sedimentatsioon

Sedimentatsioon (Estonian for sedimentation) is the process by which solid particles suspended in a fluid settle under gravity (or centrifugal forces) and accumulate as a sediment layer. In natural waters, it forms lake and river deposits and, over long timescales, contributes to sedimentary rocks through lithification.

The settling rate depends on particle size, density, shape, and on the fluid’s density and viscosity. Larger and denser particles settle faster; higher viscosity slows them. Turbulence can keep particles in suspension. For small, near-spherical particles in calm fluids, settling velocity increases with particle radius squared and with density contrast, as described by Stokes’ law.

In nature, sedimentation records climate, hydrology, and tectonics. In lakes and oceans, calm zones allow fine sediments to accumulate as laminae; in rivers, coarser material forms bars and floodplains. Over geological timescales, compacted sediments become sedimentary rocks.

In engineering, sedimentation removes suspended solids. Clarifiers and settling basins permit particles to settle, after which clarified water is drawn off. Flocculation and coagulation promote aggregation and faster settling. Sedimentation also affects reservoir storage and sediment yield from watersheds, linked to erosion, land use, and climate; dredging is often employed to manage it.