Kooperativer Bibliotheksverbund

Berlin Brandenburg

and
and

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    In: Earth Surface Processes and Landforms, January 2014, Vol.39(1), pp.71-79
    Description: Landform and landscape evolution may be convergent, whereby initial differences and irregularities are (on average) reduced and smoothed, or divergent, with increasing variation and irregularity. Convergent and divergent evolution are directly related to dynamical (in)stability. Unstable interactions among geomorphic system components tend to dominate in earlier stages of development, while stable limits often become dominant in later stages. This results in mode switching, from unstable, divergent to stable, convergent development. Divergent‐to‐convergent mode switches emerge from a common structure in many geomorphic systems: mutually reinforcing or competitive interrelationships among system components, and negative self‐effects limiting individual components. When the interactions between components are dominant, divergent evolution occurs. As threshold limits to divergent development are approached, self‐limiting effects become more important, triggering a switch to convergence. The mode shift is an emergent phenomenon, arising from basic principles of threshold modulation and gradient selection. As an example, the relationships among flow concentration, erosive force, and channel incision in fluvial systems are examined in the context of mode switching and thresholds. The commonly observed divergence in channel growth and fluvial dissection and network development, eventually transitioning to a stable, convergent configuration, is an emergent outcome of gradient selection and threshold modification, and does not imply any goal functions of balancing mass fluxes or limiting change. Copyright © 2013 John Wiley & Sons, Ltd.
    Keywords: Thresholds ; Mode Switching ; Divergent Evolution ; Convergent Evolution ; Emergence ; Geomorphic Systems
    ISSN: 0197-9337
    E-ISSN: 1096-9837
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    In: Earth Surface Processes and Landforms, July 2012, Vol.37(9), pp.936-950
    Description: The San Antonio River Delta (SARD), Texas, has experienced two major avulsions in the past 80 years, and a number of other historical and Holocene channel shifts. The causes and consequences of these avulsions – one of which is ongoing – were examined using a combination of fieldwork, geographic information system (GIS) analysis, and historical information to identify active, semi‐active, and paleochannels and the sequence of shifting flow paths through the delta. The role of deposition patterns and antecedent morphology, large woody debris jams, and tectonic influences were given special attention. Sedimentation in the SARD is exacerbated by tectonic effects. Channel aggradation is ubiquitous, and superelevation of the channel bed above the level of backswamp areas on the floodplain is common. This creates ideal setup conditions for avulsions, and stable, cohesive fine‐grained banks favor avulsions rather than lateral migration. Flood basins between the alluvial ridges associated with the aggraded channels exist, but avulsions occur by re‐occupation of former channels found within or connected to the flood basins. Large woody debris and channel‐blocking log‐jams are common, and sometimes displace flow from the channel, triggering crevasses. However, a large, recurring log‐jam at the site of the ongoing avulsion from the San Antonio River into Elm Bayou is not responsible for the channel shift. Rather, narrow, laterally stable channels resulting from flow splits lead to accumulation of wood. Some aspects of the SARD avulsion regime are typical of other deltas, while others are more novel. These includes avulsions involving tributaries and subchannels within the delta as well as from the dominant channel; tectonic influences on delta backstepping and on channel changes within the delta; avulsions as an indirect trigger for log‐jam formation (as well as vice‐versa); and maintenance of a multi‐channel flow pattern distinct from classic anastamosing or distributary systems. Copyright © 2012 John Wiley & Sons, Ltd.
