Assessing the contribution of wave runup to total water levels under extreme conditions with empirical parameterizations and global data sources: a case study of Holbox, Mexico.

Supervisors: Sanne Muis, Maialen Irazoqui Apecechea (Department of Environmental Hydrodynamics and Forecasting, Deltares, The Netherlands)
Coastal flooding is one of the major environmental phenomenos affecting an important amount of the the global population. It is expected to worsen since coastal cities continue growing, and climate change alters modes of variability and intensifies storms. The increase in magnitude of processes such as wave setup and runup during storm contiditions alters considerably the water levels in the nearshore and enhances coastal flooding events. The few studies focused on the estimation of total water levels during extreme conditions for coastal flooding at global scale have estimated the effects of astronomical tide and storm surge accurately; while the wave-induced effects on water levels have faced some limitations. In this way, the present work takes a sandy beach in the Gulf of Mexico as case study to simulate storm conditions in the XBeach model. The results of the simulations are compared with different wave runup parameterizations using local data. Further comparisonsare made when the emprical parameterizations use global datasets of waves from ERA5 and nearshore slopes. The results showed an important contribution of the wave-induced effects on total water levels (50%). The parametrizations showed a different performance according to the foreshore slope, with more similarity to the modelled runup for slopes beween 0.06-0.09. Finally, the use of global waves data from ERA5 in the parameterizations gave results similar to the local data; while the use of nearshore slopes underestimated runup and it is not recommended.