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Estuarine salinity: (a) observation sites from the FerryMon, MODMON, and PAMRIV monitoring projects and (b) model domain and initial conditions at the start of each model run.
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Pamlico Sound, a large back‐barrier estuary in North Carolina, is under threat of climate change due to increased storm activity and sea level rise. The response of this system is investigated by considering what has already happened during changes in sea level over the late Holocene epoch. The hydrodynamic changes that occurred in response to geom...
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... The Cedar Island Beach samples (n = 13) are of muddy estuarine sediments deposited within the last ~200 years (McBride et al., 2015) in an area with modern near-marine salinities of 30-34 psu (Ragone Calvo et al., 1998) although subject to lower salinities in the recent past (Hanley, 2015). The Currituck Inlet samples (n = 11) are of muddy estuarine sediments deposited between ~400 and 1700 years B.P. (Moran et al., 2014;Robinson and McBride, 2006) in an area with modern salinities of 0-10 psu (Mulligan et al., 2019). Two sample sets are from Louisiana: Core LBC on the Chenier coastal plain, and Core 19OCS-SI39 on the inner continental shelf of the Gulf of Mexico (water depth ~ 21 m). ...
... Floods are undoubtedly known as natural disasters, but in practice, floods are the most devastating natural disaster globally [1,2], both in terms of casualties and financial losses [3]. For example, floods can destroy agriculture and have severe effects on people's economy [4]. In recent decades, concerns about flood losses and damages have increased worldwide [5,6]. ...
According to the World Health Organization (WHO), floods are one of the most important natural disasters in the world, resulting in the severe loss of human lives and intense destruction of infrastructure. The frequent floods in recent decades have caused most parts of Iran to be affected by periodic and destructive floods. Consequently, the casualties and financial losses of floods have increased significantly. The present study aims to investigate redesigning the fuse plug, emergency overflow, and flood system at Ramshir Dam, Iran. In this regard, using a two-dimensional mathematical model, floods with a return period of 10 and 100 years with different scenarios have been investigated. Four scenarios were analyzed, including the current situation, flood channel dredging scenario, flood channel overhaul scenario, and flood channel overhaul scenario with reservoir dredging. The results show the following: (1) The flood channel in its current state cannot even discharge flows lower than the design, i.e., 1400 m³/s, and the flow overflows from the embankments on its sides. (2) Also, the reservoir dredging prevents the failure of the second fuse plug in the 100-year return period (flow rate 4370 m³/s). (3) Discharge more than 2400 m³/s cubic meters led to the activation of the first fuse plug. (4) The present research findings are of particular and essential importance in flood management. (5) The results of this research were based on the rehabilitation and simulation of the diversion dam facilities in the control and conveyance of flood and on three factors of spillway, flood channel, and flood plain, and the correct function of the fuse plug was reviewed.
... Once initialized, numerical circulation models require several computational cycles to achieve balance between the forcing and boundary conditions (Anderson and Gill 1975). This "spin-up" time is generally determined by observing the time it takes for model variables such as elevation or velocity to achieve quasi-steady values (Mulligan et al. 2019). The spin-up time ( T s ) of the OTB model was determined to be roughly 14-21 days, based on the convergence of the baseline model currents at two grid cells, both distant from the open boundary (Fig. 3). ...
Impermeable infrastructure such as traffic causeways can reduce the natural hydrodynamic flushing of an estuary, resulting in reduced water quality and increased incidence of harmful algal blooms (HABs). A series of cuts through the three causeways spanning Old Tampa Bay, FL, (OTB) are being considered to help restore the natural circulation of the region, but the number of possible location combinations is computationally challenging to fully assess. A prototype genetic algorithm (GA) was developed to identify the optimal configuration of these cuts through one of the bridge sections that maximizes flushing as represented in a numerical ocean circulation model of OTB. Flushing was measured by integrating the trajectories of over 21,000 passive Lagrangian “particles” using the model velocity fields. The rate of loss of particles initialized near Feather Sound (a region subject to frequent HABs) was used to quantify the “fitness” over which the configurations were optimized. The highest-scoring solution produced a 42% increase in net flushing compared to a no-change baseline. Six independently initialized applications of the GA were conducted. All converged to the same solution within no more than 7 generations. The small population size of the prototype allowed testing of the complete solution space, and verification the found solution was optimal. Elitism (preservation of the highest-ranking solution) was required for convergence. The GA also identified configurations that had similar, but slightly slower, flushing rates. These results will help area managers prioritize or rank combinations of causeway modifications to improve overall water quality conditions in Tampa Bay.
