Coastal Flood Hazard Analysis for Bandar Anzali Coast Considering Joint Probability of Significant Events

Communities accommodated along shorelines have always been under devastating threats from the
sea/ocean such as coastal flooding. Mitigation planning against such threads demands a well
understanding of the thread’s nature. In addition to the physical understanding, such planning is
always based on statistical representation of the thread generating events. Coastal hazard analysis is
the method of estimating such statistical representations based on the physics and time history of the
events and so, it is the preliminary step toward hazard mitigation planning. Methods that combine
contributing physical processes have weekly considered the dependence between the physical
processes. Using proper joint probability statistical methods, rational combinations of events can be
estimated on the ground of their history. Copula functions are a group of functions that generate such
combinations. Estimating the marginal distribution of the events, Copula functions represent the joint
probability of the events based on their historical joint occurrence. This method is used in this paper to
derive the joint probability of storm surge and wave height for Bandar Anzali coasts. The ad-hoc
method of superimposing the significant events is also pursued for comparison. The marginal
distributions are chosen from GEV, Weibull, Gumble and Lognormal probability distributions. The
model parameters are estimated using the Maximum Likelihood method, and the goodness of fit is
evaluated using the Root Mean Square Error criterion. Deep water waves with return period of 20, 50
and 100 years in addition to the joint probability results are transferred to the beach using the spectral
coefficient method. Considering wave setup and wave run up, the final inundation levels are estimated
and the inundated regions are plotted.