Abstract. The goal of this paper is to present an original real-time algorithm devised for detection of tsunami or tsunami-like waves we call TEDA (Tsunami Early Detection Algorithm), and to introduce a methodology to evaluate its performance. TEDA works on the sea level records of a single station and implements two distinct modules running concurrently: one to assess the presence of tsunami waves ("tsunami detection") and the other to identify highamplitude long waves ("secure detection"). Both detection methods are based on continuously updated time functions depending on a number of parameters that can be varied according to the application. In order to select the most adequate parameter setting for a given station, a methodology to evaluate TEDA performance has been devised, that is based on a number of indicators and that is simple to use. In this paper an example of TEDA application is given by using data from a tide gauge located at the Adak Island in Alaska, USA, that resulted in being quite suitable since it recorded several tsunamis in the last years using the sampling rate of 1 min.

Studies on coastal boulders transported inland by high‐energy events, such as tsunamis, focus mainly on the nature, magnitude and characteristics of past events and contribute to coastal hazard assessments. However, uncertainties on the transport models used in the literature are widely acknowledged. To study the minimum flow conditions for boulders transport, a laboratory experiment was carried out at the Hydraulic Engineering Laboratory (LIDR) of the University of Bologna, Italy. The main objective was to provide experimental data on boulders incipient motion and on the relationships linking boulders weight, geometry and orientation with the flow velocity and flow depth thresholds for transport initiation. The experiments reproduce idealized cases to highlight the contribution of the flow and transport processes, while the complexities due to the environment and irregular boulder shapes are reduced to a simple slope and to cubic and rectangular blocks. The most important result is that boulders move when only partially submerged by the flow, but this case is not even considered in the literature. Even for this oversimplified case, the hydrodynamic approach currently used to predict incipient motion strongly overestimates the minimum conditions for boulder transport. The main conclusions are that the drag and lift coefficients commonly used in the literature are not adequate to correctly estimate the minimum conditions for transport and need to be fine‐tuned. The main reason for this discrepancy is that the practical hydrodynamic formulas do not account for the flow variability induced by turbulence that plays a key role in influencing the start of instability. To take into account this intrinsic uncertainty, we suggest determining two dynamic thresholds, separating three distinct regimes: one where transport is impossible, one where it is certain, and an intermediate one where it is possible depending only on the actual turbulence bursts. Data are made freely available (ftp://137.204.48.34). © 2018 John Wiley & Sons, Ltd.

Abstract. Addressing coastal risks related to sea storms requires an integrative approach which combines monitoring stations, forecasting models, early warning systems, and coastal management and planning. Such great effort is sometimes possible only through transnational cooperation, which becomes thus vital to face, effectively and promptly, the marine events which are responsible for damage impacting the environment and citizens' life. Here we present a shared and interoperable system to allow a better exchange of and elaboration on information related to sea storms among countries. The proposed integrated web system (IWS) is a combination of a common data system for sharing ocean observations and forecasts, a multi-model ensemble system, a geoportal, and interactive geo-visualisation tools to make results available to the general public. The multi-model ensemble mean and spread for sea level height and wave characteristics are used to describe three different sea condition scenarios. The IWS is designed to provide sea state information required for issuing coastal risk alerts over the analysed region as well as for being easily integrated into existing local early warning systems. This study describes the application of the developed system to the exceptional storm event of 29 October 2018 that caused severe flooding and damage to coastal infrastructure in the Adriatic Sea. The forecasted ensemble products were successfully compared with in situ observations. The hazards estimated by integrating IWS results in existing early warning systems were confirmed by documented storm impacts along the coast of Slovenia, Emilia-Romagna and the city of Venice. For the investigated event, the most severe simulated scenario results provide a realistic and conservative estimation of the peak storm conditions to be used in coastal risk management.

Abstract. Real-time detection of a tsunami on instrumental sea-level records is quite an important task for a Tsunami Warning System (TWS), and in case of alert conditions for an ongoing tsunami it is often performed by visual inspection in operational warning centres. In this paper we stress the importance of automatic detection algorithms and apply the TEDA (Tsunami Early Detection Algorithm) to identify tsunami arrivals of the 2011 Tohoku tsunami in a real-time virtual exercise. TEDA is designed to work at station level, that is on sea-level data of a single station, and was calibrated on data from the Adak island, Alaska, USA, tide-gauge station. Using the parameters' configuration devised for the Adak station, the TEDA has been applied to 123 coastal sealevel records from the coasts of the Pacific Ocean, which enabled us to evaluate the efficiency and sensitivity of the algorithm on a wide range of background conditions and of signal-to-noise ratios. The result is that TEDA is able to detect quickly the majority of the tsunami signals and therefore proves to have the potential for being a valid tool in the operational TWS practice.

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