Louisiana’s wetlands are losing land in response to sea level changes, anthropogenic influences and natural marine processes. Historical satellite image analysis reveals that between 2005 and 2015, fifteen tidal creeks in Barataria Bay, Louisiana eroded at the rate of 1.80 m/yr (± 1.98 m), and the open water area behind these creeks enlarged at the rate of 530.00 m2/yr (± 204.80 m2). This research revealed that selected tidal creeks within the estuary have cross-sectional areas larger (2639% larger) than established ocean-inlet equilibrium models would predict. This work suggests that tidal prism to tidal creek cross-sectional area relationships in Barataria Bay are most strongly shaped by creek exposure to waves and secondarily by tide range and currents. A trend of increased inlet erosion rates due to large fetch distances is evident, but impacts from storm driven subtidal variations also play an important role.

The study site, Ta-pon Bay, is located in southwestern Taiwan that has the total volume of 9.92 x 106 m3, surface area of 4.46 x 106 m2, and an average depth of 2.19 m. The Ta-pon Bay is a shallow and semi-enclosed lagoon. The tidal regime at the Ta-pon Bay inlet is mixed, with diurnal dominance. There is noticeable amount of land-derived freshwater inflow in Ta-pon Bay and the mixing between the sea water and freshwater is largely determined by the tide. In order to understand the tidal exchange process between Ta-pon Bay and the coastal sea, the observation focused on the physiographic and hydrographic characteristics of this lagoon. The bathymetry of the study area was also surveyed. From the spatial sediment grain-size distribution pattern, the high energy region is at the inlet and the low energy region is in the interior of the lagoon. Our observation results indicate that freshwater outflow from the Kao-ping River was not transported into Ta-pon Bay. Tides are also the dominant cause for the water level fluctuations in the lagoon. In our winter observation, the local wind effects and atmospheric forcing dominated the subtidal sea surface fluctuations. In summer observation, the subtidal variability was strongly influenced by freshwater inflow. In Ta-pon Bay, the spatial salinity distribution was controlled by the flood and ebb tides, and the spatial temperature distribution was controlled by the different seasons. The tidal prism model can help us understand the tidal exchange between a shallow coastal lagoon and the open sea, and estimate the volume of freshwater inflow, return flow factor, and the turn-over time. Furthermore, we used a one-dimensional model to simulate the hydrodynamics of tidal inlet. The model results show good agreement with observations. We found that the superelevation of the lagoon was 20 cm. This mean sea level difference was caused by freshwater inflow and accumulation of lagoonward tidal transport of water.

The Northern Gulf of Mexico and coastal Louisiana are experiencing accelerated relative sea level rise rates; therefore, the region is ideal for modeling the global affects of sea level rise (SLR) on estuarine dynamics in a transgressive barrier island setting. The field methods and numerical modeling in this study show that as barrier islands are converted to inner shoals, tidal exchange increases between the estuary and coastal ocean. If marshes are unable to accrete at a pace comparable to SLR, wetlands will deteriorate and the tidal exchange and tidal prism will further increase. Secondary to hurricanes, winter storms are a primary driver in coastal morphology in this region, and this study shows that wind direction and magnitude, as well as atmospheric pressure change greatly affect estuarine exchange. Significant wetland loss and winter storm events produce changes in local and regional circulation patterns, thereby affecting the hydrodynamic exchange and resulting transport.

