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Lahar triggering mechanisms at Lake Albano (Rome, Italy): evidence from archaeology, volcanology and numerical modeling

Dmitri Rouwet 1, Anita Grezio1, Agnese Livia Fischetti2, Guido Giordano3, Filippo Zaniboni4, Alberto Armigliato4, Gino González5

  • Affiliations: 1Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Bologna, Bologna, Italy 2Koninklijk Nederlands Instituut, Rome, Italy 3Università Roma Tre, Dipartimento di Scienze, Rome, Italy 4Università degli Studi di Bologna, Dipartimento di Fisica e Astronomia \"Augusto Righi\", Bologna, Italy 5Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Napoli-OV, Naples, Italy

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 87

  • Programme No: 6.8.13

  • Theme 6 > Session 8

Abstract

There is geological evidence that the hydrological network on the northwest flank of Colli Albani volcano, 10 km southeast of Rome, has been buried by lahar deposits since 21 ka. The indisputable candidate of water source for lahar generation is Lake Albano: however, it remains unknown how water was expelled during numerous lahars events. A drainage tunnel, presumably constructed by the Romans after a lake flooding in 398 BC, should have mitigated lahar hazards by keeping the lake level 70 m below the lowest crater rim. Nevertheless, recent archaeological discoveries revealed that the site of Marcandreola, 4 km northwest of Lake Albano, a highly frequented centre since Archaic Age (753-510 BC) was covered by a lahar, dated to have occurred 270-280 BC, i.e. after the construction of the tunnel. Given these premises, we investigate the causes of this lahar. The lake bathymetry and crater topography show two main landslide scars, representing the sources of worst-case-scenarios, feeding subsequent numerical modeling. Based on these models we ruled out that a landslide generated tsunami alone could have caused lake throw out. Posteriorly, several scenarios of additional energy sources are explored: (1) a limnic gas burst, (2) a higher lake level (putting in discussion the age and state of the drainage tunnel), or (3) a combination of both. The recognition of numerous landslides in and around the Lake Albano basin, and the occasional co-seismic gas input causing gas build-up in the lake, highlights the need to revise and strengthen monitoring and mitigation strategies.