Flood risk management master plan in Antananarivo

Identifying the risk of flooding and modernizing wastewater systems to improve people’s day-to-day lives

The Malagasy government launched a large-scale wastewater treatment programme for the Antananarivo conurbation, one of the measures of which is to better anticipate and manage fluvial flooding risks.

Artelia was appointed to work on this project, updating the hydrology of the catchment area in which the Malagasy capital is located and carrying out an overall hydraulic study of the surrounding plain. These data were used to produce a new flood risk management master plan, which will contribute to enhanced urban planning.


Due mostly to a badly damaged sewerage and drainage system, flooding and standing water remain a persistent safety and public health problem for the city of Antananarivo (population 3.6 million). With the support of the French Agency for Development (AFD), the Malagasy government has therefore launched the Antananarivo Integrated Sanitation Programme (PIAA), the aim of which is to improve the health and living conditions of the city’s inhabitants. The programme is intended to clarify the organisation of sanitation in Greater Antananarivo, better manage the flood risks and improve the running of the sanitation networks.

One of the challenges is to consider the whole issue, unlike the previous master plan, which focused on wastewater. As involved in flood risk management, Artelia focused specifically on river flooding. These were modelled, from their sources, over the entire catchment area. This new data was used to draw up risk maps, which were themselves used to draw up a new risk management master plan. This will provide guidelines for the Greater Antananarivo urban development plan, in particular by indicating flood areas to be set aside for flood expansion.