Decadal-Timescale Estuarine Geomorphic Change Under Future Scenarios of Climate and Sediment Supply

Ganju, Neil K.; Schoellhamer, David H.

doi:10.1007/s12237-009-9244-y

Cited by 56 publications

(47 citation statements)

References 38 publications

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“…2 suggests that (i) neglecting the compounding impacts of flood drivers causes significant underestimation of failure probabilities; (ii) the assumption of independence between variables, when there is significant correlation, results in overestimation of failure probabilities; and (iii) SLR significantly increases the failure probability in the near future/midfuture in all of the cases studied here. For example, we consider New York, NY, which is projected to experience US$174 million per year of loss due to flooding if no further flood management measures are implemented (84). Based on the current conditions, the failure probability at the 20-y return level over a 10-y design life time (e.g., 2017-2026) is expected to be 0.40 based on univariate analysis, and 0.65 based on the bivariate OR analysis.…”

Section: Resultsmentioning

confidence: 99%

Compounding effects of sea level rise and fluvial flooding

Moftakhari

Salvadori

AghaKouchak

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

377

339

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Sea level rise (SLR), a well-documented and urgent aspect of anthropogenic global warming, threatens population and assets located in low-lying coastal regions all around the world. Common flood hazard assessment practices typically account for one driver at a time (e.g., either fluvial flooding only or ocean flooding only), whereas coastal cities vulnerable to SLR are at risk for flooding from multiple drivers (e.g., extreme coastal high tide, storm surge, and river flow). Here, we propose a bivariate flood hazard assessment approach that accounts for compound flooding from river flow and coastal water level, and we show that a univariate approach may not appropriately characterize the flood hazard if there are compounding effects. Using copulas and bivariate dependence analysis, we also quantify the increases in failure probabilities for 2030 and 2050 caused by SLR under representative concentration pathways 4.5 and 8.5. Additionally, the increase in failure probability is shown to be strongly affected by compounding effects. The proposed failure probability method offers an innovative tool for assessing compounding flood hazards in a warming climate.sea level rise | coastal flooding | compound extremes | copula | failure probability F looding hazard, characterized by the intensity/frequency of flood events (1), is an important consideration in local level planning and adaptation (2). Coastal cities are especially demanding sites for flood hazard assessment because of exposure to multiple flood drivers such as coastal water level (WL), river discharge, and precipitation (3, 4). Furthermore, dependence among the flood drivers [e.g., coastal surge/tide, sea level rise (SLR), and river flow] can lead to compound events (5) in which the simultaneous or sequential occurrence of extreme or nonextreme events may lead to an extreme event or impact (6). For example, in estuarine systems, the interplay between coastal WL and freshwater inflow determines the surface WL (and hence the flood probability) at subtidal (7) and tidal (8-11) frequencies.In the United States, flood hazard assessment practices are typically based on univariate methods. For example, procedures for rivers often treat oceanic contributions (e.g., tides and storm surges) using static base flood levels (e.g., ref. 12), and do not consider the dynamic effects of coastal WL (e.g., ref. 13). Similarly, flood hazard procedures for coastal WLs (e.g., ref. 14) do not account for terrestrial factors such as river discharge or direct precipitation into urban areas. Previous studies indicate that univariate extreme event analysis may not correctly estimate the probability of a given hydrologic event (15,16). This points to the potential importance of multivariate analysis of extreme events in coastal/estuarine systems and consideration of compounding effects between flood drivers (6). Bivariate extreme event analysis has been explored in a coastal context with different variables and in different areas (5, 17-33) (see SI Appendix, Table S2 for more details). B...

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Section: Resultsmentioning

confidence: 99%

Compounding effects of sea level rise and fluvial flooding

Moftakhari

Salvadori

AghaKouchak

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

377

339

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“…Currently, research effort is underway to predict future morphodynamic developments in San Pablo Bay and Suisun Bay (Ganju and Schoellhamer 2010). A central question in this research relating to bathymetric developments could be expected under different climate change scenarios.…”

Section: Area Of Interestmentioning

confidence: 99%

“…Numerical, 3D, process-based models (ROMS and Delft3D) are being used as tools. In order to validate these models, hindcasts of the depositional period (1856-1887; Ganju et al 2009; Van der Wegen et al, submitted) and the erosional period (1953-1983Ganju and Schoellhamer 2010) have been made.…”