... A growing body of literature indicates that SLR induces variations to estuarine tidal structure, including tidal range, currents, and asymmetry, and thereby to water quality (e.g., salinity), eco-geomorphology, and associated feedback loops (Dessu et al., 2018;Khojasteh et al., 2023;Mulligan et al., 2019;Rayner et al., 2021). Understanding SLR-induced changes to the tidal range (i.e., the difference between high water and low water levels), is a useful proxy to learn about the response of estuarine processes to climate change (Haigh et al., 2020;Khojasteh et al., 2021b;Talke and Jay, 2020). ...
Climate change induced sea level rise (SLR) is one of the greatest challenges threatening the sustainable management of estuaries worldwide. Current knowledge regarding SLR and estuarine hydrodynamics is primarily focused on individual case studies, which provides limited guidance on how different estuary typologies will respond to SLR. To expand the current knowledge, this research used an idealised hydrodynamic approach to analyse the tidal range dynamics of 25 real-world estuaries with diverse shapes and boundary conditions, providing insights into estuarine response to SLR-induced tidal variations. Under present-day conditions, short length estuaries with wide entrances, deep waters, strong convergence, macro-tidal conditions, low values of roughness, and low upland river inflows are likely to experience amplified tidal range patterns; whereas lengthy estuaries with narrow entrances, shallow water depths, micro/meso-tidal conditions, high values of roughness, and high upland river inflows often exhibit a mix of dampened-amplified or fully dampened tidal range patterns. Under the effects of SLR, estuarine tidal range dynamics change depending on their present-day tidal range patterns. Where the present-day tidal range pattern is either dampening, a mix of dampening/amplification, or amplification, SLR increases (up to 61 %), moderately increases (up to 26 %), and slightly decreases/increases (up to 5 %) the tidal range of estuaries, respectively. Considering the relationship between an estuary's present-day tidal range pattern and its response to SLR, the presented approach may be useful in providing an initial assessment of SLR effects in estuaries worldwide. This may help to identify sites most impacted by future SLR, and to direct decision-making towards evidence-based management approaches.
... Several high-quality bathymetric and topographic data for this study have been combined in implementing the Delft3D FM. The entire western North Atlantic Ocean built using global SRTM15_PLUS bathymetry (Tozer et al. 2019), while NCEI Bathymetric Digital Elevation Model (30 m resolution) data has been utilized to enhance the representation of the bathymetry of the barrier island and Pamlico sound (Mulligan et al. 2019). These data are merged to create an unstructured grid mesh that spans much of the west Atlantic-the model domain extends from latitude 34.0° N and longitude 78.0° W to latitude 36.5° ...
Prediction and reanalysis of storm surge rely on wind and pressure fields from either parametric tropical cyclone wind models or numerical weather model reanalysis, and both are subject to large errors during landfall. This study assesses two sets of wind/pressure fields for Hurricane Florence that made landfall along the Carolinas in September 2018, and appraises the impacts of differential structural errors in the two suites of modeled wind fields on the predictive accuracy of storm surge driven thereby. The first set was produced using Holland 2010 (H10), and the second set is the Hurricane Weather Research and Forecasting (HWRF) reanalysis created by the NWS National Centers for Environmental Prediction (NCEP). Each is validated using a large surface data set collected at public and commercial platforms, and then is used as input forcing to a 2-D coastal hydrodynamic model (Delft3D Flexible Mesh) to produce storm surge along the Carolina coasts and major sounds. Major findings include the following. First, wind fields from HWRF are overall more accurate than those based on H10 for the periphery of the storm, though they exhibit limitations in resolving high wind speeds near the center. Second, applying H10 to the best track data for Florence yields an erroneously spike in wind speed on September 15th when the storm reduced to a tropical depression. Third, HWRF wind fields exhibit a progressively negative bias after landfall, likely due to deficiencies of the model in representing boundary layer processes, and to the lack of assimilation of surface product after landfall for compensating for these deficiencies. Fourth, using HWRF reanalysis as the forcings to Delft3D yields more accurate peak surges simulations, though there is severe underestimation of surge along the shoreline close to the track center. The peak surge simulations by Delft3D are biased low when driven by H10, even though over several locations the H10 model clearly overpredicts surface wind speeds. This contrast highlights the importance of resolving wind fields further away from the center in order to accurately reproduce storm surge and associated coastal flooding.