The tidal prism, or the volume of water exchanged from the sea to an estuary from mean low to mean high tide, influences system hydrodynamics and ecological functioning. Since 1884, the tidal prism in Morro Bay, California has been estimated to be decreasing over time due to sedimentation from upstream practices. What is the current tidal prism in Morro Bay and how will that change with sea level rise? How will eelgrass respond to rising sea levels? For this study, inexpensive tidal gauges were deployed at four locations in Morro Bay from March to August 2023 to measure spatially varying tidal elevations and datums within the bay. I utilized a Digital Elevation Model (DEM) and tidal information to determine volumes of water in Morro Bay. Estimated sea level rise scenarios were utilized to project the 2022 tidal prism into the years 2050 and 2100. Additionally, I estimated the 2019 and 2022 viable eelgrass habitat area using the vertical growth range. I estimated the future potential viable habitat area in the years 2050 and 2100 using estimated sea level rise scenarios. Future projections were made assuming no change in bathymetry over time. Different instruments used to obtain water levels yielded up to ~4 percent differences in the tidal prism estimate. Measurement uncertainty in the monthly tidal datums produced ~3 percent uncertainty within the tidal prism estimate. Compared to the tidal prism in August 2019, the August 2022 tidal prism was lower by ~2 percent. Compared to the tidal prism in August 2019, the August 2023 tidal prism estimated from two nearly co-located tidal instruments at the mouth of Morro Bay were higher by ~5 and ~7 percent, respectively. Spatially varying tidal datums in Morro Bay were found to affect the tidal prism by up to ~3 percent, compared to tidal prism estimates using only a tidal datum near the estuary mouth. However, the effect of spatially varying tidal datums on the tidal prism is the same order of magnitude as measurement uncertainty and is thus not statistically significant. As sea levels rise, the tidal prism is projected to increase by ~40 percent by 2100 from 2022 under the most extreme scenario, H++. Initially, as sea levels rise, the potential viable eelgrass habitat area will increase from the area in 2022 (1108 acres (4.47E+06 m2)). After sea levels rise to 1.5 m above 2000 levels, the potential viable eelgrass area will have reached a maximum area of 1938 acres (7.82E+06 m2). However, under SLR scenario H++, potential viable habitat area is predicted to decrease by up to 59% by 2100 from 2022. The tidal prism, or the volume of water exchanged from a bay to the seathe sea to an estuary from mean lowhigh to mean highlow tide, influences system hydrodynamics and ecological functioning. Since 1884, the tidal prism in Morro Bay, California has been estimated to be decreasing over time due to sedimentation from upstream practices. What is the current tidal prism in Morro Bay and how will that change with sea level rise? How will eelgrass respond to rising sea levels? For this study, inexpensive tidal gauges were deployed at four locations in Morro Bay from March to August 2023 to obtain measure spatially varying tidal elevations and datums within the bay. I utilized a Digital Elevation Model (DEM) and tidal information from NOAA to determine volumes of water in Morro Bay at the estimated monthly mean tidal datums. Estimated sea level rise scenarios were utilized to project the 2022 tidal prism into the years 2050 and 2100. Additionally, I estimated the 2019 and 2022 viable eelgrass habitat area using the vertical growth range. I estimated the future potential viable habitat area in the years 2050 and 2100 using estimated sea level rise scenariosfor various sea level rise scenarios.Future projections were made assuming no change in bathymetry over time. Different instruments used to obtainwater levels yielded up to ~4 percent differences in the tidal prism estimate. Measurement uncertainty in the monthly tidal datums produced~3 percent uncertainty within the tidal prism estimate. Compared to the tidal prism in August 2019, the August 2022 tidal prism from Stilltek decreasedwas lower by ~2.05 percent. Compared to the tidal prism in August 2019, the August 2023 tidal prism estimated from the Stilltek gauge and the Cal Poly Coast Guard gaugetwo nearly co-located tidal instruments at the mouth of Morro Bay increased were higher by ~5.06 and ~6.777 percent, respectively. Spatially varying tidal datums in Morro Bay were found to affect the tidal prism by up to ~2.883 percent, compared to tidal prism estimates using only a tidal datum near the estuary mouth. However, the effect of spatially varying tidal datums on the tidal prism is the same order of magnitude as measurement uncertainty and is thus not statistically significant. As sea levels rise, the tidal prism is projected to increase by ~to a maximum of 40 percent by 2100 from 2022 under the most extreme scenario, H++. InitiallyInitially, as sea levels rise, the potential viable eelgrass habitat area will increase from the area in 2022 (1108 acres (4.47E+06 m2)). ABut after sea levels rise to 1.5 m above 2000 levels, the potential viable eelgrass areas will have reached the thresholda maximum area of 1938 acres (7.82E+06 m2). However, under SLR scenario H++, potential viable habitat area is predicted to decrease by up to 59% by 2100 from 2022.