: The Department of Defense (DoD) has identified climate change as a risk to its infrastructure a... more : The Department of Defense (DoD) has identified climate change as a risk to its infrastructure and is seeking to develop efficient and effective processes to assess the vulnerability of its assets to this risk. Responding to this need, we developed, piloted, and evaluated an approach for vulnerability assessment keyed to DoD decision-making needs and processes at multiple organizations levels. We developed and tested methods for use in an overall assessment framework, and a process for assessments at installations that applies extensive stakeholder involvement, a novel approach to providing climate information (likely future exposure), a range of existing models and approaches for estimating impacts, and decision making frameworks.
Wave resource assessment requires accurate calculation of the wave resource parameters recommende... more Wave resource assessment requires accurate calculation of the wave resource parameters recommended by the International Electrotechnical Commission (IEC) based on high-resolution wave hindcasts. Recent development of unstructured-grid modeling techniques demonstrates the advantages of using unstructured-grid modeling frameworks in simulating wave climates, especially in coastal regions that have complex coastlines, islands, shallow-water bays, and estuaries. The study reported herein evaluated the performance of an unstructured-grid wave model in comparison to a structured-grid model for predicting the IEC wave energy resource parameters at a common test bed site. Model skill was assessed using a set of model performance error statistics. The sensitivity of open boundary conditions and wind forcing on model results, computational efficiency, and the advantages and limitations of the unstructured-grid model were investigated. This modeling test bed study of wave resource characterization using unstructured-grid wave spectral model SWAN (UNSWAN) on the Level 4 (L4) grids and the extended grids built upon a previous model test bed study (by Sandia National Laboratories [SNL] and Pacific Northwest National Laboratory [PNNL]) of resource characterization that focused on structured-grid wave models. The PNNL study reported herein investigated model performance in simulating the IEC Technical Specification's six recommended wave energy resource parameters-omnidirectional wave power, significant wave height, energy period, spectral width, direction of maximum directionally resolved wave power, and the directionality coefficient-using UNSWAN. It identified the advantages and limitations of unstructuredgrid models in comparison to structured-grid models at the same test bed used in the previous joint study by SNL and PNNL. Model configuration and forcing used in the structured-grid model test bed study were adopted for consistency, and a four-level nested-grid approach-from the global WAVEWATCH III (WWIII) model to the local test bed-was used. All UNSWAN simulations conducted during this study were configured with spectral resolutions of 29 frequency bins and 24 direction bins. Climate Forecast System Reanalysis wind data with 0.5-degree spatial resolution and hourly temporal resolution were used to drive all the model runs. For all model test cases-WWIII (ST2), UNSWAN (ST2), UNSWAN (ST4), and UNSWAN-EX (ST2)-time series of the six IEC parameters showed good agreement with those calculated from National Data Buoy Center buoy data. The predicted time series for these six parameters from the UNSWAN model, with both ST2 and ST4 physical packages, are comparable to those from the present study's WWIII (ST2) model. This provides confidence in the UNSWAN model settings, although small differences between WWIII and UNSWAN simulations were observed. The performance of unstructured-grid SWAN on the L4 grid and on the extended grid was investigated. The number of nodes on the L4 grid is nearly two times that of those on the extended grid, but the extended UNSWAN features half of the computational time and more spatial variability for the wave resources assessment. This study demonstrates that unstructured-grid wave modeling provides advantages in computational efficiency and therefore is a practical approach for simulating wave climates near complex geometries that have localized high grid resolution within a large model domain. v
This paper presents an application of a hydrodynamic model to simulate tidal energy extraction in... more This paper presents an application of a hydrodynamic model to simulate tidal energy extraction in a tidal dominated estuary in the Pacific Northwest coast. A series of numerical experiments were carried out to simulate tidal energy extraction with different turbine array configurations, including location, spacing and array size. Preliminary model results suggest that array optimization for tidal energy extraction in a real-world site is a very complex process that requires consideration of multiple factors. Numerical models can be used effectively to assist turbine siting and array arrangement in a tidal turbine farm for tidal energy extraction.
