Karim Alizad | K.N.Toosi University of Technology (original) (raw)

Peer-Reviewed Journal Articles by Karim Alizad

Two distinct microtidal estuarine systems were assessed to advance the understanding of the coast... more Two distinct microtidal estuarine systems were assessed to advance the understanding of the coastal dynamics of sea level rise in salt marshes. A coupled hydrodynamic-marsh model (Hydro-MEM) was applied to both a marine-dominated (Grand Bay, Mississippi) and a mixed fluvial/marine (Weeks Bay, Alabama) system to compute marsh productivity, marsh migration, and potential tidal inundation from the year 2000 to 2100 under four sea level rise scenarios. Characteristics of the estuaries such as geometry, sediment availability, and topography, were compared to understand their role in the dynamic response to sea level rise. The results show that the low sea level rise scenario (20 cm) approximately doubled high-productivity marsh coverage in the marine-dominated estuary by the year 2100 due to an equilibrium between the rates of sea level rise and marsh platform accretion. Under intermediate-low sea level rise (50 cm), high-productivity marsh coverage in the year 2100 increased (doubled in the marine-dominated estuary and a seven-fold increase in the mixed estuary) by expanding into higher lands followed by the creation of interior ponds. The results also indicate that marine-dominated estuaries are vulnerable to collapse as a result of low, relatively uniform topography and lack of sediment sources, whereas mixed estuaries are able to expand due to higher elevations and sediment inputs. The results from the higher sea level rise scenarios (the intermediate-high (120 cm) and high (200 cm)) showed expansion of the bays along with marsh migration to higher land, producing a five-fold increase in wetland coverage for the mixed estuary and virtually no net change for the marine-dominated estuary. Additionally, hurricane storm surge simulations showed that under higher sea level rise scenarios, the marine-dominated estuary demonstrated weaker peak stage attenuation indicating that the PLOS ONE | https://doi.

Earth's Future, Nov 1, 2016

Coastal wetlands are likely to lose productivity under increasing rates of sea-level rise (SLR). ... more Coastal wetlands are likely to lose productivity under increasing rates of sea-level rise (SLR). This study assessed a fluvial estuarine salt marsh system using the Hydro-MEM model under four SLR scenarios. The Hydro-MEM model was developed to apply the dynamics of SLR as well as capture the effects associated with the rate of SLR in the simulation. Additionally, the model uses constants derived from a 2-year bioassay in the Apalachicola marsh system. In order to increase accuracy, the lidar-based marsh platform topography was adjusted using Real Time Kinematic survey data. A river inflow boundary condition was also imposed to simulate freshwater flows from the watershed. The biomass density results produced by the Hydro-MEM model were validated with satellite imagery. The results of the Hydro-MEM simulations showed greater variation of water levels in the low (20 cm) and intermediate-low (50 cm) SLR scenarios and lower variation with an extended bay under higher SLR scenarios. The low SLR scenario increased biomass density in some regions and created a more uniform marsh platform in others. Under intermediate-low SLR scenario, more flooded area and lower marsh productivity were projected. Higher SLR scenarios resulted in complete inundation of marsh areas with fringe migration of wetlands to higher land. This study demonstrated the capability of Hydro-MEM model to simulate coupled physical/biological processes across a large estuarine system with the ability to project marsh migration regions and produce results that can aid in coastal resource management, monitoring, and restoration efforts.

Ecological Modeling, 2016

A spatially-explicit model (Hydro-MEM model) that couples astronomic tides and Spartina alternifl... more A spatially-explicit model (Hydro-MEM model) that couples astronomic tides and Spartina alterniflora dynamics was developed to examine the effects of sea-level rise on salt marsh productivity in northeast Florida. The hydrodynamic component of the model simulates the hydroperiod of the marsh surface driven by astronomic tides and the marsh platform topography, and demonstrates biophysical feedback that non-uniformly modifies marsh platform accretion, plant biomass, and water levels across the estu-arine landscape, forming a complex geometry. The marsh platform accretes organic and inorganic matter depending on the sediment load and biomass density which are simulated by the ecological-marsh component (MEM) of the model and are functions of the hydroperiod. Two sea-level rise projections for the year 2050 were simulated: 11 cm (low) and 48 cm (high). Overall biomass density increased under the low sea-level rise scenario by 54% and declined under the high sea-level rise scenario by 21%. The biomass-driven topographic and bottom friction parameter updates were assessed by demonstrating numerical convergence (the state where the difference between biomass densities for two different coupling time steps approaches a small number). The maximum coupling time steps for low and high sea-level rise cases were calculated to be 10 and 5 years, respectively. A comparison of the Hydro-MEM model with a para-metric marsh equilibrium model (MEM) indicates improvement in terms of spatial pattern of biomass distribution due to the coupling and dynamic sea-level rise approaches. This integrated Hydro-MEM model provides an innovative method by which to assess the complex spatial dynamics of salt marsh grasses and predict the impacts of possible future sea level conditions.

Earth's Future, 2016

This work outlines a dynamic modeling framework to examine the effects of global climate change, ... more This work outlines a dynamic modeling framework to examine the effects of global climate change, and sea level rise (SLR) in particular, on tropical cyclone-driven storm surge inundation. The methodology, applied across the northern Gulf of Mexico, adapts a present day large-domain, high resolution, tide, wind-wave, and hurricane storm surge model to characterize the potential outlook of the coastal landscape under four SLR scenarios for the year 2100. The modifications include shoreline and barrier island morphology, marsh migration, and land use land cover change. Hydrodynamics of 10 historic hurricanes were simulated through each of the five model configurations (present day and four SLR scenarios). Under SLR, the total inundated land area increased by 87% and developed and agricultural lands by 138% and 189%, respectively. Peak surge increased by as much as 1 m above the applied SLR in some areas, and other regions were subject to a reduction in peak surge, with respect to the applied SLR, indicating a nonlinear response. Analysis of time-series water surface elevation suggests the interaction between SLR and storm surge is nonlinear in time; SLR increased the time of inundation and caused an earlier arrival of the peak surge, which cannot be addressed using a static (" bathtub ") modeling framework. This work supports the paradigm shift to using a dynamic modeling framework to examine the effects of global climate change on coastal inundation. The outcomes have broad implications and ultimately support a better holistic understanding of the coastal system and aid restoration and long-term coastal sustainability.

