Coastal zone management.

Each year storms impact coastal areas, sometimes causing significant
morphologic change. Cold fronts are associated with increased wave energy and
frequently occur during the winter months along many coasts, such as the Atlantic and
Gulf of Mexico. The higher wave energy can be responsible for a large quantity of the
sediment transport resulting in rapid morphologic change. Using streamer traps, the
vertical distribution of onshore-directed sediment transport during two different cold
fronts on two low-wave energy beaches (i.e., along the northern Yucatan and southeast
Florida) were compared with the resulting morphologic change. The objectives of this
study are to: 1) analyze the grain size distribution (statistics) of sediment transported
during a cold front, 2) compare the vertical sediment distribution throughout the water
column, and 3) compare characteristics of bed sediment to the sediment within the water
column. Understanding the changing grain size distribution of bottom sediments in
comparison to directional transport (throughout the water column) should help determine the sediment fraction(s) being eroded or deposited, which could greatly improve
predictions of storm-induced morphology change.

Seagrass is a key stone component for the Indian River Lagoon (IRL) ecosystem,
and therefore it is an important topic for many studies in the lagoon. This study focuses
on the effects of seagrass beds on the hydrodynamics in the IRL. A hydrodynamic model
based on the Delft3D modeling system has been developed for the southern IRL
including the St. Lucie estuary, Ft. Pierce and St. Lucie Inlets, and adjacent coastal
waters. The model is driven by freshwater inputs from the watershed, tides,
meteorological forcing, and oceanic boundary forcing. The model has been systematically calibrated through a series of numerical
experiments for key parameters, particularly the bottom roughness, and configuration
including heat flux formulation and bottom bathymetry. The model skills were evaluated
with quantitative metrics (point-to-point correlation, root-mean-square difference, and
mean bias) to gauge the agreements between model and data for key variables including temperature, salinity, and currents. A three-year (2013-2015) simulation has been
performed, and the results have been validated with available data including observations
at HBOI Land-Ocean Biogeochemistry Observatory (LOBO) stations and in situ
measurements from various sources. The validated model is then used to investigate the
effects of 1) model vertical resolution (total number of model vertical layers), 2) spatial
variability of surface winds, and 3) seagrass beds on the simulated hydrodynamics. The
study focuses on the vicinity of Ft. Pierce Inlet, where significant seagrass coverage can
be found. A series of numerical experiments were performed with a combination of
different configurations. Overall, the experiment with 2-dimensional (2-D) winds, ten
vertical layers and incorporating seagrass provided the most satisfactory outcomes.
Overall, both vertical resolution and spatial variability of surface winds affect
significantly the model results. In particular, increasing vertical resolution improves
model prediction of temperature, salinity and currents. Similarly, the model with 2-D
winds yields more realistic results than the model forced by 0-D winds.
The seagrass beds have significant effects on the model results, particularly the
tidal and sub-tidal currents. In general, model results show that both tidal and sub-tidal
currents are much weaker due to increase bottom friction from seagrass. For tidal
currents, the strongest impacts lie in the main channel (inter-coastal waterway) and
western part of the lagoon, where strong tidal currents can be found. Inclusion of seagrass
in the model also improves the simulation of sub-tidal currents. Seagrass beds also affect
model temperature and salinity including strengthening vertical stratification. In general,
seagrass effects vary over time, particularly tidal cycle with stronger effects seen in flood
and ebb tides, and seasonal cycle with stronger effects in the summer than in winter.

A confounding factor for sea level rise (SLR) is that it has a slow, steady creep,
which provides a false sense for coastal communities. Stresses caused by SLR at today’s
rate are more pronounced in southeastern Florida and as the rate of SLR accelerates, the
exposure areas will increase to a point where nearly all the state’s coastal infrastructure
will be challenged.
The research was conducted to develop a method for measuring the impact of
SLR on the City of West Palm Beach (City), assess its impact on the stormwater system,
identify vulnerable areas in the City, provide an estimate of long-term costs of
improvements, and provide a toolbox or strategies to employ at the appropriate time. The
assessment was conducted by importing tidal, groundwater, topographic LiDAR and
infrastructure improvements into geographic modeling software and performing analysis
based on current data. The data revealed that over $400 million in current dollars might
be needed to address stormwater issues arising from SLR before 2100.