ENVISAT ASAR Monitoring of the Natural and Archaeological Landscape of Nasca, Peru
Cigna, Francesca¹; Tapete, Deodato²; Lasaponara, Rosa³; Masini, Nicola^4
1British Geological Survey, UNITED KINGDOM; ²Institute for the Conservation and Valorization of Cultural Heritage, National Research Council, ITALY; ³Institute of Methodologies for Environmental Analysis, National Research Council, ITALY; ⁴Institute for Archaeological and Monumental Heritage, National Research Council, ITALY

We exploit the 4year-long archive of ENVISAT ASAR IS2 C-band imagery available over Nasca (Southern Peru), to reconstruct the temporal evolution of the Rio Grande drainage basin and its impacts on the natural and cultural heritage preserved within this region, well-known for the evidences of the ancient Paracas and Nasca Civilizations who flourished between the 4th century BC and the 6th century AD.
8 ASAR raw data acquired in descending mode in 04/02/2003-15/11/2005 and 5 ascending mode scenes acquired in 24/07/2005-11/11/2007 are focused to Single Look Complex with the Range/Doppler processing sequence, and used to analyse the history of the region through amplitude change detection approaches.
The research is performed both at the regional scale over the entire drainage basin of Rio Grande and with particular focus on its tributaries Rio Ingenio, Rio Nazca and Rio Taruga, and at the local scale over both functioning and disused puquios, i.e. ancient networks of open trenches and/or subterranean galleries built for irrigation purposes. Multi-temporal observations of agricultural and vegetated areas are highly helpful to understand the natural landscape and its mutual interactions with presence and development of ancient civilizations within the river basin. Water availability and its seasonal and yearly fluctuations exert significant control on agricultural areas and croplands, which can in turn be used as reliable indicators of the presence of groundwater over this arid region. The ASAR 2003-2007 study is coupled with NDVI- and NDWI-based soil moisture and vegetation change assessment performed with ASTER multi-spectral data acquired in 2003, 2004 and 2007. Both optical and radar image stacks help drawing a clearer picture of the recent and present hydraulic regime of the rivers within this region.
ASAR data are made available to the authors by ESA through the Cat1 project id.11073: Archaeological and environmental studies in the Nasca region (Southern Peru) using multi-temporal C- and L-band SAR imagery. The latter supports the activities of the Italian mission of heritage Conservation and Archaeogeophysics (ITACA), which directly involve researchers from the Institute for Archaeological and Monumental Heritage (IBAM) and the Institute of Methodologies for Environmental Analysis (IMAA), National Research Council (CNR) of Italy.

References
Lasaponara R., Masini N. 2012. Following the Ancient Nasca Puquios from Space, In: Lasaponara R., Masini N. (Eds) 2012, Satellite Remote Sensing: a new tool for Archaeology, Springer, Verlag Berlin Heidelberg, pp. 269-290, doi: 10.1007/978-90-481-8801-7_12
Masini N., Lasaponara R., Rizzo E., Orefici G. 2012. Integrated Remote Sensing Approach in Cahuachi (Peru): Studies and Results of the ITACA Mission (2007-2010), In: Lasaponara R., Masini N. (Eds) 2012, Satellite Remote Sensing: a new tool for Archaeology, Springer, Verlag Berlin Heidelberg, pp. 307-344, doi: 10.1007/978-90-481-8801-7_14