The use of modeling and suspended sediment concentration measurements for quantifying net suspended sediment transport through a large tidally dominated inlet

Suspended sediment concentration is an important estuarine health indicator. Estuarine ecosystems rely on the maintenance of habitat conditions, which are changing due to direct human impact and climate change. This study aims to evaluate the impact of climate change relative to engineering measures on estuarine fine sediment dynamics and sediment budgets. We use the highly engineered San Francisco Bay-Delta system as a case study. We apply a process-based modeling approach (Delft3D-FM) to assess the changes in hydrodynamics and sediment dynamics resulting from climate change and engineering scenarios. The scenarios consider a direct human impact (shift in water pumping location), climate change (sea level rise and suspended sediment concentration decrease), and abrupt disasters (island flooding, possibly as the results of an earthquake). Levee failure has the largest impact on the hydrodynamics of the system. Reduction in sediment input from the watershed has the greatest impact on turbidity levels, which are key to primary production and define habitat conditions for endemic species. Sea level rise leads to more sediment suspension and a net sediment export if little room for accommodation is left in the system due to continuous engineering works. Mitigation measures like levee reinforcement are effective for addressing direct human impacts, but less effective for a persistent, widespread, and increasing threat like sea level rise. Progressive adaptive mitigation measures to the changes in sediment and flow dynamics Climatic Change (2017) resulting from sea level rise may be a more effective strategy. Our approach shows that a validated process-based model is a useful tool to address long-term (decades to centuries) changes in sediment dynamics in highly engineered estuarine systems. In addition, our modeling approach provides a useful basis for long-term, process-based studies addressing ecosystem dynamics and health.

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“…5). This behavior is observed in historical observations comparing wet and dry years (Erikson et al 2013;Wright and Schoellhamer 2004).…”

Section: Sediment Dynamicssupporting

confidence: 60%

How can climate change and engineered water conveyance affect sediment dynamics in the San Francisco Bay-Delta system?

et al. 2017

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“…The validation results are summarized in Appendix A. A detailed validation of the numerical scheme can be found in Wang et al () and the construction and validation of the Coastal Storm Modeling System across the region (Barnard et al, ; Elias & Hansen, ; Erikson et al, ; Martyr‐Koller et al, ). About 250 levees and seawalls (Doehring et al, ) are incorporated in the simulation to reproduce the existing shoreline configuration and 11 river discharges (McKee et al, ) are introduced to simulate the major freshwater sources in the area.…”

Section: Simulation Of Coastal Floodingmentioning

confidence: 99%

The Influence of Sea Level Rise on the Regional Interdependence of Coastal Infrastructure

et al. 2018

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Sea level rise (SLR) is placing both immediate and long‐term pressures on coastal communities to take protective actions. Projects in the United States, and in many locations throughout the world, generally involve local jurisdictions raising the elevation of shoreline protection elements, with limited or no analysis of the feedback between shoreline management decisions and the impacts to water levels regionally. Our study examines the impact of local shoreline development on regional flood risk and considers SLR scenarios up to 1.5 m using a large‐scale numerical model, as an example, for San Francisco Bay. Here we show that measures to prevent flooding along an embayment shoreline in one location or subregion may increase inundation elsewhere in the system. The network of interactions occurs not only within subbasins of the Bay but also across the greater geographic extent from one end of the Bay to the other, and local jurisdiction may have either reciprocal relationships with or asymmetric impacts on one other. Importantly, the nature of the interaction network is seen to evolve with SLR: interactions are purely subregional at current sea level but with higher sea level (e.g., 1 m of SLR), not only do the subregional interdependencies strengthen but also regional interdependences emerge.

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“…For evaluation of wave‐model skill (section 3.2.1), the effects of SLR (section 3.2.3), and sensitivity testing (see the supporting information), the SWAN model was coupled with a previously calibrated Delft3D circulation model [ Elias and Hansen , ; Erikson et al , ], extending into the Pacific Basic to accurately account for tidal exchange through the Golden Gate (see the supporting information). These simulations are run over multiple tidal cycles to capture the effects of water‐level changes, tidal impacts, and wave‐current interaction.…”

Section: Methodsmentioning

confidence: 99%

Downscaling wind and wavefields for 21st century coastal flood hazard projections in a region of complex terrain

O’Neill

Erikson

Barnard

2017

Earth and Space Science

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While global climate models (GCMs) provide useful projections of near-surface wind vectors into the 21st century, resolution is not sufficient enough for use in regional wave modeling. Statistically downscaled GCM projections from Multivariate Adaptive Constructed Analogues provide daily averaged near-surface winds at an appropriate spatial resolution for wave modeling within the orographically complex region of San Francisco Bay, but greater resolution in time is needed to capture the peak of storm events. Short-duration high wind speeds, on the order of hours, are usually excluded in statistically downscaled climate models and are of key importance in wave and subsequent coastal flood modeling. Here we present a temporal downscaling approach, similar to constructed analogues, for near-surface winds suitable for use in local wave models and evaluate changes in wind and wave conditions for the 21st century. Reconstructed hindcast winds recreate important extreme wind values within San Francisco Bay. A computationally efficient method for simulating wave heights over long time periods was used to screen for extreme events. Wave hindcasts show resultant maximum wave heights of 2.2 m possible within the Bay. Changes in extreme over-water wind speeds suggest contrasting trends within the different regions of San Francisco Bay, but 21th century projections show little change in the overall magnitude of extreme winds and locally generated waves Plain Language Summary Near-surface winds are temporally downscaled for use in historical and 21st century wave models. Extreme wave height events are identified using an efficient simulation method for long time periods. Potential changes in 21st century extreme wind and wave conditions are evaluated.

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The use of modeling and suspended sediment concentration measurements for quantifying net suspended sediment transport through a large tidally dominated inlet

Cited by 36 publications

References 28 publications

How can climate change and engineered water conveyance affect sediment dynamics in the San Francisco Bay-Delta system?

How can climate change and engineered water conveyance affect sediment dynamics in the San Francisco Bay-Delta system?

The Influence of Sea Level Rise on the Regional Interdependence of Coastal Infrastructure

Downscaling wind and wavefields for 21st century coastal flood hazard projections in a region of complex terrain

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