    Keywords: Avulsion ; Delta ; San Antonio River ; Large Woody Debris ; Channel Evolution
    ISSN: 0197-9337
    E-ISSN: 1096-9837
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    In: Earth Surface Processes and Landforms, January 2016, Vol.41(1), pp.16-26
    Description: Biotic influences on geomorphology (and vice‐versa) are ubiquitous. This paper explores whether landforms may be extended (composite) phenotypes of biota, based on four criteria: process–form relationships between biota and landforms; evolutionary synchrony; selective pressure via ecosystem engineering and niche construction; and positive feedback benefitting the engineer organism(s). Coral reefs, peat bogs, biomantles, insect mounds, grassland soils, salt marshes, mangrove swamps, and some vegetation‐dependent sand dune types clearly meet these criteria. Karst landforms, meandering rivers, and tree uprooting pit‐mound systems meet the first three criteria, but positive feedback to engineer organisms has not been established. Research in biogeomorphology will surely identify other extended phenotypes. Implications are that biological evolution will continue to drive landscape metamorphosis, the appearance of new landform types, and presumably the disappearance of extended phenotypes associated with extinct species. Independently of extended phenotypes, tightly‐coupled geomorphological–ecological interactions such as coevolution, and biogeomorphic forms of ecosystem engineering and niche construction are common. The toposphere, encompassing Earth's landforms, is partly a biotic construct. Some elements would be present in an abiotic world, but the toposphere would not exist in anything resembling its contemporary state without a biosphere. This raises important questions with respect to Earth system evolution. The bio, litho‐, atmo‐, hydro‐, topo‐, and pedospheres coevolve at the global scale. Major biotic events have driven revolutions in the other spheres, but the atmosphere and the global hydrological system seem to have been relatively steady‐state at the global scale. The toposphere and pedosphere have not. This suggests that perhaps landforms and soils provide the major mechanisms or degrees of freedom by which Earth responds to biological evolution. Landforms and soils may thus be the ‘voice’ of the biosphere as it authors planetary change, even if clear biotic signatures are lacking. Copyright © 2015 John Wiley & Sons, Ltd.
    Keywords: Biogeomorphology ; Niche Construction ; Extended Phenotype ; Biogenic Landforms ; Toposphere
    ISSN: 0197-9337
    E-ISSN: 1096-9837
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    In: Earth Surface Processes and Landforms, November 2014, Vol.39(14), pp.1888-1899
    Description: Active and semi‐active anastomosing Holocene channels upstream of the delta in the lower valley of the meandering Neches River in southeast Texas represent several morphologically distinct and hydrologically independent channel systems. These appear to have a common origin as multi‐thread crevasse channels strongly influenced by antecedent morphology. Levee breaching leads to steeper cross‐valley flows toward floodplain basins associated with Pleistocene meander scars, creating multi‐thread channels that persist due to additional tributary contributions and ground water inputs. Results are consistent with the notion of plural systems where main channels, tributaries, and sub‐channels may have different morphologies and hydrogeomorphic functions. The adjacent Trinity and Sabine Rivers have similar environmental controls, yet the Trinity lacks evidence of extensive anastomosing channels on its floodplain, and those of the Sabine appear to be of different origin. The paper highlights the effects of geographical and historical contingency and hydrological idiosyncrasy. Copyright © 2014 John Wiley & Sons, Ltd.
    Keywords: Anastamosing Channels ; Anabranching ; Crevasse ; Neches River ; Path‐Dependence
    ISSN: 0197-9337
    E-ISSN: 1096-9837
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    In: Earth Surface Processes and Landforms, February 2017, Vol.42(2), pp.347-354
    Description: The state of an Earth surface system (ESS) is determined by three sets of factors: laws, place, and history. Laws ( =  are the general principles applicable to any such system at any time. Place factors (  ) are the relevant characteristics of the local or regional environment. History factors (  ) 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 [  ], and the three rivers have undergone the same sea‐level, climate, and tectonic histories, as well as the same general anthropic impacts [  ]. Though regional environmental controls are similar, local details such as the location of the modern main channel relative to Pleistocene meander channels differ, and thus these place factors explain the differences between the rivers. The LPH framework, or similar types of reasoning, is implicit in many types of geoscience analysis. Explicit attention to the triad can help solve or address many specific problems and remind us of the importance of all three sets of factors. Copyright © 2016 John Wiley & Sons, Ltd.
