Long-Term Cross-Shoreface Sediment Fluxes

Abstract

There exists a large uncertainty about the importance of crossshoreface sediment fluxes both in relation to the dynamic evolution of the shoreface profile and the potential role as a sink or souree to the 'active' zone. The increasing availability of more reliable long-term observational data (direct and indirect) and of more detailed shoreface field observations seems to support earlier suggestions that the shoreface may be a potential souree of coarser sediments to the nearshore. Here, this process is investigated by hindcasting and extrapolating long- and short-term observations available for the shoreface along the Ebro Delta. Analysis of the field data indicates that a structural onshore sediment flux is likely. Although a direct proofthat this is also true on longer-term seales is not easy to substantiate, the careful conclusion is drawn that there exists circumstantial evidence that there is a net long-term feeding of coarser sediment towards the nearshore to an amount which is just about enough to compensate for 'Iosses' due to the present sea-level rise rate in the region.