Quantitative estimate of the damages from human activities at the Apurlec Monumental Archaeological Complex (7th-14th century AD, Peru) from multitemporal photogrammetry

Archaeological sites may be exposed to different types of risks related to wars, natural phenomena, and illicit human activities. Quantitative data on the type and extent of the damages and destructions suffered by these sites are of primary importance for their reparation and the planning of conservation and defence actions. The Apurlec Monumental Archaeological Complex (about seventh-fourteenth century AD, Peru, "Intangible and Essential Heritage" of the Peruvian Ministry of Culture) includes platforms, canals, and rectangular ceremonial/administrative enclosures. Between June and August 2021, Apurlec has been affected by a partial destruction of its southern sector. Here we present the results of two UAV photogrammetric surveys conducted before (23 January 2021) and after (30 August 2021) the destructive event. The comparison of the orthoimages and the Digital Surface Models obtained form the two surveys allow us to detect illicit activities as earth removal to collect construction material, creation of cultivable areas, and steal manufacts from archeological excavations. We calculate that the area covered by the destruction is 121,665 m(2) (perimeter of about 2 km(2)) the removed material amount to 401,513.5 m(3), a value corresponding to a mass of about 702,648.63 ton. The post-destruction topography is lower of about 3.3 m with respect to the original one. Our anytical and metholodological approach could be extended to other archeological sites potentially exposed to anthropic and natural hazards.