The International Journal of Ocean and Climate Systems, 2011
It is a great challenge to specify meteorological forcing in estuarine and coastal circulation mo... more It is a great challenge to specify meteorological forcing in estuarine and coastal circulation modeling using observed data because of the lack of complete datasets. As a result of this limitation, water temperature is often not simulated in estuarine and coastal modeling, with the assumption that density-induced currents are generally dominated by salinity gradients. However, in many situations, temperature gradients could be sufficiently large to influence the baroclinic motion. In this paper, we present an approach to simulate water temperature using outputs from advanced meteorological models. This modeling approach was applied to simulate annual variations of water temperatures of Puget Sound, a fjordal estuary in the Pacific Northwest of USA. Meteorological parameters from North American Region Re-analysis (NARR) model outputs were evaluated with comparisons to observed data at real-time meteorological stations. Model results demonstrated that NARR outputs can be used to drive...
A 3D hydrodynamic and sediment transport modeling analysis was conducted to evaluate the feasibil... more A 3D hydrodynamic and sediment transport modeling analysis was conducted to evaluate the feasibility of restoring natural fish habitat in the Skagit River estuary, located in the northern Puget Sound, Washington. The Cottonwood Island restoration site is located where the north and the south forks of the Skagit River bifurcate approximately 10 river miles upstream from the mouth of the river. The study site is a riverine tidal and floodplain forest zone which is influenced by tide but not mixed with marine water, and is periodically inundated by flooding events. Fish habitat and migration pathway in the area was lost due to sedimentation in the channel around Cottonwood Island. Restoration actions were proposed to reconnect the channel sloughs to the main stem of the river to restore fish habitat. The analysis focused on estimating the potential for success associated with the proposed three restoration alternatives including dike setback and channel modification. In this study, the unstructured Finite Volume Coastal Ocean Model (FVCOM) was used to evaluate the effects of proposed alternatives on hydrodynamic response and potential channel re-sedimentation. The numerical model was calibrated with ADCP and CTD measurements. The calibrated hydrodynamic model was used to drive the sediment transport model to calculate sediment erosion and deposition patterns under different flow conditions. The model was applied to baseline and alternative conditions for 5 different flood hydrographs (1-yr, 2-yr, 5-yr, 10-yr, 25-yr). Model results for the alternatives were compared with baseline condition to assess the relative effects and potential re-sedimentation.
In this report we describe 1) the development, test, and validation of the marine hydrokinetic en... more In this report we describe 1) the development, test, and validation of the marine hydrokinetic energy scheme in a three-dimensional coastal ocean model (FVCOM); and 2) the sensitivity analysis of effects of marine hydrokinetic energy configurations on power extraction and volume flux in a coastal bay. Submittal of this report completes the work on Task 2.1.2, Effects of Physical Systems, Subtask 2.1.2.1, Hydrodynamics and Subtask 2.1.2.3, Screening Analysis, for fiscal year 2011 of the Environmental Effects of Marine and Hydrokinetic Energy project. v Project Overview Energy generated from the world's oceans and rivers offers the potential to make substantial contributions to the domestic and global renewable energy supply. The U.S. Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy (EERE) Wind and Water Power Program supports the emerging marine and hydrokinetic (MHK) energy industry. As partners in an emerging industry, MHK project developers face challenges with siting, permitting, construction, and operation of pilot-and commercial-scale facilities, as well as the need to develop robust technologies, secure financing, and gain public acceptance. In many cases, little is known about the potential effects of MHK energy generation on the aquatic environment from a small number of devices or a large-scale commercial array. Nor do we understand potential effects that may occur after years or decades of operation. This lack of knowledge affects the solvency of the industry, the actions of regulatory agencies, the opinions and concerns of stakeholder groups, and the commitment of energy project developers and investors. vii Acronyms and Abbreviations 1-D one-dimensional 2-D two-dimensional 3-D three-dimensional
To re-establish the intertidal wetlands with full tidal interaction and improve salmonid rearing ... more To re-establish the intertidal wetlands with full tidal interaction and improve salmonid rearing habitat in the Lower Snohomish River estuary, the Everett Public Works Department restored the Union Slough project site in 2007 by breaching the existing dike and constructing bridges across the breaches. Pacific Northwest National Laboratory (PNNL) was contracted by the U.S. Amy Corps of Engineers to conduct a modeling study to evaluate additional project design scenarios at the restoration site for potential improvement of drainage conditions. In this study, a three-dimensional Snohomish River estuary model previously developed by PNNL was updated with fine-grid resolution for the Union Slough project site and validated with observed water level data collected in the project site and Union Slough. The drainage area percentage throughout entire range of tidal conditions was predicted for a number of proposed restoration alternatives. This study report summarizes the modeling approach, the data used, model validation, and model application results. The structure of the report is as follows. The methodology of the study is described in Section 2. Model validation to the new existing condition of the project site is presented in Section 3. Error statistics for model validation and uncertainty of the model analysis are provided in Section 4. Model applications to proposed restoration scenarios are presented in Sections 5 and 6. A summary of this study and recommendations are provided in Section 7. References are given in Section 8.