Earth's Future, 2016

This study examines the integrated influence of sea level rise (SLR) and future morphology on tid... more This study examines the integrated influence of sea level rise (SLR) and future morphology on tidal hydrodynamics along the Northern Gulf of Mexico (NGOM) coast including seven embayments and three ecologically and economically significant estuaries. A large-domain hydrodynamic model was used to simulate astronomic tides for present and future conditions (circa 2050 and 2100). Future conditions were simulated by imposing four SLR scenarios to alter hydrodynamic boundary conditions and updating shoreline position and dune heights using a probabilistic model that is coupled to SLR. Under the highest SLR scenario, tidal amplitudes within the bays increased as much as 67% (10.0 cm) because of increases in the inlet cross-sectional area. Changes in harmonic constituent phases indicated that tidal propagation was faster in the future scenarios within most of the bays. Maximum tidal velocities increased in all of the bays, especially in Grand Bay where velocities doubled under the highest SLR scenario. In addition, the ratio of the maximum flood to maximum ebb velocity decreased in the future scenarios (i.e., currents became more ebb dominant) by as much as 26% and 39% in Weeks Bay and Apalachicola, respectively. In Grand Bay, the flood-ebb ratio increased (i.e., currents became more flood dominant) by 25% under the lower SLR scenarios, but decreased by 16% under the higher SLR as a result of the offshore barrier islands being overtopped, which altered the tidal prism. Results from this study can inform future storm surge and ecological assessments of SLR, and improve monitoring and management decisions within the NGOM.

Earth's Future, 2016

The response of runoff and sediment loading in the Apalachicola River under projected climate cha... more The response of runoff and sediment loading in the Apalachicola River under projected climate change scenarios and land use land cover (LULC) change is evaluated. A hydrologic model using the Soil and Water Assessment Tool was developed for the Apalachicola region to simulate daily runoff and sediment load under present (circa 2000) and future conditions (2100) to understand how parameters respond over a seasonal time frame to changes in climate, LULC, and coupled climate/LULC. The Long Ashton Research Station-Weather Generator was used to downscale temperature and precipitation from three general circulation models, each under Intergovernmental Panel on Climate Change (IPCC) carbon emission scenarios A2, A1B, and B1. Projected 2100 LULC data provided by the United States Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center was incorporated for each corresponding IPCC scenario. Results indicate that climate change may induce seasonal shifts to both runoff and sediment loading. Changes in LULC showed that more sediment load was associated with increased agriculture and urban areas and decreased forested regions. A nonlinear response for both runoff and sediment loading was observed by coupling climate and LULC change, suggesting that both should be incorporated into hydrologic models when studying the future conditions. The outcomes from this research can be used to better guide management practices and mitigation strategies.

Earth's Future, 2015

Coastal responses to sea level rise (SLR) include inundation of wetlands, increased shoreline ero... more Coastal responses to sea level rise (SLR) include inundation of wetlands, increased shoreline erosion, and increased flooding during storm events. Hydrodynamic parameters such as tidal ranges, tidal prisms, tidal asymmetries, increased flooding depths and inundation extents during storm events respond nonadditively to SLR. Coastal morphology continually adapts toward equilibrium as sea levels rise, inducing changes in the landscape. Marshes may struggle to keep pace with SLR and rely on sediment accumulation and the availability of suitable uplands for migration. Whether hydrodynamic, morphologic, or ecologic, the impacts of SLR are interrelated. To plan for changes under future sea levels, coastal managers need information and data regarding the potential effects of SLR to make informed decisions for managing human and natural communities. This review examines previous studies that have accounted for the dynamic, nonlinear responses of hydrodynamics, coastal morphology, and marsh ecology to SLR by implementing more complex approaches rather than the simplistic “bathtub” approach. These studies provide an improved understanding of the dynamic effects of SLR on coastal environments and contribute to an overall paradigm shift in how coastal scientists and engineers approach modeling the effects of SLR, transitioning away from implementing the “bathtub” approach. However, it is recommended that future studies implement a synergetic approach that integrates the dynamic interactions between physical and ecological environments to better predict the impacts of SLR on coastal systems.

In this study, potential climate change impacts on runoff and sediment load in Apalachicola River... more In this study, potential climate change impacts on runoff and sediment load in Apalachicola River basin in Florida are assessed using Soil and Water Assessment Tool (SWAT), a semi-distributed hydrologic model. The observed streamflow and sediment load from 1984 to 1994 are used for the model calibration and validation. The streamflow Nash-Sutcliffe Coefficients (NSEs) for the simulation and validation periods (1984-1989 and 1990-1994 years) are 0.92 and 0.88, respectively. The sediment NSEs for the simulation and validation periods are calculated to be 0.46 and 0.36, respectively, with excellent description of trend variability. Rainfall data under climate change effects is applied as the calibrated SWAT model input to estimate the streamflow and sediment load change. The rainfall and temperature data is prepared using two regional climate models (RCM); HRM3-HADCM3, and RCM3-GFDL. Results show that the average daily level of streamflow and sediment load will not vary significantly, but the peak flow and peak sediment load will increase dramatically due to the more intense and less frequent rainfall events. The impact of climate change during an extreme rainfall event is also investigated. A storm event with 25-year return period and 24-hour duration in 1991 is taken as the baseline event. Based on the projection using RCM3-GFDL scenario, the streamflow and sediment load may increase by 50% and 89%, respectively.

