In Alabama, the term "coastal shoreline" applies to the Gulf shoreline and the shorelines of estuaries, bays, and sounds connected to the Gulf of Mexico and subject to its tides. However, Alabama shoreline studies have yet to include Little Lagoon, which has been connected to the Gulf of Mexico for most of the last 200 years, according to historical charts. This study used historical nautical charts, aerial photographs, and LIDAR derived shorelines from 1917 to 2004 to analyze shoreline change on Little Lagoon and its adjacent Gulf shoreline. The high water line was used as the common reference feature, and all shorelines were georeferenced, projected, and digitized in a Geographic In-formation System. Between 1917 and 2001, the Gulf shoreline eroded an average of 40 m over 12.7 km, with some transects eroding almost 120 m while others accreted almost 60 m. The greatest changes to the Gulf shoreline were found near natural inlets, downdrift of jetties, and coincident with nourishment projects. Between 1955 and 1997, Little Lagoon shrank 0.5%, or 51.4 km², from 10,285.9 km² to 10,234.5 km². The greatest changes to Little Lagoon were found on its southern shoreline and near inlets, human development, and hurricane overwash fans. A correlation analysis conducted on the Gulf shoreline and Little Lagoon' s southern shoreline indicated that although weak overall correlation values exist when the entire 12.7 km study area is compared, strong correlation values are obtained in some areas when compared over one kilometer sections. The strongest correlations were found in the same locations as the greatest changes. / Master of Science

I assessed the composition of zooplankton communities at the three tidal inlets connecting Lake Pontchartrain to Lake Borgne and subsequently to the Gulf of Mexico. The objectives of my research were to better understand the factors contributing to both spatial and temporal differences in zooplankton communities at the three locations. Monthly samplings of the neuston were conducted from September 2009 until April 2011 and then again from September 2012 until May 2013. Sampling consisted of triplicate tows using SeaGear “Bongo” nets. Water quality data along with water turbidity were recorded at each site and during each sampling effort. All specimens collected during the survey were quantified and identified to the lowest taxonomical unit. The results indicated that there were significant differences among the aquatic invertebrate communities composition among the three sites groups averaged across months (ANOSIM, R= 0.162, p = 0.001). The outcomes from this study could have strong implications for fisheries management and will provide a baseline for future research.

Blind Pass, a heavily structured wave-dominated tidal inlet on the west central coast of Florida, has undergone substantial morphologic changes in the past 150 years. Initially Blind Pass was a mixed-energy inlet. In 1848 a hurricane opened a new inlet to the north called Johns Pass, which captured a large portion of the tidal prism of Blind Pass. Since then Blind Pass migrated southward until it was structurally stabilized in 1937. The decreasing tidal prism resulted in significant inlet channel filling. The channel has been dredged 12 times since 1937. The present inlet is stabilized by two jetties and a series of seawalls. Detailed time-series field measurements of bathymetry and tidal flows were conducted between 2001 and 2004, after the last channel dredging in the summer of 2000. The measured depositional rate in the inlet channel approximately equals the net southward longshore transport rate. This suggests that the inlet has served as a trap for the southward longshore transport allowing negligible bypassing to the eroding downdrift beach. Most of the active sedimentation occurs on the northern side of the inlet. The sediment in the thalweg is largely coarse shell lag, indicating adequate sediment flushing by the ebbing tide. The cross-channel flow measurements revealed that ebb flow was approximately twice as high in the channel thalweg as compared with the rest of the channel. The flood flow was largely uniform across the entire inlet and dominated over the northern portion of the inlet due to the weak ebb flow there. This cross-channel flow pattern is crucial to the understanding of the sedimentation patterns in the Blind Pass channel. Two years after the last dredging the mouth has become shallow enough to induce wave breaking across the shoal area. Distinctive seasonal patterns of sedimentation were measured thereafter in the inlet channel, influenced by seasonal wave climate. The sedimentation is event driven from passage of cold fronts bringing elevated wave energy that accelerates the southward longshore transport. During normal conditions the sediment deposited in the mouth area is redistributed further into the inlet by the flood current combined with wave-driven current.

Tidal inlets play a significant role in barrier island sustainability along the barrier islands of southern Louisiana. With increasing tidal prism, major changes are taking place within and adjacent to the inlets. The purpose of this thesis is to examine how Caminada Pass, a tidal inlet along the Caminada-Moreau headland, has evolved through time. Fundamental to this effort is evaluating which processes have contributed toward inlet evolution and what is the response of the inlet-bordering barrier island shorelines of Grand Isle and Elmer’s Island. This effort summarizes previous results and utilizes published bathymetric data, aerial photographs, vector shorelines, satellite images, and seafloor grab samples. The intent of this research is to document the variety of data that are available for future studies of Caminada Pass, an evaluation of long and short-term changes to the system, and an overall better understanding of the inlet dynamics of Caminada Pass.