To re-establish the intertidal wetlands with full tidal exchange and improve salmonid rearing hab... more To re-establish the intertidal wetlands with full tidal exchange and improve salmonid rearing habitat in the Skagit River estuary, State of Washington, USA, a diked agriculture farm land along the Skagit Bay front is proposed to be restored to a fully functional tidal wetland. The complex and dynamic Skagit River estuarine system calls for the need of a multi-facet and multi-dimensional analysis using observed data, numerical and analytical methods. To assist the feasibility study of the restoration project, a hydrodynamic modeling analysis was conducted using a high-resolution unstructured-grid coastal ocean model to evaluate the hydrodynamic response to restoration alternatives and to provide guidance to the engineering design of a new levee in the restoration site. A set of parameters were defined to quantify the hydrodynamic response of the nearshore restoration project, such as inundation area, duration of inundation, water depth and salinity of the inundated area. To assist the design of the new levee in the restoration site, the maximum water level near the project site was estimated with consideration of extreme high tide, wind-induced storm surge, significant wave height and future sea-level rise based on numerical model results and coastal engineering calculation.
Hydropower reservoirs impounded by high-head dams exhibit complex circulation which confuses the ... more Hydropower reservoirs impounded by high-head dams exhibit complex circulation which confuses the downstream migrating salmon and limits successful collection and passage of fish. Fish passage engineers attempt to modify the hydrothermal behavior at reservoirs through structural and operational modi fications and use hydrodynamic simulations to guide their actions. Simulation of key hydrothermal processes such as (a) development of a stable 2-layer stratified system, (b) density driven currents over the reservoir length, and (c) discharge hydraulics near the power generation and fish collection intakes, require highly specialized models applied at differing temporal and spatial scales. A staged modeling approach is presented which uses external coupling of models of varying temporal scales and spatial resolution to simulate the entire hydraulic regime from the mouth of the reservoir at the upstream end to the discharge at the dam. The staged modeling approach is illustrated using a case study where operational modifications are being evaluated to improve reservoir stratification and density driven currents. The model results provide input and valuable insight in the development of a new structure design and configuration for effective fish collection near the forebay of a high head dam.
Through extensive field data collection and analysis efforts conducted since the 1950s, researche... more Through extensive field data collection and analysis efforts conducted since the 1950s, researchers have established an understanding of the characteristic features of circulation in Puget Sound. The pattern ranges from the classic fjordal behavior in some basins, with shallow brackish outflow and compensating inflow immediately below, to the typical two-layer flow observed in many partially mixed estuaries with saline inflow at depth. An attempt at reproducing this behavior by fitting an analytical formulation to past data is presented, followed by the application of a three-dimensional circulation and transport numerical model. The analytical treatment helped identify key physical processes and parameters, but quickly reconfirmed that response is complex and would require site-specific parameterization to include effects of sills and interconnected basins. The numerical model of Puget Sound, developed using unstructured-grid finite volume method, allowed resolution of the sub-basin geometric features, including presence of major islands, and site-specific strong advective vertical mixing created by bathymetry and multiple sills. The model was calibrated using available recent short-term oceanographic time series data sets from different parts of the Puget Sound basin. The results are compared against 1) recent velocity and salinity data collected in Puget Sound from 2006 and 2) a composite data set from previously analyzed historical records, mostly from the 1970s. The results highlight the ability of the model to reproduce velocity and salinity profile characteristics, their variations among Puget Sound subbasins, and tidally averaged circulation. Sensitivity of residual circulation to variations in freshwater inflow and resulting salinity gradient in fjordal sub-basins of Puget Sound is examined.
