A Framework for Storm Classification and Hydrograph Generation From Total Water Level in Europe

Extreme sea levels leading to coastal flooding result of the combined action of waves, storm suges and astronomical tides, often referred to as the total water level (TWL), under storm conditions. Identifying different types of storms, along with their associated durations and uncertainties, provides valuable information for constructing accurate hydrographs and generating reliable flood maps. In this study, we characterize TWL storms, considering their shape and duration, with a focus on coastal flood analysis across Europe. Our proposed approach comprises three steps. First, we classify TWL storms based on their shape. We identify four storm types around Europe that reflect the different relative contributions of TWL components. Second, we introduce a method to determine the duration of individual historical storms, which is applied to estimate the durations of return level events using storm duration functions. We emphasize the importance of accurate duration functions, especially for the longest storms observed in the Mediterranean Sea, for both historical and extrapolated return period events. Third, we implement a new method to design hydrographs for extreme events, enabling the assessment of water volumes resulting from different scenarios. Due to regional variability of scenarios, the semi‐enclosed Baltic and Mediterranean Seas exhibit storm surge‐dominated and mixed‐type storms, respectively, with associated uncertainties exceeding 20%. Our approach considers uncertainties in both storm shape and duration, particularly when the contribution of TWL components is unknown.