Evaluation of wave damage in urbanized lagoons

On the basis of the studies carried out for the Venice lagoon (Cecconi [4], M.A.V.-C.V.N. [9]), this work aims to set up an analytical method for the assessment, by means of proper indicators, of wave damages on both natural and artificial structures in urbanized lagoons. Recent field studies have revealed that wind and boats generated waves produce continuous actions on these structures that cause progressive damage (such as: loss of soil and vegetation from salt marshes and tidal flats; sedimentation in the channels; deterioration of timber piles and building foundations). Load and resistance parameters to be adopted for the calculation of the induced damages are affected by great uncertainties due to the stochastic nature of the wave forcings and the variability of mechanical characteristics of the different structures (caused by material factors and environmental conditions, such as biochemical activity and weather regime). In order to provide reliable estimations of the expected damages, a probabilistic approach that takes into account the large spatial and temporal variability of both load and resistance of the different structures is required. The proposed method starts with the definition of the failure mechanisms to be adopted for the structure in general terms and the estimation of the statistical parameters for the stochastic variables. Sensitivity analysis allows to assess the effects of different choices adopted in the overall modelling of waves and failure processes. The present study aims, in particular, at developing a reliable analytical instrument to support planning and regulation of motor-boat navigation and the design of protection systems against the erosion of natural and artificial structures in the Venice lagoon.