Flooding is dominant in shaping the biological, chemical and physical processes of the Amazon basin: an area of 350,000 km2 is flooded at high water (Junk et al. 1989), representing 20% of the Earth’s fresh water (this area is around 17 times the size of Wales, or about half the size of Texas). The Amazon has great biodiversity (2.5 million insect species, for example) and absorbs 500 million tonnes of carbon per year (compared to 13 billion emitted by human activity) – it is one of the most important ecosystems on the planet.
The Amazon has a tropical climate with wet and dry seasons. Given the size of the basin, this results in a large annual floodwave with several metres amplitude. The typical amplitude at Manacapuru in our study reach is 10 m. At this location, the peak flow rate is 120,000 m3s-1 (or 120,000,000 litres per second) – compare this to a large flood event on the Mississippi (around 30,000 m3s-1), or a large flood event on the UK’s largest river, the Severn (around 700 m3s-1), and you start to appreciate just how big this river is. Yet this location is still around 1,500 km from the sea, and the river doubles in size before it gets there. The shear volume of water passing down the river means that the flood process dominates everything close to the river. 2005 and 2012 saw some of the highest flood stages on record.
The over-riding aim of this research is to develop a computational model capable of simulating the inundation dynamics of the Amazon floodplain (varzea). There are many potential uses of such a model, since many applications require hydrodynamic information. These include studies of ecology, the carbon cycle, and the potential impact of an oil spill on the Amazon. Once fully developed, this model will be able to provide useful data for such studies and allow for scenario-based analyses, such as the assessment of the impact of climate change on the varzea ecosystem.
The study site is located along a 400 km the Rio Solimões, just upstream its confulence with the Rio Negro in Brazil (downsteam of this confluence, the river is known as the Rio Amazonas). The Rio Purus flows in from the south and the two rivers share a large floodplain (varzea) some 50 km across, the majority of which is floodplain forest. The mixing of floodplain water between the Rio Solimões and Rio Purus is complex and creates an interesting hydraulic modelling challenge.