Measurements of fast ferry waves in Helsinki-Tallinn run

As more and more high speed ferries are operating between Tallinn and Helsinki questions have arisen concerning the impact these ships are having on both the environment, and on the populations recreational activities. To this end, experiments were conducted at five different locations, Pihlajasaari and Harmaja in Helsinki, and Katariina, Viimsi, and Naissaar in Tallinn, to measure the ship waves generated by the various fast ferries. Each of the locations differed in local seabed geology and bathymetry, as well as distance to the shipping lane. Instruments including a capacitance type wave gage, pressure sensor, and an acoustic Doppler velocity meter were mounted on a tripod and deployed in water of approximately 2 meters of depth in the near shore region. Data was recorded as the waves from the vessels approached the measurement location. The data was analysed in terms of average wave height and period, maximum wave height and period, and maximum water velocity. In addition, the maximum run-up or swash height was calculated using the results of the initial analysis. Following Kelvin's ship wave theory, there was a strong correlation between wave period and ship velocity. In addition, the data demonstrates that wave height decreases with distance and with ship velocity as the theory predicts. A rudimentary analysis of wind waves was also conducted for comparison purposes. Additional experiments should be conducted using similar methods to increase the size of the data set so that more definite conclusions can be drawn.