the opportunity for transport onto the marsh surface occurs. These conditions frequently coincide 

 during the passage of winter frontal systems. Increasing sediment deposition requires an increase 

 in sediment availability for deposition, by increasing the suspended-sediment concentrations at times 

 when it would otherwise be low, but also at times when it can be transported onto the marsh 

 surface. Under natural conditions, suspended-sediment concentrations increase during periods of 

 strong southerly winds. Increasing suspended-sediment concentrations in marsh floodwaters, other 

 than by these natural processes, is one of the keys to increasing marsh-surface sedimentation. 

 Diverting sediments from the Mississippi River into coastal basins will achieve an increase in 

 suspended-sediment concentration over the basin as a whole while sediment is actively being 

 diverted. Such sediments will, however, be readily deposited unless sufficient hydraulic gradients can 

 be maintained as sediment-laden waters diffuse throughout the basins. Deposition will only occur 

 on the marsh surface if increased sediment suspensions coincide with marsh inundation events. The 

 natural processes and patterns of marsh flooding should be incorporated into plans to divert 

 sediments for increasing marsh-surface accretion. Increasing sediment concentrations without 

 consideration of sediment delivery processes will merely increase sediment storage within basins, 

 coastal bays, and deeper channels. This sediment will only be available for deposition on the marsh 

 surface when mobilized by natural sediment transport processes. 



Where marsh inundations are actively managed and, thus, the opportunity for marsh-surface 

 deposition exists, it may be possible to allow sediment inputs to a marsh area and gain some nutrient 

 stimulus to plant growth and soil development, while minimizing the incursion of saltwater. Careful 

 assessment of individual events and high-tide elevations could allow water-control structures to allow 

 maximum sediment input in short periods. Similarly, identifying those events which increase 

 suspended-sediment concentration, and excluding them, is an important management concern for 

 areas where reduced turbidity is considered desirable. 



CONCLUSIONS 



Marsh-surface sedimentation appears to be limited by suspended-sediment availability in flood 

 waters rather than by inundation events. Optimal natural conditions for marsh-surface deposition 

 occur during the passage of cold fronts and tropical storm or hurricane conditions. This has 

 frequently been observed by workers studying seasonal variations in salt marsh accretion. While 

 it is important to recognize that suspended-sediment availability is the limiting factor in natural 

 depositional processes, the role of inundation events in delivering that suspended sediment to the 

 marsh surface should not be dismissed. Techniques to increase suspended-sediment availability may 

 be more readily available than those which successfully manipulate marsh-surface flooding. 

 Understanding the combination of the two processes and their coincidence under certain natural 

 conditions can assist management schemes at all scales which attempt to either minimize or maximize 

 sediment delivery to the marsh surface. 



ACKNOWLEDGMENTS 



This study was completed with the support of the Louisiana Universities Marine Consortium and 

 its facilities. Daniel Lee assisted with data analysis and presentation. 



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