John’s Pass is a stable mixed-energy inlet located on a microtidal coast in Pinellas County, Florida. It is hydraulically connected to the northern portion of Boca Ciega Bay. Morphological analysis using a time-series of aerial photographs indicated that anthropogenic activities have influenced the evolution of the tidal deltas and adjacent shorelines at John’s Pass. Previous studies have documented the channel dimensions at the location of the existing bridge and calculated the tidal prism. A chronological analysis of these data yielded an increasing trend in the cross-sectional area at John’s Pass from 1873 to 2001. Anthropogenic activities occurring in Boca Ciega Bay impacting this trend begin in the 1920’s when Indian Pass, approximately 7 km north of John’s Pass, was artificially closed. Other significant events causing an increase or decrease in the crosssectional area at John’s Pass include dredging and filling in the bay, channel dredging at John’s Pass, and jetty construction. More recent data collected from a simultaneous current meter deployment at John’s Pass and Blind Pass were used to calculate the bay area serviced by each inlet resulting in an area serviced by John’s Pass being 1.8x104 km2 and 0.33x104 km2 serviced by Blind Pass. In comparison, Blind Pass captures 14 percent of the tidal prism that John’s Pass captures and John’s Pass captures 87 percent of the bay prism while Blind Pass captures 13 percent. Using the discharge equation and assuming the channel area was largely constant the tidal prism at John’s Pass was 1.07x107 m3 during the twenty-one day deployment. Based on a historical analysis of the tidal prism this study is within 40 percent of the tidal prism calculated by Mehta (1976) and Becker and Ross (2001) and within 20 percent of the tidal prism calculated by Jarrett (1976) and Davis and Gibeaut (1990). An analysis of the current meter time-series indicated that flood velocities in the channel were influenced by a frontal system passing through the study area during the deployment increasing the amount of potential sediment being deposited in the channel thalweg. The maximum ebb and flood-tidal velocities during the deployment were 143 cm/s and 115 cm/s, respectively. Morphological analysis of cross-sectional data from 1995 to 2004 indicated that sediment tends to accumulate along the northern portion of the channel. The channel thalweg tends to accumulate more sediment east of the bridge where wave energy is lower and currents are not as strong. An average net accumulation of 0.5 m per year was estimated along all seven cross-sections. Given the length and width of the surveyed channel, 610 m by approximately 150 m, the sediment flux through the inlet is approximately 45,800 m3 /yr along the channel thalweg. A small amount of sediment accumulation has occurred southwest of the bridge in response to channelized flood flows along the newly constructed jetty. An annual sediment budget was estimated for the John’s Pass inlet system using the beach profiles and inlet bathymetry data between 2000 and 2001. Overall, the inlet system has accumulated more sediment than it has lost during this time period.

Florida's Department of Transportation requires design storm tide hydrographs for coastal waters surrounding tidal inlets along the coast of Florida. These hydrographs are used as open ocean boundary conditions for local bridge scour models. At present, very little information is available on the effect that tidal inlets have on these open coast storm tide hydrographs. Furthermore, current modeling practice enforces a single design hydrograph along the open coast boundary for bridge scour models. This thesis expands on these concepts and provides a more fundamental understanding on both of these modeling areas. A numerical parameter study is undertaken to elucidate the influence of tidal inlets on open coast storm tide hydrographs. Four different inlet-bay configurations are developed based on a statistical analysis of existing tidal inlets along the Florida coast. The length and depth of the inlet are held constant in each configuration, but the widths are modified to include the following four inlet profiles: 1) average Florida inlet width; 2) 100 meter inlet width; 3) 500 meter inlet width; and 4) 1000 meter inlet width. In addition, two unique continental shelf profiles are used to design the ocean bathymetry in the model domains: a bathymetry profile consistent with the west/northeast coast of Florida (wide continental shelf width), and a bathymetry profile similar to the southeast coast of Florida (narrow continental shelf width). The four inlet-bay configurations are paired with each of the bathymetry profiles to arrive at eight model domains employed in this study. Results from these domains are compared to control cases that do not include any inlet-bay system in the computational domain. The ADCIRC-2DDI numerical code is used to obtain water surface elevations for all studies performed herein. The code is driven by astronomic tides at the open ocean boundary, and wind velocities and atmospheric pressure profiles over the surface of the computational domains. Model results clearly indicate that the four inlet-bay configurations do not have a significant impact on the open coast storm tide hydrographs. Furthermore, a spatial variance amongst the storm tide hydrographs is recognized for open coast boundary locations extending seaward from the mouth of the inlet. The results and conclusions presented herein have implications toward future bridge scour modeling efforts. In addition, a hindcast study of Hurricane Ivan in the vicinity of Escambia Bay along the Panhandle of Florida is performed to assess the findings of the numerical parameter study in a real-life scenario. Initially, emphasis is placed on domain scale by comparing model results with historical data for three computational domains: an ocean-based domain, a shelf-based domain, and an inlet-based domain. Results indicate that the ocean-based domain favorably simulates storm surge levels within the bay compared to the other model domains. Furthermore, the main conclusions from the numerical parameter study are verified in the hindcast study: 1) the Pensacola Pass-Escambia Bay system has a minimal effect on the open coast storm tide hydrographs; and 2) the open coast storm tide hydrographs exhibit spatial dependence along typical open coast boundary locations.