... While the SLR effects on salinity is a well-studied issue and general patterns are being elucidated (Ross et al., 2015), other important variables for benthic macroinvertebrates such as sediment still have high uncertainty. Numerical simulations of SLR influence on estuarine sediments transport suggest that for moderate scenarios (i.e., 30 cm in 2050) there is no expected change in the distribution of sediments, while for extreme scenarios (i.e., 100 cm in 2100) there is still great uncertainty about such changes due to the complexity of erosion and deposition processes (Mulligan et al., 2019). ...
The sea-level rise induced by climate change has caused impacts (e.g., floods and saline intrusion) in estuaries. In this work, we used monitoring data (salinity, sediment and taxa occurrence), simulated saline intrusion and Species Distribution Model to predict the spatial distribution of families in the estuary at two levels of SLR (0.5 m and 1 m) for two scenarios (moderate and extreme). For the simulation, we used the ensemble method applied to five models (MARS, GLM, GAM, RF and BRT). High AUC and TSS values indicated “good” to “excellent” accuracy. RF and GLM obtained the best and worst values, respectively. The model predicted local extinctions and new colonization in the upper estuarine zones. With the effects of climate change intensifying, it is extremely important that managers consider the use of predictive tools to anticipate the impacts of climate change on a local scale on species migration.
... Estuaries are assumed to experience prominent changes in morphology at a decadal timescale due to natural estuarine evolution and human activities (Besset et al., 2019;Zhang et al., 2022), implying the possibility of salinity redistributions and variations in response to these changes. Mulligan et al. (2019) found that the morphological changes induced by sedimentation in the Pamlico Sound Estuary (North Carolina, USA) affected the local hydrodynamics and salinity dynamics. The sea surface area in the Tokyo Bay, Japan has decreased due to land reclamation, and consequently, the salinity residence time decreased during the period 1947-1974to 2002(Okada et al., 2011. ...
... The Delft3D model solves the unsteady shallow water equations in two (depth-averaged) or three dimensions (Lesser et al., 2004). It has been widely used in numerical simulations of hydrodynamics (Hu et al., 2009;Martyr-Koller et al., 2017), salinity dynamics (Martyr-Koller et al., 2017;Mulligan et al., 2019), sediment dynamics (Boudet et al., 2017;Zhu et al., 2021) and morphodynamics (Luan et al., 2017;van der Wegen and Roelvink, 2008) for coastal and estuarine environments. The numerical model in this study is two-dimensional and only depth-averaged processes are included. ...
Salinity distributions and gradients within an estuary are of great socioeconomic and ecological importance. In this study, a well-validated and process-based hydrodynamic model (Delft3D) was applied to investigate the salinity distributions and variations in the Yangtze Estuary subject to river discharge regulation by the Three Gorges Reservoir and morphological evolution of the estuary. The results indicate that the regulation of river discharge is the controlling factor for salinity variations in the estuary. Following construction of the Three Gorges Reservoir, the salinity significantly decreased during the dry season and slightly increased during the flood season. The morphological evolution of the estuary induced spatial salinity variations and affected the salinity in the estuarine wetlands (the Jiuduansha Shoal and East Chongming Mudflat). The salinity in the Jiuduansha Shoal increased from 1998 to 2010, whereas it decreased from 2010 to 2018. During the period 1998 to 2018, the salinity in the East Chongming Mudflat exhibited an increasing trend. These findings provide implications for management of water resources and wetlands in the Yangtze and other similar estuaries.
... The integration of field data and numerical modelling also helps to test, quantify and visualize the spatio-temporal changes in tidal processes resulting from changes in basin configuration (Collins et al., 2021). For instance, in depositional basins, the sedimentary record can be interpreted and numerical models can be used to confirm or enhance knowledge of these systems (Mallinson et al., 2018;Mulligan et al., 2019b). This increased knowledge of past basins will improve understanding of how tidal processes will evolve in response to today's sea-level rise, including assisting coastal areas in their planning by demonstrating how and where the tidal regime will significantly change (Hayden et al., 2020). ...
