page_title: Siltation
section_title: Causes
hierarchical_section_title: Siltation / Causes
caption_attribution_description: English: Faecal sludge that has been manually removed from pits is dumped into the local river at the Korogocho slum in Nairobi, Kenya.
context_page_description: Siltation, or sans, is water pollution caused by particulate terrestrial clastic material, with a particle size dominated by silt or clay. It refers both to the increased concentration of suspended sediments and to the increased accumulation of fine sediments on bottoms where they are undesirable. Siltation is most often caused by soil erosion or sediment spill.
  Sometimes siltation is called sediment pollution, but that is an undesirable term since it is ambiguous and also refer to a chemical contamination of sediments accumulated on the bottom or to pollutants bound to sediment particles. Siltation is the preferred term for being unambiguous although it is not entirely stringent since it also includes particle sizes other than silt.
context_section_description: The origin of the increased sediment transport into an area may be erosion on land or activities in the water.
  In rural areas, the erosion source is typically soil degradation by intensive or inadequate agricultural practices, leading to soil erosion, especially in fine-grained soils such as loess. The result will be an increased amount of silt and clay in the water bodies that drain the area. In urban areas, the erosion source is typically construction activities, which involve clearing the original land-covering vegetation and temporarily creating something akin to an urban desert from which fines are easily washed out during rainstorms.
  In water, the main pollution source is sediment spill from dredging, the transportation of dredged material on barges, and the deposition of dredged material in or near water. Such deposition may be made to get rid of unwanted material, such as the offshore dumping of material dredged from harbours and navigation channels. The deposition may also be to build up the coastline, for artificial islands, or for beach replenishment.
  Climate change also affect siltation rates.
  Another important cause of siltation is the septage and other sewage sludges that are discharged from households or business establishments with no septic tanks or wastewater treatment facilities to bodies of water.
caption: Siltation caused by fecal sludge collected from pit latrines and dumped into a river at the Korogocho slum in Nairobi, Kenya.
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