Bart Schultz
The coastline with the Atlantic Ocean is almost 750,000 kilometres long. In 2024, there were 212 million inhabitants, or 0.25 people per hectare.
Most of Brazil has a tropical climate, but due to the varied topography and size of the country, there are five other climate types: desert, equatorial, semi-arid, oceanic, and subtropical. The temperature is around 25°C. The variation in daytime and nighttime temperatures is greater than that between the seasons. In terms of precipitation, much of the North has no true dry season. In the central region, rain is seasonal. This region is similar to the Amazon River Basin, but has a quite different climate due to its higher elevation in the South. In the northeastern interior, seasonal rainfall variations are more extreme. In this semi-arid region, annual rainfall is generally below 800 mm, most of it falls over a period of three to five months, and sometimes shorter, resulting in prolonged periods of drought.
Brazil's landscape consists of lowlands and gently sloping mountains. Much of the country is covered by the Amazon River Basin. The main branch of the river originates in the Andes Mountains of Peru. South of this it flows through the Brazilian lowlands. Between the Brazilian lowlands and the Atlantic Ocean lie narrow lowlands along the coast. Besides mountain ranges, the Central Highlands feature a vast central plateau at an average elevation of 1,000 metres. The rest of the territory consists primarily of river valleys through which the largest, the Amazon River and its tributaries, flow. The coastal zone comprises thousands of kilometres of tropical beaches interspersed with mangrove forests, lagoons, and dunes. A large coastal area is influenced by the tides of the Atlantic Ocean.
Brazil has one of the most extensive river systems in the world, with eight major rivers that flow into the Atlantic Ocean. Of these, the Amazon and Tocantins-Araguaia rivers comprise more than half of the total area of the river basins. The Amazon and its tributaries carry one-fifth of the world's freshwater. The main river in the northeast is the São Francisco River. The Paraná River flows southward and discharges into the Atlantic Ocean between Argentina and Uruguay.
Although Brazil is a very large and predominantly sparsely populated country, there are also a number of polders, especially in the densely populated areas around the mouths of rivers. Some examples can be found in World Bank reports on the Lower São Francisco Polders Project. Based on these reports, it can be concluded that this project provides flood protection for an area of 32,000 hectares. This includes six large varzeas: Betume (8,100 hectares), Boacica (7,200 hectares), Brejo Grande (4,800 hectares), Cotinguiba (1,600 hectares), Marituba (6,650 hectares), Pindoba (1,150 hectares), and small varzeas (2,500 hectares). Although not specifically referred to as such, these are polders.
The Polder Compendium (1982) mentions polders along the Paraná River in southern Brazil. There are also some polders in the Amazon River Basin. However, specific areas are not given here.
Although I have not been able to find any clear proposals for new polders, the situation of the city of Recife on the coast at the mouth of the Capibaribe River provides clear indications that polders will have to be built sooner or later, and may already have been built to protect flood-prone parts of the city.
