Didenkulova, I., Parnell, K.E., Soomere, T., Pelinovsky, E., and Kurennoy, D. (2009) Shoaling and runup of long waves induced by high-speed ferries in Tallinn Bay. Journal of Coastal Research, 56 (1). pp. 491-495.

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Abstract

High-amplitude water waves induced by high-speed ferries arc regularly observed in Tallinn Bay, the Baltic Sea, where, during the high season, high-speed ferries service the Tallinn-Helsinki route up to 50 times per day. Long-wave runup is examined theoretically and experimentally, focusing on the dependence of runup height on the incident wave properties. Experimental data include measurements of wave parameters 100 m from the coast and measurements of wave runup on a beach. Data from 212 ship wake events in Tallinn Bay demonstrate that ship wakes in the nearshore have large heights (up to 1.6 m) and periods (10-15 s), whereas wind waves have typical heights of <0.5 m and periods of 3-6 s. The largest ship generated waves approaching the coast break (plunging or spilling breaking) in the nearshore (with a typical breaking parameter Br > 13) and have only weak wave amplification at the beach. On average the runup height of ship wakes exceeds the wave height offshore at the depth of 2.7 m by a factor of 1.3, and this amplification factor decreases with an increase in wave amplitude. This effect is explained by wave breaking and dissipation in the turbulent bottom boundary layer. Estimates of the amplit1cation factor given in the framework of shallow water theory are in agreement with the observed data.

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