Journal of Hydrology, 2013

Climate change impact on rainfall intensity–duration–frequency (IDF) curves at the Apalachicola R... more Climate change impact on rainfall intensity–duration–frequency (IDF) curves at the Apalachicola River basin (Florida Panhandle coast) is assessed using an ensemble of regional climate models (RCMs) obtained from the North American Regional Climate Change Assessment Program. The suitability of seven RCMs on simulating temporal variation of rainfall at the fine-scale is assessed for the case study region. Two RCMs, HRM3–HADCM3 and RCM3–GFDL, are found to have good skill scores in generating high intensity events at the mid-afternoon (2:00–4:00 PM). These two RCMs are selected for assessing potential climate change impact on IDF curves. Two methods are used to conduct bias correction on future rainfall IDF curves, i.e., maximum intensity percentile-based method, and sequential bias correction and maximum intensity percentile-based method. Based on the projection by HRM3–HADCM3, there is no significant change in rainfall intensity at the upstream and middle stream stations but higher intensity at the downstream station. RCM3–GFDL projected increased rainfall intensity from upstream to downstream, particularly at the downstream. The potential temporal shift of extreme rainfall events coupled with overall increased intensities may exacerbate flood magnitudes and lead to increased sediment and nutrient loadings to the estuary, especially in light of sea level change.

International Journal of Heat and Mass Transfer, 2012

Thermal performance, transient behavior and operational start-up characteristics of flat-shaped h... more Thermal performance, transient behavior and operational start-up characteristics of flat-shaped heat pipes using nanofluids are analyzed in this work. Three different primary nanofluids namely, CuO, Al2O3, and TiO2 were utilized in our analysis. A comprehensive analytical model, which accounts in detail the heat transfer characteristics within the pipe wall and the wick within the condensation and evaporation sections, was utilized. The results illustrate enhancement in the heat pipe performance while achieving a reduction in the thermal resistance for both flat-plate and disk-shaped heat pipes throughout the transient process. It was shown that a higher concentration of nanoparticles increases the thermal performance of either the flat-plate or disk-shaped heat pipes. We have also established that for the same heat load a smaller size flat-shaped heat pipe can be utilized when using nanofluids.

Thermal performance, transient behavior and operational start-up characteristics of flat-shaped h... more Thermal performance, transient behavior and operational start-up characteristics of flat-shaped heat pipes using nanofluids are analyzed in this work. Three different primary nanofluids namely, CuO, Al2O3, and TiO2 were utilized in our analysis. A comprehensive analytical model, which accounts in detail the heat transfer characteristics within the pipe wall and the wick within the condensation and evaporation sections, was utilized.

Trade Journal Articles by Karim Alizad

The northern Gulf of Mexico is home to a vast amount of coastal ecosystems that provide natural a... more The northern Gulf of Mexico is home to a vast amount of coastal ecosystems that provide natural and economic resources. Rising sea levels may threaten these resources with increased flood magnitude and frequency, accelerated erosion, loss of wetlands, and saltwater intrusion. The Ecological Effects of Sea Level Rise in Northern Gulf Of Mexico (EESLR-NGOM), a five year interdisciplinary effort funded by the National Oceanic and Atmospheric Administration (NOAA), aims to assess these effects and provide local coastal managers with the knowledge and tools to prepare for the dynamic impacts of tides and storm surge magnified by sea level rise (SLR). The project builds on field observations centered at three National Estuarine Research Reserves (NERR) including Apalachicola, Grand Bay and Weeks Bay. The field observations aid in the development, parameterization and validation of integrated models (e.g. hydrodynamic and biologic) to predict the response of the coastal system under variou...

Conference Proceedings by Karim Alizad

The resilience of an ecosystem can be described as the system's ability to absorb changes and ada... more The resilience of an ecosystem can be described as the system's ability to absorb changes and adapt to new situations (Elliott et al., 2007). Coastal wetlands, specifically salt marsh systems, are ecosystems that are at risk of increased flooding, reduced productivity, and potential collapse under increasing rates of sea level rise (SLR). Estuarine systems will respond differently to changes in mean sea level due to their geographic location, sediment source, salinity, and tide range. Therefore, it is critical to study how various estuaries and their salt marshes may respond to SLR. Herein, we focus on micro and macro estuarine systems along the northern Gulf of Mexico (NGOM), Mid-Atlantic, and New England coasts. Hydrodynamics and biomass productivity for each study site are simulated using the Hydro-MEM model (Alizad et al., 2016a; Alizad et al., 2016b) to examine the marsh response to changes in mean sea level across four SLR projections for the year 2100: 0.2 m (low), 0.5 m, (intermediate low), 1.2 m (intermediate high), and 2.0 m (high) (Parris et al., 2012). The Hydro-MEM model uses the ADvanced CIRCulation (ADCIRC) code (Luettich and Westerink, 2006) to incorporate the dynamics of SLR and the complex daily wetting and drying within a marsh system. Results demonstrate the response of salt marsh productivity and the potential for upland migration for each estuarine system. One of the smartest methods to aid ecosystems becoming more resilient through natural recovery from an environmental or human-induced change is to remove additional stressors and provide suitable conditions for their adaptation (Elliott et al., 2007). We consider that proper preparation and providing suitable conditions of upland areas can allow for uninterrupted and natural landward migration. Our assessments indicate that wetlands can play an important role in reducing shoreline vulnerability to storm surge. This was mentioned in the US federal government report as the " role of green infrastructure in enhancing resilience " by including the significance of the natural and nature-based features (NNBF) in coastal resiliency (Committee on Environment, Natural Resources and Sustainability of the National Science and Technology Council, 2015). This research demonstrates that preparing higher lands for wetland migration can help these ecosystems become more resilient to SLR. Moreover, the maps should be divided into the small regions to facilitate management process for coastal managers. Several studies used the Hydrologic Unite Codes (HUCs) to facilitate georeferencing and mapping wetland or erosion assessments (Jang et al., 2015; Nestlerode et al., 2014). This study employed this geographical reference to provide marsh migration and biomass density projection maps for coastal managers to make informed decisions about wetlands vulnerability to SLR and plan properly for their resiliency.

