Within-catchment variability in landscape connectivity measures in the Garang catchment, upper Yellow River

Nicoll, Tami; Brierley, Gary

doi:10.1016/j.geomorph.2016.03.014

Cited by 48 publications

(29 citation statements)

References 56 publications

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“…Four times the amount of sediment is stored in alluvial fan deposits within the upper catchment relative to the lower catchment; however, the high volumes that are stored appear to have minimal impact upon contemporary sediment dynamics due to the absence of efficient linkages within the upper catchment to allow for onward transport. This is inferred through both field observation and connectivity indices (see Nicoll and Brierley, for analysis). Sediment input to the channel network within the upper catchment is limited to localised reworking of the toe of the alluvial fan deposits by the mainstem Garang channel, and minor reworking within the active portions of the larger fan deposit (Figure (C)).…”

Section: Discussionmentioning

confidence: 99%

“…In saying this, it must be remembered that the Garang catchment is one of the smaller tributary catchments within the upper Yellow River basin. Under closed basin conditions, the landscapes were likely adjusted to spatial variations in erosion rate, and behaved in a similar manner to the highly disconnected landscapes of the contemporary upper catchment zone (Nicoll and Brierley, 2017). Incision would have induced dramatic changes to sediment dynamics, with high rates of sediment reworking and increased sediment availability due to the drop in base level that allowed for reactivation of alluvial fans and reworking of former deposits.…”

Section: Discussionmentioning

confidence: 99%

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Reworking of basin fill deposits along a tributary of the upper Yellow River: Implications for changes to landscape connectivity

Nicoll

Brierley

2017

Earth Surf Processes Landf

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Recent emphasis on sediment connectivity in the literature highlights the need for quantitative baseline studies on the patterns and distribution of sediment stores to facilitate understanding of how sediment moves through the landscape at various temporal and spatial scales. This study evaluates the distribution and make‐up of sediment stores within the dramatically incised landscapes of the upper Yellow River, where basin fill deposits up to 1200 m in depth have been extensively reworked following incision by the Yellow River. Field and GIS analyses highlight the discontinuous distribution of sediment stores in Garang catchment, a 236 km2 tributary of the upper Yellow River. Volumetric estimates of sediment storage were obtained through a combination of field mapping, GPR transects, and GIS analyses. Sediment stores cover 20% of the Garang catchment, with an estimated volume of 474.0 × 106 m3, and inferred residence times from OSL and 14C dating of 103–104 years. Fans and terraces reworked from basin fill deposits, and associated cut and fill terrace features, are the dominant forms of sediment storage (~90% of total). A space‐for‐time argument is used to assess stages of basin infilling and subsequent landscape responses to incision, outlining a dramatic example of changes to sediment dynamics and connectivity relationships within the upper Yellow River. Sediments within the upper catchment lie above the regional basin fill level, offering a glimpse of pre‐incisional conditions. This contrasts markedly with the enduring influence of basin incisional history seen within the middle catchment, and the contemporary landscapes of the lower catchment where nearly all available sediment has been excavated from the basin and the landscape effectively operates under post‐incisional conditions. The need to contextualise catchment‐scale studies in terms of landscape history is emphasised. Copyright © 2017 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Reworking of basin fill deposits along a tributary of the upper Yellow River: Implications for changes to landscape connectivity

Nicoll

Brierley

2017

Earth Surf Processes Landf

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“…(), which describes reduced coupling between hillslopes and channels due to wider valley bottoms and gentler hillslope gradients in catchments upstream of bedrock‐controlled waterfalls. IC are static representations of connectivity that can be very useful for determining areas of high and low structural connectivity within a geomorphic system under study (Nicoll and Brierley, ).…”

Section: Measuring Connectivitymentioning

confidence: 99%

“…Other studies that quantify geomorphic drivers of connectivity include: Rice (2017), which uses drainage area, Strahler order and other catchment attributes to predict the relative disconnectivity of tributary junctions; Cadol and Wine (2017), which infers differential connectivity between streams and riparian vegetation in various geomorphic settings defined by measurements of valley width, topographic curvature and slope; and May et al (2017), which describes reduced coupling between hillslopes and channels due to wider valley bottoms and gentler hillslope gradients in catchments upstream of bedrock-controlled waterfalls. IC are static representations of connectivity that can be very useful for determining areas of high and low structural connectivity within a geomorphic system under study (Nicoll and Brierley, 2017).…”

