The scope for a system-based approach to determine fine sediment targets for chalk streams

Mondon, Beth; Sear, David; Collins, Adrian L.; Shaw, Peter J.; Sykes, Tim

doi:10.1016/j.catena.2021.105541

Cited by 8 publications

(19 citation statements)

References 158 publications

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“…This has been attributed to a combination of anthropogenic activities (e.g., expansive areas of winter cereal production on free-draining soils) and the natural hydrological conditions within chalk streams (e.g., low bed mobilising flows). However, current approaches to fine sediment management and targets have failed to address fundamental issues specific to the chalk stream fine sediment problem (Mondon et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

The sedimentology of gravel beds in groundwater‐dominated chalk streams: Implications for sediment modelling and management

Mondon,

Sear,

Collins

et al. 2024

River Research & Apps

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Elevated fine sediment accumulation in a river system's gravel bed is known to cause detrimental ecological impacts. Current sediment targets and approaches to mitigation have failed due to the oversimplification of geomorphological processes controlling fine sediment accumulation and the lack of relevant scientific knowledge underpinning them. This is particularly apparent in chalk streams (groundwater‐dominated systems) which regularly exhibit high rates of sediment accumulation despite low suspended sediment yields. A necessary first step is to better characterise their sedimentology; thus, the novelty of this study was to determine the sedimentological characteristics of chalk stream gravel beds, specifically the quantity and distribution of fine sediment with depth. We collated published and unpublished freeze‐core data, encompassing 90 sites across 11 UK chalk streams. Results showed average quantities of fine sediment (<2 mm) in chalk stream gravel beds were 25% by weight, with >75% of beds exceeding thresholds for ecological degradation. Quantities of fine sediment increased with increasing depth into the bed, with an average increase between surface and subsurface layers of 54%, and 89% of the gravel bed over‐saturated with fine sediment. Regional differences were attributed to differences in stream power and local sediment sources, including surficial geology and catchment land use. Additionally, a major contrast was identified between experimental conditions in flume studies used to establish models describing interactions/mechanisms of fine sediment infiltration into immobile gravel beds and the natural conditions observed in chalk streams. As such, the use of such models as a basis to explore sediment management scenarios is unlikely to predict the outcome of such management techniques correctly in a real‐world situation.

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Section: Discussionmentioning

confidence: 99%

The sedimentology of gravel beds in groundwater‐dominated chalk streams: Implications for sediment modelling and management

Mondon,

Sear,

Collins

et al. 2024

River Research & Apps

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“…With a new harmonised trait database (Kunz et al, 2022) , 2000). Where available, regulatory guidelines are not always based on explicit evidence of ecological degradation (Mondon et al, 2021) and are not necessarily thresholds at which populations or communities change abruptly or shift to alternate stables states (sensu the definition of ecological threshold by Groffman et al, 2006). Ecological threshold analysis, which investigates such abrupt changes, could therefore represent a valuable tool to aid in the establishment of management thresholds for fine sediment (Groffman et al, 2006).…”

Section: Anthropogenic Activities Such As Agricultural Intensificatio...mentioning

confidence: 99%

Freshwater invertebrate responses to fine sediment stress: A multi‐continent perspective

McKenzie,

Brooks,

Callisto

et al. 2023

Global Change Biology

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Excessive fine sediment (particles <2 mm) deposition in freshwater systems is a pervasive stressor worldwide. However, understanding of ecological response to excess fine sediment in river systems at the global scale is limited. Here, we aim to address whether there is a consistent response to increasing levels of deposited fine sediment by freshwater invertebrates across multiple geographic regions (Australia, Brazil, New Zealand and the UK). Results indicate ecological responses are not globally consistent and are instead dependent on both the region and the facet of invertebrate diversity considered, that is, taxonomic or functional trait structure. Invertebrate communities of Australia were most sensitive to deposited fine sediment, with the greatest rate of change in communities occurring when fine sediment cover was low (below 25% of the reach). Communities in the UK displayed a greater tolerance with most compositional change occurring between 30% and 60% cover. In both New Zealand and Brazil, which included the most heavily sedimented sampled streams, the communities were more tolerant or demonstrated ambiguous responses, likely due to historic environmental filtering of invertebrate communities. We conclude that ecological responses to fine sediment are not generalisable globally and are dependent on landscape filters with regional context and historic land management playing important roles.

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“…(Brunke, 1999;Evans & Wilcox, 2014;Lisle, 1989;Perret et al, 2018;Schälchli, 1992;Wooster et al, 2008). Collectively, these processes make gravel-bed rivers important for the transient storage of fine sediment (Mondon et al, 2021;Owens et al, 2005). Yet, field studies of fine sediment ingress in-situ are still relatively limited, and the methodologies currently available lack standardization to allow direct and easy comparison of field study results.…”

Section: Introductionmentioning

confidence: 99%

Challenges in measuring fine sediment ingress in gravel‐bed rivers using retrievable sediment trap samplers

Maltauro,

Stone,

Collins

et al. 2023

River Research & Apps

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Abstract“Excess” interstitial fine sediment (<2 mm) is known to cause deleterious impacts on streambed ecosystems. Current methodologies available to assess ingress and its vertical and horizontal components still lack standardization, and the accuracy of commonly used assessments is still debatable. Here, we evaluate three fine sediment trap designs that measure only vertical (V), only horizontal (H), and both vertical and horizontal (HV) ingress mechanisms. Sediment traps were deployed in triplicates to: (i) evaluate measurement variability within traps of the same type; (ii) evaluate the effects of trap design on particle size distributions of infiltrated fine sediment and; (iii) assess methodologies used to calculate vertical and horizontal ingress mechanisms. Ingress rates were recorded for each sediment trap during seven deployment periods (lasting from 2 to 10 days) at a range of flow conditions at four sites. A total of 252 traps were deployed. Results from the triplicate assessment of traps with the same design showed that most measurements presented high variability and that particle size distributions were significantly affected by trap design. Here, different sediment traps were able to estimate directional ingress mechanisms. However, direct comparison between HV with either H or V traps led to an overestimation of horizontal or vertical ingress mechanisms, respectively. Better estimations were found when comparing HV observations to half the accumulation in either H or V, due to the proportional trap volume available for each accumulation mechanism according to trap design.

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The scope for a system-based approach to determine fine sediment targets for chalk streams

Cited by 8 publications

References 158 publications

The sedimentology of gravel beds in groundwater‐dominated chalk streams: Implications for sediment modelling and management

The sedimentology of gravel beds in groundwater‐dominated chalk streams: Implications for sediment modelling and management

Freshwater invertebrate responses to fine sediment stress: A multi‐continent perspective

Challenges in measuring fine sediment ingress in gravel‐bed rivers using retrievable sediment trap samplers

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