    Keywords: Laws ; Place ; History ; Earth Surface System ; Contingency
    ISSN: 0197-9337
    E-ISSN: 1096-9837
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    In: Earth Surface Processes and Landforms, July 2018, Vol.43(9), pp.1768-1781
    Description: Anticipating geomorphic tipping points requires that we learn from the past. Major geomorphic changes in coastal plain rivers of Texas resulting in river metamorphosis or regime shifts were identified and the major driving factors determined. Eleven such transformations – possible tipping points – were identified from contemporary observations, historical records, and Quaternary reconstructions. Two of the tipping points (between general aggrading and degrading valley states) are associated with reversals in a fundamental system control (sea‐level). One (stable or aggrading versus degrading channels) is associated with an abrupt change in sediment supply due to dam construction, and two others (changes from meandering to anastomosing channel patterns, and different anastomosis styles) are similarly related to changes in sediment supply and/or transport capacity, but with additional elements of historical contingency. Three tipping points are related to avulsions. One, from a regime dominated by re‐occupation of former channels to one dominated by progradation into flood basins, is driven by progressive long‐term filling of incised valleys. Another, nodal avulsions, is triggered by disturbances associated with tectonic uplift or listric faults. The third, avulsions and related valley metamorphosis in unfilled incised valleys, is due to fundamental dynamical instabilities within the fluvial system. This synthesis and analysis suggests that geomorphic tipping points are sometimes associated with general extrinsic or intrinsic (to the fluvial system) environmental change, independent of any disturbances or instabilities. Others are associated with natural (e.g. tectonic) or human (dams) disturbances, and still others with intrinsic geomorphic instabilities. This suggests future tipping points will be equally diverse with respect to their drivers and dynamics. Copyright © 2018 John Wiley & Sons, Ltd. Major geomorphic changes in coastal plain rivers of Texas resulting in river metamorphosis or regime shifts were identified and the major driving factors determined. Eleven such transformations – possible tipping points – were identified.
    Keywords: Tipping Point ; Threshold ; Regime Shift ; River Metamorphosis ; Fluvial System
    ISSN: 0197-9337
    E-ISSN: 1096-9837
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    In: Earth Surface Processes and Landforms, December 2017, Vol.42(15), pp.2623-2639
    Description: Geomorphic and hydraulic units in river channels are closely linked to geodiversity and habitats, and thus to biodiversity. In a ~ 200 km reach of the lower Sabine River, in the northern Gulf of Mexico Coastal Plain, 72 different hydraulic units (HU) were identified in six geomorphic zones or river styles. Richness–area relationships indicate a linear or logarithmic increase of HUs, as opposed to the less steep power functions generally found in biogeographic species–area curves or in soil richness–area analyses. Different results are obtained when starting from the upstream or downstream end of the study area, indicating the importance of directionality in such analyses. These results show that HUs (and related habitats and biotopes) are both richer and more variable than a repeated sequence of units. The number of HUs inundated increases linearly with flow stage categories, indicating the importance of high within‐bank flows in maintaining and activating HUs. Aggregated HUs (AHUs) associated with similar geomorphic units are highly connected, both with respect to patterns of spatial adjacency and potential connectivity at similar flow levels. Spectral graph theory metrics applied to a graph representation of spatial adjacency shows a highly complex network with a high potential for rapid propagation of changes—and even more so for a graph based on flow connectivity. The flow connectivity graph shows far higher synchronization as indicated by algebraic connectivity. Thus suggests more rapid and coherent changes for processes driven by river flow, as opposed to phenomena driven by other factors between flow events. These findings have important implications for understanding relationships between geodiversity and habitat diversity, managing habitat and biodiversity, and linking the latter to instream flows. Copyright © 2017 John Wiley & Sons, Ltd. 72 different hydraulic units (HU) were identified in six geomorphic zones or river styles. Richness‐area relationships indicate a linear or logarithmic increase of HUs, as opposed to the less steep power functions generally found in biogeographic species‐area curves or in soil richness‐area analyses. Spectral graph theory metrics applied to a graph representation of spatial adjacency shows a highly complex network with a high potential for rapid propagation of changes—and even more so for a graph based on flow connectivity.
