Refereed Journal Articles

Model Sensitivity to Topographic Uncertainty in Meso- and Microtidal Marshes



Light detection and ranging (Lidar) derived digital elevation models are widely used in modeling coastal marsh systems. However, the topographic error in these models can affect simulations of marsh coverage and characteristics. We investigated the relevance and impact of this error in micro- and mesotidal systems. Lidar-derived and RTK-adjusted topography were each used in a dynamic marsh model, and the resulting marsh coverages were examined. For two microtidal sites (Apalachicola, FL, USA, and Grand Bay, MS, USA) using solely lidar-derived topography, the model produced Cohen Kappa values of 0.1 for both estuaries when compared with National Wetland Inventory data indicating “very poor agreement.” Applying the RTK-adjusted topography improved the model marsh coverage results to “substantial agreement” with the values to 0.6 and 0.77, respectively. The mesotidal site in Plum Island, MA, USA, contained similar topographic errors, but the model produced a Cohen Kappa value of 0.73, which categorized it as “very good agreement” with no need for a further topographic adjustment given its present robust biomass productivity. ...

Dynamic Responses and Implications to Coastal Wetlands and the Surrounding Regions Under Sea Level Rise

PLoSONE - 2018


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 ...

Coastal Wetland Response to Sea Level Rise in a Fluvial Estuarine System

Earth's Future - 2016


Coastal wetlands are likely to lose productivity under increasing rates of sea-level rise. This study assessed a fluvial estuarine salt marsh system using the Hydro-MEM under four sea-level rise scenarios. The Hydro-MEM was developed to apply the dynamics of sea-level rise as well as capture the effects associated with the rate of sea-level rise in the simulation. Additionally, the model uses constants derived from a two-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 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) sea-level rise scenarios and lower variation with an extended bay under higher sea level rise scenarios. The low sea-level rise scenario increased biomass density in some regions and created a more uniform marsh platform in others ...

A Coupled, Two-Dimensional Hydrodynamic-Marsh Model with Biological Feedback

Ecological Modeling - 2016


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 estuarine 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) ...

Dynamic Simulation and Numerical Analysis of Hurricane Storm Surge Under Sea Level Rise with Geomorphologic Changes along the Northern Gulf of Mexico

Earth's Future - 2016


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... 

Tidal Hydrodynamics Under Future Sea Level Rise and Coastal Morphology in the Northern Gulf of Mexico

Earth's Future - 2016


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...

The Response of Runoff and Sediment Loading in the Apalachicola River, Florida to Climate and Land Use Land Cover Change

Earth's Future - 2016


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.

Karim Alizad Earth's Future Dynamic SLR
The Dynamic Effects of Sea Level Rise on Low-Gradient Coastal Landscapes: A Review

Earth's Future - May 2015


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 ...

Karim Alizad Coastal Research Publication
Climate Change Impact on Runoff and Sediment Loads to the Apalachicola River at Seasonal and Event Scales

Journal of Coastal Research - August 2014


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.  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...

Karim Alizad Journal of Hydrology IDF Apalachicola
Climate Change Impact and Uncertainty Analysis of Extreme Rainfall Events in the Apalachicola River basin, Florida

Journal of Hydrology - February 2013


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... 

Karim Alizad Heat and Mass Transfer Nanofluids heat pipe startup
Thermal performance and operational attributes of the startup characteristics of flat-shaped heat pipes using nanofluids

International Journal of Heat and Mass Transfer - January 2012


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.

Peer-Reviewed Trade Journal Articles

Karim Alizad Florida Watershed Journal
Integrated Modeling of Hydrodynamics and Marsh Evolution Under Sea Level Rise in Apalachicola, Fl

Florida Watershed Journal - June 2013


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...