Storm surge in Spain: Factors and effects on the coast

Storm surge is a fundamental process to understanding the behaviour of sea level. This variable, which depends on atmospheric pressure and wind action, has been widely documented. However, few studies quantify these relationships for various geographic areas. This study analyses the most influential factors in the variation of storm surges at several points on the Spanish coast. The results show that the event duration and the regional geographic factor are very relevant in the correlation of storm surge with pressure drop, so assigning a single value as has been commonly done, typically 1 cm/hPa, is an error. The Mediterranean Sea experiences a greater sensitivity to the atmospheric pressure drop than the Atlantic Ocean, with sea level rise of up to 2 or 3 cm/hPa for a storm surge event below 40 h, compared to those of 1.5 cm/hPa for the Atlantic Ocean. Additionally, higher wind speeds intensify storm surge, whether it results in positive or negative superelevation. However, the storm surge does not always increase when the wind blows towards the coast but also depends on the location of the water masses and the continent. Finally, there is no perception of a growing trend of storm surges in the context of climate change in a general way. A precise knowledge of these elements will help all those agents involved in coastal protection to define more accurate alert levels, enhancing safety along the waterfront.