Seasonal Controls on Sediment Delivery and Hydrodynamics in a Vegetated Tidally Influenced Interdistributary Island

Styles, Richard; Snedden, Gregg A.; Smith, S. Jarrell; Bryant, Duncan B.; Boyd, Brandon; Gailani, Joseph Z.; Couvillion, Brady R.; Race, E.

doi:10.1029/2020jc016146

Cited by 9 publications

(9 citation statements)

References 51 publications

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“…Yet, even without the confirmation of detailed chemical analysis, this seasonal shift in SE‐channel turbidity coupled with the seasonally consistent import suggest that sediment resuspended from the clinoform or transported from nearby river systems can be deposited on land surfaces. Coastal sediment recycling has been observed in other well‐studied deltas such as the Mekong in Vietnam (Fricke et al ., 2017), Ganges‐Brahmaputra in Bangladesh (Rogers et al ., 2013; Hale et al ., 2019) and Wax Lake in the USA (Styles et al ., 2021). This recycling increases the short‐term capacity for the subaerial delta to keep pace with sea‐level rise (Yang et al ., 2020), at least until the submarine delta is depleted (Nienhuis et al ., 2020).…”

Section: Discussionmentioning

confidence: 99%

“…These deviations in salinity were either driven by salt exchange with groundwater or long residence times of previously imported water from the river, as they would not be produced by the seasonal rainfall patterns. Similarly, in the microtidal Wax Lake Delta, intra‐island residence times for water were significantly greater than those in adjacent channels (Hiatt & Passalacqua, 2015; Hiatt et al ., 2018) and substantially altered deltaic fluxes of nutrients (Styles et al ., 2021). These observations in Meinmahla Island demonstrate that there are comparably long intra‐island residence times in ME channels of a macrotidal environment.…”

Section: Discussionmentioning

confidence: 99%

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Pathways for sediment transport and retention in a vegetated, mid‐channel island: Connecting sediment dynamics to morphology in Meinmahla Island, Ayeyarwady Delta, Myanmar

et al. 2022

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Vegetated mid-channel islands play an important though poorly understood role in the sediment dynamics and morphology of tide-dominated deltas. Meinmahla Island is a mangrove-forest preserve at the mouth of the Bogale distributary channel, in the Ayeyarwady Delta, Myanmar. In this relatively unaltered mid-channel island, sediment dynamics can be directly connected to morphology. Field measurements from 2017 to 2019 provide insight into the pathways for sediment transport and resulting morphological evolution. Water depth, salinity and turbidity were monitored semi-continuously, and velocity profilers with turbidity and salinity sensors were deployed seasonally in single-entrance (dead-end/blind) and multi-entrance tidal channels of the island. The morphological evolution was evaluated using grain size, 210 Pb geochronology, remote sensing and channel surveys. The data show that ebb-dominant, single-entrance channels along the island exterior import sediment year-round to the land surface. However, these exterior channels do not deliver enough sediment to maintain the observed ca 0.8 cm/yr accretion rate, and most of the sediment import occurs via interior, multientrance channels. Interior channels retain water masses that are physically distinct from the water in the Bogale distributary, and estuarine processes at the tidal-channel mouths import sediment into the island. Sediment is sourced to the island from upriver in the wet season and from the Gulf of Mottoma in the dry season, as the location of the estuary shifts seasonally within the Bogale distributary. The salinity and biogeochemistry of the distributary water are affected by interactions with sediment and groundwater in the island interior. The largest interior channels have remained remarkably stable while the island has aggraded and prograded over decadal timescales. However, the studied multi-entrance channel is responding to a drainage-network change by narrowing and shoaling. Overall, mid-channel islands trap sediment and associated nutrients at the river-ocean interface, and these resilient landscape features evolve in response to changes in drainage-network connectivity.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Pathways for sediment transport and retention in a vegetated, mid‐channel island: Connecting sediment dynamics to morphology in Meinmahla Island, Ayeyarwady Delta, Myanmar

et al. 2022

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“…Wetland vegetation has a strong influence on sediment transport in river deltas 13 , 14 . It is widely believed that vegetation enhances sedimentation in both fresh- and saltwater marshes as vegetation increases hydraulic roughness, which reduces flow velocity 15 , enhancing sediment retention, stabilizing deposited sediment, and minimizing erosion 16 , 17 However, some field observations and numerical models have shown that vegetation does not always enhance sedimentation on deltaic marshes 13 , 18 .…”

