Deformation and degradation study using point clouds in natatio of the Western Baths at La Alcudia in Elche (Alicante)

This paper deals with the study of construction and geometry, as well as with the analysis of deformations and active degradations of the natatio belonging to the Western Baths in La Alcudia archaeological site. Its location in Elche-Alicante, Spain (Colonia Iulia Ilici Augusta), is widely known for the discovery of The Lady of Elche in 1897. The dimensions of this natatio in the frigidarium are 6.60 x 9.30 m (22 x 31 Roman feet) and 1.50 m deep, making it one of the largest Roman swimming pools documented to date on the Iberian Peninsula. The natatio has several cracks sealed with materials used in earlier interventions at the end of the third century. Its comparison with the hypothetical original form allowed the researchers to quantify the current deformations. A damage evolution study has been made comparing the 2016 point cloud with the 2022 cloud, both obtained by light detection and ranging (LIDAR). There is evidence that an active process of degradation and deformation is gradually increasing damage to the pool. By studying the geometry and constructive systems of the natatio, relevant data to understand the historical evolution of the Western Baths have been provided. A results analysis conclusion is that the pool was built in two different stages. The eastern half corresponds to the original natatio, while the western half was extended or rebuilt after having collapsed. The early abandonment of the use of the natatio was most likely due to deformations caused by differential settlement; this occurred when the western half was cemented on landfill between the ancient wall and that of the last third of the 1st century AD.