BLUE-Coast
PHYSICAL PROCESSES AND COASTAL RECOVERY    

The complexity of sediment dynamics processes in the water column, at the seabed, and at the water-land interface are not well understood. Important questions include: i) which processes dictate cross-shore and/or alongshore sediment fluxes? ii) Which processes govern the recovery period of coastal systems? iii) How sensible are coastal areas to changes in external forcing? 

The goal of BLUEcoast is to answer these and many other questions by using field data and numerical models. (NERC Highlight topics, at University of Liverpool, National Oceanographic center, Cambridge University, Plymouth University, British Geological Survey, HR Wallingford, University of Southempton, University of St Andrews, Birbeck Univerisity of London, Cardiff University). 


IMPACT OF HURRICANE SANDY ON THE SALT MARSHES OF CHINCOTEGUE BAY, VIRGINIA, AND BARNEGAT BAY 

In October 2012 Hurricane Sandy impacted the United States Atlantic Coast with its >68 billion of dollars of damage. We are working with the United States Geological Survey to understand salt marsh resilience to violent storms and hurricanes, and to develop new numerical models and routines for wetlands erosion and sediment transport processes.  

We are using the numerical model COAWST (ROMS+SWAN+WRF) to model wetlands behavior under different wave climate and storms conditions. (Cooperative agreement with US Geological Survey, Woods Hole Science Center, Boston University, University of Liverpool; with Sergio Fagherazzi (BU), and Neil Kamal Ganju (USGS)). 



TIDAL HYDRODYNAMIC AND EXTREME WATER LEVELS IN HYPERTIDAL ESTUARIES

Predicting extreme water levels within estuaries is essential for coastal management strategies. The interaction between storm surges and tides is nonlinear and influences water levels. Huge spatial variability can occur between tidal gauges along estuaries, and even small changes in elevation can cause huge differences in inundation extent. 

We are studying the tide-surge interaction in the Severn Estuary by using the ocean model POLCOMS and Delft3D. (with Jennifer Brown (NOC), Charlotte Lyddon (NOC, UoL), Andy Plater).



 SALT MARSH
            

Salt marshes are coastal wetlands. They are ecosystem based flood defenses, and among the most productive ecosystems on earth. In recent years, there has been a flurry of restoration projects aimed at mitigating the impact of coastal storms using salt marshes and vegetated surfaces. However, salt marsh losses have been documented worldwide because of land use changes, wave erosion and sea level rise. 

We are studying salt marsh evolution and erosion by wind waves using cellular automata models, and 3D hydrodynamic and sediment transport models like COAWST (ROMS+SWAN+WRF), and Delft 3D.

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SIMPLIFIED COMPLEXITY MODELS

Cellular automata ad simplified complexity models use simple stochastic rules to reproduce systems behavior. Simplified complexity models are useful in geomorphology as they can help extracting universal features of the systems, and model emergent properties. 

Above a simple invasion percolation model for salt marsh erosion under low and high wave energy conditions (white is the sea; black is the eroding marsh). Low wave energy and slowly eroding salt marshes correspond to rough marsh boundary profiles (right plot, higher fractal dimension). High wave energy and rapidly eroding salt marshes correspond to smooth marsh boundaries (left plot, low fractal dimension).

 

 HYDRODINAMIC & SEDIMENT TRANSPORT MODELS  

Hydrodynamic and sediment transport models solve the Navier-Stokes equations, and the advection diffusion equation to simulate hydrodynamic and sediment transport processes. These models can be also used to simulate the morphological evolution of coastal environments. 

I have been using the numerical model Delft3D, and COAWST (ROMS+SWAN+WRF) to model the behavior of estuaries and bays, and to simulate their morphological evolution. I have been also using the same models to investigate the efficiency of different coastal protection schemes.


HYDRODYNMIC FIELD MEASUREMENTS

Acoustic instruments like ADCP (acoustic Doppler current profiler) transmit and receive sound signals. The traveling time and frequency shift of the echo gives an estimate for water velocity along the acoustic path. 

I have been deploying acoustic instrumentation, and analyzed the resulting data to investigate the interaction between riverine discharge and tidal hydrodynamic in Apalachicola Bay, Florida.


RIVER DELTAS AND MOUTH BARS

Mouth bars are the building units of river deltas. The hydrodynamic, morphology and stratigraphy of mouth bars can be affected by tides and river discharge regimes. For instance, even small tides can strongly impact mouth bars formation and evolution. 

I used the model Delft3D, as well as analytical formulations for turbulent jet and sediment transport to study mouth bars evolution and create analytical facies models for these morphological units.

FULL CURRICULUM VITAE (pdf)


School of Environmental Sciences, Institute for Sustainable Coasts and Oceans      I      Roxby Building, Liverpool, L69 7ZT          I       email: N.Leonardi@liverpool.ac.uk