In this study, a storm surge model of the Salish Sea was developed to simulate storm surge in Pug... more In this study, a storm surge model of the Salish Sea was developed to simulate storm surge in Puget Sound using the unstructured-grid, finite-volume community ocean model (FVCOM). The model was based on Pacific Northwest National Laboratory's existing Puget Sound hydrodynamic model that has been validated extensively in previous studies. To identify representative historical storm events, a systematic approach was developed based on the nontidal residual (NTR) method. A total of 34 storm surge events between 1980 and 2016 were identified and simulated. To accurately simulate storm surge inside Puget Sound, the model was driven by reanalyzed Climate Forecast System Reanalysis meteorological forcing and observed water levels at the entrance of Strait of Juan de Fuca and southern entrance of Johnstone Strait. Model results for total water level, storm surge, and currents were compared with field measurements. A series of error statistics parameters were also calculated to quantify the model's skills in simulating storm surge in the Salish Sea. Error statistics of model performance metrics demonstrated that the Salish Sea storm surge model was able to simulate storm surge inside Puget Sound with high accuracy. Storm surge propagation into Puget Sound is a nonlinear process that cannot be simply determined by a static approach for the entire domain. The maximum NTR distribution inside Puget Sound suggests that storm surge tends to be amplified in several sub-basins and inlets of the Puget Sound, such as Bellingham Bay, Hood Canal, south Puget Sound, and the multi-inlet basin behind Agate and Rich Passages. Therefore, future study is necessary to further quantify the storm surge level in these high-risk areas through field measurements and refined model simulations.
The northern coasts of the Gulf of Mexico (GoM) are highly vulnerable to the direct threats of cl... more The northern coasts of the Gulf of Mexico (GoM) are highly vulnerable to the direct threats of climate change, such as hurricane-induced storm surge, and such risks are exacerbated by land subsidence and global sea-level rise. This paper presents an application of a coastal storm surge model to study the coastal inundation process induced by tide and storm surge, and its response to the effects of land subsidence and sea-level rise in the northern Gulf coast. The unstructured-grid finite-volume coastal ocean model was used to simulate tides and hurricane-induced storm surges in the GoM. Simulated distributions of co-amplitude and co-phase lines for semi-diurnal and diurnal tides are in good agreement with previous modeling studies. The storm surges induced by four historical hurricanes (Rita, Katrina, Ivan, and Dolly) were simulated and compared to observed water levels at National Oceanic and Atmospheric Administration tide stations. Effects of coastal subsidence and future global sea-level rise on coastal inundation in the Louisiana coast were evaluated using a ''change of inundation depth'' parameter through sensitivity simulations that were based on a projected future subsidence scenario and 1-m global sea-level rise by the end of the century. Model results suggested that hurricane-induced storm surge height and coastal inundation could be exacerbated by future global sea-level rise and
Along the Pacific Northwest coast, much of the estuarine habitat has been lost over the last cent... more Along the Pacific Northwest coast, much of the estuarine habitat has been lost over the last century to agricultural land use, residential and commercial development, and transportation corridors. As a result, many of the ecological processes and functions have been disrupted. To protect and improve these coastal habitats that are vital to aquatic species, many projects are currently underway to restore estuarine and coastal ecosystems through dike breaches, setbacks, and removals. Understanding site-specific information on physical processes is critical for improving the success of such restoration actions. In this study, a three-dimensional hydrodynamic model was developed to simulate estuarine processes in the Stillaguamish River estuary, where restoration of a 160-acre parcel through dike setback has been proposed. The model was calibrated to observed tide, current, and salinity data for existing conditions and applied to simulate the hydrodynamic responses to two restoration alternatives. Model results were then combined with biophysical data to predict habitat responses within the restoration footprint. Results showed that the proposed dike removal would result in desired tidal flushing and conditions that would support four habitat types on the restoration footprint. At the estuary scale, restoration would substantially increase the proportion of area flushed with freshwater (<5 ppt) at flood tide. Potential implications of predicted changes in salinity and flow dynamics are discussed relative to the distribution of tidal marsh habitat.
In this study, a hydrodynamic model based on the unstructured-grid finite volume coastal ocean mo... more In this study, a hydrodynamic model based on the unstructured-grid finite volume coastal ocean model (FVCOM) was developed for Bellingham Bay, Washington. The model simulates water surface elevation, velocity, temperature, and salinity in a three-dimensional domain that covers the entire Bellingham Bay and adjacent water bodies, including Lummi Bay, Samish Bay, Padilla Bay, and Rosario Strait. The model was developed using Pacific Northwest National Laboratorys high-resolution Puget Sound and Northwest Straits circulation and transport model. A sub-model grid for Bellingham Bay and adjacent coastal waters was extracted from the Puget Sound model and refined in Bellingham Bay using bathymetric light detection and ranging (LIDAR) and river channel cross-section data. The model uses tides, river inflows, and meteorological inputs to predict water surface elevations, currents, salinity, and temperature. A tidal open boundary condition was specified using standard National Oceanic and At...
