Rethinking the Mississippi River diversion for effective capture of riverine sediments

Abstract

Many river deltas in the world are vibrant economic regions, serving as transportation hubs, population centres, and commercial hotspots. However, today, many of these deltaic areas face a tremendous challenge with land loss due to a number of factors, such as reduced riverine sediment supply, coastal land erosion, subsidence, and sea level rise. The development of the Mississippi River Deltaic Plain (MRDP) in southeast Louisiana, USA, over the past century is a good example. Since 1932, approximately 4877 km 2 of the coastal land of MRDP has become submerged. The lower Mississippi River main channel entering the Gulf of Mexico has become an isolated waterway with both sides losing land. In contrast, large open water areas in the Mississippi River's distributary basin, the Atchafalaya River basin, have been silted up over the past century, and the river mouth has developed a prograding delta feature at its two outlets to the Gulf of Mexico. The retrospective analysis of this paper makes it clear that the main cause of the land loss in the MRDP is not the decline of riverine sediment, but the disconnection of the sediment sources from the natural flood plains. Future sediment management efforts in the MRDP should focus on restoring the natural connection of riverine sediment supplies with flood plains, rather than solely using channelized river diversion. This could be achieved through controlled overbank flooding (COF) and artificial floods in conjunction with the use of a hydrograph-based sediment availability assessment.

Assessing Resilience and Sustainability of the Mississippi River Delta as a Coupled Natural-Human System

“…Across the main channels of the Upper Mississippi, Ohio, Missouri, Tennessee, and Arkansas-White-Red Rivers, which are five tributaries of the Lower Mississippi River, approximately 100 dams and locks were built. Annual sediment load to the Lower Mississippi River has reduced from 400 million tons (MT) a century ago to the current annual load of about 180 million tons combined from the Lower Mississippi River main channel and its Atchafalaya distributary channel [5,6]. Levees were built after the 1927 mega flood along both sides of the river from its mouth at the Gulf of Mexico to Baton Rouge in Louisiana, 367 km upstream, which prohibited the sediment supply to the river delta plain.…”

“…Levees were built after the 1927 mega flood along both sides of the river from its mouth at the Gulf of Mexico to Baton Rouge in Louisiana, 367 km upstream, which prohibited the sediment supply to the river delta plain. Since 1932, the Mississippi River Delta has lost nearly 5000 km 2 of land and the lower Mississippi River main channel entering the Gulf of Mexico has become an isolated waterway with land on both sides submerging into water [6].…”