Accumulation of waste in the main canal of Vallon de Metzinger in Mahajanga threatens to cause severe flooding when the rainy season arrives in a few months. Annual dredging work has not yet begun along this drainage channel as the wet season approaches.
This natural waterway and its main discharge canal, stretching 3,600 meters, flows through ten densely populated fokontany, including Tsararano Ambany, Tsararano Anosikely, Ambalavola, Mahavoky Avaratra, and Tsaramandroso Plateforme.
During the rainy season or cyclone passages, water stagnates and overflows from the canal, sometimes submerging homes in lower-lying neighborhoods for extended periods. Flooding risks are significant across all ten fokontany bordering the valley.
Approximately 110,000 residents live in these ten fokontany surrounding the canal. Mahajanga municipality has already agreed to reduce the minimum distance between constructions and the Vallon from 25 meters to 10 meters. However, some homes are currently built less than 5 meters from the main canal.
The drainage channel also serves as an open-air dump for solid waste. Accumulation of plastic materials—particularly bags and bottles—along with mud and water hyacinths, obstructs the evacuation network. Secondary canals within the fokontany are equally affected by waste and pollution. The speed of water flow to the main channel depends on proper functioning of these intermediate conduits.
The Vallon de Metzinger's operation is essential for evacuating wastewater to the sea. Waste dumped there compromises this critical function.
Each year, Mahajanga municipality plans maintenance and dredging work through High-Intensity Labor programs, particularly from Fitim Bridge in Fiofio, at the main wastewater evacuation conduit. Water is then channeled to the sea.
Waste management along Vallon de Metzinger represents a major sanitary and environmental challenge for Mahajanga. On July 22, a workshop was organized by the Emergency Prevention and Management Unit (CPGU) on the role of canals in preventing flood-related disasters, as part of the Regional Project for Climate Resilience (PRRC) in Mahajanga.