: The Department of Defense (DoD) has identified climate change as a risk to its infrastructure a... more : The Department of Defense (DoD) has identified climate change as a risk to its infrastructure and is seeking to develop efficient and effective processes to assess the vulnerability of its assets to this risk. Responding to this need, we developed, piloted, and evaluated an approach for vulnerability assessment keyed to DoD decision-making needs and processes at multiple organizations levels. We developed and tested methods for use in an overall assessment framework, and a process for assessments at installations that applies extensive stakeholder involvement, a novel approach to providing climate information (likely future exposure), a range of existing models and approaches for estimating impacts, and decision making frameworks.
Wave resource assessment requires accurate calculation of the wave resource parameters recommende... more Wave resource assessment requires accurate calculation of the wave resource parameters recommended by the International Electrotechnical Commission (IEC) based on high-resolution wave hindcasts. Recent development of unstructured-grid modeling techniques demonstrates the advantages of using unstructured-grid modeling frameworks in simulating wave climates, especially in coastal regions that have complex coastlines, islands, shallow-water bays, and estuaries. The study reported herein evaluated the performance of an unstructured-grid wave model in comparison to a structured-grid model for predicting the IEC wave energy resource parameters at a common test bed site. Model skill was assessed using a set of model performance error statistics. The sensitivity of open boundary conditions and wind forcing on model results, computational efficiency, and the advantages and limitations of the unstructured-grid model were investigated. This modeling test bed study of wave resource characterization using unstructured-grid wave spectral model SWAN (UNSWAN) on the Level 4 (L4) grids and the extended grids built upon a previous model test bed study (by Sandia National Laboratories [SNL] and Pacific Northwest National Laboratory [PNNL]) of resource characterization that focused on structured-grid wave models. The PNNL study reported herein investigated model performance in simulating the IEC Technical Specification's six recommended wave energy resource parameters-omnidirectional wave power, significant wave height, energy period, spectral width, direction of maximum directionally resolved wave power, and the directionality coefficient-using UNSWAN. It identified the advantages and limitations of unstructuredgrid models in comparison to structured-grid models at the same test bed used in the previous joint study by SNL and PNNL. Model configuration and forcing used in the structured-grid model test bed study were adopted for consistency, and a four-level nested-grid approach-from the global WAVEWATCH III (WWIII) model to the local test bed-was used. All UNSWAN simulations conducted during this study were configured with spectral resolutions of 29 frequency bins and 24 direction bins. Climate Forecast System Reanalysis wind data with 0.5-degree spatial resolution and hourly temporal resolution were used to drive all the model runs. For all model test cases-WWIII (ST2), UNSWAN (ST2), UNSWAN (ST4), and UNSWAN-EX (ST2)-time series of the six IEC parameters showed good agreement with those calculated from National Data Buoy Center buoy data. The predicted time series for these six parameters from the UNSWAN model, with both ST2 and ST4 physical packages, are comparable to those from the present study's WWIII (ST2) model. This provides confidence in the UNSWAN model settings, although small differences between WWIII and UNSWAN simulations were observed. The performance of unstructured-grid SWAN on the L4 grid and on the extended grid was investigated. The number of nodes on the L4 grid is nearly two times that of those on the extended grid, but the extended UNSWAN features half of the computational time and more spatial variability for the wave resources assessment. This study demonstrates that unstructured-grid wave modeling provides advantages in computational efficiency and therefore is a practical approach for simulating wave climates near complex geometries that have localized high grid resolution within a large model domain. v
This paper presents an application of a hydrodynamic model to simulate tidal energy extraction in... more This paper presents an application of a hydrodynamic model to simulate tidal energy extraction in a tidal dominated estuary in the Pacific Northwest coast. A series of numerical experiments were carried out to simulate tidal energy extraction with different turbine array configurations, including location, spacing and array size. Preliminary model results suggest that array optimization for tidal energy extraction in a real-world site is a very complex process that requires consideration of multiple factors. Numerical models can be used effectively to assist turbine siting and array arrangement in a tidal turbine farm for tidal energy extraction.
