount of sediment travelling further, the downstream reaches were gradually disconnected from the upstream section, and the channel forms changed more moderately than in the upstream section. This reduction in sediment travelling with distance transformed a once-braided reach at the end of the course to development of a supply-limited condition with time. The overall channel evolution was accelerated by major rainfall events, including prolonged rainfall in 1956 and Cyclone Bola in 1988, which activated gully complexes and contributed to subsequent channel widening, particularly in the upstream section. Although reforestation starting in the 1980s contributed to deactivation of gully complexes after 1988, the difficulty in controlling their total remission together with the lower USP values of the river in 2012/2013 compared to those before the previous major wet events indicate that the river has been evolving in an irreversible direction, triggered by land use changes of more than a century ago.
Nine axioms for interpreting landscapes from a geoscience perspective are presented, and illustrated via a case study. The axioms are the self-evident portions of several key theoretical frameworks: multiple causality; the law–place–history triad; individualism; evolution space; selection principles; and place as historically contingent process. Reading of natural landscapes is approached from a perspective of place formation. Six of the axioms relate to processes or phenomena: (1) spatial structuring and differentiation processes occur due to fluxes of mass, energy, and information; (2) some structures and patterns associated with those fluxes are preferentially preserved and enhanced; (3) coalescence occurs as structuring and selection solidify portions of space into zones (places) that are internally defined or linked by mass or energy fluxes or other functional relationships, and/or characterized by distinctive internal similarity of traits; (4) landscapes have unique, individualistic aspects, but development is bounded by an evolution space defined by applicable laws and available energy, matter, and space resources; (5) mutual adjustments occur between process and form (pattern, structure), and among environmental archetypes, historical imprinting, and environmental transformations; and (6) place formation is canalized (constrained) between clock-resetting events. The other three axioms recognize that Earth surface systems are always changing or subject to change; that some place formation processes are reversible; and that all the relevant phenomena may manifest across a range of spatial and temporal scales. The axioms are applied to a study of soil landscape evolution in central Kentucky, USA.
Our understanding of braided river morphodynamics has improved significantly in recent years, however, there are still large knowledge gaps relating to both long‐term and event‐based change in braided river morphologies. Furthermore, we still lack methods that can take full advantage of the increasing availability of remotely sensed datasets that are well suited to braided river research. Network analysis based on graph theory, the mathematics of networks, offers a largely unexplored toolbox that can be applied to remotely sensed data to quantify the structure and function of braided rivers across nearly the full range of spatiotemporal scales relevant to braided river evolution. In this article, important commonalities between braided rivers and other types of complex network are described, providing a compelling argument for the wider uptake of complex network analysis methods in the study of braided rivers. We provide an overview of the extraction of graph representations of braided river networks from remotely sensed data and detail a suite of metrics for quantitative analysis of these networks. Application of these metrics as new tools for multiscale characterization of braided river planforms that improve upon traditional, spatially averaged approaches is discussed and potential approaches to network‐based analysis of braided river dynamics are proposed, drawing on a range of different concepts from braided river research and other network sciences. Finally, the potential for using graph theory metrics to validate numerical models of braided rivers is discussed.
This article is categorized under:
• Science of Water > Methods
Field geologists and geomorphologists are increasingly looking to numerical modelling to understand landscape change over time, particularly in river catchments. The application of Landscape Evolution Models (LEMs) started with abstract research questions in synthetic landscapes. Now, however, studies using LEMs on real‐world catchments are becoming increasingly common. This development has philosophical implications for model specification and evaluation using geological and geomorphological data, besides practical implications for fieldwork targets and strategy. The type of data produced to drive and constrain LEM simulations has very little in common with that used to calibrate and validate models operating over shorter timescales, making a new approach necessary. Here we argue that catchment fieldwork and LEM studies are best synchronised by complementing the Pattern Oriented Modelling (POM) approach of most fluvial LEMs with Pattern Oriented Sampling (POS) fieldwork approaches. POS can embrace a wide range of field data types, without overly increasing the burden of data collection. In our approach, both POM output and POS field data for a specific catchment are used to quantify key characteristics of a catchment. These are then compared to provide an evaluation of the performance of the model. Early identification of these key characteristics should be undertaken to drive focused POS data collection and POM model specification. Once models are evaluated using this POM/POS approach, conclusions drawn from LEM studies can be used with greater confidence to improve understanding of landscape change.
Sediment connectivity has been shown in recent years to explain how the watershed configuration controls sediment transport. However, we find no studies develop a watershed erosion modeling framework based on sediment connectivity, and few, if any, studies have quantified sediment connectivity for gently rolling systems. We develop a new predictive sediment connectivity model that relies on the intersecting probabilities for sediment supply, detachment, transport, and buffers to sediment transport, which is integrated in a watershed erosion model framework. The model predicts sediment flux temporally and spatially across a watershed using field reconnaissance results, a high-resolution digital elevation models, a hydrologic model, and shear-based erosion formulae. Model results validate the capability of the model to predict erosion pathways causing sediment connectivity. More notably, disconnectivity dominates the gently rolling watershed across all morphologic levels of the uplands, including, microtopography from low energy undulating surfaces across the landscape, swales and gullies only active in the highest events, karst sinkholes that disconnect drainage areas, and floodplains that de-couple the hillslopes from the stream corridor. Results show that sediment connectivity is predicted for about 2% or more the watershed’s area 37 days of the year, with the remaining days showing very little or no connectivity. Only 12.8 ± 0.7% of the gently rolling watershed shows sediment connectivity on the wettest day of the study year. Results also highlight the importance of urban/suburban sediment pathways in gently rolling watersheds, and dynamic and longitudinal distributions of sediment connectivity might be further investigated in future work. We suggest the method herein provides the modeler with an added tool to account for sediment transport criteria and has the potential to reduce computational costs in watershed erosion modeling.
