Lake Bardawil is a hypersaline, shallow coastal lagoon located along the coast of the northern Sinai Peninsula in Egypt. Coastal systems are understood to be hypersaline when the salinity exceeds values of 30 parts per thousand throughout the year.
Being located in the arid climate region of North Africa the lagoon is subject to year-round extreme weather conditions which are dominated by high air temperatures, extreme evaporation rates, and limited precipitation. All the above in combination with the lagoon’s shallow bathymetry and restricted freshwater input causes Lake Bardawil to inhibit hypersaline conditions throughout the whole year. For Lake Bardawil this means average salinity values in the order of 42 – 51 parts per thousand.
The here conducted study is the first in the line of five successive studies focusing on three-dimensional hydrodynamics. Making use of the three-dimensional hydrodynamics, the movement of the water and salt through the lagoon is considered. Here the response of the system to the extreme meteorological conditions around Lake Bardawil is investigated. The meteorological forcing causes subtidal flows in coastal waters which are responsible for the propagation of waterborne materials such as salt and pollutants.
The results show that during periods of extreme meteorological forcing the response of the lagoon and its inlets is in line with expectations one might have from literature. During periods and events of high evaporation, the lagoon shows an overall increase in top and bottom layer salinity. Furthermore, the largest compensation flow due to evaporative losses of approximately 34 m3/s from the Mediterranean Sea into the lagoon is observed. While the lagoon waters act rather inert as shown for the average conditions during the month of April, it is the wind that initiates the motion. Successively the phenomenon of gravitational circulation in the deeper areas around the inlets can be observed with more saline waters propagating towards the inlets, along the bottom layer. At times, these processes cause subtidal velocities up to 0.15 m/s, which were computed in the inlets.
Crucial for the overall response of Lake Bardawil to meteorological forcing is the complex lagoon geometry and shallowness. Here the tidal divide, on the verge of the western bottleneck to the eastern basin is found to be of great importance. At this location very calm flow conditions are present promoting stagnant waters. The eastern basin with its vast areal extent experiences wind-driven circulations, while the western bottleneck is bound by its narrowness and tide dominance. As a consequence, the western inlet Boughaz 1 can be described as continuously well-mixed, while its eastern counterpart, Boughaz 2, experiences periodic stratification.
The application of system adaptations as proposed by The Weather Makers (TWM) proves to increase the exchange flow with the Mediterranean Sea. Here the dredging of two new inlets as well as dedicated tidal gullies through the lagoon established a more dynamic system where the inner lagoon connectivity is significantly enhanced. This is evident by the widespread presence of Mediterranean waters and the decreased salinity in a broad stretch along the barrier island as well as on the full lagoon scale. However, the lagoon waters in remote locations along the fringes of the large eastern basin remain of high salinity and show still little interaction with the tidal flow.

Sandy barriers comprise 12% of coastlines around the world, and most of these barriers enclose tidal bays and lagoons. These systems accommodate human settlements vulnerable to climate change, which offer enough economic, social, and environmental utility to require further research on the impact of climate change and subsequent best management practices.

The present work aims to analyze how climate change impacts the hydrodynamics and morphodynamics of two barrier inlet systems: Katama Bay (United States of America), and the Santa Lucia Estuary (South Africa). The goal is to estimate future changes in forcing variables (e.g., sea level rise, wave climate, river discharge, tides), implement them in process-based models (coupled SWAN and Delft3D), and identify changes in the dynamics of both systems by comparing present and future state simulations.

This thesis develops a replicable and flexible methodology that can be used as a systematic tool to assess the impacts of climate change on the overall dynamics of tidal inlet systems. A novel approach (copula analysis) was used to derive the wave climate implemented in Delft3D, which was then qualitatively validated for both sites. Model results were used to compare changes to inlet stability, inlet geometry, and sediment pathways for present and future hydrodynamic conditions.

Results show that sea level rise is the primary contributor to the overall morphodynamics at both sites, whereas changes in wave direction strongly impact the rate of inlet migration. Other changes (e.g., significant wave height, wave period, and river discharge) play a secondary role in the dynamics of both systems. Comparisons with previous studies suggest that wave direction impacts each system differently. These impacts must be specifically addressed for each tidal inlet, as the results from one site should not be used to determine a general behavior for the assessment of CC impacts in tidal inlet systems.