Decadal evolution of a spit in the Baram river mouth in eastern Malaysia
Résumé
WestudiedanewlyformedspitintheBaramRivermouthinEasternMalaysiaandevaluatedtheeffectsof climaticconditionsandhumaninterferenceoverthelastfourdecades(1974–2014).Thedevelopmentof aspitduringadecade(1998–2008)anditsmaximumexpansionovertheperiod2005–2010isrelatedto theerosionassociatedwithdeforestationandlandusechangesintheupstreamregion.Thedown-stream transportationoftheheavysedimentloadoccurredduringtheeventsofhigherprecipitationandflash floods. Therecentspitwasidentified forthe first timeasamud flat postthe flash flooding ofJanuary 2005.Itextendedtowardsthesouthwestoftherivermouthtill2010(sixfoldincreaseinareafrom 2005to0.29km2) andgraduallydisintegratedoverthenext3years.Depositionalfeatureofcoarsesediments andorganicdebrisisclearlysupportedbythealternatingthicklayersinthetop25cmofthethree coresamples(C1–C3) collectedfromtheregion.Thenon-existenceof finer particlesclearlyin-dicates thesupremacyoflongshorecurrentsintheregioncarryingawaythe fines todeeperregions.Gradual disappearanceofthesandbarrierpost2011isduetothereductionintheamountofsedimentload asaresultofreductioninrecentrainfallactivity,landuse/landcoverchangesmainlyasrefor-estation, strengtheningofpalmplantation(controllingsoilerosionintheriverbanks)intheupstreamregion. ThedominantNWwinddirectionduringthemajorpartoftheyearisalsooneofthefactorsforthe shiftindepositionalsequenceanditishelpedbythelongshorecurrentswhichleadtothespitbeingpartially connectedtothemainland.