A key skill that geomorphologists possess is the ability to use multi‐scale perspectives in their interpretations of landscapes. One way to gain these perspectives is with the use of nested hierarchical frameworks. In fluvial geomorphology, such frameworks help with assessment of large‐scale controls (e.g., tectonic activity, climate change) on the pattern and dynamics of smaller‐scale physical features (e.g., channels, floodplains, bars), and conversely illustrate how these smaller‐scale features provide the building blocks from which to make interpretations of fluvial processes and dynamics over larger spatial and temporal scales. Given the rapid pace of technological developments, the range of relatively inexpensive tools available for visualising and mapping landscapes at different spatial scales is expanding exponentially. In this paper, which focuses on the World Heritage‐listed Okavango Delta in Botswana, we demonstrate how various visualisations generated by different technologies at different spatial scales (catchment, landscape unit, reach, site and geomorphic unit) are providing critical baseline information to enhance interpretation and communication of fluvial geomorphology, with potential application in water resources management. In particular, our nested hierarchical approach could be used as an interactive communication tool for non‐specialists and embedded within existing and future management plans for the Delta. The construction of nested hierarchies that synthesise information and analyses can be a valuable addition to the environmental manager's toolkit.
Landscape evolution models (LEMs) are an increasingly popular resource for geomorphologists as they can operate as virtual laboratories where the implications of hypotheses about processes over human to geological timescales can be visualized at spatial scales from catchments to mountain ranges. Hypothetical studies for idealised landscapes have dominated, although model testing in real landscapes has also been undertaken. So far however, numerical landscape evolution models have rarely been used to aid field-based reconstructions of the geomorphic evolution of actual landscapes. To help make this use more common, we review numerical landscape evolution models from the point of view of model use in field reconstruction studies. We first give a broad overview of the main assumptions and choices made in many LEMs to help prospective users select models appropriate to their field situation. We then summarize for various timescales which data are typically available and which models are appropriate. Finally, we provide guidance on how to set up a model study as a function of available data and the type of research question.
The state of an Earth surface system (ESS) is determined by three sets of factors: Laws, place, and history. Laws (L = L1, L2, . . . , Ln) are the n general principles applicable to any such system at any time. Place factors (P = P1, P2, . . . , Pm) are the m relevant characteristics of the local or regional environment. History factors (H = H1 , H2, . . . , Hq) include the previous evolutionary pathway of the ESS, its stage of development, past disturbance, and initial conditions. Geoscience investigation may focus on laws, place, or history, but ultimately all three are necessary to understand and explain ESS. The LPH triad is useful as a pedagogical device, illustrated here via application to explaining the world's longest cave (Mammoth Cave, KY). Beyond providing a useful checklist, the LPH framework provides analytical traction to some difficult research problems. For example, studies of the avulsions of three southeast Texas rivers showed substantial differences in avulsion regimes and resulting alluvial morphology, despite the proximity and superficial similarity of the systems. Avulsions are governed by the same laws in all cases [L(A) = L(B) = L
The interdependent relationship between humans and landscapes is an important but still under-developed concept in geomorphology. It is clear, from case studies introduced in this chapter that a detailed understanding of how people impact on geomorphic processes and how, in turn, these processes impact on society, is an essential contribution towards the goal of a sustainable future.
In an era of river repair, the concept of recovery enhancement has become central to river management practice. However, until about the early 2000s there were no coherent geomorphic frameworks with which to forecast river recovery potential. While the practical uptake of such frameworks has been slow, and debates continue about what recovery means, some river management agencies in different parts of the world have applied related concepts within catchment scale, process-based approaches to river management. Agencies that make use of recovery enhancement approaches have reframed the way that vision setting, planning, and prioritization are undertaken. In this study, we review river recovery as a principle. We then present, using examples, an updated version of the framework for assessing river recovery and river recovery potential that is embedded in the River Styles framework. Finally, we show how the application of this framework can be used to better inform river management practice.
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Complexity has long been recognized and is increasingly becoming mainstream in geomorphology. However, the relative novelty of various concepts and techniques associated to it means that ambiguity continues to surround complexity. In this commentary, we present and discuss a variety of recent contributions that have the potential to help clarify issues and advance the use of complexity in geomorphology. This article is protected by copyright. All rights reserved.
This book provides a theory to overcome the problem of identifying the principles behind the interdependence of different aspects of nature. Climate, vegetation, geology, landforms, soils, hydrology, and other environmental factors are all linked. Many scientists agree that there must be some general principles about the way in which earth surface systems operate, and about the ways in which the interactions of the biosphere, lithosphere, hydrosphere, and atmosphere manifest themselves. Yet there may be inherent limits on our ability to understand and isolate these interactions using traditional reductionist science. The argument of this book is that the simultaneous presence of order and chaos reflects fundamental, common properties of earth surface processes and systems. It shows how and why this is the case, with examples ranging from evolutionary and geological times scales to microscale examinations of process mechanics.
Much geomorphological enquiry has been devoted to the understanding of landscapes via the construction of models based on the relationships between process and form. This paper examines the philosophical, theoretical and practical problems involved in bridging the gap between studies of geomorphological processes and explanations of landscape development. It argues that process geomorphology is essentially reductionist and discusses the practical and logical limitations of such an approach to science. It suggests that landscapes are emergent phenomena and, by drawing from the philosophical and practical lessons derived from the physics of non-linear systems, demonstrates that they are not amenable to reductionist explanations.
Base-level lowering plays an important role in cave passage development and morphology. Cave conduits are commonly formed at depth below the water table, and subhorizontal conduits can form at depths of more than 100 m below the water table. Subsequent base-level lowering is responsible for evolution from a deep phreatic to a shallow phreatic to a vadose, water table setting. Most caves do not evolve to a vadose passage stretching from sink to spring because the flow is captured by undercaptures: passages at a lower elevation and below the water table. Undercaptures provide much of the complexity seen in cave maps. Distributary springs and bypass passages can also be formed during short-term rises in base level that also produce wall notches.
