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1、EnglishForWaterResourcesSoilerosionandsoilconservationAbstract:Themajormovementofsoilerosionandsoilerosion,soilerosionhazardstohumansistheerosionofthefirstoverofthelandbarrenexception,andthereforecannotgrowcrops,farmersbankruptandhadtomovetoabetterplace.Themainmethodstopreventsoilerosioni
2、sagoodmethodofcultivation.BasedonU.S.soilasanexampleabouthowtobuildterracesandothermethods.1IntroductionAllcivilengineersknowtwomaintypesofsoilmovement,soilcreeportheslowflowofsoil,andthefasterflows,calledslides,slipsoravalanches.Thefastermovementgenerallymoveslayersthataredeeperthanthose
3、movedbysoilcreep.Butmoreimportantthaneitherofthesetwotypes(atleastinthequantityofsoilremovedeveryyear)aresoilerosion,theremovalofsoilbyflowingwaterfromgroundthatisusuallydry,andscourtheremovalofsoilorrockfromthebedorbankofariverorstream.Forestsoilundergrowingtreesgenerallydoesnoterodebeca
4、usetheleavesanddeadorbrokenwoodholduptherainlikeblottingpaperandpreventitsattackingthesoil.Themainactionofdeadleavesindelayingrunoffisthattheyholdopenthedrainagechannelsintothesoil.Inbaresoilthatisnotprotectedinthisway,thesoilporesarequicklyblockedduringrainbythefinesoilgrainsflowingintot
5、hem.Therainrunsoverthesurfaceandnotintoit,smallchannelsform,tobedeepenedeventuallyintothereallydamagingdeep,scouredditchescalledgullies.Thefirstdisadvantageofsoilerosiontomankindisthaterodedlandissopoorthatcropswillnotgrowonit,farmersareruined,andhavetomovetobetterland.Thishashappenedtoma
6、nythousandsoffarmersintheUnitedStates,whichinthelasthundredyearshasprobablysufferedmoreformerosionthananyothercountry.Theseconddisadvantageisthatsoilerosionmakesfloodingbothmoresevereandmorefrequentsincethewaterrunsoffthesoilmorequickly.Inforestareas,95percentoftherainfallisabsorbedwhileo
7、nbaresoilabout95percentmayrunoff.Thisproportioniscalledtherunoffcoefficient.Nearlyallcivilengineeringstructures,roofs,roads,andanyconcreteworkhavearunoffcoefficientofabout95percent.Thedamagecausedbythesoildepositedduringfloodinginacitystreethasoftenbeencalculated,bu