The International Journal of Ocean and Climate Systems, 2011
It is a great challenge to specify meteorological forcing in estuarine and coastal circulation mo... more It is a great challenge to specify meteorological forcing in estuarine and coastal circulation modeling using observed data because of the lack of complete datasets. As a result of this limitation, water temperature is often not simulated in estuarine and coastal modeling, with the assumption that density-induced currents are generally dominated by salinity gradients. However, in many situations, temperature gradients could be sufficiently large to influence the baroclinic motion. In this paper, we present an approach to simulate water temperature using outputs from advanced meteorological models. This modeling approach was applied to simulate annual variations of water temperatures of Puget Sound, a fjordal estuary in the Pacific Northwest of USA. Meteorological parameters from North American Region Re-analysis (NARR) model outputs were evaluated with comparisons to observed data at real-time meteorological stations. Model results demonstrated that NARR outputs can be used to drive...
A 3D hydrodynamic and sediment transport modeling analysis was conducted to evaluate the feasibil... more A 3D hydrodynamic and sediment transport modeling analysis was conducted to evaluate the feasibility of restoring natural fish habitat in the Skagit River estuary, located in the northern Puget Sound, Washington. The Cottonwood Island restoration site is located where the north and the south forks of the Skagit River bifurcate approximately 10 river miles upstream from the mouth of the river. The study site is a riverine tidal and floodplain forest zone which is influenced by tide but not mixed with marine water, and is periodically inundated by flooding events. Fish habitat and migration pathway in the area was lost due to sedimentation in the channel around Cottonwood Island. Restoration actions were proposed to reconnect the channel sloughs to the main stem of the river to restore fish habitat. The analysis focused on estimating the potential for success associated with the proposed three restoration alternatives including dike setback and channel modification. In this study, the unstructured Finite Volume Coastal Ocean Model (FVCOM) was used to evaluate the effects of proposed alternatives on hydrodynamic response and potential channel re-sedimentation. The numerical model was calibrated with ADCP and CTD measurements. The calibrated hydrodynamic model was used to drive the sediment transport model to calculate sediment erosion and deposition patterns under different flow conditions. The model was applied to baseline and alternative conditions for 5 different flood hydrographs (1-yr, 2-yr, 5-yr, 10-yr, 25-yr). Model results for the alternatives were compared with baseline condition to assess the relative effects and potential re-sedimentation.
In this report we describe 1) the development, test, and validation of the marine hydrokinetic en... more In this report we describe 1) the development, test, and validation of the marine hydrokinetic energy scheme in a three-dimensional coastal ocean model (FVCOM); and 2) the sensitivity analysis of effects of marine hydrokinetic energy configurations on power extraction and volume flux in a coastal bay. Submittal of this report completes the work on Task 2.1.2, Effects of Physical Systems, Subtask 2.1.2.1, Hydrodynamics and Subtask 2.1.2.3, Screening Analysis, for fiscal year 2011 of the Environmental Effects of Marine and Hydrokinetic Energy project. v Project Overview Energy generated from the world's oceans and rivers offers the potential to make substantial contributions to the domestic and global renewable energy supply. The U.S. Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy (EERE) Wind and Water Power Program supports the emerging marine and hydrokinetic (MHK) energy industry. As partners in an emerging industry, MHK project developers face challenges with siting, permitting, construction, and operation of pilot-and commercial-scale facilities, as well as the need to develop robust technologies, secure financing, and gain public acceptance. In many cases, little is known about the potential effects of MHK energy generation on the aquatic environment from a small number of devices or a large-scale commercial array. Nor do we understand potential effects that may occur after years or decades of operation. This lack of knowledge affects the solvency of the industry, the actions of regulatory agencies, the opinions and concerns of stakeholder groups, and the commitment of energy project developers and investors. vii Acronyms and Abbreviations 1-D one-dimensional 2-D two-dimensional 3-D three-dimensional
To re-establish the intertidal wetlands with full tidal interaction and improve salmonid rearing ... more To re-establish the intertidal wetlands with full tidal interaction and improve salmonid rearing habitat in the Lower Snohomish River estuary, the Everett Public Works Department restored the Union Slough project site in 2007 by breaching the existing dike and constructing bridges across the breaches. Pacific Northwest National Laboratory (PNNL) was contracted by the U.S. Amy Corps of Engineers to conduct a modeling study to evaluate additional project design scenarios at the restoration site for potential improvement of drainage conditions. In this study, a three-dimensional Snohomish River estuary model previously developed by PNNL was updated with fine-grid resolution for the Union Slough project site and validated with observed water level data collected in the project site and Union Slough. The drainage area percentage throughout entire range of tidal conditions was predicted for a number of proposed restoration alternatives. This study report summarizes the modeling approach, the data used, model validation, and model application results. The structure of the report is as follows. The methodology of the study is described in Section 2. Model validation to the new existing condition of the project site is presented in Section 3. Error statistics for model validation and uncertainty of the model analysis are provided in Section 4. Model applications to proposed restoration scenarios are presented in Sections 5 and 6. A summary of this study and recommendations are provided in Section 7. References are given in Section 8.
