Lake Bardawil is a hypersaline shallow micro-tidal double-inlet lagoon on the northern coast of the Sinai Peninsula in Egypt. The inlets, named Boughaz 1 and Boughaz 2, connect Lake Bardawil to the Mediterranean Sea. The local population relies on the fishing yields from the lagoon, however, in the current situation, the lagoon’s inlets are unstable, needing constant maintenance dredging to stay open. Additionally, due to the hypersaline situation (limiting fish attraction) and high fish catch demand, the current fishing situation is unsustainable. The Weather Makers propose a solution to the problem using dredging interventions. Enlarging the inlets of Lake Bardawil is expected to result in increased fish migration, decreased salinity in the lagoon and increased stability of the inlets. This research aims to investigate the short-term response of Lake Bardawil and specifically its inlets to the dredging interventions proposed. To investigate the response to the interventions, two numerical models are used; a hydrodynamic model in D-flow FM and a coupled morphological model using D-flow FM and D-waves. The model results are analysed in terms of the hydrodynamic tidal response, combined hydrodynamic response to tide and weather and finally the morphological response to tidal and weather effects. From the hydrodynamic model, it can be concluded that the interventions result in a larger tidal prism for the lagoon by a factor of 1.6. This is expected to result in increased fish migration and reduced salinity in the lagoon. As the tidal prism increases, so does the discharge through the inlets. The increased discharge through the inlets results in inlet velocity amplitudes that exceed the theoretical critical value for convergence to a dynamically stable inlet cross-section for both inlets. The interventions affect more than just tidal currents in Lake Bardawil. Weather effects in the lagoon are amplified by the interventions. This is demonstrated by increased interaction between the inlets in terms of net import and export of water. During winter storms, the wind-induced flow from Boughaz 1 to Boughaz 2 is greater in magnitude. The wind waves caused by these winter storms result in sediment resuspension. This results in larger sediment transport from the basin to Boughaz 2. Using the coupled model, the morphological response in both inlets can be predicted. In Boughaz 1, the present sediment-importing character is amplified. Whereas the similar summertime sediment-importing character of Boughaz 2 is reduced substantially. The sediment export of Boughaz 2 during winter is larger in the new situation. The interventions result in increased sedimentation in the dredged channel of Boughaz 1. This does not hinder the increased tidal discharge at Boughaz 1, which is the main intended function of the interventions. This means the increased sedimentation does not influence the intended functioning of the interventions in the short term. Due to the increased sedimentation in the inner dredged channel, there is no indication of increased stability in Boughaz 1. Boughaz 2 shows less morphological activity in the situation after interventions. As is the case with Boughaz 1, there is no hindrance to the functioning of the interventions during the short simulation period. There is reduced deposition of sediment in the inner flood delta region of the inlet and the updrift side of the inlet channel compared to the known unstable situation during both winter and summer simulations. This indicates improved stability for Boughaz 2. The short-term response to the interventions in the inlets of the Lake Bardawil system is as intended, the tidal prism is increased and while there is only an indication of increased stability in Boughaz 2, there are no short-term impediments to the intended primary functioning of the interventions in either of the inlets. ... Read more

Lagoons are connected to the sea by the presence of openings along their barriers. These openings, also known as tidal inlets, can either be natural or man-made and they highly determine the hydrodynamics within the lagoon system. Tidal inlet systems are found worldwide, and many of them are difficult to be understood due to their complex processes and lack of data. One of these systems is Lake Bardawil. Lake Bardawil, is located at the North coast of the Sinai Peninsula in Egypt and its ecological value is of great importance. Its existence mainly depends on the presence of three inlets which connect the lagoon with the Mediterranean Sea, called Boughaz 1, Boughaz 2 and Zaranik inlet. Boughaz 1 is located in the western side of the lake while Boughaz 2 and Zaranik are in the eastern side.
One of the recent researches that is carried out by the Dredging, Environmental and Marine Engineering (DEME), The Weather Makers (TWM) and Lanters (2016), studied how the ecosystem and the fish population of Lake Bardawil can be restored by new hydraulic interventions. This thesis is an extension of the aforementioned work, but current focus is put on the determination of an innovative design and associated methodology which is based on natural design elements and can improve the functionality of Boughaz 1 inlet.
Boughaz 1 was constructed in 1955 to allow the water exchange between the sea and the lagoon. Over the passing years, it has been subjected to a reduced tidal prism resulting in poor water quality in the lagoon, limited fish migration from the sea and sedimentation causes the need for dredging maintenance works. This led to the construction of breakwaters in 1985 until 1995 for the stabilization of the inlet and for the protection of the fish population in the lagoon. Although, the dredging works and constructed breakwaters minimized the abrupt sedimentation through the inlet and improved its stability in short term, the natural behavior of the system is gradually changed which worsen these conditions in longer term. For that reason, a design methodology is carried out to understand and improve the functionality of the Boughaz 1 inlet. The design methodology is based on the most important natural design elements, namely inlet cross sectional area, approach channel and inlet nourishment. Numerical models (Delft3D and Delft3D FM) are used to assess the influence of the different designs on the functionality of the system. A hydrodynamic analysis is carried out for each design element to define the final combined design of the initial phase of this design process. This final design is examined under hydrodynamics and the initial deposition and erosion patters. It is concluded that the functionality of the Boughaz 1 inlet can be optimized with the adapted design methodology. The tidal prism and flow velocities have been increased while the aim to mimic nature is validated with the initial deposition and erosion patterns.
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