Editing Sediment (section)

===Erosion and agricultural sediment delivery to rivers===
One cause of high sediment loads is [[slash and burn]] and [[shifting cultivation]] of [[tropical]] forests. When the ground surface is stripped of vegetation and then seared of all living organisms, the upper soils are vulnerable to both wind and water erosion. In a number of regions of the earth, entire sectors of a country have become erodible. For example, on the [[Madagascar]] high central [[plateau]], which constitutes approximately ten percent of that country's land area, most of the land area is devegetated, and gullies have eroded into the underlying soil to form distinctive gulleys called ''[[lavaka]]s''. These are typically {{convert|40|m||sp=us}} wide, {{convert|80|m||sp=us}} long and {{convert|15|m||sp=us}} deep.<ref>{{cite web |last1=Sawe |first1=Benjamin Elisha |title=Erosion Landforms: What Is A Lavaka? |date=25 April 2017 |url=https://www.worldatlas.com/articles/erosion-landforms-what-is-a-lavaka.html |publisher=WorldAtlas |access-date=24 September 2021}}</ref> Some areas have as many as 150 lavakas/square kilometer,<ref>{{cite journal |last1=Voarintsoa |first1=N. R. G. |last2=Cox |first2=R. |last3=Razanatseheno |first3=M.O.M.|last4=Rakotondrazafy |first4=A.F.M. |title=Relation Between Bedrock Geology, Topography and Lavaka Distribution in Madagascar |journal=South African Journal of Geology |date=1 June 2012 |volume=115 |issue=2 |pages=225–250 |doi=10.2113/gssajg.115.225|bibcode=2012SAJG..115..225V }}</ref> and lavakas may account for 84% of all sediments carried off by rivers.<ref>{{cite journal |last1=Cox |first1=Rónadh |last2=Bierman |first2=Paul |last3=Jungers |first3=Matthew C.|last4=Rakotondrazafy |first4=A.F. Michel|title=Erosion Rates and Sediment Sources in Madagascar Inferred from 10 Be Analysis of Lavaka, Slope, and River Sediment |journal=The Journal of Geology |date=July 2009 |volume=117 |issue=4 |pages=363–376 |doi=10.1086/598945|bibcode=2009JG....117..363C |s2cid=55543845 }}</ref> This [[siltation]] results in discoloration of rivers to a dark red brown color and leads to fish kills. In addition, sedimentation of river basins  implies sediment management and siltation costs. The cost of removing an estimated 135 million m<sup>3</sup> of accumulated sediments due to water erosion only is likely exceeding 2.3 billion euro (€) annually in the EU and UK, with large regional differences between countries.<ref>{{Cite journal |last1=Panagos |first1=Panos |last2=Matthews |first2=Francis |last3=Patault |first3=Edouard |last4=De Michele |first4=Carlo |last5=Quaranta |first5=Emanuele |last6=Bezak |first6=Nejc |last7=Kaffas |first7=Konstantinos |last8=Patro |first8=Epari Ritesh |last9=Auel |first9=Christian |last10=Schleiss |first10=Anton J. |last11=Fendrich |first11=Arthur |last12=Liakos |first12=Leonidas |last13=Van Eynde |first13=Elise |last14=Vieira |first14=Diana |last15=Borrelli |first15=Pasquale |date=January 2024 |title=Understanding the cost of soil erosion: An assessment of the sediment removal costs from the reservoirs of the European Union |url=https://linkinghub.elsevier.com/retrieve/pii/S095965262304341X |journal=Journal of Cleaner Production |language=en |volume=434 |pages=140183 |doi=10.1016/j.jclepro.2023.140183|bibcode=2024JCPro.43440183P }}</ref>

Erosion is also an issue in areas of modern farming, where the removal of native vegetation for the cultivation and harvesting of a single type of crop has left the soil unsupported.<ref>{{cite journal |last1=Ketcheson |first1=J. W. |title=Long-Range Effects of Intensive Cultivation and Monoculture on the Quality of Southern Ontario Soils |journal=Canadian Journal of Soil Science |date=1 March 1980 |volume=60 |issue=3 |pages=403–410 |doi=10.4141/cjss80-045}}</ref> Many of these regions are near rivers and drainages. Loss of soil due to erosion removes useful farmland, adds to sediment loads, and can help transport anthropogenic fertilizers into the river system, which leads to [[eutrophication]].<ref>{{cite book |last1=Ohlsson |first1=Thomas |editor1-last=Motarjemi |editor1-first=Yasmine |editor2-last=Lelieveld |editor2-first=Hubb |title=Food safety management: a practical guide for the food industry |date=2014 |publisher=Elsevier |isbn=9780128056820 |chapter-url=https://books.google.com/books?id=sCR3DAAAQBAJ&dq=%22Monoculture+agriculture%22+%22eutrophication%22&pg=PP6 |access-date=24 September 2021 |chapter=Sustainability and Food Production}}</ref>

The Sediment Delivery Ratio (SDR) is fraction of gross erosion (interill, rill, gully and stream erosion) that is expected to be delivered to the outlet of the river.<ref>{{Cite journal|last1=Fernandez|first1=C.|last2=Wu|first2=J. Q.|last3=McCool|first3=D. K.|last4=Stöckle|first4=C. O.|date=2003-05-01|title=Estimating water erosion and sediment yield with GIS, RUSLE, and SEDD|url=http://www.jswconline.org/content/58/3/128|journal=Journal of Soil and Water Conservation|language=en|volume=58|issue=3|pages=128–136|issn=0022-4561}}</ref> The sediment transfer and deposition can be modelled with sediment distribution models such as WaTEM/SEDEM.<ref>{{Cite journal|last1=Van Rompaey|first1=Anton J. J.|last2=Verstraeten|first2=Gert|last3=Van Oost|first3=Kristof|last4=Govers|first4=Gerard|last5=Poesen|first5=Jean|date=2001-10-01|title=Modelling mean annual sediment yield using a distributed approach|journal=Earth Surface Processes and Landforms|language=en|volume=26|issue=11|pages=1221–1236|doi=10.1002/esp.275|issn=1096-9837|url=https://lirias.kuleuven.be/handle/123456789/76728|bibcode=2001ESPL...26.1221V|s2cid=128689971}}</ref> In Europe, according to WaTEM/SEDEM model estimates the Sediment Delivery Ratio is about 15%.<ref>{{Cite journal|date=2018-02-01|title=A step towards a holistic assessment of soil degradation in Europe: Coupling on-site erosion with sediment transfer and carbon fluxes|journal=Environmental Research|language=en|volume=161|pages=291–298|doi=10.1016/j.envres.2017.11.009|pmid=29175727|pmc=5773246|issn=0013-9351|last1=Borrelli|first1=P.|last2=Van Oost|first2=K.|last3=Meusburger|first3=K.|last4=Alewell|first4=C.|last5=Lugato|first5=E.|last6=Panagos|first6=P.|bibcode=2018ER....161..291B}}</ref>