Stream channels in peatlands: The role of biological processes in controlling channel form

Watters, Jeffrey R.; Stanley, Emily H.

doi:10.1016/j.geomorph.2006.07.015

Cited by 38 publications

(42 citation statements)

References 46 publications

(60 reference statements)

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“…In keeping with other research, the constraining effect of bank vegetation will be shown to be clearly evident in the Barrington peatland channels, where specific stream power values (typically b5 W/m 2 , Table 1) are balanced by relatively high bank strengths. Unlike channels in some other peatland systems (Watters and Stanley, 2007), we will demonstrate that the morphologies of the Barrington peatland channels are the product of both botanical and physical (discharge and sediment load) controls. Leopold and Maddock (1953) obtained empirically derived values of 0.5, 0.4, and 0.1 from a wide range of rivers as the exponents for b, f, and m in log-linear relationships between width, depth, and velocity (respectively) with downstream changes in the mean annual flood discharge (approximating bankfull discharge) as the independent variable.…”

Section: Barrington Peatland Channels: General Observationsmentioning

confidence: 65%

“…The hydraulic geometry of self-adjusting channels currently free of bedload transport has rarely been investigated (cf. Watters and Stanley, 2007) and is the focus of this study.…”

Section: Barrington Peatland Channels: General Observationsmentioning

confidence: 99%

“…Eaton and Giles (2008) obtained a similar finding in relatively unstable gravel bed streams, showing that vegetation dominated the geometry of relatively small streams but had virtually no effect on large ones. Watters and Stanley (2007) examined peatland channels in Wisconsin and concluded that biological forces had overridden physical drivers such as discharge and sediment load in determining peatland channel morphologies in those systems. High bank strength provided by fine, cohesive sediment (Schumm, 1960;Knighton, 1975;Millar and Quick, 1993) or vegetation and the associated tensile strength of roots (Zimmerman et al, 1967;Andrews, 1984;Hickin, 1984;Hey and Thorne, 1986;Thorne, 1990;Abernethy and Rutherfurd, 1998, 2001Huang and Nanson, 1998;Simon and Collison, 2002;Eaton and Giles, 2008) can allow for steep channel banks and low width hydraulic geometry exponents.…”

Section: Barrington Peatland Channels: General Observationsmentioning

confidence: 99%

“…However, these are very different to the sediment-free Barrington system because accreting sandy bedload is decreasing depths and eventually blocking the channels and causing avulsion. Watters and Stanley (2007) examined deep peatlands in Wisconsin formed by the long-term vegetative infilling of lakes. W/d ratios (mean depth) averaged 20 and the b, f and m exponents were −0.79, 0.40 and 1.5 (for b, f and m, respectively) This is remarkably different from the Barrington system, probably because these very low-energy groundwater-fed channels have no mineral substrate but rather a bed of loose semi-fluid, amorphous organic matter and banks, sometimes unstable, of living plants.…”

Section: At-a-station Summarymentioning

confidence: 99%

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The hydraulic geometry of narrow and deep channels; evidence for flow optimisation and controlled peatland growth

Nanson

Huang

2010

Geomorphology

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At-a-station and bankfull hydraulic geometry analyses of peatland channels at Barrington Tops, New South Wales, Australia, reveal adjustments in self-forming channels in the absence of sediment load. Using Rhodes ternary diagram, comparisons are made with hydraulic geometry data from self-forming channels carrying bedload in alluvial settings elsewhere. Despite constraints on channel depths caused at some locations by the restricted thickness of peat, most stations have cohesive, near-vertical, well-vegetated banks, and width/depth (w/d) ratios of similar to 2 that are optimal for sediment-free flow. Because banks are strong, resist erosion and can stand nearly vertical, and depth is sometimes constrained, adjustments to discharge are accommodated largely by changes in velocity. These findings are consistent with the model of maximum flow efficiency and the overarching least action principle in open channels. The bankfull depth of freely adjusting laterally active channels in clastic alluvium is well known to be related to the thickness of floodplain alluvium and a similar condition appears to apply to these swamps that grow in situ and are formed almost entirely of organic matter. The thickness of peat in these swamps rarely exceeds that required to form a bankfull channel of optimum w/d ratio for the transport of sediment-free water. Swamp vegetation is highly dependent on proximity to the water table. To maintain a swamp-channel and associated floodplain system, the channels must flow with sufficient water much of the time; they not only offer an efficient morphology for flow but do so in a way that enables bankfull conditions to occur many times a year. They also prevent the swamp from growing above a level linked to the depth of the channel. Once the channel attains the most efficient cross section, further growth of the swamp vertically is restricted by enhanced flow velocities and limited flow depths. This means that the volume of peat in such swamps is determined by the hydraulic efficiency of their channels. The development and maintenance of the hydraulic geometry of these swamp channels is biogeomorphic and biohydraulic in nature and yet accords to the same optimising principles that govern the formation of self-adjusting channels and floodplains in clastic alluvium. At-a-station and bankfull hydraulic geometry analyses of peatland channels at Barrington Tops, New South Wales, Australia, reveal adjustments in self-forming channels in the absence of sediment load. Using Rhodes ternary diagram, comparisons are made with hydraulic geometry data from self-forming channels carrying bedload in alluvial settings elsewhere. Despite constraints on channel depths caused at some locations by the restricted thickness of peat, most stations have cohesive, near-vertical, well-vegetated banks, and width/ depth (w/d) ratios of ∼ 2 that are optimal for sediment-free flow. Because banks are strong, resist erosion and can stand nearly vertical, and depth is sometimes constrained, adjustments to discharge are acc...