Geomorphology offers an effective entry point into wider debates across geography and the sciences, framing understandings of landscapes as manifestations of complex and emergent relationships that can be used as a platform to support conversations among multiple and diverse worldviews. Physical geographers have much to contribute in moving beyond monological (one only) views of landscapes. This paper draws upon concepts of emergence, connectivity and space-time relationality to develop an ‘ethnogeomorphic’ outlook upon biophysical-and-cultural (‘living’) landscapes. This perspective is grounded through ethnographic case studies with Indigenous1 communities in Australia and Canada that examine knowledge production and concerns for environmental negotiation and decision-making. Extending beyond a traditional approach to ethnosciences, ethnogeomorphology seeks to move beyond cross-disciplinary scientific disciplines (and their associated epistemologies) towards a shared (if contested) platform of knowledge transfer and communication that reflects multiple ways of connecting to landscapes. Convergent perspectives upon landscape understandings are highlighted from Indigenous knowledges and emerging, relational approaches to geomorphic analysis. Ethnogeomorphology presents a situated, non-relativist response to people–landscape connections that reflects and advocates sentient relationships to place. Potential applications of ethnogeomorphology as an integrating theme of geographic inquiry are explored, highlighting important tensions in the knowledge production process.
Fluvial geomorphology has witnessed a continuing reduction in the time- and space-scales of research, with increasing emphasis on the dynamics of small site-specific river reaches. This shift can be regarded as part of a trend towards the understanding and explanation rather than description of how rivers change, which raises important questions regarding the relevance of such short time-scale and small space-scale research to understanding longer-term aspects of landform behaviour. The methodological challenges that arise from such intensive case study research are illustrated here using a detailed investigation of a river reach. Morphological changes within this reach are shown to be driven by: (i) catchment- scale processes associated with the interaction of discharge and sediment supply waves; and (ii) modification of these processes through morphological controls on erosion and deposition patterns and hence net channel change. The 'morphological conditioning' of channel response reflects the configurational aspects of channel change, and the importance of local characteristics in the understanding of system behaviour. Sensitivity to local conditions implies that short time-scale and small space-scale processes may be critical to channel behaviour, particularly if the system is interpreted in non-linear terms. Although it may be possible to identify statistically averaged stable states, non-linear system behaviour implies that system trajectories are sensitively dependent upon instantaneous system states. Thus, changes between average states can only be understood through an understanding of the sequence of configurational states through which the system evolves. © 1997 by John Wiley & Sons, Ltd.
Traditional conceptual models of landscape evolution view topography as an outcome of endogenic forces (uplift) working against exogenic forces of denudation. The energy considerations of these concepts have focused on the conver-sion of the potential energy of landscape relief to kinetic energy. The concept of the biosphere as a planetary membrane for capturing and converting solar energy, coupled with the critical geomorphic role of biota, call for a consideration of biotic contribu-tions to geomorphic work. A review of estimates of global rates of kinetic energy of denudation and uplift, and net primary production (NPP) indicates that the energy density of NPP is, on average, three to seven orders of magnitude greater than the others. If even a tiny fraction of NPP is geologically significant, then the biological subsidy to the energy of landscape evolution must be considered on a par with that of geophysical and geochemical phenomena. A case study in eastern Kentucky shows that even if only 0.1 percent of NPP is geomorphically significant, it still far exceeds the energy inputs from uplift and conversion of potential to kinetic energy by denudation. This is unlikely to be unique, though the relative importance of biological and geophysical processes must obviously vary with climate, tectonic setting, and other factors. Results indicate that, particularly where biological activity is significant, geomorphic work performed by biota may be greater than that associated with endogenic processes and with die kinetic energy of denudation.
The karstic canyon of Lower Ardèche is located in the Middle Rhône valley, which is directly tributary to the Mediterranean Sea. The Rhône River is emblematic of the Messinian Salinity Crisis (MSC) impact on landscape morphology. Along the edge of the Saint-Remèze Plateau, the Rhône valley displays four benchmark levels generated by the MSC: the Pre-evaporitic abandonment surface (1), the Messinian erosional surface (2), the Marine/non-marine surface of the Pliocene ria (3) and the Pliocene abandonment surface (4).
In this research, karstification in Menteşe Region of southwest of Turkey has been studied by GIS and remote sensing applications. Macro karstic features (doline, uvala, tectono-karstic depression and fluvio-karstic valley) of the area extending from Lake Bafa to Gökova Bay have been mapped with digitized geology and topography maps and satellite image. Micro and macro karstification have developed in dolomitic and cherty limestones belonging to Dogger-Createcous, Campanian-Maestrihtien, Senonian, Jurassic-Createcous, Middle Triassic-Liassic, Permian and terrestrial limestones of Pliocene. Dislocation lines (fault-lineament) in the direction of northwest-southeast and northeast-southwest extracted from geology maps and satellite image are important agents in evaluation of macro karstic forms. Relief generation cycles at three levels have been defined according to the TIN surface (Triangulated Irregular Network) and geomorphology map of Turkey. Based on this application, it is possible to say that changing climatic and tectonic conditions from Miocene to Pliocene have affected to the course of karstification. Slope and elevation maps extracted from DEM have been compared with macro karstic features in GIS environment. Macro karst features have mostly developed between 0–40° and in areas where slope is greater than 40° a clear macro karst hasn't become. Tectono-karstic depressions and uvalas have formed between 0–1,000 m, doline type karstic depressions have developed between 1,000–1,500 m and an evident macro karst form hasn't become at elevations higher than 1,500 m. Shaded relief image of the area originated from DEM has designated that the area has a rough relief being created by neotectonic movements. This uneven area dissected by rivers is a suitable environment for karstic process. According to the agents functioning on karstification, it has been described that Menteşe Region has a "structure-erosion-corrosion karst" type.
