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The Yemen LNG Company Ltd. is working on the design and construction of an LNG plant in the Republic of Yemen. The LNG plant, located at Balhaf on the Gulf of Aden, includes a jetty approximately 750 m from the shore to allow loading of LNG carriers. The bathymetry around the jetty is very complex and includes a large variation in water depth along the berth. Furthermore a cape near the jetty affects the incoming wave conditions. Deltares (formerly WL | Delft Hydraulics), together with MARIN, carried out a study of combined hydrodynamic scale model tests and computer simulations. The aim of the project was to determine the limiting environmental conditions for safe mooring of the LNG carriers at the jetty. The hydrodynamic scale model tests at Deltares focused on an accurate modeling of the wave conditions at the jetty and the motion response of the moored ship. To achieve this, the bathymetry around the jetty was modeled in detail, including the cape partially shielding the jetty from incoming waves from the open sea. Wind was applied to the moored ship as constant forces. The time-domain computer simulations were carried out by MARIN, using their TERMSIM simulation model. After calibration against scale model test results, the numerical model was used to quantify the effect of gusting wind for all environmental conditions and all ships as tested in the basin. The results of the scale model tests, corrected for the effect of gusting wind, indicated that the vessel can stay safely moored at the jetty in quite severe conditions. This leads to a high jetty availability, which is a favorable outcome of the project. After describing, in a general way, the methodology and results of the project, this paper focuses on the comparison of the results of the model tests with those of the computer simulations. This comparison showed that the low frequency effects, both excitation and response, in the complex bathymetry that was considered here, are very complex and beyond the present numerical modeling capabilities. Therefore, in the short term, physical model testing will remain necessary for an accurate prediction of the moored ship’s response in such situations. For the longer term the development of additional analysis and simulation methods is required.

Sea level rise (SLR) will affect water levels and increase flood risk in river deltas. To adapt river deltas to SLR, various strategies can be followed. Many urbanised river deltas already have flood protection in place. Continuing a protection strategy under an increasing SLR, would mean higher embankments along the coast and rivers and possibly closing off the river mouths from the sea. However, closing of rivers will hamper the river flow. How to adapt river deltas and enabling rivers to discharge into the sea is a challenging question. This paper assesses impacts of SLR on flood risks in the Rhine‐Meuse Delta in the Netherlands in case the current protection strategy is continued and explores two alternative protection strategies: (1) a closed system with pumps and discharge sluices and (2) an open system in which rivers are diverted to less densely populated areas. The second alternative results in a more flexible river delta, which can accommodate larger SLR. The paper shows that a systems approach and using quantitative assessments of the implications of strategies is possible. This is needed to further assess the adaptation options, so we can anticipate and adapt when needed and avoid regret of decisions.

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