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Section: Barrington Peatland Channels: General Observationsmentioning

confidence: 65%

“…The hydraulic geometry of self-adjusting channels currently free of bedload transport has rarely been investigated (cf. Watters and Stanley, 2007) and is the focus of this study.…”

Section: Barrington Peatland Channels: General Observationsmentioning

confidence: 99%

Section: Barrington Peatland Channels: General Observationsmentioning

confidence: 99%

Section: At-a-station Summarymentioning

confidence: 99%

See 2 more Smart Citations

The hydraulic geometry of narrow and deep channels; evidence for flow optimisation and controlled peatland growth

Nanson

Huang

2010

Geomorphology

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“…Groundwater discharge to surface water is one of the most important physical controls on peatlands stability (Siegel et al, 1995;Watters and Stanley, 2007); yet the underlying physical hydrogeologic framework governing the development of surface seepage distribution in these systems is not well understood. Preferential flow paths, hydraulic conductivity (K) anisotropy, and geologic heterogeneities likely influence the surface expression of discharge zones (Chason and Siegel, 1986;Drexler et al, 1999;Smart et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Hydrogeological controls on spatial patterns of groundwater discharge in peatlands

Hare

Boutt

Clement

et al. 2017

Hydrol. Earth Syst. Sci.

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Abstract. Peatland environments provide important ecosystem services including water and carbon storage, nutrient processing and retention, and wildlife habitat. However, these systems and the services they provide have been degraded through historical anthropogenic agricultural conversion and dewatering practices. Effective wetland restoration requires incorporating site hydrology and understanding groundwater discharge spatial patterns. Groundwater discharge maintains wetland ecosystems by providing relatively stable hydrologic conditions, nutrient inputs, and thermal buffering important for ecological structure and function; however, a comprehensive site-specific evaluation is rarely feasible for such resource-constrained projects. An improved process-based understanding of groundwater discharge in peatlands may help guide ecological restoration design without the need for invasive methodologies and detailed sitespecific investigation.Here we examine a kettle-hole peatland in southeast Massachusetts historically modified for commercial cranberry farming. During the time of our investigation, a large process-based ecological restoration project was in the assessment and design phases. To gain insight into the drivers of site hydrology, we evaluated the spatial patterning of groundwater discharge and the subsurface structure of the peatland complex using heat-tracing methods and groundpenetrating radar. Our results illustrate that two groundwater discharge processes contribute to the peatland hydrologic system: diffuse lower-flux marginal matrix seepage and discrete higher-flux preferential-flow-path seepage. Both types of groundwater discharge develop through interactions with subsurface peatland basin structure, often where the basin slope is at a high angle to the regional groundwater gradient. These field observations indicate strong correlation between subsurface structures and surficial groundwater discharge. Understanding these general patterns may allow resource managers to more efficiently predict and locate groundwater seepage, confirm these using remote sensing technologies, and incorporate this information into restoration design for these critical ecosystems.

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CO₂ and CH₄ emissions from streams in a lake‐rich landscape: Patterns, controls, and regional significance

Crawford

Lottig

Stanley

et al. 2014

Global Biogeochemical Cycles

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133

121

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Aquatic ecosystems are important components of landscape carbon budgets. In lake-rich landscapes, both lakes and streams may be important sources of carbon gases (CO 2 and CH 4 ) to the atmosphere, but the processes that control gas concentrations and emissions in these interconnected landscapes have not been adequately addressed. We use multiple data sets that vary in their spatial and temporal extent during 2001-2012 to investigate the carbon gas source strength of streams in a lake-rich landscape and to determine the contribution of lakes, metabolism, and groundwater to stream CO 2 and CH 4 . We show that streams emit roughly the same mass of CO 2 (23.4 Gg C yr À1 ; 0.49 mol CO 2 m À2 d À1 ) as lakes at a regional scale (27 Gg C yr À1 ) and that stream CH 4 emissions (189 Mg C yr À1 ; 8.46 mmol CH 4 m À2 d À1 ) are an important component of the regional greenhouse gas balance. Gas transfer velocity variability (range = 0.34 to 13.5 m d À1 ) contributed to the variability of gas flux in this landscape. Groundwater inputs and in-stream metabolism control stream gas supersaturation at the landscape scale, while carbon cycling in lakes and deep groundwaters does not control downstream gas emissions. Our results indicate the need to consider connectivity of all aquatic ecosystems (lakes, streams, wetlands, and groundwater) in lake-rich landscapes and their connections with the terrestrial environment in order to understand the full nature of the carbon cycle.

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Stream channels in peatlands: The role of biological processes in controlling channel form

Cited by 38 publications

References 46 publications

The hydraulic geometry of narrow and deep channels; evidence for flow optimisation and controlled peatland growth

The hydraulic geometry of narrow and deep channels; evidence for flow optimisation and controlled peatland growth

Hydrogeological controls on spatial patterns of groundwater discharge in peatlands

CO₂ and CH₄ emissions from streams in a lake‐rich landscape: Patterns, controls, and regional significance

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Stream channels in peatlands: The role of biological processes in controlling channel form

Cited by 38 publications

References 46 publications

The hydraulic geometry of narrow and deep channels; evidence for flow optimisation and controlled peatland growth

The hydraulic geometry of narrow and deep channels; evidence for flow optimisation and controlled peatland growth

Hydrogeological controls on spatial patterns of groundwater discharge in peatlands

CO2 and CH4 emissions from streams in a lake‐rich landscape: Patterns, controls, and regional significance

Contact Info

Product

Resources

About

CO₂ and CH₄ emissions from streams in a lake‐rich landscape: Patterns, controls, and regional significance