Reach-scale morphodynamics: Insights from 20 years of observations and model simulations

Al-Ghorani, Nisreen G.; Hassan, Marwan A.; Langendoen, Eddy J.

doi:10.1016/j.geomorph.2022.108375

Cited by 4 publications

(5 citation statements)

References 46 publications

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“…Therefore, the Carmel River evolved as expected for a largely vegetated, gravel-dominated river (e.g. Al-Ghorani et al, 2022) experiencing a relatively small sediment pulse.…”

Section: Contextualizing the Sediment Release From San Clementementioning

confidence: 81%

Six years of fluvial response to a large dam removal on the Carmel River, California, USA

East

Harrison

Smith

et al. 2023

Earth Surf Processes Landf

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Measuring river response to dam removal affords a rare, important opportunity to study fluvial response to sediment pulses on a large field scale. We present a before-after/control-impact study of the Carmel River, California, measuring fluvial geomorphic and grain-size evolution over 8 years, six of which postdated removal of a 32 m-high dam (one of the largest dams removed worldwide) and included 11 flow events exceeding the 2-year flood magnitude. We find that the reservoir-sediment pulse following dam removal was relatively small (97 000 ± 24 000 t over 4 years), owing to deliberate reservoir-sediment stabilization. Scaled to the size of the Carmel River watershed and compared against long-term bedrock denudation rates, the post-dam-removal sediment release was slightly less than the annualized long-term sediment export from this basin. New sediment transited >30 km to the river mouth in less than 2 years, assisted by floods 2 and 4 years after dam removal. The sediment pulse fined the downstream riverbed while causing mostly low-magnitude bed-elevation changes: commonly 0.5 to 1 m or smaller, occurring as discontinuous sediment patches or interstitial deposits, aside from the filling and subsequent partial scour of deep pools. There was no major geomorphic reset downstream from the dam site. Geomorphic changes were driven almost entirely by flow rather than by the modest increase in sediment supply, in contrast to recent examples from other large dam removals. The relatively minor disturbance caused by dam removal on the Carmel River is likely analogous to many future dam removals: a relatively small sediment pulse after deliberate limitation of reservoir-sediment erosion, and with an upstream dam remaining in place. Thus, a large dam removal need not lead to major downstream impacts.

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“…Therefore, the Carmel River evolved as expected for a largely vegetated, gravel-dominated river (e.g. Al-Ghorani et al, 2022) experiencing a relatively small sediment pulse.…”

Section: Contextualizing the Sediment Release From San Clementementioning

confidence: 81%

Six years of fluvial response to a large dam removal on the Carmel River, California, USA

East

Harrison

Smith

et al. 2023

Earth Surf Processes Landf

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“…Disconnectivity in turn controls the location and volume of sediment inputs to the channel and subsequently channel morphology, channel geometry, and bed texture . Channel characteristics determine the functioning of the fluvial system including channel stability and migration , flooding and its' geomorphic effectiveness (Al-Ghorani et al, 2022), and aquatic ecosystems (e.g., ). An understanding of disconnectivity is then required to interpret the system at different scales, both temporal (e.g., geomorphic effectiveness of floods relating to tectonic and glacial cycles), and spatial (e.g., channel bed texture relating to valley geometry).…”

Section: Introductionmentioning

confidence: 99%

“…, flooding and its' geomorphic effectiveness (Al-Ghorani et al, 2022), and aquatic ecosystems (e.g., ). An understanding of disconnectivity is then required to interpret the system at different scales, both temporal (e.g., geomorphic effectiveness of floods relating to tectonic and glacial cycles), and spatial (e.g., channel bed texture relating to valley geometry).…”

mentioning

confidence: 99%

Spatial patterns of disconnectivity explain catchment-scale sediment dynamics and transfer efficiencies