Section: Area Of Interestmentioning

confidence: 99%

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Bed composition generation for morphodynamic modeling: case study of San Pablo Bay in California, USA

et al. 2010

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Applications of process-based morphodynamic models are often constrained by limited availability of data on bed composition, which may have a considerable impact on the modeled morphodynamic development. One may even distinguish a period of "morphodynamic spin-up" in which the model generates the bed level according to some ill-defined initial bed composition rather than describing the realistic behavior of the system. The present paper proposes a methodology to generate bed composition of multiple sand and/or mud fractions that can act as the initial condition for the process-based numerical model Delft3D. The bed composition generation (BCG) run does not include bed level changes, but does permit the redistribution of multiple sediment fractions over the modeled domain. The model applies the concept of an active layer that may differ in sediment composition above an underlayer with fixed composition. In the case of a BCG run, the bed level is kept constant, whereas the bed composition can change. The approach is applied to San Pablo Bay in California, USA. Model results show that the BCG run reallocates sand and mud fractions over the model domain. Initially, a major sediment reallocation takes place, but development rates decrease in the longer term. Runs that take the outcome of a BCG run as a starting point lead to more gradual morphodynamic development. Sensitivity analysis shows the impact of variations in the morphological factor, the active layer thickness, and wind waves. An important but difficult to characterize criterion for a successful application of a BCG run is that it should not lead to a bed composition that fixes the bed so that it dominates the "natural" morphodynamic development of the system. Future research will focus on a decadal morphodynamic hindcast and comparison with measured bathymetries in San Pablo Bay so that the proposed methodology can be tested and optimized.

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“…The Computational Assessments of Scenarios of Change for the Delta Ecosystem (CASCaDE II) project [2] is developing a better understanding of how potential future changes in the characteristics and climate of watersheds draining into the Bay-Delta will affect water quality, ecosystem processes, and critical species. Turbidity, geomorphic change, and wetland stability all depend on sediment supply; therefore, sediment supply has critical implications for the ecology of the Bay-Delta [3]. The total sediment load has decreased by 50% during the last 50 years for a suite of interacting reasons, including the diminishment of the sediment pulse created during 19th century hydraulic mining in the Sierra Nevada, sediment trapping behind reservoirs, deposition of sediment in flood bypasses, and armoring of river channels [4].…”

Section: Introductionmentioning

confidence: 99%

Characterizing Changes in Streamflow and Sediment Supply in the Sacramento River Basin, California, Using Hydrological Simulation Program—FORTRAN (HSPF)

Stern¹,

Flint²,

Minear³

et al. 2016

Water

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A daily watershed model of the Sacramento River Basin of northern California was developed to simulate streamflow and suspended sediment transport to the San Francisco Bay-Delta. To compensate for sparse data, a unique combination of model inputs was developed, including meteorological variables, potential evapotranspiration, and parameters defining hydraulic geometry. A slight decreasing trend of sediment loads and concentrations was statistically significant in the lowest 50% of flows, supporting the observed historical sediment decline. Historical changes in climate, including seasonality and decline of snowpack, contribute to changes in streamflow, and are a significant component describing the mechanisms responsible for the decline in sediment. Several wet and dry hypothetical climate change scenarios with temperature changes of 1.5 • C and 4.5 • C were applied to the base historical conditions to assess the model sensitivity of streamflow and sediment to changes in climate. Of the scenarios evaluated, sediment discharge for the Sacramento River Basin increased the most with increased storm magnitude and frequency and decreased the most with increases in air temperature, regardless of changes in precipitation. The model will be used to develop projections of potential hydrologic and sediment trends to the Bay-Delta in response to potential future climate scenarios, which will help assess the hydrological and ecological health of the Bay-Delta into the next century.

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Decadal-Timescale Estuarine Geomorphic Change Under Future Scenarios of Climate and Sediment Supply

Cited by 56 publications

References 38 publications

Compounding effects of sea level rise and fluvial flooding

Compounding effects of sea level rise and fluvial flooding

Bed composition generation for morphodynamic modeling: case study of San Pablo Bay in California, USA

Characterizing Changes in Streamflow and Sediment Supply in the Sacramento River Basin, California, Using Hydrological Simulation Program—FORTRAN (HSPF)

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