Open expansion tanks are applied vastly in central heating and airconditioning systems. Central h... more Open expansion tanks are applied vastly in central heating and airconditioning systems. Central heating systems are subjected to great deals of energy losses, owing to the lack of proper design. In this paper, the structure of Open Expansion Tanks is revised and some modifications for reducing energy and heat loss are made to their elements. Moreover, some common designs available in the market are studied in order to better recognize their defects and capabilities. To reach an efficient design, several scenarios are tested using Computational methods (CFD based). In order to validate the new design, an experimental model was created and heat and energy survey operations were performed. The results of energy auditing were analyzed to show the convergence of numerical and experimental models. Additionally, the proposed model was economically evaluated. The final presented model named " Optimized OET with twin containers " is capable of reducing the energy loss by 85 to 95 percent.

One of the most effective tools for water resources planning and studying coastal ecosystem dynam... more One of the most effective tools for water resources planning and studying coastal ecosystem dynamics is simulating river flow under various scenarios. These scenarios may represent proposed anthropogenic changes to the basin such as construction projects or anticipated natural changes such as sea level rise. In this study, a hydrologic model for the Apalachicola River basin is developed to investigate the potential changes in the flow characteristics. This river was affected by dams and human water use in the past (Gibson, et al., 2005). Climate change affecting the hydrologic water cycle and in turn impacting water resources is a major concern (Milly, et al., 2008).
The Apalachicola River as shown in Figure 1 is formed by the conflux of Chattahoochee and Flint Rivers and it has the largest discharge in Florida (Iseri and Langbein, 1974). This river is the home for a variety of species. Altered water levels in future scenarios could cause disconnection between channel and floodplain and decrease in habitat areas (Gibson, et al., 2005).
Assessment of extreme rainfall events under climate change scenarios in the river basin using rainfall intensity-duration-frequency (IDF) curves is carried out using the WASH2D numerical model. This model is derived from WASH123D, which can model surface flow in a watershed system using three approaches: kinematic, diffusive, and dynamic wave models (Yeh, et al., 1998). A two dimensional mesh for the Apalachicola River basin with defined boundaries applying the rainfall storm scenarios was
developed. The primary driving force for this simulation is varied design storms derived from IDF curves (Wang, et al., 2011). These design storms are applied to the assigned nodes and WASH2D solves 2-dimensional overland flow equations by applying finite element methods in the region. These simulation results are used to predict the response of the river to various storms. Then, predicted future IDF curves derived from the North American Regional Climate Change Assessment Program data were implemented to forecast future river flow.
Estimated flows are in agreement with observations in the Apalachicola River. Several methods within the WASH2D model were applied to validate the simulation. Grid independency test was also demonstrated using different element sizes in order to study the sensitivity of the model to grid resolution. Results from the WASH2D numerical model using future IDF curves were examined to gain insight into the flow and watershed response to potential future storms.

Conference Presentations by Karim Alizad

An assessment of the sea level rise (SLR) impact on coastal salt marsh biomass productivity for a... more An assessment of the sea level rise (SLR) impact on coastal salt marsh biomass productivity for a marine dominated estuary in Grand Bay, MS is presented. The projection of salt marsh productivity is conducted using an integrated hydro-marsh model, which is comprised of a hydrodynamic and a parametric marsh model. The results include the dynamic effects of SLR scenarios on hydrodynamics, marsh platform accretion, and salt marsh productivity. The Grand Bay estuary is a marine dominant estuary located along the border of Alabama and Mississippi with dominant salt marsh species including Juncus roemerianus and Spartina alterniflora (Eleuterius and Criss, 1991). Sediment transport in this estuary is driven by wave forces from the Gulf of Mexico and SLR that cause salt marshes to migrate landward (Schmid2000). Therefore, the Grand Bay estuarine system is vulnerable to SLR under extreme scenarios. The hydro-marsh model used to project biomass productivity is based on a coupled twodimension...

Two distinct microtidal estuarine systems were assessed to advance the understanding of the coast... more Two distinct microtidal estuarine systems were assessed to advance the understanding of the coastal dynamics of sea level rise in salt marshes. A coupled hydrodynamic-marsh model (Hydro-MEM) was applied to both a marine-dominated (Grand Bay, Mississippi) and a mixed fluvial/marine (Weeks Bay, Alabama) system to compute marsh productivity, marsh migration, and potential tidal inundation from the year 2000 to 2100 under four sea level rise scenarios. Characteristics of the estuaries such as geometry, sediment availability, and topography, were compared to understand their role in the dynamic response to sea level rise. The results show that the low sea level rise scenario (20 cm) approximately doubled high-productivity marsh coverage in the marine-dominated estuary by the year 2100 due to an equilibrium between the rates of sea level rise and marsh platform accretion. Under intermediate-low sea level rise (50 cm), high-productivity marsh coverage in the year 2100 increased (doubled in the marine-dominated estuary and a seven-fold increase in the mixed estuary) by expanding into higher lands followed by the creation of interior ponds. The results also indicate that marine-dominated estuaries are vulnerable to collapse as a result of low, relatively uniform topography and lack of sediment sources, whereas mixed estuaries are able to expand due to higher elevations and sediment inputs. The results from the higher sea level rise scenarios (the intermediate-high (120 cm) and high (200 cm)) showed expansion of the bays along with marsh migration to higher land, producing a five-fold increase in wetland coverage for the mixed estuary and virtually no net change for the marine-dominated estuary. Additionally, hurricane storm surge simulations showed that under higher sea level rise scenarios, the marine-dominated estuary demonstrated weaker peak stage attenuation indicating that the PLOS ONE | https://doi.