Turley

Hassan

2023

Preprint

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While connectivity studies are becoming common in the Earth sciences, disconnectivity has received much less attention. Sediment storage is the direct result of sediment disconnectivity and can provide concrete evidence of the spatial patterns of disconnectivity at the catchment-scale. In this study we explore the catchment-scale sediment dynamics of the Tahoma Creek watershed, a high-gradient glacio-volcanic landscape, within a sediment budget framework and identify and map sources of disconnectivity to determine if they explain the spatial patterns and estimated efficiencies of sediment transfers. We found that up to 80% of the total eroded sediment is sourced from the proglacial zone. The proglacial zone is characterized by high connectivity resulting from frequent debris flows and floods, and rapidly responds to changing conditions. Down valley however, sources of disconnectivity become increasingly more prevalent, the hillslopes become decoupled from the channel, and a majority of the eroded sediment is redeposited with as little as ~15% reaching the outlet. The spatial distribution of sources of disconnectivity and their upslope affected areas explains, to a large degree, catchment-scale sediment dynamics and sediment transfer efficiencies and is in close agreement with quantitative connectivity estimates. We find that steep, glaciated watersheds are predominantly disconnected over human timescales and suggest that disconnectivity is the dominant state of landscapes over most timescales of interest. Mapping sources of disconnectivity provides a straightforward and concrete approach to estimating system disconnectivity and can increase confidence when paired with quantitative indices.

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“…Disconnectivity in turn controls the location and volume of sediment inputs to the channel and subsequently channel morphology, channel geometry, and bed texture (Hassan et al., 2018; Reid et al., 2021). Channel characteristics determine the functioning of the fluvial system, including channel stability and migration (Eaton et al., 2020), flooding and its geomorphic effectiveness (Al‐Ghorani et al., 2022), and aquatic ecosystems (e.g., Cienciala & Hassan, 2013). An understanding of disconnectivity is then required to interpret the system at different scales, both temporal (e.g., geomorphic effectiveness of floods relating to tectonic and glacial cycles), and spatial (e.g., channel bed texture relating to valley geometry).…”

Section: Introductionmentioning

confidence: 99%

Spatial Patterns of Disconnectivity Explain Catchment‐Scale Sediment Dynamics and Transfer Efficiencies

Turley

Hassan

2023

JGR Earth Surface

Self Cite

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While connectivity studies are becoming common in the Earth sciences, disconnectivity has received much less attention. Sediment storage is the direct result of sediment disconnectivity and can provide concrete evidence of the spatial patterns of disconnectivity at the catchment‐scale. In this study, we explore the catchment‐scale sediment dynamics of the Tahoma Creek watershed, a high‐gradient glacio‐volcanic landscape, within a sediment budget framework and identify and map sources of disconnectivity to determine whether they explain the spatial patterns and estimated efficiencies of sediment transfers. We found that up to 80% of the total eroded sediment is sourced from the proglacial zone. The proglacial zone is characterized by high connectivity resulting from frequent debris flows and floods, and rapidly responds to changing conditions. Down valley, however, sources of disconnectivity become increasingly more prevalent, the hillslopes become decoupled from the channel, and a majority of the eroded sediment is redeposited with as little as ∼15% reaching the outlet. The spatial distribution of sources of disconnectivity and their upslope affected areas explains, to a large degree, catchment‐scale sediment dynamics and sediment transfer efficiencies and is in close agreement with quantitative connectivity estimates. We find that steep, glaciated watersheds are predominantly disconnected over human timescales and suggest that disconnectivity is the dominant state of landscapes over most timescales of interest. Mapping sources of disconnectivity provides a straightforward and concrete approach to estimating system disconnectivity and can increase confidence when paired with quantitative indices.

show abstract

Reach-scale morphodynamics: Insights from 20 years of observations and model simulations

Cited by 4 publications

References 46 publications

Six years of fluvial response to a large dam removal on the Carmel River, California, USA

Six years of fluvial response to a large dam removal on the Carmel River, California, USA

Spatial patterns of disconnectivity explain catchment-scale sediment dynamics and transfer efficiencies

Spatial Patterns of Disconnectivity Explain Catchment‐Scale Sediment Dynamics and Transfer Efficiencies

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