At a basin-wide scale the wetlands of coastal Louisiana have been built and maintained by river-borne sediment primarily transported by the Mississippi River system. At more local scales individual marsh platforms have often maintained elevation without the direct influx of river-borne sediment. In the latter stages of the delta cycle for any given delta lobe, the main river channel has usually avulsed to another portion of the delta plain and may be providing no direct sediment input to the area. Coastal marshes that have maintained elevation for long periods of time by sediment accretion are shown to have significant rates of carbon sequestration.

A detailed review of a particular marsh platform in Plaquemines Parish shows that with minimal influx of river-borne sediment, the area experienced sediment accretion rates in excess of 9 mm/yr for most of the last decade, as measured by stations in the Coast-Wide Reference Monitoring System (CRMS). The maximum rates of sediment accretion on the marsh platform occurred in a berm that generally parallels the outer edge of the marsh platform. These sediment deposits are the result of the transportation of sediment onto the marsh platform by tidal flux. Rates of edge erosion have been measured along the same marsh platform, and it appears that the volume of sediment derived from edge erosion is much too small to account for the volume of accretion occurring on the platform. It is likely that sediment is being eroded from the bottom of the bays adjacent to the marsh platform and carried in by the tides.

Supplementing this natural process of sediment transportation and accretion with dredged sediment could allow for the long-term sustainability of this type of marsh platform. Sediment berms could be deposited along the edges of the marsh platform. Over time these sediment berms would be washed away, but a significant volume of the sediment would be carried onto the marsh platform. Placing the berms along the marsh edges would serve the dual purpose of mitigating the rates of edge erosion, which would further enhance sustainability. This process could be repeated over time.