Influences on Discharge Partitioning on a Large River Delta: Case Study of the Mississippi-Atchafalaya Diversion, 1916-1950

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John B Shaw, Kashauna Mason, Hongbo Ma, Gordon McCain


The modern Mississippi River Delta is plumbed by the Mississippi and Atchafalaya rivers, setting water and sediment dispersal pathways for Earth’s fifth-largest river. The Atchafalaya River’s (AR) partial annexation of discharge from the Mississippi River (MR) in the early 20th century prompted warnings of a rapid river avulsion and the construction of the Old River Control Structure to regulate flow. While this flow annexation is interpreted as a natural process in the avulsion-constructed delta, it was influenced by human activities. Here, we test how several significant changes between 1916 and 1950 influenced partitioning. Simulations show that erosion of the upper AR was the primary cause of discharge increase. Dredging in the lower AR between 1932 and 1950 produced minor increases, but was an important control on shear stress. The lower MR was also slightly erosional during the study period, and therefore hindered the discharge increase slightly. As a prototype system, attribution of discharge partitioning allows for various drivers of change to be quantitatively compared. Given the essential nature of this river junction to society, transportation, and commerce of the United States, improved attribution of discharge increases may lead to future management strategies that are broadly impactful.



Earth Sciences, Hydrology, Physical Sciences and Mathematics



Published: 2020-07-02 02:46


CC BY Attribution 4.0 International

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