Erosion of single particles at water-seabed interface has been assumed to be the dominate cause of sediment resuspension all over the world,with previous estimates of the re-suspension flux mostly based on the counterbalance between bottom shear stress and critical shear stress of bottom materials.In fact,the importance of pore pressure build ups in fluidizing the substrate to influence the erosion process has always been under investigation in the past few decades.So far,however,few studies have reliably determined the mechanism,much less to quantify the contribution.The severe erosion and great losses due to geologic hazards is therefore poorly constrained.In this study,we attibute the influence mechanism of this process to the attenuation of erodibility and seepage failures or seabed liquefaction i.e."sub-bottom sediment pump action",using field experiments on the intertidal flat zone and in-situ observation on the subaqueous delta.We also evaluated this contribution throuth controlled variable experiments using laboratory large wave flume and specially designed annular flume,based on the new understanding of mechanism.We obtained a total contribution of 50%-80%to the re-suspension flux by different seabed properties.This means that more than half of re-suspended materials originate from the under-component of seabed under the driving of upward seepage flows,when pore pressure build ups are large enough to induce subbottom sediment pump action.We suggest that pore pressure build ups are valuable metric for predicting future seabed vulnerability to oceanic forcing.