    Keywords: Hydraulic Units ; Geomorphic Units ; Richness–Area Analysis ; Connectivity ; Complexity
    ISSN: 0197-9337
    E-ISSN: 1096-9837
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Language: English
    In: Hydrological Sciences Journal, 02 September 2015, Vol.60(9), pp.1631-1648
    Description: River science and management often require a design or reference discharge. The common (and sometimes unavoidable) use of such discharges may, however, obscure the fact that the magnitude and frequency of critical flows can differ due to various hydrological, geomorphological, and ecological...
    Keywords: Threshold Discharge ; Flow Regime ; Geomorphic Threshold ; Channel-Floodplain Connectivity ; Brazos River ; Seuil de Débit ; Régime D'Écoulement ; Seuil Géomorphologique ; Connectivité Du Chenal et de La Plaine D'Inondation ; Rivière Brazos ; Geography
    ISSN: 0262-6667
    ISSN: 01979337
    E-ISSN: 2150-3435
    E-ISSN: 10969837
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Article
    Article
    Language: English
    In: Earth Surface Processes and Landforms, 15 March 2010, Vol.35(3), pp.305-313
    Description: Earth scientists have traditionally conceptualized rivers and streams as geomorphic machines, whose role is to transfer sediment and to sculpt the landscape. Steady‐state relationships between sediment supply and transport capacity have traditionally been considered normative in fluvial systems. Rivers are hydrological entities, however, whose function is to redistribute excess moisture on land. The geomorphic work of the river – erosion, transport, deposition, etc. – is a byproduct of the hydrological job of the river. There is therefore no reason to expect any particular relationship between sediment supply and transport capacity to develop as a normative condition in fluvial systems. The apparent steady‐state equilibrium slope adjustments of rivers are a byproduct of four basic phenomena: (1) hydraulic selection, which favors channels and branching networks over other flux patterns; (2) water flows along the available path of least resistance; (3) energy dissipation; and (4) finite relaxation times. Recognizing converging trends of stream power or slope and sediment supply as common (but far from inevitable) side effects rather than self‐regulation has important implications for interpreting and predicting fluvial systems, and for river management and restoration. Such trends are variable, transient, contingent, and far from universal. Where they occur, they are an emergent byproduct of fundamental physical mechanisms, not a goal function or attractor state. Copyright © 2009 John Wiley & Sons, Ltd.
    Keywords: Rivers ; Fluvial Systems ; Equilibrium ; Steady‐State ; Emergence
    ISSN: 0197-9337
    E-ISSN: 1096-9837
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Language: English
    In: Earth Surface Processes and Landforms, 2014, Vol.39(14), p.1888(12)
    Description: To purchase or authenticate to the full-text of this article, please visit this link: http://onlinelibrary.wiley.com/doi/10.1002/esp.3582/abstract Byline: Jonathan D. Phillips ABSTRACT Active and semi-active anastomosing Holocene channels upstream of the delta in the lower valley of the meandering Neches River in southeast Texas represent several morphologically distinct and hydrologically independent channel systems. These appear to have a common origin as multi-thread crevasse channels strongly influenced by antecedent morphology. Levee breaching leads to steeper cross-valley flows toward floodplain basins associated with Pleistocene meander scars, creating multi-thread channels that persist due to additional tributary contributions and ground water inputs. Results are consistent with the notion of plural systems where main channels, tributaries, and sub-channels may have different morphologies and hydrogeomorphic functions. The adjacent Trinity and Sabine Rivers have similar environmental controls, yet the Trinity lacks evidence of extensive anastomosing channels on its floodplain, and those of the Sabine appear to be of different origin. The paper highlights the effects of geographical and historical contingency and hydrological idiosyncrasy. Copyright [c] 2014 John Wiley & Sons, Ltd.
    ISSN: 0197-9337
    Source: Cengage Learning, Inc.
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. Further information can be found on the KOBV privacy pages