The Impacts of Pulsed Reintroduction of River Water on a Mississippi Delta Coastal Basin

Abstract

DAY, J.W.; CABLE, J.E.; COWAN, J.H.; DELAUNE, R.; DE MUTSERT, K.; FRY, B.; MASHRIQUI, H.; JUSTIC, D.; KEMP, P.; LANE, R.R.; RICK, J.; ROZAS, L.P.; SNEDDEN, G.; SWENSON, E.; TWILLEY, R.R., and WISSEL, B., 2009. The impacts of pulsed reintroduction of river water on a Mississippi delta coastal basin. Journal of Coastal Research, SI(54), 225-243. West Palm Beach (Florida), ISSN 0749-0208.During the twentieth century about 25% of the wetlands of the Mississippi delta was lost, partially a result of isolation of the river from the delta. River diversions are being implemented to reintroduce river water to the delta plain. We synthesize here the results of extensive studies on a river diversion at Caernarvon, Louisiana, one of the largest diversions in the delta.

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

“…Use of the flood pulse has been proposed as an effective method to maintain deltas against relative sea level rise [30]. Observational data from Snedden et al [16] and Day et al [55] Utilization of this hydrograph-based approach could also be beneficial to diversion regulation of the Mississippi River's water into the Atchafalaya River at the Old River Control Structure (ORCS). Currently the structure controls an average diversion rate of approximately 25% of the Mississippi River's flow [27].…”

Predicting the effects of freshwater diversions on juvenile brown shrimp growth and production: a Bayesian-based approach

“…They found that initially, habitat fragmentation increases shrimp access to the marsh surface, which enhances their production, but over time the remaining habitat erodes away or subsides and is eliminated. By implementing freshwater diversions, it is hoped that the rate of marsh fragmentation in coastal Louisiana can be slowed or reversed (Day et al 2009). However, it is not clear whether the sediment supply of the Mississippi River system is adequate to accomplish this goal (Blum & Roberts 2009) or whether river diversions will perform as expected (e.g.…”

“…The primary goal of constructing freshwater diversions in coastal Louisiana is to reconnect the Mississippi River with the deltaic plain (Day et al 2009). As such, the pattern of flow from these diversions will be tied to the pattern of river flow.…”

Broader perspective on ecosystem sustainability: Consequences for decision making

“…Management options being developed and applied in wetlands renewal and land building initiatives include large-scale river diversions, marsh terracing, sediment-slurry additions, plantings, dam modifications, shoreline protection, sediment fences, and placement of dredged materials (59,(66)(67)(68). Major river diversions are critical to supplying sediment and nutrients, precipitating sulfides, and preventing saltwater intrusion in coastal wetlands, but require understanding of diverse considerations during implementation (59,66). For example, positive and negative ancillary impacts on a range of attributes including eutrophication, hazardous algal blooms, and salinity changes in estuaries could occur from diversion discharges (60,66,68).…”

“…Major river diversions are critical to supplying sediment and nutrients, precipitating sulfides, and preventing saltwater intrusion in coastal wetlands, but require understanding of diverse considerations during implementation (59,66). For example, positive and negative ancillary impacts on a range of attributes including eutrophication, hazardous algal blooms, and salinity changes in estuaries could occur from diversion discharges (60,66,68). Restoration decisions require understanding dynamic surficial and subsidence processes (63).…”