Section: Introductionmentioning

confidence: 99%

“…Based on typical conditions in marshes 18 – 21 , 16 base cases considered vegetation area density n = 0 to 500 stems/m 2 , with stem diameter d = 1.0 cm, water depth H = 0.3 m, and water surface slope S = 0.0005. To consider seasonal effects on vegetation growth and water flux 14 , additional slopes ( S = 0.00025 and 0.001) and stem diameters ( d = 0.5 and 1.5 cm) were considered, for a total of 80 cases. Finally, the model was compared to a field study within the MRD, reported in ref.…”

Section: Introductionmentioning

confidence: 99%

Competing effects of vegetation density on sedimentation in deltaic marshes

et al. 2022

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Marsh vegetation, a definitive component of delta ecosystems, has a strong effect on sediment retention and land-building, controlling both how much sediment can be delivered to and how much is retained by the marsh. An understanding of how vegetation influences these processes would improve the restoration and management of marshes. We use a random displacement model to simulate sediment transport, deposition, and resuspension within a marsh. As vegetation density increases, velocity declines, which reduces sediment supply to the marsh, but also reduces resuspension, which enhances sediment retention within the marsh. The competing trends of supply and retention produce a nonlinear relationship between sedimentation and vegetation density, such that an intermediate density yields the maximum sedimentation. Two patterns of sedimentation spatial distribution emerge in the simulation, and the exponential distribution only occurs when resuspension is absent. With resuspension, sediment is delivered farther into the marsh and in a uniform distribution. The model was validated with field observations of sedimentation response to seasonal variation in vegetation density observed in a marsh within the Mississippi River Delta.

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“…However, these methods rely on elevation maps acquired months to years apart, making it impossible to mechanistically link specific hydrodynamic or environmental conditions to bathymetric change. Bathymetric change is sensitive to a variety of factors, including floods, cold fronts, hurricanes, tides, wind, and vegetation (Bevington et al, 2017;Carle et al, 2015;Styles et al, 2021). Remote-sensed synoptic measurement of deposition and erosion would provide a way to directly link specific processes to resulting patterns of bathymetric evolution.Several studies have derived relationships between suspended sediment concentration (SSC) and remotely-sensed spectral radiance in order to generate maps of SSC (Curran & Novo, 1988;Peckham, 2008;Van der Wal et al, 2010).…”

mentioning

confidence: 99%

Spatial Patterns of Deltaic Deposition/Erosion Revealed by Streaklines Extracted From Remotely‐Sensed Suspended Sediment Concentration

Salter

Passalacqua

Wright

et al. 2022

Geophysical Research Letters

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Deltas are vulnerable landscapes, making it crucial to understand their spatial patterns of deposition/erosion. Here, we used patterns in suspended sediment concentration (SSC) measured by a NASA airborne spectrometer, AVIRIS‐NG, to infer deposition/erosion within Wax Lake Delta, Louisiana. Conceptually, change in SSC within a fluid parcel traveling downstream reflects settling and/or entrainment from the bed. We found that remotely‐sensed SSC displays curvilinear features, which we interpret as streaklines. We developed a semi‐automated technique for extracting streaklines using a cost function based on SSC and its geometric curvature. We measured SSC change along streaklines, which when combined with flow velocities obtained from a hydrodynamic model, allowed us to infer instantaneous deposition/erosion rates. These rates are realistic in magnitude and record coherent spatial patterns across the delta. Our novel method provides a promising avenue for relating spatial patterns of land change to flow conditions over wide areas in vulnerable deltas.

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Seasonal Controls on Sediment Delivery and Hydrodynamics in a Vegetated Tidally Influenced Interdistributary Island

Cited by 9 publications

References 51 publications

Pathways for sediment transport and retention in a vegetated, mid‐channel island: Connecting sediment dynamics to morphology in Meinmahla Island, Ayeyarwady Delta, Myanmar

Pathways for sediment transport and retention in a vegetated, mid‐channel island: Connecting sediment dynamics to morphology in Meinmahla Island, Ayeyarwady Delta, Myanmar

Competing effects of vegetation density on sedimentation in deltaic marshes

Spatial Patterns of Deltaic Deposition/Erosion Revealed by Streaklines Extracted From Remotely‐Sensed Suspended Sediment Concentration

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