MODELING OF CLIMATE CHANGE IMPACTS ON COASTAL STRUCTURES - CONTRIBUTION TO THEIR RE-DESIGN

摘要

Climate change is expressed on the open sea and the coastal zone through a number of impacts, such as: sea level rise, increase of the frequency of extreme wind events, change of the annual winds frequency, more frequent storm surge events, higher waves, changes of the dominant wave direction, stronger currents on the coastal zone etc. The above impacts, mainly due to a new sea level design and higher waves attack, induce morphodynamic responses such as beach and dune erosion, inundation on low-lying areas leading to increased flooding risk of the coastal zone, increase of wave penetration into harbours, failure of the existing coastal protection structures to protect sandy beaches from erosion.In the present work, a numerical model, for the re-design of the existing coastal structures, is presented. The model is based on the higher order Boussinesq equations and describes non linear wave transformation in the nearshore zone as well as wave structure interaction.By introducing a moving boundary scheme, the nonlinear wave propagation model is adapted to simulate wave run up on beaches and breakwaters, as well as overtopping and propagation behind the coastal structures. Using the proposed numerical model the Coastal Engineer can re-design coastal structures aiming to reduce the overtopping, by increasing crest level or/and offshore slope or by constructing a berm/submerged breakwater offshore the coastal structure. In addition since the model describe wave penetration into harbours, it can be used for the redesign of ports and harbours under the future climate change conditions.The model is also able to describe breaking wave-induced current (simply after time integration of the wave horizontal velocities). After the coastal current simulation and together with the wave hydrodynamics prediction, sediment transport formulae are easily incorporated. Therefore, the model can be applied to simulate beach cross-shore morphology evolution and consequently can be used to estimate coastal erosion caused by extreme marine events.The wave-structure interaction simulation together with the sediment transport simulation, lead to the description of the two-dimensional erosion-accretion processes and the simulation of the effects of coastal protection structures on coastal morphology. Thus, the model, can be used for the re-design of coastal protection structures under the future conditions (higher waves, changes of the dominant wave direction, sea level rise, etc). Concluding, the model provides a useful tool to Coastal Engineers for the redesign of the existing coastal structures (higher waves, changes of the dominant wave direction, sea level rise, etc).