Influence of sediment cohesion on deltaic shoreline dynamics and bulk sediment retention: A laboratory study

While boundary and forcing conditions influence the average location of a shoreline in deltaic systems, internal morphodynamics can drive high‐magnitude deviations from the long‐term trend. Here we explore the role of sediment cohesion on these morphodynamics using physical experiments. Specifically, we explore the role of sediment cohesion on the scales of autogenic shoreline transgressions and regressions. Results indicate that sediment cohesion enhances the time and space scales associated with autogenic cycles of channel formation, elongation, and abandonment. In systems with high sediment cohesion, this cycle can drive shoreline transgressions that produce flooding surfaces in the resulting stratigraphy which could be confused with surfaces produced by increases in sea level rise or subsidence rates. Enhanced channelization resulting from sediment cohesion also increases the pumping of fine‐grained sediment into the marine realm, where it can bypass the delta foreset, thus decreasing total delta sediment retention rate. Key Points Sediment cohesion on its own is inversely related to deltaic sediment retention Sediment cohesion increases scales of autogenic shoreline transgressions Autogenic shoreline transgressions scale with backwater length in deltas