German
Das Menteşe Gebiet, das sich vom Bafa See bis zur Gökova Bucht erstreckt, wurde mit digitalisierten topographischen und geologischen Karten und Satellitendaten analysiert. Große Karstformen (Dolinen, Uvalas, tektonisch bedingte Karsthohlformen und Trockentäler) sowie Kleinformen sind in dolomitischen und feuersteinhaltigen Kalken (Perm–Pliozän) entwickelt. Tektonische NE-SE und NE-SW verlaufende Linien, die aus geologischen Karten und Satellitenbildern ermittelt wurden, haben einen großen Einfluss auf die Formenentwicklung. In Anlehnung an das TIN Netz (Triangulated Irregular Network) und die geomorphologische Karte der Türkei wurden drei Reliefgenerationszyklen bestimmt. Diese Grundlagen erlauben die Aussage, dass die Veränderungen der klimatischen und tektonischen Bedingungen vom Miozän zum Pliozän den Verlauf der Verkarstung beeinflusst haben. Aus dem digitalen Geländemodell entwickelte Hang- und Höhenkarten zeigten im Vergleich mit den Karstformen, dass sich die Makrokarstformen überwiegend in Gebieten mit Hangneigungen zwischen 0–40° entwickelten, während klare Makrokarstformen bei Hangneigungen über 40° fehlten. Tektonisch bedingte Karsthohlformen und Uvalas bestimmen den Formenschatz der Höhenlage zwischen 0 und 1,000 m, von 1,000 bis 1,500 m Höhe sind Dolinen dominant und oberhalb 1,500 m fehlen augenscheinlich große Karstformen. Schattierte Darstellungen aus dem digitalen Geländemodell zeigen ein schroffes Relief, das auf die neotektonischen Bewegungen zurückgeht.
Das durch Flüsse gegliederte Menteşe Gebiet bietet günstige Faktoren für Verkarstungsvorgänge und wird nach den die Verkarstung bestimmenden Elementen als ein von Struktur, Erosion und Korrosion geprägter Karsttyp eingestuft.
French
Dans cette recherche, karstification dans Menteşe Région de sud-ouest de Turquie a été étudiée par les applications de GIS et télédétection. Les caractéristiques de karstic de macro (doline, uvala, la dépression de tectono-karstic et la vallée de fluvio-karstic) du domaine s'étendant de Bafa de Lac à la Baie de Gökova a été fait la carte d'avec la géologie digitalisée et les cartes de topographie et l'image de satellite. Micro et karstification de macro a développé dans les calcaire de dolomitic et cherty étant au Dogger-Createcous, le Campanian-Maestrihtien, Senonian, le Jurassique-Createcous, le Triassic-Liassic de Milieu, Permian et les calcaire terrestres de Pliocene. Les lignes de luxation (le défaut-trait) dans la direction de nord-ouest-sud-est et de nord-est-sud-ouest extrait des cartes de géologie et de l'image de satellite sont des agents importants dans l'évaluation de formes de karstic de macro. Les cycles de génération de soulagement à trois niveaux ont été définis selon la surface d'ETAIN (Triangulated le Réseau Irrégulier) et la carte de géomorphologie de Turquie. Basé sur cette application, c'est possible de dire que cela changeant climatique et les conditions de tectonic de Miocene à Pliocene ont affecté au cours de karstification. Les cartes de pente et élévation extraites de DEM comparé aux caractéristiques de karstic de macro dans l'environnement de GIS. Les caractéristiques de karst de macro ont développé surtout entre 0–40° et dans les domaines où la pente est plus grande que 40° un macro karst hasn clair't est devenu. Les dépressions de Tectono-karstic et uvalas ont formé entre 0–1.000 m, les dépressions de karstic de type de doline ont développé entre 1.000–1.500 m et un hasn de forme de karst de macro évident't est devenu aux élévations plus hautes que 1.500 m. L'image ombragée de soulagement du domaine provenu de DEM a désigné que le domaine a un soulagement rude étant créé par les mouvements de neotectonic. Ce domaine inégal disséqué par les rivières est un environnement convenable pour le procédé de karstic. Selon les agents fonctionnant sur karstification, il a été décrit que Menteşe Région a un «structure-erosion-corrosion karst» le type.
Assertions of a ‘naughty world’ (Kennedy, 1979) point to the importance of place-based knowledge in informing landscape interpretations and management applications. Building upon conceptual and theoretical insights into the geomorphic character, behaviour and evolution of rivers, this paper outlines an approach to the practice of fluvial geomorphology: ‘reading the landscape’. This scaffolded framework of field-based interpretations explicitly recognizes the contingent nature of biophysical interactions within any given landscape. A bottom-up, constructivist approach is applied to identify landforms, assess their morphodynamics, and interpret the interaction and evolution of these features at reach and catchment scales. Reading the landscape is framed as an open-ended and generic set of questions that inform process-form interpretations of river landscapes. Rather than relying unduly on conceptual or theoretical representations of landscapes that suggest how the world ‘should’ ideally look and behave, appropriately contextualized, place-based understandings can be used to detect where local differences matter, thereby addressing concerns for the transferability of insights between locations and the representativeness of sample or reference sites. The approach provides a basis for scientifically informed management efforts that respect and work with the inherent diversity and dynamics of any given river system.
Geomorphic systems are typically nonlinear, owing largely to their threshold-dominated nature (but due to other factors as well). Nonlinear geomorphic systems may exhibit complex behaviors not possible in linear systems, including dynamical instability and deterministic chaos. The latter are common in geomorphology, indicating that small, short-lived changes may produce disproportionately large and long-lived results; that evidence of geomorphic change may not reflect proportionally large external forcings; and that geomorphic systems may have multiple potential response trajectories or modes of adjustment to change. Instability and chaos do not preclude predictability, but do modify the context of predictability. The presence of chaotic dynamics inhibits or excludes some forms of predictability and prediction techniques, but does not preclude, and enables, others. These dynamics also make spatial and historical contingency inevitable: geography and history matter. Geomorphic systems are thus governed by a combination of "global" laws, generalizations and relationships that are largely (if not wholly) independent of time and place, and "local" place and/or time-contingent factors. The more factors incorporated in the representation of any geomorphic system, the more singular the results or description are. Generalization is enhanced by reducing rather than increasing the number of factors considered. Prediction of geomorphic responses calls for a recursive approach whereby global laws and local contingencies are used to constrain each other. More specifically a methodology whereby local details are embedded within simple but more highly general phenomenological models is advocated. As landscapes and landforms change in response to climate and other forcings, it cannot be assumed that geomorphic systems progress along any particular pathway. Geomorphic systems are evolutionary in the sense of being path dependent, and historically and geographically contingent. Assessing and predicting geomorphic responses obliges us to engage these contingencies, which often arise from nonlinear complexities. We are obliged, then, to practice evolutionary geomorphology: an approach to the study of surface processes and landforms which recognizes multiple possible historical pathways rather than an inexorable progression toward some equilbribrium state or along a cyclic pattern.