To re-establish the intertidal wetlands with full tidal exchange and improve salmonid rearing hab... more To re-establish the intertidal wetlands with full tidal exchange and improve salmonid rearing habitat in the Skagit River estuary, State of Washington, USA, a diked agriculture farm land along the Skagit Bay front is proposed to be restored to a fully functional tidal wetland. The complex and dynamic Skagit River estuarine system calls for the need of a multi-facet and multi-dimensional analysis using observed data, numerical and analytical methods. To assist the feasibility study of the restoration project, a hydrodynamic modeling analysis was conducted using a high-resolution unstructured-grid coastal ocean model to evaluate the hydrodynamic response to restoration alternatives and to provide guidance to the engineering design of a new levee in the restoration site. A set of parameters were defined to quantify the hydrodynamic response of the nearshore restoration project, such as inundation area, duration of inundation, water depth and salinity of the inundated area. To assist the design of the new levee in the restoration site, the maximum water level near the project site was estimated with consideration of extreme high tide, wind-induced storm surge, significant wave height and future sea-level rise based on numerical model results and coastal engineering calculation.
Hydropower reservoirs impounded by high-head dams exhibit complex circulation which confuses the ... more Hydropower reservoirs impounded by high-head dams exhibit complex circulation which confuses the downstream migrating salmon and limits successful collection and passage of fish. Fish passage engineers attempt to modify the hydrothermal behavior at reservoirs through structural and operational modi fications and use hydrodynamic simulations to guide their actions. Simulation of key hydrothermal processes such as (a) development of a stable 2-layer stratified system, (b) density driven currents over the reservoir length, and (c) discharge hydraulics near the power generation and fish collection intakes, require highly specialized models applied at differing temporal and spatial scales. A staged modeling approach is presented which uses external coupling of models of varying temporal scales and spatial resolution to simulate the entire hydraulic regime from the mouth of the reservoir at the upstream end to the discharge at the dam. The staged modeling approach is illustrated using a case study where operational modifications are being evaluated to improve reservoir stratification and density driven currents. The model results provide input and valuable insight in the development of a new structure design and configuration for effective fish collection near the forebay of a high head dam.
Through extensive field data collection and analysis efforts conducted since the 1950s, researche... more Through extensive field data collection and analysis efforts conducted since the 1950s, researchers have established an understanding of the characteristic features of circulation in Puget Sound. The pattern ranges from the classic fjordal behavior in some basins, with shallow brackish outflow and compensating inflow immediately below, to the typical two-layer flow observed in many partially mixed estuaries with saline inflow at depth. An attempt at reproducing this behavior by fitting an analytical formulation to past data is presented, followed by the application of a three-dimensional circulation and transport numerical model. The analytical treatment helped identify key physical processes and parameters, but quickly reconfirmed that response is complex and would require site-specific parameterization to include effects of sills and interconnected basins. The numerical model of Puget Sound, developed using unstructured-grid finite volume method, allowed resolution of the sub-basin geometric features, including presence of major islands, and site-specific strong advective vertical mixing created by bathymetry and multiple sills. The model was calibrated using available recent short-term oceanographic time series data sets from different parts of the Puget Sound basin. The results are compared against 1) recent velocity and salinity data collected in Puget Sound from 2006 and 2) a composite data set from previously analyzed historical records, mostly from the 1970s. The results highlight the ability of the model to reproduce velocity and salinity profile characteristics, their variations among Puget Sound subbasins, and tidally averaged circulation. Sensitivity of residual circulation to variations in freshwater inflow and resulting salinity gradient in fjordal sub-basins of Puget Sound is examined.
