Forloadingandunloadingofboatsorshipsroundtheclock,theaccesschannelanditsexpandedpart-aportareexcavatedonthelagoonandoceanreefflatsinthetropicPacificoceanicislands.Withoutmoles,theaccesschannel-porttrapssedimentandfurthertransportsittotheoceanorlagoon,resultingincoastalerosion.Thewideunevenreefflatwithalargecatchmentareatendstocausetheformationoftidecurrentsinthechannel-port,whilestrongwavesonthenarrowevenreefflatcangiverisetoripcurrents.Anaccesschannel-portwithamoleononesideortwomolesonbothsidesresultsinlesserosion.Amodelisrecommendedasanartificialharborontheoceancoast,whichisanexcavatedportsurroundedbyamole,connectedwiththeoceanbyanaccesschannelandwiththeshorebyabridge-shapedpier.