When meander incision occurs into soluble rock materials such as limestone, karst processes can alter river flow patterns in a manner, and with a rapidity, that is not available on insoluble rocks. The development of dissolution conduits or caves through meander necks is especially important. Efficient self-piracy of a stream through a meander cutoff cave causes abandonment of the meander loop. Abandonment of the meander loop will inhibit further development of any meander cutoff cave draining the abandoned meander loop to the next meander downstream. Examples of meander cutoff cave formation from flatlying Paleozoic limestones in Kentucky, and from glaciated Precambrian marbles in New York demonstrate the complex interaction of meander cutoff cave development. Structure, carbonate lithology and climate in this type of speleogenesis is subordinate to the geomorphologic and hydrologic setting of the surface meanders. -from Authors
The exogenic processes are not only random, but also unstable (instability principle). Their activity is greatest in those places where a deviation from uniformity has occurred previously through some accidental fluctuation. Many examples from nature of the operation of the 'instability principle' are shown, as well as how pertinent time-parameters characterizing them can be defined.-from Author
Environmental Change explores the nature, causes, rates and directions of environmental change throughout earth history. Huggett introduces the interdependent parts of the natural environment - cosmic, ecological, geological - and the dynamic nature of the environmental system. Integrating a wealth of examples and illustrations from around the world, the book examines evidence and causes of change in life, climate (air and water), soils, sediments and landforms, and the impacts of human-environment interaction.
This chapter focuses upon the ‘sediment bucket’ in the Lane diagram (sediment calibre and volume). Processes of sediment entrainment, transport and deposition are discussed in the context of the Hjulström diagram. The influence of grain-by-grain interactions on the channel bed (i.e. packing arrangements), bedform generation in sand- and gravel-bed rivers, partial and equal mobility, supply- and transport-limited rivers and the role of material cohesiveness in fine-grained (silt-clay) channels is discussed, followed by an outline of the controls upon depositional processes in river systems. Prior to outlining key principles in the development of a practical approach to river sediment analysis, scales of depositional features in river systems and contrasting sedimentary sequences in bedload, mixed-load and suspended-load depositional environments are briefly summarised, and key considerations in efforts to interpret sediment sequences when reading the landscape are outlined.
Human impacts do not directly alter the fundamental hydraulic and geomorphic processes such as the mechanics of sediment transport, erosion, and deposition along rivers. However, human disturbance modifies the spatial distribution and rate of these processes. This chapter first presents a summary history of human interactions with river systems. This is followed by an appraisal of direct human impacts (impacts of dams and inter-basin transfers, channelisation programmes, removal of riparian vegetation and wood, sand/gravel extraction and impacts of rehabilitation schemes) and indirect human impacts (water abstraction, urbanisation, mining and other indirect factors) upon rivers. Finally, river responses to human disturbance are framed in relation to recovery notions, adding a further layer of complexity to the river evolution diagram.
We decipher the Earth's diary that has been left us as a legacy. We read with trained senses and interpret with the tools of disciplined thinking. We translate the Earth's language into our own, and enrich the already bright and colourful surface of the present with the knowledge of the inexhaustible abundance of the past. Almost alone among modern sciences, geology has preserved a method of inquiry that emphasizes synthetic reasoning for the interpretation of Earth's signified causal processes. Though geologists interpret Earth's signs via all manner of measurement, quantitative modeling, and experimentation, these are but tools for an inquiry ultimately directed at the truth of Earth's message. Geologists have always considered that message to be signified in rocks, sediments, fossils, and other signs of Earth processes. To interpret these signs, geologists do not need a foundational metaphysics to ground their reasoning, as Lyell attempted with his uniformitarianism. Instead, geologists can benefit from understanding the formal conditions of what will count as true in these signs, a topic explored through the branch of philosophy known as semiotics. The geologically relevant philosophy involves a semiotic point of view wherein signs are not mere objects of thought or language, but rather are vital entities comprising a web of signification that is continuous from outcrops to reasoning about outcrops. Such an action of signs constitutes a geosemiosis that leads geological investigators on a fruitful course of hypothesis generation. Semiotic grammar provides the means to describe the representational character of signification that is inherent in this geological reasoning. Critical logic explores the modes of inference used to seek truth in the representations, and georhetoric attains truth as a matter of belief. While not being a method for doing geology, semiotics provides a means of describing the highly productive reasoning processes of geologists.
Fluvial geomorphology has witnessed a continuing reduction in the time- and space-scales of research, with increasing emphasis on the dynamics of small site-specific river reaches. This shift can be regarded as part of a trend towards the understanding and explanation rather than description of how rivers change, which raises important questions regarding the relevance of such short time-scale and small space-scale research to understanding longer-term aspects of landform behaviour. The methodological challenges that arise from such intensive case study research are illustrated here using a detailed investigation of a river reach. Morphological changes within this reach are shown to be driven by: (i) catchment-scale processes associated with the interaction of discharge and sediment supply waves: and (ii) modification of these processes through morphological controls on erosion and deposition patterns and hence net channel change, The 'morphological conditioning' of channel response reflects the configurational aspects of channel change, and the importance of local characteristics in the understanding of system behaviour, Sensitivity to local conditions implies that short time-scale and small space-scale processes may be critical to channel behaviour, particularly if the system is interpreted in non-linear terms. Although it may be possible to identify statistically averaged stable states, non-linear system behaviour implies that system trajectories are sensitively dependent upon instantaneous system states. Thus, changes between average states can only be understood through an understanding of the sequence of configurational states through which the system evolves.
The key to understanding the development of most solution depressions in karst is concluded to lie in subcutaneous processes in the epikarstic aquifer at the top of the vadose zone but beneath the soil. The epikarstic water-table is drawn-down above highly permeable vertical leakage paths at the base of the subcutaneous zone. This focuses stream-lines and hence corrosion activity. The radius of the cone of depression initially determines doline size. Positive feed-back factors reinforce these processes. A distinction can be made between 'draw-down depressions' and 'point-recharge depressions'. -from Author
The recent suggestions by Chapman and by Bennett and Chorley that geographers should transfer their attention to the analysis of environmental systems, with the especial aim of developing effective prediction and control models, are examined. It is concluded that such a change would leave many basic questions concerning the nature of environmental complexity unanswered and that there remains a need for two, distinct fields of endeavour: the call to abandon much of the sphere of existing geographical enquiry is therefore seen to be premature.
