A Hydrograph-Based Sediment Availability Assessment: Implications for Mississippi River Sediment Diversion

Water

Timothy Rosen¹ 

关键词: riverine sediment;    total suspended solids;    flood hydrograph;    river diversion;    sediment management;    Mississippi River;   

DOI  :  10.3390/w6030564

来源: mdpi

【 摘 要 】

The Mississippi River Delta Plain has undergone substantial land loss caused by subsidence, relative sea-level rise, and loss of connectivity to the Mississippi River. Many restoration projects rely on diversions from the Mississippi River, but uncertainty exists about the timing and the amount of actually available sediment. This study examined long-term (1980–2010) suspended sediment yield as affected by different hydrologic regimes to determine actual suspended sediment availability and how this may affect diversion management. A stage hydrograph-based approach was employed to quantify total suspended sediment load (SSL) of the lower Mississippi River at Tarbert Landing during three river flow conditions: Peak Flow Stage (stage = 16.8 m, discharge >32,000 m³ s⁻¹), High Flow Stage (stage = 14.6 m, discharge = 25,000–32,000 m³ s⁻¹), and Intermediate Flow Stage (Stage = 12.1 m, discharge = 18,000–25,000 m³ s⁻¹). Suspended sediment concentration (SSC) and SSL were maximized during High Flow and Intermediate Flow Stages, accounting for approximately 50% of the total annual sediment yield, even though duration of the stages accounted for only one-third of a year. Peak Flow Stage had the highest discharge, but significantly lower SSC (p < 0.05), indicating that diversion of the river at this stage would be less effective for sediment capture. The lower Mississippi River showed significantly higher SSC (p < 0.0001) and SSL (p < 0.0001) during the rising than the receding limb. When the flood pulse was rising, Intermediate Flow and High Flow Stages showed greater SSC and SSL than Peak Flow Stage. Together, Intermediate Flow and High Flow Stages on the rising limb annually discharged 28 megatonnes over approximately 42 days, identifying this to be the best period for sediment capture and diversion.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.