In this study, a storm surge model of the Salish Sea was developed to simulate storm surge in Pug... more In this study, a storm surge model of the Salish Sea was developed to simulate storm surge in Puget Sound using the unstructured-grid, finite-volume community ocean model (FVCOM). The model was based on Pacific Northwest National Laboratory's existing Puget Sound hydrodynamic model that has been validated extensively in previous studies. To identify representative historical storm events, a systematic approach was developed based on the nontidal residual (NTR) method. A total of 34 storm surge events between 1980 and 2016 were identified and simulated. To accurately simulate storm surge inside Puget Sound, the model was driven by reanalyzed Climate Forecast System Reanalysis meteorological forcing and observed water levels at the entrance of Strait of Juan de Fuca and southern entrance of Johnstone Strait. Model results for total water level, storm surge, and currents were compared with field measurements. A series of error statistics parameters were also calculated to quantify the model's skills in simulating storm surge in the Salish Sea. Error statistics of model performance metrics demonstrated that the Salish Sea storm surge model was able to simulate storm surge inside Puget Sound with high accuracy. Storm surge propagation into Puget Sound is a nonlinear process that cannot be simply determined by a static approach for the entire domain. The maximum NTR distribution inside Puget Sound suggests that storm surge tends to be amplified in several sub-basins and inlets of the Puget Sound, such as Bellingham Bay, Hood Canal, south Puget Sound, and the multi-inlet basin behind Agate and Rich Passages. Therefore, future study is necessary to further quantify the storm surge level in these high-risk areas through field measurements and refined model simulations.
The northern coasts of the Gulf of Mexico (GoM) are highly vulnerable to the direct threats of cl... more The northern coasts of the Gulf of Mexico (GoM) are highly vulnerable to the direct threats of climate change, such as hurricane-induced storm surge, and such risks are exacerbated by land subsidence and global sea-level rise. This paper presents an application of a coastal storm surge model to study the coastal inundation process induced by tide and storm surge, and its response to the effects of land subsidence and sea-level rise in the northern Gulf coast. The unstructured-grid finite-volume coastal ocean model was used to simulate tides and hurricane-induced storm surges in the GoM. Simulated distributions of co-amplitude and co-phase lines for semi-diurnal and diurnal tides are in good agreement with previous modeling studies. The storm surges induced by four historical hurricanes (Rita, Katrina, Ivan, and Dolly) were simulated and compared to observed water levels at National Oceanic and Atmospheric Administration tide stations. Effects of coastal subsidence and future global sea-level rise on coastal inundation in the Louisiana coast were evaluated using a ''change of inundation depth'' parameter through sensitivity simulations that were based on a projected future subsidence scenario and 1-m global sea-level rise by the end of the century. Model results suggested that hurricane-induced storm surge height and coastal inundation could be exacerbated by future global sea-level rise and
Along the Pacific Northwest coast, much of the estuarine habitat has been lost over the last cent... more Along the Pacific Northwest coast, much of the estuarine habitat has been lost over the last century to agricultural land use, residential and commercial development, and transportation corridors. As a result, many of the ecological processes and functions have been disrupted. To protect and improve these coastal habitats that are vital to aquatic species, many projects are currently underway to restore estuarine and coastal ecosystems through dike breaches, setbacks, and removals. Understanding site-specific information on physical processes is critical for improving the success of such restoration actions. In this study, a three-dimensional hydrodynamic model was developed to simulate estuarine processes in the Stillaguamish River estuary, where restoration of a 160-acre parcel through dike setback has been proposed. The model was calibrated to observed tide, current, and salinity data for existing conditions and applied to simulate the hydrodynamic responses to two restoration alternatives. Model results were then combined with biophysical data to predict habitat responses within the restoration footprint. Results showed that the proposed dike removal would result in desired tidal flushing and conditions that would support four habitat types on the restoration footprint. At the estuary scale, restoration would substantially increase the proportion of area flushed with freshwater (<5 ppt) at flood tide. Potential implications of predicted changes in salinity and flow dynamics are discussed relative to the distribution of tidal marsh habitat.
In this study, a hydrodynamic model based on the unstructured-grid finite volume coastal ocean mo... more In this study, a hydrodynamic model based on the unstructured-grid finite volume coastal ocean model (FVCOM) was developed for Bellingham Bay, Washington. The model simulates water surface elevation, velocity, temperature, and salinity in a three-dimensional domain that covers the entire Bellingham Bay and adjacent water bodies, including Lummi Bay, Samish Bay, Padilla Bay, and Rosario Strait. The model was developed using Pacific Northwest National Laboratorys high-resolution Puget Sound and Northwest Straits circulation and transport model. A sub-model grid for Bellingham Bay and adjacent coastal waters was extracted from the Puget Sound model and refined in Bellingham Bay using bathymetric light detection and ranging (LIDAR) and river channel cross-section data. The model uses tides, river inflows, and meteorological inputs to predict water surface elevations, currents, salinity, and temperature. A tidal open boundary condition was specified using standard National Oceanic and At...
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Papers by Zhaoqing Yang