Many scientists believe that there is a uniform, interdisciplinary method for the practice of good science. The paradigmatic examples, however, are drawn from classical experimental science. Insofar as historical hypotheses cannot be tested in controlled laboratory settings, historical research is sometimes said to be inferior to experimental research. Using examples from diverse historical disciplines, this paper demonstrates that such claims are misguided. First, the reputed superiority of experimental research is based upon accounts of scientific methodology (Baconian inductivism or falsificationism) that are deeply flawed, both logically and as accounts of the actual practices of scientists. Second, although there are fundamental differences in methodology between experimental scientists and historical scientists, they are keyed to a pervasive feature of nature, a time asymmetry of causation. As a consequence, the claim that historical science is methodologically inferior to experimental science cannot be sustained.
The principal karst region of south-central Kentucky encompasses an area of some two hundred square miles, including a segment of doline karst, the Sinkhole plain, and a karst plateau. The plateau lies mainly within Mammoth Cave National Park and is underlain by the Flint Ridge cave system, the largest known cave in the world, and by Mammoth Cave, the third largest. The plateau is ringed with a complex of vertical shafts that are an integral part of the drainage from the perched groundwater body in the protective cap rock. The development of the karst area can be interpreted in terms of the unique relationship between the stratigraphic sequence of thick, bedded limestones and of clastic rocks and the location of recharge and discharge areas. Lateral flow from the Sinkhole plain beneath the protected plateau has generated a cave complex of long tubular conduits connected by shafts, shaft drains, and piracy routes. Enough of the system is preserved to permit a fairly complete interpretation of the physiographic development of the region.
The twenty largest perennial springs of Kentucky were identified and ranked over a ten-year period. Since most large springs are not shown on topographic or geologic maps, ranked springs were primarily located from previous hydrogeologic surveys, field reconnaissance, and literature review. Spring flows were ranked by minimum annual discharge, which ranged from 0.15-0.68 m 3/s. These springs are classified as 3rd Magnitude, based on the Meinzer (1923) discharge scale. Unit base flow (the ratio of minimum discharge to basin area) revealed diverse hydrogeologic yield of the karst spring group, ranging from 0.22-12.27 L/s/km 2, suggesting significant unattributed losses and gains. Most large springs are derived from classic fluviokarst basins draining well-developed karst of Mississippian-age limestones. However, one-third result from short stream or meander cutoffs of less than 5 km, which are not necessarily related to well-developed karst terrane. An index of karst basin development can be obtained by the ratio of subsurface flow length to total basin length.
This book outlines a generic set of procedures, termed the River Styles Framework, which provides a set of tools for interpreting river character, behavior, condition, and recovery potential. Applications of the framework generate a coherent package of geomorphic information, providing a physical template for river rehabilitation activities. management and restoration of rivers is a rapidly growing topic for environmental scientists, geologists and ecologists - this book provides a learning tool with which to approach geomorphic applications to river management describes the essential geomorphological principles underlying river behaviour and evolution demonstrates how the River Styles Framework can turn geomorphic theory into practice, to develop workable strategies for restoration and management based on real case studies and authors extensive experience applicable to river systems worldwide synthesises fluvial geomorphology, ecology and management.
This book investigates the structure and function of geoecosystems. It does so using a simple dynamic systems model, the "brash' equation, as a conceptual and analytical tool. In brief, the "brash' equation is a set of equations describing the dynamics of the geoecosphere. The geoecosphere is defined as interacting terrestrial life and life support systems - the biosphere, toposphere, atmosphere, pedosphere, and hydrosphere. The rate of change of each component depends on the state of all the others, plus the effect of cosmic, geological, and other forcing factors. The book is divided into three parts. Part one introduces geoecosystems, describing their nature, hierarchical structure, and ideas about their interdependence and integrity. Part two explores the internal (ecological) interactions between geoecosystems and their near-surface environment. Chapters deal with the environmental factors listed in the "brash' equation.: climate and soils; climate and life; altitude; substrate; topography; and insularity. Part three prospects the role of external factors (ecological, geological, and cosmic) as agencies disturbing the dynamics of geoecosystems. -from Author
Geomorphic threshold conditions have been identifed at which stream patterns change and gully initiation occurs. For both, the threshold conditions are defined by the parameter of "relative shear stress" which is a measure of the energy state of the system and is based on known values of stream slope and mean annual discharge (for patterns) or drainage area (for gullies). The probability of passing from a stream pattern to another, or from stable to gullied valley floors, is a smooth function of relative shear stress and so the thresholds separating the different states of the geomorphic systems are gradational. The singularity of landforms prevents the identification of a sharp threshold, and as a result landform sensitivity will differ within the same area and under the same conditions. Therefore, geomorphic predictions and postdictions will be uncertain, and Quaternary correlations will lack precision.
This textbook provides a modern, quantitative and process-oriented approach to equip students with the tools to understand geomorphology. Insight into the interpretation of landscapes is developed from basic principles and simple models, and by stepping through the equations that capture the essence of the mechanics and chemistry of landscapes. Boxed worked examples and real-world applications bring the subject to life for students, allowing them to apply the theory to their own experience. The book covers cutting edge topics, including the revolutionary cosmogenic nuclide dating methods and modeling, highlights links to other Earth sciences through up-to-date summaries of current research, and illustrates the importance of geomorphology in understanding environmental changes. Setting up problems as a conservation of mass, ice, soil, or heat, this book arms students with tools to fully explore processes, understand landscapes, and to participate in this rapidly evolving field.
