Integrated approach for landslide hazard assessment in the High City of Antananarivo, Madagascar (UNESCO tentative site)

Abstract The High City of Antananarivo is one the most important cultural heritage sites Madagascar, on UNESCO Tentative List since 2016. Built hilltop Analamanga Hill, a granite ridge overlooking Ikopa River valley, it renowned for its baroque-style palaces, such as Rova royal complex, and neo-Gothic cathedrals dating back to nineteenth century. During winter 2015, twin cyclones Bansi Chedza hit urban area Antananarivo, triggering floods shallow landslides, well causing thousands evacuees many casualties. Between 2018 2019 several rockfalls occurred from rock cliffs hills, destroying housings killing over 30 people. Both events showed that landslides can pose high risk safety inhabitants, infrastructure, City. To assess landslide hazard in Hill area, an integrated approach was adopted by means following actions: (i) creation multitemporal detailed scale map; (ii) geotechnical characterization involved materials; (iii) analysis susceptibility soils/loose deposits; (iv) runout debris flows channeling within large creek gullies; (v) kinematic rockmass; (vi) simulation rockfall trajectories; (vii) rainfall data. results show main factors affecting are slope, lithology, creek-gully erosion, anthropization, while clearly triggered heavy rainfall. landslide-prone areas (the phenomena include falls, flows) located primarily along cliff bounding western hill southeastern sector (where abandoned quarries form slope cuts), subordinately steep catchment just east Rova. thematic maps produced represent fundamental land use management tools be used Geo Disaster Risk Reduction (GDRR) scientists, practitioners decision-makers protection conservation. study conducted represents contribution improving knowledge processes with limited data may reproduced characterized similar geomorphological scenarios.