Assessment of Selected Erosion- Related Parameters in Owerri West Local Government Area, Imo State.

ErosionisamajorecologicalproblemintheSouthEast.Int hestudyareaalonethereareseveralgullyerosionsites(e.g. Nekedeerosionsites,IhiagwaFUTOerosionsites,AkwakumaMarketerosionsitesetc.) ThesegulliescontributesignificantsedimentstoNwaorie andOtamiririversystem.Thisresearchwascarriedouttoa ssessandestablisherodibilityfactorsunderlyingtheform ationofgullyerosioninthestudyarea.Themethodologya doptedincludedtheselectionoftwogullyerosionsites,me asurementoftheircrosssectionalareastodeterminetheir morphometricattributesfortwoyears(2018and2019).C ollectionofsoilsamplesineachgullyformation,thesampl esweresealedincellophanebagsandtransportedtotheSoi llaboratoryoftheInstituteofErosionStudies(IES)FUTO forgeotechnicalanalysis(soilconsistencytesttodetermi netheatterberglimits(Plasticlimits,LiquidLimitandPlas ticityIndex),Shearstrength,drydensity,bulkdensity,and soiltexture/sieveanalysis).Theresultsofthemorphometr icmeasurementshowedthatthegulliesinthestudyareaare Ushape,runningatrightangletotheOtamiriRiver.Elevatio nis65m,Slopeisbetween2and6%.ThelengthofFUTOgu llywas145.2min2018and140min2019;averagewidthis 2.37min2018,5.24min2019;averagedepthis1.70min20 18and1.20min2019.Thisindicatethatwhilegullywidthi ncreasedby10.28%between2018and2019,thedepthand lengthdecreased,anindicationoflateralsidefailureandse dimentationatthegullytoe.Theresultofsoillaboratoryan alysisshowedFUTOgullyhasplasticlimit(PL)47.7%,Li quidLimit(LL)63%andPlasticityIndex(PI)of12.3%wh ileatNekedegullyerosiontheLLwas19.1%,PL19.1%an dPI10.4%thisresultisindicativeoflowcohesion.Theshe aringresistanceofthesoilislowandpronetodeformationo ncethresholdof30˚- 35˚isreachedbyrunoff.Theconclusiondrawnfromthisst udyisthatgullyerosioninthestudyareaareformedbythep rocessesoflateralerosionandundercuttingwhenthegrass coverareremoved.Thesoilconditionbeinglesscohesive, weakshearstrengthetc.arethemajorerodibilityfactorsth atinfluencethegullyformations.Itisrecommendedthatre medialmeasuresforgullyerosionshouldbesitespecificas notwogulliesarethesame.Inconstructionofroadsidedrai ns,returnperiodofcertainrainfalleventbedetermined.Cl earingofriparianvegetationandinstreamminingatsensitiveareasshouldbediscouraged