Earth's Future, Nov 1, 2016

Coastal wetlands are likely to lose productivity under increasing rates of sea-level rise (SLR). ... more Coastal wetlands are likely to lose productivity under increasing rates of sea-level rise (SLR). This study assessed a fluvial estuarine salt marsh system using the Hydro-MEM model under four SLR scenarios. The Hydro-MEM model was developed to apply the dynamics of SLR as well as capture the effects associated with the rate of SLR in the simulation. Additionally, the model uses constants derived from a 2-year bioassay in the Apalachicola marsh system. In order to increase accuracy, the lidar-based marsh platform topography was adjusted using Real Time Kinematic survey data. A river inflow boundary condition was also imposed to simulate freshwater flows from the watershed. The biomass density results produced by the Hydro-MEM model were validated with satellite imagery. The results of the Hydro-MEM simulations showed greater variation of water levels in the low (20 cm) and intermediate-low (50 cm) SLR scenarios and lower variation with an extended bay under higher SLR scenarios. The low SLR scenario increased biomass density in some regions and created a more uniform marsh platform in others. Under intermediate-low SLR scenario, more flooded area and lower marsh productivity were projected. Higher SLR scenarios resulted in complete inundation of marsh areas with fringe migration of wetlands to higher land. This study demonstrated the capability of Hydro-MEM model to simulate coupled physical/biological processes across a large estuarine system with the ability to project marsh migration regions and produce results that can aid in coastal resource management, monitoring, and restoration efforts.

Ecological Modeling, 2016

A spatially-explicit model (Hydro-MEM model) that couples astronomic tides and Spartina alternifl... more A spatially-explicit model (Hydro-MEM model) that couples astronomic tides and Spartina alterniflora dynamics was developed to examine the effects of sea-level rise on salt marsh productivity in northeast Florida. The hydrodynamic component of the model simulates the hydroperiod of the marsh surface driven by astronomic tides and the marsh platform topography, and demonstrates biophysical feedback that non-uniformly modifies marsh platform accretion, plant biomass, and water levels across the estu-arine landscape, forming a complex geometry. The marsh platform accretes organic and inorganic matter depending on the sediment load and biomass density which are simulated by the ecological-marsh component (MEM) of the model and are functions of the hydroperiod. Two sea-level rise projections for the year 2050 were simulated: 11 cm (low) and 48 cm (high). Overall biomass density increased under the low sea-level rise scenario by 54% and declined under the high sea-level rise scenario by 21%. The biomass-driven topographic and bottom friction parameter updates were assessed by demonstrating numerical convergence (the state where the difference between biomass densities for two different coupling time steps approaches a small number). The maximum coupling time steps for low and high sea-level rise cases were calculated to be 10 and 5 years, respectively. A comparison of the Hydro-MEM model with a para-metric marsh equilibrium model (MEM) indicates improvement in terms of spatial pattern of biomass distribution due to the coupling and dynamic sea-level rise approaches. This integrated Hydro-MEM model provides an innovative method by which to assess the complex spatial dynamics of salt marsh grasses and predict the impacts of possible future sea level conditions.

Earth's Future, 2016

This work outlines a dynamic modeling framework to examine the effects of global climate change, ... more This work outlines a dynamic modeling framework to examine the effects of global climate change, and sea level rise (SLR) in particular, on tropical cyclone-driven storm surge inundation. The methodology, applied across the northern Gulf of Mexico, adapts a present day large-domain, high resolution, tide, wind-wave, and hurricane storm surge model to characterize the potential outlook of the coastal landscape under four SLR scenarios for the year 2100. The modifications include shoreline and barrier island morphology, marsh migration, and land use land cover change. Hydrodynamics of 10 historic hurricanes were simulated through each of the five model configurations (present day and four SLR scenarios). Under SLR, the total inundated land area increased by 87% and developed and agricultural lands by 138% and 189%, respectively. Peak surge increased by as much as 1 m above the applied SLR in some areas, and other regions were subject to a reduction in peak surge, with respect to the applied SLR, indicating a nonlinear response. Analysis of time-series water surface elevation suggests the interaction between SLR and storm surge is nonlinear in time; SLR increased the time of inundation and caused an earlier arrival of the peak surge, which cannot be addressed using a static (" bathtub ") modeling framework. This work supports the paradigm shift to using a dynamic modeling framework to examine the effects of global climate change on coastal inundation. The outcomes have broad implications and ultimately support a better holistic understanding of the coastal system and aid restoration and long-term coastal sustainability.

Earth's Future, 2016

This study examines the integrated influence of sea level rise (SLR) and future morphology on tid... more This study examines the integrated influence of sea level rise (SLR) and future morphology on tidal hydrodynamics along the Northern Gulf of Mexico (NGOM) coast including seven embayments and three ecologically and economically significant estuaries. A large-domain hydrodynamic model was used to simulate astronomic tides for present and future conditions (circa 2050 and 2100). Future conditions were simulated by imposing four SLR scenarios to alter hydrodynamic boundary conditions and updating shoreline position and dune heights using a probabilistic model that is coupled to SLR. Under the highest SLR scenario, tidal amplitudes within the bays increased as much as 67% (10.0 cm) because of increases in the inlet cross-sectional area. Changes in harmonic constituent phases indicated that tidal propagation was faster in the future scenarios within most of the bays. Maximum tidal velocities increased in all of the bays, especially in Grand Bay where velocities doubled under the highest SLR scenario. In addition, the ratio of the maximum flood to maximum ebb velocity decreased in the future scenarios (i.e., currents became more ebb dominant) by as much as 26% and 39% in Weeks Bay and Apalachicola, respectively. In Grand Bay, the flood-ebb ratio increased (i.e., currents became more flood dominant) by 25% under the lower SLR scenarios, but decreased by 16% under the higher SLR as a result of the offshore barrier islands being overtopped, which altered the tidal prism. Results from this study can inform future storm surge and ecological assessments of SLR, and improve monitoring and management decisions within the NGOM.

