Hydraulics & Mass of the Amazon Flood

1. Hydraulics & Mass of the Amazon Flood Floods, which restore and damage ecosystems as well as threaten communities near rivers, consist of interacting flow paths of varying depth, velocity, source, sediment concentration, and chemistry. However, data taken from monitoring stations along flooding rivers are geographically sparse and are oversimplifications of floodplain water flux. To reflect the true complexity of floods, interferometric SAR (left side), is used to measure water fluctuations (dh/dt) during several floods of the Amazon River. Contrary to many models which assume that the water surface is horizontal and equal to the changing level of water in main river channels, this data shows that water surfaces during a flood have sharp variations. Further, flow paths, previously thought to be controlled by surface topography, are also be driven by the hydraulic momentum of the rushing floodwaters. The amount of water in the annual Amazon flood is poorly known. Geodynamics may help us to “weigh” this mass. GPS data from Manaus shows the Earth’s lithosphere elastically contracting and expanding, timed perfectly with the arrival and departure of the flood wave (respectively, right side). Because the Amazon flood wave moves ~3000 km over four months, the Amazon craton is also likely to experience an elastic wave – yet unlike seismic waves which move at sonic velocities, this elastic wave takes months to move.