Section: Measured Fluxesmentioning

confidence: 99%

Connectivity as an emergent property of geomorphic systems

Wohl

Brierley

Cadol

et al. 2018

Earth Surf Processes Landf

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Connectivity describes the efficiency of material transfer between geomorphic system components such as hillslopes and rivers or longitudinal segments within a river network. Representations of geomorphic systems as networks should recognize that the compartments, links, and nodes exhibit connectivity at differing scales. The historical underpinnings of connectivity in geomorphology involve management of geomorphic systems and observations linking surface processes to landform dynamics. Current work in geomorphic connectivity emphasizes hydrological, sediment, or landscape connectivity. Signatures of connectivity can be detected using diverse indicators that vary from contemporary processes to stratigraphic records or a spatial metric such as sediment yield that encompasses geomorphic processes operating over diverse time and space scales. One approach to measuring connectivity is to determine the fundamental temporal and spatial scales for the phenomenon of interest and to make measurements at a sufficiently large multiple of the fundamental scales to capture reliably a representative sample. Another approach seeks to characterize how connectivity varies with scale, by applying the same metric over a wide range of scales or using statistical measures that characterize the frequency distributions of connectivity across scales. Identifying and measuring connectivity is useful in basic and applied geomorphic research and we explore the implications of connectivity for river management. Common themes and ideas that merit further research include; increased understanding of the importance of capturing landscape heterogeneity and connectivity patterns; the potential to use graph and network theory metrics in analyzing connectivity; the need to understand which metrics best represent the physical system and its connectivity pathways, and to apply these metrics to the validation of numerical models; and the need to recognize the importance of low levels of connectivity in some situations. We emphasize the value in evaluating boundaries between components of geomorphic systems as transition zones and examining the fluxes across them to understand landscape functioning. © 2018 John Wiley & Sons, Ltd.

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“…Much has been written in geomorphology on the subject of sediment connectivity in its various forms, and has been extensively reviewed and critiqued (Bracken et al, 2015;Brierley et al, 2006;Fryirs, 2013;Wohl, 2017). Furthermore, there has been a profusion of geomorphic research addressing sediment connectivity to better understand sediment transfers at differing scales in the catchment sediment cascade (e.g., Cavalli, Trevisani, Comiti, & Marchi, 2013;Croke, Fryirs, & Thompson, 2013;Faulkner, 2008;Fryirs, Brierley, Preston, & Spencer, 2007;Fuller et al, 2016;Fuller & Marden, 2011;Harvey, 2001;Harvey, 2012;Heckmann & Schwanghart, 2013;Johnson, Warburton, & Mills, 2008;Jones & Preston, 2012;Kuo & Brierley, 2014;Mekonnen, Keesstra, Baartman, Stroosnijder, & Maroulis, 2016;Messenzehl, Hoffmann, & Dikau, 2014;Nicoll & Brierley, 2017;Warburton, 2009;Wethered, Ralph, Smith, Fryirs, & Heijnis, 2015). However, the broader impacts of catchment-scale sediment connectivity (as studied by geomorphologists) on the functioning of stream ecosystems have largely been overlooked, beyond an acknowledgement that high (i.e., exceeding transport capacity) sediment delivery is generally bad for stream health (e.g., Sandercock & Hooke, 2011;Waters, 1995).…”

Section: Aims and Rationalementioning

confidence: 99%

The science of connected ecosystems: What is the role of catchment‐scale connectivity for healthy river ecology?

Fuller

Death

2018

Land Degrad Dev

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Riverine biological communities are highly resilient to extreme flood and/or drying disturbance regimes that would otherwise be destructive because these organisms can recolonise from upstream, floodplain, or hyporheic refugia when suitable conditions return. Healthy rivers require a high degree of connectivity to support complex life cycles of many lotic organisms and associated ecosystem functioning. Similarly, connectivity is required for appropriate geophysical functioning; permitting flux of water and sediment that drives channel‐forming and ecological processes. Ecological and geophysical processes have operated in this temporal and spatial patchwork of disturbance and recovery pre‐Anthropocene. Human impacts are increasing constraints on river and floodplain connectivity, severing many natural pathways, and degrading river ecosystem functioning. River restoration seeks to re‐establish some of those biological and physical connections to enhance some level of system health. However, increasing sediment connectivity may be detrimental to river health in some instances. Strongly connected catchments can transmit excessive quantities of sediment from inappropriate land management, detrimental invasive species can spread more widely, and many ecosystem processes can exceed positive feedback control. Simply restoring connectivity will not necessarily lead to healthy river ecosystems. River management requires a greater understanding of how and when connectivity can and should be restored. Although current thinking is often that greater connectivity is better, we illustrate with examples from New Zealand rivers that this is not always the case. The benefits and costs of maintaining or restoring river connectivity need to be given as much attention as the restoration and maintenance of river systems per se.

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Within-catchment variability in landscape connectivity measures in the Garang catchment, upper Yellow River

Cited by 48 publications

References 56 publications

Reworking of basin fill deposits along a tributary of the upper Yellow River: Implications for changes to landscape connectivity

Reworking of basin fill deposits along a tributary of the upper Yellow River: Implications for changes to landscape connectivity

Connectivity as an emergent property of geomorphic systems

The science of connected ecosystems: What is the role of catchment‐scale connectivity for healthy river ecology?

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