Assessing the capabilities of VHR satellite data for debris flow mapping in the Machu Picchu area (C101-1)

Machu Picchu is an ancient Inca city located on a narrow ridge, within the Andes, approximately 80 km north-west of Cusco, Peru. This site of exceptional cultural heritage and its related infrastructure are being undermined by rapid debris flows, that are related to the presence of thick debris deposits produced by granite weathering, past slides and climatic conditions. On 26 December 1995 a rock fall/debris flow occurred on the road that leads to the citadel (Carretera Hiram Bingham) interrupting the traffic coming from the railway station of Aguas Calientes, and on 10 April 2004 a major debris flow, channeled in the Alcamayo stream, devastated the village of Aguas Calientes, causing 11 casualties and damaging the railway. Within the framework of the International Consortium on Landslides (ICL) a program of monitoring the instability conditions at this site was undertaken. In this work the preliminary results of the field survey and the analysis of some very high resolution (VHR) satellite images are presented. A multi-temporal analysis of Quickbird satellite (from Digitalglobe((R))) panchromatic and multi-spectral data was carried out: an archive image dated 18 June 2002 was available while a new acquisition with a good image was obtained on 18 May 2004. The main purpose of the analysis was the reconnaissance of debris flows using remote sensing techniques. The remote sensing data analysis was integrated with a field survey, carried out in September 2004. This allowed us to confirm the interpretation of the images,to produce a detailed geomorphological map of the area around the Carretera Hiram Bingham and to assess the thickness of debris deposits on the slopes. The results constitute a first step towards a complete debris flow hazard assessment in the area, where the interactions between slope instability and land use can produce very critical conditions.