Day 4

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Paper title Use of satellite multi- and hyperspectral data for environmental and urban monitoring in the High City of Antananarivo (Madagascar)
  1. Giacomo Lazzeri University of Florence Speaker
  2. William Frodella Università degli Studi di Firenze
  3. Sandro Moretti University of Florence
Form of presentation Poster
  • D2. Sustainable Development
    • D2.12 Cultural and Natural Heritage
Abstract text The High City of Antananarivo (Madagascar), part of the UNESCO tentative List since 2016, represents the urban historical centre and hosts one of the most important built cultural heritage sites of Madagascar: the Rova royal complex as well as baroque and gothic-style palaces and cathedrals churches dating back to the XIX century. The site is built on a hilltop (Analamanga hill) elevating above the Ikopa river alluvial plain and rice fields, and is often affected by geohazards: during the winter of 2015, the twin cyclones Bansi and Chedza hit the urban area of Antananarivo, triggering floods and shallow landslides, while between 2018 and 2019, several rockfalls occurred from the hill granite cliffs and many losses; all of these phenomena caused evacuees, damage to housings and infrastructures as well as several casualties. In this complex geomorphological setting the rapid and often uncontrolled urbanization (often represented by shacks and hovels), and a not proper land use-planning (illegal quarrying, dumping and slope terracing, slash and burn deforestation, lack of a proper drainage-sewer system) can seriously exacerbate slope instability and soil erosion, posing a high risk to the High City cultural heritage and the natural landscape connected infrastructures (roads and pathways in particular).
In the recent years, thanks to the availability of the Copernicus products and new satellite missions (such as ASI PRISMA), the integration of multi- and hyperspectral data has undergone an increase of use in the field of EO for land use-cover mapping applications, for the evaluation of climate change impacts and the monitoring of geohazards. The UNESCO Chair on Prevention and Sustainable Management of Geo-Hydrological hazards is collaborating since 2017 with Paris Region Expertise (PRX), the municipality of Antananarivo and BNGRC (Bureau National de Gestion des Risques et des Catastrophes) for assessing geohazards in the High City, and therefore support the nomination of the site for the UNESCO World Heritage List. In this context the use of EO data can give an important contribution in order to face the challenges posed in the next future to this complex and fragile cultural heritage by the growing urban pressure (which trend in the last few decades is generally increasing in African developing countries) and by the environmental modifications in a context of climate change.
The aim of this work is to test the potential of Sentinel and PRISMA data for the monitoring of the High City of Antananarivo UNESCO zone and of the surrounding urban area and natural landscape. In particular, satellite multi- and hyperspectral data will be applied in a multi-scale methodology for an updated assessment of land cover-use, for highlighting areas frequently affected by flooding and prone to erosion/landsliding (e.g., bare residual and clay-rich soils, granite outcrops and abandoned quarries), for the evaluation of the urban sprawl in the Antananarivo urban area, as well as for the remote classification of the building vulnerability in the UNESCO core zone. The final goal is to implement a tailored, innovative and sustainable strategy to be shared with the institutions and actors involved in the protection of the High City of Antananarivo and used as a tool for land-use planning and management, for the detection of conservation criticalities, as well as for improving the site’s resilience to geohazards. The use of open-source data, platforms and tools can promote capacity building of local practitioners and end users (to be trained as local experts), and can facilitate the reproducibility of the methodology in other sites characterized by similar geomorphological and urban scenarios. Expected outcomes are also the improvement of the site’s touristic fruition in order to support the local economy and stimulate a community empowerment approach to sustainable heritage management.