... The geological record from the innermost Curtis Sea is relatively well-constrained (Gilluly & Reeside, 1928;Pipiringos & O'Sullivan, 1978;Kreisa & Moila, 1986;Caputo & Pryor, 1991;Wilcox & Currie, 2008;Doelling et al., 2013;Danise & Holland, 2017Zuchuat et al., 2018Zuchuat et al., , 2019aDanise et al., 2020) and was used to inform and interpret series of numerical modelling experiments in Delft3D. The methods employed in this study followed common practice for hydrodynamic modelling in present-day tidal basins (Hu et al., 2009;Elias et al., 2012;Brown et al., 2014;Mulligan et al., 2015;Mulligan et al., 2019b); however, the lack of observations of water levels and currents necessitate the use of geological interpretations of palaeoenvironmental conditions. The modelling of tides in the Upper Jurassic Sundance and Curtis seas used the Oxfordian palaeogeographical map ( Fig. 1) from Deep Time MapsÔ (Colorado Plateau Geosystems Inc. Maps), which was palaeogeoreferenced using GPlates and projected on a Lambert Conformal Conic projection. ...
... Various palaeophysiographies were generated by converting the maps to a physiographic raster (Python code; Appendix A) and importing them into Deltares open-source Delft3D numerical modelling software. Delft3D is a three-dimensional hydrodynamic simulation suite used for solving hydrostatic and nonhydrostatic equations (see Delft3D user manual for details), and it has been used to model a variety of coastal systems, including river deltas, beaches, estuaries, lagoons and barrier islands− inlet systems (Hu et al., 2009;Elias et al., 2012;Brown et al., 2014;Mulligan et al., 2015;Mulligan et al., 2019b). Due to the unknown true water depths and the need to investigate different realistic palaeophysiographies (Byrne et al., 2020), a series of different depth grids were generated using the colour-gradient in the original palaeogeographical map. ...
Simulating hydrodynamic conditions in palaeo‐ocean basins is needed to better understand the effects of tidal forcing on the sedimentary record. When combined with sedimentary analyses, hydrodynamic modelling can help inform complex temporal and spatial variability in the sediment distribution of tide‐dominated palaeo‐ocean basins. Herein, palaeotidal modelling of the epicontinental Upper Jurassic (160 Ma, lower Oxfordian) Sundance and Curtis Seas of North America reveals possible regional‐scale variations in tidal dynamics in response to changes in ocean tidal forcing, physiographic configuration and bottom drag coefficient. A numerical model forced with an M2 tidal constituent at the open boundary shows that the magnitude and location of tidal amplification, and the variability in current velocity and bed shear stress in the basin, were controlled by palaeophysiography. Numerical results obtained using a depth of 600 m at the ocean boundary of the system enable the prediction of major facies trends observed in the lower Curtis Formation. The simulation results also highlight that certain palaeophysiographic configurations can either permit or prevent tidal resonance, leading to an overall amplification or dampening of tides across the basin. Furthermore, some palaeophysiographic configurations generated additional tidal harmonics in specific parts of the basins. Consequently, similar sedimentary successions can emerge from a variety of relative sea‐level scenarios, and a variety of sedimentary successions may be deposited in different parts of the basin in any given relative sea‐level scenario. These results suggest that the interpretation of sedimentary successions deposited in strongly tide‐influenced basins should consider changes in tidal dynamics in response to changing sea level and basin physiography.
... The paleo-stormy period (1400e1675 CE) was recognized by Donnelly et al. (2015) as extending along the entire western North Atlantic region, suggesting that the increase in saltmarsh transgression rates at Jones and Long bays, >10 and 2 times higher than the subsequent paleo-quiescent period, respectively, was more widespread. In addition to frequent storm surge, the sites experienced a higher astronomical tidal range during the paleo-stormy period, a result of more inlets along the Outer Banks that increased connectivity between Pamlico Sound and the open ocean (Mallinson et al., 2011;Mulligan et al., 2019). The increase in storminess and higher astronomical tidal range, which could have been as much as 5 cm higher than present on average (Mulligan et al., 2019), extended inundation of the upland landward, driving the high rates of saltmarsh transgression observed at Jones and Long bays. ...
