Porto-Novo is characterised by an extension of its housing area which occupy all the urban territory. It is a 290 000 inhabitants urban fabric (2010 census) with a 2,6% growing rate, and a density of 5300 inhabitants/km2. The urban landscape is intricate with several depressions that are invading the urban territory. These depressions are natural areas made of unconstructible wetlands which have resisted to the pressure from the intensive urbanisation : Zounvi, Donoukin and Boué.

They were once considered as lagoon branches on the continent and used to irrigate the city with water on a wide area. But the sitting-up, the accumulation of solid waste and the urban pressure have considerably reduced them. Indeed, while it spreaded to the North and the East, Porto-Novo has reached the suburban areas like Louho and engulfed Zounvi, and is now threatening Boué which is located further away. The demographic boom is linked to the soaring and agressive urbanisation and has reduced these natural wetlands to a draining activities (rainwater).

How to preserve, protect, plan and promote the different depressions (Zounvi, Donoukin and Boué) of Porto-Novo and create integrated ecological areas on the one hand,
and on the other hand, create farming, tourism and leisure areas ?