Earth's Future, 2016

The response of runoff and sediment loading in the Apalachicola River under projected climate cha... more The response of runoff and sediment loading in the Apalachicola River under projected climate change scenarios and land use land cover (LULC) change is evaluated. A hydrologic model using the Soil and Water Assessment Tool was developed for the Apalachicola region to simulate daily runoff and sediment load under present (circa 2000) and future conditions (2100) to understand how parameters respond over a seasonal time frame to changes in climate, LULC, and coupled climate/LULC. The Long Ashton Research Station-Weather Generator was used to downscale temperature and precipitation from three general circulation models, each under Intergovernmental Panel on Climate Change (IPCC) carbon emission scenarios A2, A1B, and B1. Projected 2100 LULC data provided by the United States Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center was incorporated for each corresponding IPCC scenario. Results indicate that climate change may induce seasonal shifts to both runoff and sediment loading. Changes in LULC showed that more sediment load was associated with increased agriculture and urban areas and decreased forested regions. A nonlinear response for both runoff and sediment loading was observed by coupling climate and LULC change, suggesting that both should be incorporated into hydrologic models when studying the future conditions. The outcomes from this research can be used to better guide management practices and mitigation strategies.

Earth's Future, 2015

Coastal responses to sea level rise (SLR) include inundation of wetlands, increased shoreline ero... more Coastal responses to sea level rise (SLR) include inundation of wetlands, increased shoreline erosion, and increased flooding during storm events. Hydrodynamic parameters such as tidal ranges, tidal prisms, tidal asymmetries, increased flooding depths and inundation extents during storm events respond nonadditively to SLR. Coastal morphology continually adapts toward equilibrium as sea levels rise, inducing changes in the landscape. Marshes may struggle to keep pace with SLR and rely on sediment accumulation and the availability of suitable uplands for migration. Whether hydrodynamic, morphologic, or ecologic, the impacts of SLR are interrelated. To plan for changes under future sea levels, coastal managers need information and data regarding the potential effects of SLR to make informed decisions for managing human and natural communities. This review examines previous studies that have accounted for the dynamic, nonlinear responses of hydrodynamics, coastal morphology, and marsh ecology to SLR by implementing more complex approaches rather than the simplistic “bathtub” approach. These studies provide an improved understanding of the dynamic effects of SLR on coastal environments and contribute to an overall paradigm shift in how coastal scientists and engineers approach modeling the effects of SLR, transitioning away from implementing the “bathtub” approach. However, it is recommended that future studies implement a synergetic approach that integrates the dynamic interactions between physical and ecological environments to better predict the impacts of SLR on coastal systems.

In this study, potential climate change impacts on runoff and sediment load in Apalachicola River... more In this study, potential climate change impacts on runoff and sediment load in Apalachicola River basin in Florida are assessed using Soil and Water Assessment Tool (SWAT), a semi-distributed hydrologic model. The observed streamflow and sediment load from 1984 to 1994 are used for the model calibration and validation. The streamflow Nash-Sutcliffe Coefficients (NSEs) for the simulation and validation periods (1984-1989 and 1990-1994 years) are 0.92 and 0.88, respectively. The sediment NSEs for the simulation and validation periods are calculated to be 0.46 and 0.36, respectively, with excellent description of trend variability. Rainfall data under climate change effects is applied as the calibrated SWAT model input to estimate the streamflow and sediment load change. The rainfall and temperature data is prepared using two regional climate models (RCM); HRM3-HADCM3, and RCM3-GFDL. Results show that the average daily level of streamflow and sediment load will not vary significantly, but the peak flow and peak sediment load will increase dramatically due to the more intense and less frequent rainfall events. The impact of climate change during an extreme rainfall event is also investigated. A storm event with 25-year return period and 24-hour duration in 1991 is taken as the baseline event. Based on the projection using RCM3-GFDL scenario, the streamflow and sediment load may increase by 50% and 89%, respectively.

Journal of Hydrology, 2013

Climate change impact on rainfall intensity–duration–frequency (IDF) curves at the Apalachicola R... more Climate change impact on rainfall intensity–duration–frequency (IDF) curves at the Apalachicola River basin (Florida Panhandle coast) is assessed using an ensemble of regional climate models (RCMs) obtained from the North American Regional Climate Change Assessment Program. The suitability of seven RCMs on simulating temporal variation of rainfall at the fine-scale is assessed for the case study region. Two RCMs, HRM3–HADCM3 and RCM3–GFDL, are found to have good skill scores in generating high intensity events at the mid-afternoon (2:00–4:00 PM). These two RCMs are selected for assessing potential climate change impact on IDF curves. Two methods are used to conduct bias correction on future rainfall IDF curves, i.e., maximum intensity percentile-based method, and sequential bias correction and maximum intensity percentile-based method. Based on the projection by HRM3–HADCM3, there is no significant change in rainfall intensity at the upstream and middle stream stations but higher intensity at the downstream station. RCM3–GFDL projected increased rainfall intensity from upstream to downstream, particularly at the downstream. The potential temporal shift of extreme rainfall events coupled with overall increased intensities may exacerbate flood magnitudes and lead to increased sediment and nutrient loadings to the estuary, especially in light of sea level change.