The primary goal of this project is to develop a relative chronology of events in the geologic history of the Kentucky River, and to consider the geologic controls on those events. This study utilized published geologic and topographic data, as well as field observations and extensive compilation and comparison of digital data, to examine the fluvial record preserved in the Kentucky River valley in central Kentucky. Numerous fluvial features including abandoned paleovalleys, fluvial terraces and deposits, bedrock benches, and relict spillways between adjacent river valleys were identified during the course of the study. The morphology of the modern valley coincides with bedrock lithology and can be used to describe the distribution and preservation of modern and ancient fluvial deposits and features in the study area. Bedrock lithology is the dominant control on valley morphology and on the distribution and preservation of fluvial deposits and features in the study area. Some stream trends are inherited from the late Paleozoic drainage of the Alleghanian orogeny. More recent inheritance of valley morphology has resulted from the erosion of the river from one lithology down into another lithology with differing erosional susceptibility, thus superposing the meander patterns of the overlying valley style onto the underlying lithology. One major drainage reorganization related to a pre-Illinoisan glacial advance disrupted the northward flow of the Old Kentucky River toward the Teays River system and led to organization of the early Ohio River. This greatly reduced the distance to baselevel, and led to abrupt incision and a change in erosional style for the Kentucky River. The successful projection of valley morphologies on the basis of bedrock stratigraphy, the history of erosion suggested by fission track data and the results of this study, as well as soil thickness and development, all argue against the existence of a midto late-Tertiary, low-relief, regional erosional surface. This study instead hypothesizes that the apparent accordance of ridge-top elevations in the study area is a reflection of a fluvially downwasted late Paleozoic depositional surface.
Subsurface solutional pathways make limestone terrains sensitive to changes in soil properties that regulate flows to the epikarst. This study examines biogeomorphic factors responsible for changed water movements and erosion in fluviokarst slopes deforested 200 years ago along the Kentucky River, Kentucky. In this project, infiltration and water content data from forest and fescue grass soil profiles were analyzed within a detailed overview of system factors regulating hillslope hydrology. Results show that grass has growth and rooting characteristics that tend to create a larger volume of lateral water movement in upper soil layers than occurs under forests. This sets up the current emergent pattern of erosion in which water perches at grass slope bases and overwhelms pre-existing epikarst drainage. Tree roots are able to cause solution at multiple discrete points of entry into fractures and bedding planes, increasing storage capacity and releasing sediment over time. Grass roots do not enter bedrock, and their rooting depth limits diffuse vertical preferential flow in root channels to above one meter. In the areas dense clay soils, flow under grass is conducted sideways either through the regolith or at the bedrock surface. Rapid flow along rock faces in hillslope benches likely moves fines via subsurface routes from the hillslope shoulders, causing the exposure of flat outcrops under grass. Lower growing season evapotranspiration also promotes higher grass summer flow volumes. Gullying occurs at sensitive points where cutters pass from the uphill grassed area into the forest, or where flow across the bedrock surface crosses grass/forest boundaries oriented vertical to the slope. At these locations, loss of the protective grass root mat, coupled with instigation of tree root preferential flow in saturated soils, causes soil pipes to develop. Fluviokarst land management decisions should be based on site-specific slope, soil depth, and epkarst drainage conditions, since zones sensitive to erosion are formed by spatial and temporal conjunctions of a large number of lithologic, karst, soil, climate, and vegetation factors. This study shows that it is the composite of differing influences created by forest and grass that make forests critical for soil retention in high-energy limestone terrains.
Nickpoint recession in the Buchan karst, southeastern Australia, has resulted in the formation of an underground meander cut-off system in the Murrindal River valley. Three nickpoints have been stranded in the surface channel abandoned by the subterranean piracy, and these can be correlated with river terraces and epiphreatic cave passages in the nearby Buchan River valley. The presence of palaeomagnetically reversed sediments in the youngest cave passage in the Buchan valley implies that the topographically lowest nickpoint in the Murrindal valley is more than 730 ka old, and the other nickpoints are probably several million years old. The nickpoints are occasionally active during floods, but the diversion of most surface flow underground has slowed down their retreat to the extent that they have been effectively stationary for several million years.
Underground nickpoint migration has been by both incision within major phreatic conduits and their abandonment for lower-level passages. The nickpoints are all present in the upstream part of the cave system, but have not migrated past the sink in the river channel, despite the long period of time available for this to happen. The sink is characterized by collapsed limestone blocks; these filter out the coarse bedload from the river channel. As a result, erosion within the cave passages is dominantly solutional and therefore slower than in the surface channel, where it is mostly mechanical. In addition, to transmit a drop in base level the cave system requires the removal of a larger volume of rock than for the surface migration of a nickpoint, because any roof collapse material in the subsurface system must be removed. These factors have slowed the migration of the base-level changes through the subsurface system, and may be a general feature in caves that have diffuse sinks as their main inputs.
Previous experimental, field, and modeling studies of confluence dynamics have focused mainly on junctions formed by straight channels. In contrast, natural rivers often meander and tributaries can enter meandering rivers on the outside of bends to form a junction planform known as a confluent meander bend. In this study, field measurements of three-dimensional velocity components and bed topography at a confluent meander bend reveal a complex hydrodynamic environment that responds to changes in momentum-flux ratio, while channel morphology remains relatively stable. Flow from the tributary deflects high-velocity flow and helical motion in the curving main river toward the inside of the bend, inducing bed scour and inhibiting point-bar development. The high junction angle forces the tributary flow to abruptly realign to the orientation of the downstream channel, initiating a counter-rotating helical cell over the outer portion of the bend. Two surface-convergent helical cells persist through the downstream channel, where the combined flows accelerate as the channel cross-sectional area is constricted by a bar along the downstream junction corner, precluding flow separation. Long-term stability of its planform suggests that this confluent meander bend represents a quasi-stable channel configuration. Overall, patterns of flow and channel morphology are quite different from typical patterns in most meander bends, but are generally consistent with a conceptual model of confluent meander bends derived from previous laboratory experiments and numerical modeling.
