Imprints of the AD 1755 Tsunami in Algarve (South Portugal) Lowlands and Post-impact Recovery
The AD 1755 tsunami was the most devastating tsunami that affected Atlantic Europe in historical times. In this work we summarize its sedimentological signatures in lowlands (Martinhal, Barranco, Furnas, Boca do Rio, Salgados-Alcantarilha) of the Algarve coast that contrast in geologic and geomorphological settings and sediment abundance. We found remarkable similarities between tsunami deposits and the materials available for transport at the coast prior to the tsunami. A number of 2–4 m high and 30–70 m wide scarps (i.e. steep slopes in dunes resulting from erosion) are the only erosive geomorphic signature preserved in the study areas (Boca do Rio and Salgados-Alcantarilha). Recovery of the coastal system to pre-event conditions, inferred from the documentary records, is evaluated and analyzed in terms of sediment availability and supply, climate, hydrodynamic regime and geomorphic setting. Sediment-starved pocket beaches bypassed landward most of the sediment previously accumulated in the coastal system, failing to recover the pre-event morphology. Moreover, and solely in Martinhal, the abrupt morphological changes translated in increased and lasting permeability of the barrier and adjacent wetland to storms. The Alcantarilha-Salgados beach-dune system, in moderate sand supply, was extensively scarped but not fully overtopped. Here, recovery was partly achieved by destabilization of the remnant dune, formation and (limited) advance of parabolic dunes following the 1755 event. A schematic conceptual model is presented summarizing: the pre-event conditions; the depositional and geomorphological features directly related with the tsunami impact; and the post-event geomorphological adaptation. In the studied cases post-event recovery seems to be reduced mainly due to a conjugation of pre-event geomorphological setting and low sediment input.
The need to conduct further studies in the impacts of palaeotsunamis is evidenced here, especially because older events allow a large time window to observe post-tsunami adaptation.
KeywordsGeomorphology Tsunami deposit Sand barrier Erosional features Recovery
MA Oliveira and PJM Costa benefited from FCT (Portuguese Science Foundation) PhD and Post-Doc Scholarships. R. González-Villanueva benefited from an IDL Post-Doc Fellowship and Xunta de Galicia (PlanI2C-ED481B 2014/132-0) Post-Doc Fellowship.
- Andrade C (1990) O ambiente de barreira da Ria Formosa (Algarve, Portugal). PhD dissertation. University of Lisbon, Portugal, 645 ppGoogle Scholar
- Andrade C (1992) Tsunami generated forms in the Algarve barrier islands (South Portugal). Sci Tsunami Haz 10:21–34Google Scholar
- Andrade C, Andrade AM, Kortekaas S, Dawson A (1997) Sedimentological traces of tsunamigenic overwash of the Martinhal lowland (Western Algarve – Portugal). In: Proceedings Seminar Zona Costeira do Algarve, Faro, 10–12 July 1997, Eurocoast-Portugal, pp 11–18Google Scholar
- Atwater BF, Cisternas M, Yulianto E, Prendergast AL, Jankaew K, Eipert AA, Fernando WIS, Tejakusuma I, Schiappacasse I, Sawai Y (2013) The 1960 tsunami on beach-ridge plains near Maullín, Chile: landward descent, renewed breaches, aggraded fans, multiple predecessors. Andean Geol 40:393–418Google Scholar
- Costa PJM, Andrade C, Freitas MC, Oliveira MA, Lopes V, Dawson AG, Moreno J, Fatela F, Jouanneau J-M (2012a) A tsunami record in the sedimentary archive of the central Algarve coast, Portugal: characterizing sediment, reconstructing sources and inundation paths. The Holocene 22(8):899–914CrossRefGoogle Scholar
- Dinis J, Andrade C, Oliveira MA, Freitas MC, Cunha PP, Martins A, Costa P (2010) Geomorphological constraining of tsunami (?) run-up in the Alcantarilha coastal lowland (central Algarve, Portugal). In: Proceedings Iberian coastal holocene paleoenvironmental evolution ‘Coastal Hope 2010’, Lisbon, pp 40–41Google Scholar
- Goff JR (2008) The New Zealand Palaeotsunami database. NIWA technical report 131, ISSN 1174–2631, 24 pp + AppendixGoogle Scholar
- Kortekaas S (2002) Tsunamis, storms and earthquakes: distinguishing coastal flooding events. Coventry, PhD dissertation. Coventry University, United Kingdom, 171 ppGoogle Scholar
- Lopes JBS (1841) Corografia ou Memória Económica, Estatística e Topográfica do Reino do Algarve. Academia R. das Sciencias de Lisboa, Lisboa, Portugal, 528 pp (in Portuguese)Google Scholar
- Oliveira MA (2009) Influência da geomorfologia local na preservação de assinaturas sedimentares de eventos de alta energia no Algarve ocidental. MSc dissertation, University of Lisbon, Portugal, 178 ppGoogle Scholar
- Oliveira MA, Andrade C, Freitas MC, Costa PJ (2009) Modeling volume transfer between beach-foredune and the backshore by the 1755 Lisbon tsunami at Boca do Rio lowland, Algarve (Portugal). J Coast Res SI56(2):1547–1551Google Scholar
- Paris R, Wassmer P, Sartohadi J, Lavigne F, Barthomeuf B, Desgages E, Grancher D, Baumert P, Vautier F, Brunstein D, Gomez CH (2009) Tsunamis as geomorphic crises: lessons from the December 26, 2004 tsunami in Lhok Nga, West Banda Aceh (Sumatra, Indonesia). Geomorphology 104:59–72CrossRefGoogle Scholar
- Pires HO (1985) Alguns aspectos do clima de agitação marítima de interesse para a navegação na costa de Portugal. Instituto Nacional de Metereologia e Geofísica, Lisboa, Portugal, 30pp (in Portuguese)Google Scholar