Restoring Deltaic Functions on the Mississippi Harley S. Winer, Ph.D., P.E. Atkins, Metairie, LA Harley S. Winer, Ph.D., P.E. Atkins, Metairie, LA

Outline of Presentation Alarming Land Loss RateAlarming Land Loss Rate Importance of Louisiana Coastal AreaImportance of Louisiana Coastal Area Multiple CausesMultiple Causes Principal Cause is Disruption of Delta ProcessPrincipal Cause is Disruption of Delta Process Explanation of Delta ProcessExplanation of Delta Process History of Delta Building DisruptionHistory of Delta Building Disruption Solution is to Restore Delta Building Process.Solution is to Restore Delta Building Process. Alarming Land Loss RateAlarming Land Loss Rate Importance of Louisiana Coastal AreaImportance of Louisiana Coastal Area Multiple CausesMultiple Causes Principal Cause is Disruption of Delta ProcessPrincipal Cause is Disruption of Delta Process Explanation of Delta ProcessExplanation of Delta Process History of Delta Building DisruptionHistory of Delta Building Disruption Solution is to Restore Delta Building Process.Solution is to Restore Delta Building Process.

Natural Causes Subsidence - Consolidation Weight of the Delta Deposits

Induced Causes Alteration of the Natural River System - Reduction of Sediment Load Construction of Canals -Canal Banks Create Impoundments -Salinity Intrusion -Boat Wake Erosion Subsurface Fluid Removal

Some History

1831 Captain Henry M. Shreve, dug a cut across the narrow neck of Turnbull's Bend. The river accepted the shortcut and abandoned the old channel, the upper part eventually silted up, leaving the lower section open. This section came to be called "Old River"

1839, the State of Louisiana began to dislodge a 30 mile long log jam in the Atchafalaya and open up the river to navigation.

The Atchafalaya is a shorter outlet to the Gulf of Mexico; 142 miles compared to 315.

The removal of the log jam allowed the Atchafalaya to capture more and more of the Mississippi's flow.

The Mississippi River Commission engaged Harold N. Fisk and a team of geographers and geologists to investigate Fisk, H. N., 1944, Geological Investigation of the Alluvial Valley of the Lower Mississippi Valley, Vicksburg, Mississippi, Mississippi River Commission

The Paradigm: We Need To Prevent the River from Changing Course

Because of the Consequences for:  Navigation  Flood Control  Water Supply  Navigation  Flood Control  Water Supply

The solution was the construction of the Old River Control Structures

With the Congressional Mandate to maintain the 1950 distribution of flows - 70% down the Mississippi and 30% down the Atchafalaya

The Unintended Consequence is that very little new land is being built to compensate for land loss

A New Paradigm: Allow the River to Change Course; Preserve Flood Control, Navigation and Water Supply on the Lower Mississippi River

Red River Mississippi River Atchafalaya River Lower Mississippi

Instead of diverting water from the Mississippi; Allow the Mississippi to change course and divert a minimum necessary amount to the lower Miss.

Allowing the bulk of the flow and more importantly a predominance of the sediment to go down the Atchafalaya, where it will build marsh.

How to reconfigure Old River was discussed in a paper presented at Coastal Sediments 07 in New Orleans.

How to distribute flows:  Normal Flows  Low Flows  Flood Flows

Normal Flows Maximum Flow down the Atchafalaya; divert the minimum necessary for fresh water supply to the Lower Mississippi

Low Flows Maintain the 70% - 30% distribution

Flood Flows Utilize the every avenue to pass the flood

What is needed is a Feasibility Study to address all of the potential problems associated with this proposal.

Changing one aspect of a system results in changes throughout the system – just as preventing the shift of the river did.

Potential Issues:  Channel Change - Relocations  Stage Changes  Reduced Dredging

The present paradigm results in the waste of a valuable resource. It is time for a new paradigm.

ReferencesReferences Winer, H. (2006), “A New Paradigm for Managing the Lower Mississippi River,” 30th International Conference on Coastal Engineering, pp , San Diego, CA Winer, H. (2007), “Re-Engineering the Mississippi River as a Sediment Delivery System,” Proceedings of Coastal Sediments ’07 Conference, pp , ASCE Winer, H (2011), “Re-Engineering the Mississippi River as a Sediment Delivery System,” Proceedings, Symposium to Honor Dr. Nicholas C. Kraus, Journal of Coastal Research, Special Issue, No. 59, pp Winer, H. (2006), “A New Paradigm for Managing the Lower Mississippi River,” 30th International Conference on Coastal Engineering, pp , San Diego, CA Winer, H. (2007), “Re-Engineering the Mississippi River as a Sediment Delivery System,” Proceedings of Coastal Sediments ’07 Conference, pp , ASCE Winer, H (2011), “Re-Engineering the Mississippi River as a Sediment Delivery System,” Proceedings, Symposium to Honor Dr. Nicholas C. Kraus, Journal of Coastal Research, Special Issue, No. 59, pp