Many geomorphic system states and behaviors often interpreted as tendencies toward establishment and maintenance of steady-state equilibrium are actually emergent outcomes of two simple principles: gradient selection and threshold-mediated modulation. The principle of gradient selection is simply that geomorphic features associated with gradient-driven flows persist and grow relative to other features and pathways. The principle of threshold-mediated modulation reflects the inherent limits on system development along any particular pathway. Thresholds not only define a restricted state space for any given geomorphic system, but may also result in oscillatory behavior around an intermediate condition that resembles fluctuations around a steady-state equilibrium. Together, these principles often produce outcomes that mimic steady-state equilibria. Examples are given involving several aspects of fluvial systems (channel profiles, alluvial channel changes, and drainage density), hillslope gradients, and barchan dunes. Steady-states indeed occur in Earth surface systems, and are a useful simplification in some models. However, the assumption that such states are somehow normative, or the only natural condition, is incorrect, and can lead to problems in geomorphic interpretations, environmental restoration and management, and conceptions of how Earth systems work.
This investigation attempts to analyze the spatial patterns of karst depression elongation and orientation relative to structural trends in a part of south central Kentucky. Depression elongation is defined by the ratio of the long axis of the depression to its short axis. Depression orientation is measured by the azimuth of the long axis in relation to the azimuth of an associated line of structural fracture. From these data the percentage of structurally aligned depressions was determined.
The percentage of structurally aligned depressions was found to be highest where the following conditions prevailed: 1) in areas where limestones were characterized by low insoluble residue contents; 2) in areas where hydraulic gradients were high, as indicated by the existence of high karst relief ratios; 3) in areas where a high proportion of the surface runoff was concentrated in the subterranean drainage systems; and 4) in areas, which were located near the mouth of the subterranean drainage system. (Location in the subterranean drainage system was estimated by the mean distance to the drainage system mouth.) The percentage of structurally aligned depressions tended to decrease as the insoluble residue contents in the limestones increased, the karst relief ratios decreased, the percent area drained by subterranean streams decreased, and the mean distance from the drainage system mouth increased.
Depression elongation ratios were highest in areas characterized by the following conditions: 1) low limestone insoluble residue contents; 2) high karst relief ratios, indicating high hydraulic gradients; 3) the presence of dense limestones; 4) proximity to the drainage system mouth; and 5) a high proportion of structurally aligned depressions (in this region this tended to be the most important factor influencing depression elongation). Depression elongation ratios decreased where any combination of the five previously described conditions did not occur in the optimum state. Regression analysis accounted for fifty-seven percent of the spatial variation of the distribution of structurally aligned depressions and eighty-eight percent of the variation of elongation ratios.
An analysis of 40 winding streams and valleys reveals that a higher proportion of large tributaries than small ones occurs on the concave (out) side of bends. The principal reason for this is that large tributaries experience greater difficulty than small ones forming in the limited amount of space on the convex (in) side of bends. The proportions of small and large tributaries on the concave side of bends are determined largely by the spatial requirements of tributaries, valley sinuosity, mean valley bend length, and mean rate of bend migration. In addition, the proportion of large tributaries on the concave side of bends is affected by junction angle adjustments that deflect a main stream toward a large tributary, thereby creating a bend with the large tributary on its concave side. These adjustments increase the proportion of large tributaries on the concave side of bends, especially along low-sinuosity headwater streams.
The exponent of the mainstream length-drainage area relationship is interpreted as a fractal quantity, superseding the previous allometric interpretation. The fractal interpretation is based on the assumption that cartographic generalization is applied evenly to all map scales. Twenty-three drainage basins of the Eaton River (Quebec, Canada) were delineated from topographic maps at three different scales (1:20,000, 1:50,000, and 1:125,000). The exponent of the length-area relation is much lower (0.546) at the largest scale than at the smallest scales (0.65), and its value corresponds to that obtained from a Richardson analysis of 10 interior stream segments. At the 1:20,000 map scale, the exponent is entirely fractal. The larger exponent values obtained at the smallest scales exceed the fractal value and incorporate an allometric component. This component is not functional, however, and it merely reflects the generalization process of cartographic abstraction of stream heads as scale is reduced. The fractal dimension of streams should not be inferred from the exponent of the length-area relation because its value is likely to be scale-dependent.
Examines some of the formal relations between landform parameters themselves, or between them and supposed governing processes in terms of the information required in geomorphological theories and the constraints imposed by sound mechanical theories. It is principally concerned with empirical proportional relations and the sections include: allometric analysis; the form of alluvial fans; functionally; determined allometry: total stream length and drainage area; allometry as a test of formal assumptions; hydromorphological equations; dimensional analysis and similitude. -Keith Clayton
The sequential arrangement of tributaries along trunk channels of 45 basins display complex patterns that cannot be fully explained either by assuming that a single process dominated tributary organization or that streams are topologically random. The arrangement of tributaries can be considered as representing a response to geometrical and spatial requirements imposed by other basin attributes, the effects of which are not equally influential along the entire length of a channel. However, because these factors are usually considered stable or normal properties of dentritic streams, it may be assumed that the observed tributary arrangement represents a normal characteristic of such networks. -from Author
The 1920s-1930s debates over the origin of the 'Channeled Scabland' landscape of eastern Washington, northwestern USA, focused on the cataclysmic flooding hypothesis of J Harlen Bretz. During the summer of 1922, Bretz began leading field parties of advanced University of Chicago students into the region. In his first paper, published in the Bulletin of the Geological Society of America, Bretz took special care not to mention cataclysmic origins. However, in a subsequent paper in the Journal of Geology, to the editorial board of which he had recently been added, Bretz formally described his hypothesis that an immense late Pleistocene flood, which he named the 'Spokane Flood', had derived from the margins of the nearby Cordilleran Ice Sheet. This cataclysm neatly accounted for numerous interrelated aspects of the Channeled Scabland landscape and nearby regions. Nevertheless, the geological community largely resisted Bretz's hypothesis for decades, despite his enthusiastic and eloquent defence thereof. Resolution of the controversy came gradually, initially through the recognition by J. T. Pardee of a plausible source for the flooding: ice-dammed Pleistocene glacial Lake Missoula in northern Idaho and western Montana. Eventually, by the 1960s, the field evidence for cataclysmic flooding became overwhelming, and physical processes were found to be completely consistent with that evidence. The controversy is of philosophical interest in regard to its documentation of the attitudes of geologists toward hypotheses, which illustrate aspects of geological reasoning that are distinctive in degree from those of other sciences.