The Record of Extreme Wave Events in the Bay of Cadiz During Historical Times

The Bay of Cadiz is a complex coastal area, formed by confining sandy barriers, tidal flats, vegetated saltmarshes, fluvial mouths, and other coastal plains. Such physiographic characteristics have made them a very attractive place for human settlements since ancient times. At the same time this is a very vulnerable area, often affected by extreme wave events, both sea storms and tsunamis. Although such events produced damage in anthropic infrastructures and left different morpho-sedimentary records, subsequent human activity erased or distorted a substantial part of the remains. As a consequence, at present it is very difficult to identify correctly forms and deposits associated with events of this type, especially the oldest ones, for having suffered a higher number of later modifications. Only some places, like the Valdelagrana system of historical littoral ridges, have well-preserved indicators of historical extreme wave events. The systematic review and summary of historical records analyzed in the last decades by different research groups has allowed for establishing a chronology of historical energetic events, regardless their climatic or seismic origin (calibrated ages in years BP): 7.0–6.8, 5.7–5.6, 5.3–4.9, 2.7–2.3, 2.3–1.9 ka, 873–750, 269, and 245 (AD 1755). Some of them were very probably related to storms. Future research should focus on specific events recorded along the Gulf of Cadiz coast, in order to contrast dates, energy, and effects, which would help to gain a better understanding of their nature and to establish reliable return periods.