International Journal of Heat and Mass Transfer, 2012

Thermal performance, transient behavior and operational start-up characteristics of flat-shaped h... more Thermal performance, transient behavior and operational start-up characteristics of flat-shaped heat pipes using nanofluids are analyzed in this work. Three different primary nanofluids namely, CuO, Al2O3, and TiO2 were utilized in our analysis. A comprehensive analytical model, which accounts in detail the heat transfer characteristics within the pipe wall and the wick within the condensation and evaporation sections, was utilized. The results illustrate enhancement in the heat pipe performance while achieving a reduction in the thermal resistance for both flat-plate and disk-shaped heat pipes throughout the transient process. It was shown that a higher concentration of nanoparticles increases the thermal performance of either the flat-plate or disk-shaped heat pipes. We have also established that for the same heat load a smaller size flat-shaped heat pipe can be utilized when using nanofluids.

Thermal performance, transient behavior and operational start-up characteristics of flat-shaped h... more Thermal performance, transient behavior and operational start-up characteristics of flat-shaped heat pipes using nanofluids are analyzed in this work. Three different primary nanofluids namely, CuO, Al2O3, and TiO2 were utilized in our analysis. A comprehensive analytical model, which accounts in detail the heat transfer characteristics within the pipe wall and the wick within the condensation and evaporation sections, was utilized.

The northern Gulf of Mexico is home to a vast amount of coastal ecosystems that provide natural a... more The northern Gulf of Mexico is home to a vast amount of coastal ecosystems that provide natural and economic resources. Rising sea levels may threaten these resources with increased flood magnitude and frequency, accelerated erosion, loss of wetlands, and saltwater intrusion. The Ecological Effects of Sea Level Rise in Northern Gulf Of Mexico (EESLR-NGOM), a five year interdisciplinary effort funded by the National Oceanic and Atmospheric Administration (NOAA), aims to assess these effects and provide local coastal managers with the knowledge and tools to prepare for the dynamic impacts of tides and storm surge magnified by sea level rise (SLR). The project builds on field observations centered at three National Estuarine Research Reserves (NERR) including Apalachicola, Grand Bay and Weeks Bay. The field observations aid in the development, parameterization and validation of integrated models (e.g. hydrodynamic and biologic) to predict the response of the coastal system under variou...

The resilience of an ecosystem can be described as the system's ability to absorb changes and ada... more The resilience of an ecosystem can be described as the system's ability to absorb changes and adapt to new situations (Elliott et al., 2007). Coastal wetlands, specifically salt marsh systems, are ecosystems that are at risk of increased flooding, reduced productivity, and potential collapse under increasing rates of sea level rise (SLR). Estuarine systems will respond differently to changes in mean sea level due to their geographic location, sediment source, salinity, and tide range. Therefore, it is critical to study how various estuaries and their salt marshes may respond to SLR. Herein, we focus on micro and macro estuarine systems along the northern Gulf of Mexico (NGOM), Mid-Atlantic, and New England coasts. Hydrodynamics and biomass productivity for each study site are simulated using the Hydro-MEM model (Alizad et al., 2016a; Alizad et al., 2016b) to examine the marsh response to changes in mean sea level across four SLR projections for the year 2100: 0.2 m (low), 0.5 m, (intermediate low), 1.2 m (intermediate high), and 2.0 m (high) (Parris et al., 2012). The Hydro-MEM model uses the ADvanced CIRCulation (ADCIRC) code (Luettich and Westerink, 2006) to incorporate the dynamics of SLR and the complex daily wetting and drying within a marsh system. Results demonstrate the response of salt marsh productivity and the potential for upland migration for each estuarine system. One of the smartest methods to aid ecosystems becoming more resilient through natural recovery from an environmental or human-induced change is to remove additional stressors and provide suitable conditions for their adaptation (Elliott et al., 2007). We consider that proper preparation and providing suitable conditions of upland areas can allow for uninterrupted and natural landward migration. Our assessments indicate that wetlands can play an important role in reducing shoreline vulnerability to storm surge. This was mentioned in the US federal government report as the " role of green infrastructure in enhancing resilience " by including the significance of the natural and nature-based features (NNBF) in coastal resiliency (Committee on Environment, Natural Resources and Sustainability of the National Science and Technology Council, 2015). This research demonstrates that preparing higher lands for wetland migration can help these ecosystems become more resilient to SLR. Moreover, the maps should be divided into the small regions to facilitate management process for coastal managers. Several studies used the Hydrologic Unite Codes (HUCs) to facilitate georeferencing and mapping wetland or erosion assessments (Jang et al., 2015; Nestlerode et al., 2014). This study employed this geographical reference to provide marsh migration and biomass density projection maps for coastal managers to make informed decisions about wetlands vulnerability to SLR and plan properly for their resiliency.

Open expansion tanks are applied vastly in central heating and airconditioning systems. Central h... more Open expansion tanks are applied vastly in central heating and airconditioning systems. Central heating systems are subjected to great deals of energy losses, owing to the lack of proper design. In this paper, the structure of Open Expansion Tanks is revised and some modifications for reducing energy and heat loss are made to their elements. Moreover, some common designs available in the market are studied in order to better recognize their defects and capabilities. To reach an efficient design, several scenarios are tested using Computational methods (CFD based). In order to validate the new design, an experimental model was created and heat and energy survey operations were performed. The results of energy auditing were analyzed to show the convergence of numerical and experimental models. Additionally, the proposed model was economically evaluated. The final presented model named " Optimized OET with twin containers " is capable of reducing the energy loss by 85 to 95 percent.

