The Last Naturally Active Delta Complexes of the Mississippi River (LNDM): Discovery and Implications

Can Continental Shelf River Plumes in the Northern and Southern Gulf of Mexico Promote Ecological Resilience in a Time of Climate Change?

“…Anthropogenic management, in contrast, has aimed to reduce this self-organized redundancy by confining flow to fewer channels to enhance navigation, flood control and economic development [11,[19][20][21][22][23][24][25][26]. For the MAR delta, this has compromised the capacity for the Mississippi River to supply sediment to wetlands experiencing high rates of subsidence [10].…”

“…The Mississippi River has built a composite Holocene delta ( Figure 5) through upstream avulsion and sequential creation and abandonment of onlapping and offlapping lobes [10,25,49,[52][53][54]. Under natural conditions, crevasses and distributaries formed along the supply channels of major lobes remained important to sediment distribution even in the lobe abandonment phase [19,25,49,52,54]. As long as sediment provenance from the basin was high, this land building system was resilient to high rates of Holocene sea level rise even though the MAR delta is subsiding faster than any other coast in North America (5-20 mm·year −1 ) as recent deposits dewater and compact [55][56][57].…”

Sediment Deposition at the Caernarvon Crevasse during the Great Mississippi Flood of 1927: Implications for Coastal Restoration

“…Before river embankment became widespread in many of the world's rivers, overbank flooding and crevasses were important and common mechanisms for replenishing floodplain and delta sediments and fertilizing the landscape [24,25,28,[45][46][47]. Crevasses function during high water via temporary channels through low points along the natural levee, forming crevasse splays, which have areas on the order of 10 to 100 s of km 2 compared to 100 to 1000 s of km 2 for full deltaic lobes [26,38,48].…”

“…Since then, approximately half of the original wetlands have disappeared by the processes of shore-line erosion and coastal subsidence [23] exacerbated by human activity [3,5]. Numerous natural crevasses and minor distributaries as well as seasonal overbank flooding occurred along the lower Mississippi River prior to human manipulation [24][25][26]. The upper perimeter of the Breton Sound estuary was fringed by 1 to 3 km of freshwater forested wetlands (i.e., see USGS St. Bernard map 1892).…”

Decline of the Maurepas Swamp, Pontchartrain Basin, Louisiana, and Approaches to Restoration

“…There have been numerous natural crevasses and minor distributaries as well as seasonal overbank flooding along the lower Mississippi River prior to major human manipulation, that had peak flows ranging from 5000-10,000 m 3¨s´1 for several months [12,[73][74][75]. Two examples of crevasses are the 1927 crevasse at Caernarvon and the Bonnet Carré Spillway.…”