... In addition to frequent storm surge, the sites experienced a higher astronomical tidal range during the paleo-stormy period, a result of more inlets along the Outer Banks that increased connectivity between Pamlico Sound and the open ocean (Mallinson et al., 2011;Mulligan et al., 2019). The increase in storminess and higher astronomical tidal range, which could have been as much as 5 cm higher than present on average (Mulligan et al., 2019), extended inundation of the upland landward, driving the high rates of saltmarsh transgression observed at Jones and Long bays. As conditions became less stormy, the Outer Banks became more continuous, the astronomical tidal range decreased, and saltmarsh transgression rates decreased in response. ...
... This suggests that at the centennial time scale, an increase in storminess can be as effective as an increase in SLR at accelerating saltmarsh transgression across low-gradient upland areas. Like SLR, increased storminess at our sites caused elevated estuarine water level from surge and a higher astronomical tidal range from the additional inlets that increased exchange between the coastal ocean and Pamlico Sound (Mallinson et al., 2011;Mulligan et al., 2019). ...
Saltmarsh area is decreasing globally from natural and anthropogenic stressors. Accelerating relative sea-level rise (SLR) is projected to exacerbate losses if not offset by upland saltmarsh migration (transgression). In the absence of coastal upland development, saltmarsh transgression rates increase with accelerating SLR and lower upland surface gradients. Storm wind and surge stress coastal upland forests causing defoliation, uprooting, and soil salinization, which makes upland areas more habitable for saltmarsh species and can promote transgression. This study aims to elucidate the contribution of storms to saltmarsh transgression by reconstructing transgression rates over the past 600 years during stormy and non-stormy conditions and fast and slow SLR rates. Our reconstructions are based on the stratigraphic record and historical aerial photography at three sites in North Carolina, U.S.A. where low-gradient pocosin upland grades into expansive saltmarsh. When sea level was rising <0.9 mm yr⁻¹, saltmarsh transgression rates at the two sites where saltmarsh is > 100 years were an average of 2 and 10 times faster during a paleo-stormy period (1400–1675 CE) than a subsequent non-stormy period. After 1865 CE when SLR accelerated to 2.4 mm yr⁻¹, transgression rates were an average of 7 times faster than the preceding slow SLR non-stormy period. The two sites where the historical record was not confounded by dredging show transgression was 7 times faster and saltmarsh areas increased an average of 28% during stormy decades than non-stormy decades; however, the rate of transgression only increased at the site with greatest surge during the stormy period characterized by strong northeast winds. Modeled transgression rates, using the paleo-upland slope and a sea level curve, do not match observed transgression rates for the paleo-stormy and rapid SLR periods. Furthermore, the thickness of saltmarsh peat younger than 1957 CE is greater than what would be predicted from independent records of SLR. Changes in the elevation of the upland surface, which is composed of peat, contributes to the disparity between predicted and observed transgression rates. The upland surface elevation can keep pace with some rates of SLR through vertical accretion; however, salinization and decomposition of upland vegetation from storm surge plus SLR decreases the elevation of the paleo-upland surface and increases accommodation and transgression rates. Along low-gradient coastlines with pocosin upland areas, SLR, subsidence, and storminess are coupled in modulating transgression rates and those processes need to be included in forecasts of saltmarsh response to climate change.
... Estuarine processes are largely controlled by the interaction between climate-related changes in sea level, environmental factors, such as the oceanographic regime, sediment availability, and tectonics, as well as anthropogenic impacts [14][15][16][17][18][19]. The interplay of these factors results in a variety of different estuarine settings, ranging from wavedominated, microtidal estuaries to macrotidal estuaries with extensive gently sloping coastal plains [14]. ...
The rapid advance of remote sensing technology during the last few decades provides a new opportunity for measuring detectable estuarine spatial change. Although estuarine surface area and convergence are important hydraulic parameters often used to predict long-term estuarine evolution, the majority of automated analyses of channel plan view dynamics have been specifically written for riverine systems and have limited applicability to most of the estuaries in the world. This study presents MorphEst, a MATLAB-based collection of analysis tools that automatically measure estuarine planform geometry. MorphEst uses channel masks to extract estuarine length, convergence length, estuarine shape, and areal gain and loss of estuarine surface area due to natural or human factors. Comparisons indicated that MorphEst estimates closely matched with independent measurements of estuarine surface area (r = 0.99) and channel width (r = 0.92) of 39 estuaries along the South Korean coast. Overall, this toolbox will help to improve the ability to solve research questions commonly associated with estuarine evolution as it introduces a tool to automatically measure planform geometric features from remotely sensed imagery.