One of the most effective tools for water resources planning and studying coastal ecosystem dynam... more One of the most effective tools for water resources planning and studying coastal ecosystem dynamics is simulating river flow under various scenarios. These scenarios may represent proposed anthropogenic changes to the basin such as construction projects or anticipated natural changes such as sea level rise. In this study, a hydrologic model for the Apalachicola River basin is developed to investigate the potential changes in the flow characteristics. This river was affected by dams and human water use in the past (Gibson, et al., 2005). Climate change affecting the hydrologic water cycle and in turn impacting water resources is a major concern (Milly, et al., 2008).
The Apalachicola River as shown in Figure 1 is formed by the conflux of Chattahoochee and Flint Rivers and it has the largest discharge in Florida (Iseri and Langbein, 1974). This river is the home for a variety of species. Altered water levels in future scenarios could cause disconnection between channel and floodplain and decrease in habitat areas (Gibson, et al., 2005).
Assessment of extreme rainfall events under climate change scenarios in the river basin using rainfall intensity-duration-frequency (IDF) curves is carried out using the WASH2D numerical model. This model is derived from WASH123D, which can model surface flow in a watershed system using three approaches: kinematic, diffusive, and dynamic wave models (Yeh, et al., 1998). A two dimensional mesh for the Apalachicola River basin with defined boundaries applying the rainfall storm scenarios was
developed. The primary driving force for this simulation is varied design storms derived from IDF curves (Wang, et al., 2011). These design storms are applied to the assigned nodes and WASH2D solves 2-dimensional overland flow equations by applying finite element methods in the region. These simulation results are used to predict the response of the river to various storms. Then, predicted future IDF curves derived from the North American Regional Climate Change Assessment Program data were implemented to forecast future river flow.
Estimated flows are in agreement with observations in the Apalachicola River. Several methods within the WASH2D model were applied to validate the simulation. Grid independency test was also demonstrated using different element sizes in order to study the sensitivity of the model to grid resolution. Results from the WASH2D numerical model using future IDF curves were examined to gain insight into the flow and watershed response to potential future storms.

An assessment of the sea level rise (SLR) impact on coastal salt marsh biomass productivity for a... more An assessment of the sea level rise (SLR) impact on coastal salt marsh biomass productivity for a marine dominated estuary in Grand Bay, MS is presented. The projection of salt marsh productivity is conducted using an integrated hydro-marsh model, which is comprised of a hydrodynamic and a parametric marsh model. The results include the dynamic effects of SLR scenarios on hydrodynamics, marsh platform accretion, and salt marsh productivity. The Grand Bay estuary is a marine dominant estuary located along the border of Alabama and Mississippi with dominant salt marsh species including Juncus roemerianus and Spartina alterniflora (Eleuterius and Criss, 1991). Sediment transport in this estuary is driven by wave forces from the Gulf of Mexico and SLR that cause salt marshes to migrate landward (Schmid2000). Therefore, the Grand Bay estuarine system is vulnerable to SLR under extreme scenarios. The hydro-marsh model used to project biomass productivity is based on a coupled twodimension...

Coastal wetlands are at the risk of losing their productivity under increasing rates of sea level... more Coastal wetlands are at the risk of losing their productivity under increasing rates of sea level rise (SLR). Studies show that under extreme enough stressors, salt marshes will not have time to establish an equilibrium and may migrate landward (Donnelly and Bertness 2001; Warren and Niering 1993) or become open water. In order to investigate salt marsh productivity under SLR scenarios, an integrated hydrodynamic-marsh model was incorporated to dynamically couple physics and biology. The hydrodynamic model calculates mean high water (MHW) and mean low water (MLW) within the river and tidal creeks by analysis of simulated tidal constituents. The response of MHW and MLW is nonlinear due to local changes in the salt marsh platform elevation and biomass productivity. Spatially-varying MHW and MLW are utilized in a biologic model that is a two-dimensional application of the Marsh Equilibrium Model (Morris et al. 2002) to capture the effects of the hydrodynamics on biomass productivity an...

ABSTRACT In this study, an integrated model to assess the effect of sea level rise on salt marsh ... more ABSTRACT In this study, an integrated model to assess the effect of sea level rise on salt marsh systems is presented. It is based on a coupled two-dimensional hydrodynamic model and a parametric marsh model. The model shows marsh productivity as a function of mean high water (MHW), mean low water (MLW), and the elevation of the marsh platform. MHW and MLW are the mean high and low water levels over a tidal record and the marsh platform elevation is the elevation of the thick and smooth piled up sediments and biomass that support the productivity of the marsh. MHW and MLW throughout a river and tidal creeks are determined by time varying tides resulting from the two-dimensional hydrodynamic model. In order to calculate accurate biomass productivity, and MHW and MLW elevations, a digital elevation model (DEM) representing the marsh table elevation and tidal creeks with high accuracy is necessary (Hagen et al., 2013). There are optimum ranges for relative sea level rise (RSLR), mean sea level (MSL), and depth of inundation for salt marshes to increase productivity. Because of the constantly changing MSL, the marsh always adjusts itself to a new equilibrium (Morris, et al., 2002). In the marsh model, the sediment accretion rate, which is a function of the marsh productivity, is considered. The tidal record is calculated by the hydrodynamic model and the DEM is adjusted by incorporating the accretion rate over a period of time, provided by the marsh model. Then, the new tidal record is assessed by running the hydrodynamic model, considering sea level rise with the new marsh table elevations. Using the new tidal record, the marsh productivity is simulated. This process can be divided into short time steps to capture changes in the rate of sea level rise. For example, a 68 cm sea level rise over 63 years can be split into five- or ten- year periods to have a linear trend for sea level rise in each period. The model is examined for the lower St. Johns River and Apalachicola River and associated salt marsh systems and their response to sea level rise scenarios. These examples show that this comprehensive model is an advanced tool that can be utilized in different sites to capture sea level rise effects on the salt marsh systems. References: Hagen, S., Morris, J., Bacopoulos, P., and Weishampel, J. (2013). 'Sea-Level Rise Impact on a Salt Marsh System of the Lower St. Johns River.' J. Waterway, Port, Coastal, Ocean Eng., 139(2), 118-125. Morris, J. T., Sundareshwar, P. V., Nietch, C. T., Kjerfve, B. and Cahoon, D. R. (2002). Responses of coastal wetlands to rising sea level. Ecology, 83(10), 2869-2877.