Comprehensive Recommendations Supporting the Use of the Multiple Lines of Defense Strategy to

Sustain Coastal Louisiana August 17, 2007

Multiple Lines of Defense Assessment Team

John Lopez, Ph.D. (Chair) Coastal Scientist Carlton Dufrechou, AICP Planner Engineer

Mark Hester, Ph.D. Biologist (wetland plants) Paul Keddy, Ph.D. Wetland plant ecologist Paul Kemp, Ph.D. Oceanographer Barry Kohl, Ph.D. Geologist

Subhash Kulkarni PE Structural Engineer Alex McCorquodale, Ph.D. PE Engineer (hydrologic modeler)

Martin O’Connell, Ph.D. Biologist (fish) Bryan Rogers, BS GIS & Documentation support Natalie Snider, MS Wetland Ecologist Joe Suhayda, Ph.D. Coastal Oceanographer (hydrologic modeler)

Acknowledgments

This paper has benefited tremendously from comments and suggestions from engineers, biologists, geologists and knowledgeable locals. Those listed below contributed, but this does not necessarily indicate an endorsement of the concepts described here. Their contributions are appreciated.

Comments Provided

Sue Hawes; Len Bahr, Ph.D.; Rod Emmer, Ph.D.; John Day, Ph.D.; Hassan Mashriqui, Ph.D.; Shirley Laska, Ph.D.; Gene Turner, Ph.D.; Rune Storesund, Ph.D.; Rick Hartman; Jim Tripp; Oliver Houck, Ph.D.;

Robert Thomas, Ph.D.; LA DNR

Other Contributors John Walthers, Tom Moorman

Editors

Emily Vokes, Ph.D. & Sharon White Funding Provided by the McKnight Foundation

FINAL DRAFT

Planning Unit 3a (Terrebonne Basin) General Description Planning Unit 3a is composed of Terrebonne Basin, which includes numerous small bayous and ridges branching off of Bayou Lafourche north of Houma, and extending south toward Terrebonne and Timbalier Bays (Figure 52). It is the confluence of bayous around Houma that provides a concentration of ridges and encouraged settlements and development there. Several state highways are located along these bayou ridges extending as much as 30 miles south of Houma. These state highways are continuously developed with residences, camps or businesses that form several small communities such as Theriot, Dulac, Chauvin, etc. Typically, these communities were developed with a single row of development immediately adjacent to the bayou on each bank.

Figure 52: 2002 Satellite image of PU-3a. Note white or light green areas are bayou ridges emanating from Bayou Lafourche and extending south. Most highways and development is located on these ridges.

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The bayous around Houma, such as Little Bayou Black and Bayou Terrebonne, once carried freshwater from Bayou Lafourche southward into the estuary around Terrebonne Bay. It is likely that, before damming Bayou Lafourche in 1904, some portion of the Bayou Lafourche discharge flowed into these bayous. The volume of historic discharge is not known, but must have been much less than Bayou Lafourche itself which at most discharged 81,000 cfs (possibly as little as 6000 cfs) prior to being dammed in 1904 (BTNEP, 1996). Timbalier and Terrebonne Bays were already large open bays in 1900. The barrier islands separating the bays from the Gulf of Mexico were certainly larger than now, and the major tidal pass (Cat Island Pass) was about 2 ½ miles wide rather than the 5 miles it is now (Williams, et al., 1992). Nevertheless, compared to Barataria Basin, these large bays were historically much more open to the gulf. A result of the historic low freshwater input and the openness of the bays to the gulf is that the Terrebonne Basin in general has had higher salinity than the adjacent basins (Barataria or Atchafalaya). The historic distribution (circa 1900) of oysters appears to have been at the outer rim of Terrebonne and Timbalier Bays. The implication of these characteristics is that the Basin was in a state of slow natural collapse including reduction in the extent of barrier islands and wetlands. The state of natural collapse does not account for the extreme rates of land loss after 1932 that are due to several types of human impacts to the basin. Figures 53 & 55 illustrate the patterns of land loss in Planning Unit 3a. From 1932 to 1956 significant land loss occurred in a band of “interior land loss” running east to west, south of Houma. The marshes adjacent to the Terrebonne and Timbalier Bays have been relatively stable. Major causes of the interior loss are impoundments, oil and gas canals, and saltwater intrusion (Coast 2050, 1998). The barrier islands of Planning Unit 3a have diminished in their areal extent due to natural processes and human impacts (such as canals). The natural process of an abandoned delta is that over hundreds of years the barrier islands become smaller and evolve into submerged shoals (Penland et al., 1988). Man-made canals across the islands accelerate erosion and fragment the islands. Maintaining these islands in the future will likely become increasingly difficult. Sand nourishment of the islands may become prohibitively expensive in the future and is not by itself a self-sustaining measure, requiring multiple applications into the future. The islands are separated by large passes. The passes allow sediment to be swept bayward or gulfward, and are lost to longshore transport and the islands. Successful sand replenishment has been accomplished on East Timbalier Island. Raccoon Island has offshore breakers that seem to have an overall positive effect. This is due to the fact the breakers are located near the terminal end of the longshore transport of the islands. Although some localized success has been achieved with sand nourishment and breakwater projects, most of the islands will continue to experience loss of sediments from oceanic and natural processes.

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Figure 53: Historic Land Loss and the Morganza to the Gulf Levee Alignment. Map shows historic land loss in blue (upper) & red (lower). Projected land loss to 2050 in yellow (lower) (Source: USGS). Note the massive anticipated land loss south of the levee alignment. Also note the funnel geometry created in conjunction with the Bayou Lafourche back levee (solid yellow).

Planning Unit 3a currently has minimal flood protection provided by levees. Terrebonne Parish Levee District for many years has, at its own expense, increased levee heights and attempted to regionalize the levee system. This effort consists mostly of a patchwork of levees built on ridges, spoil banks, roadways, etc, which are located as a broad arc around the southward extent of bayou/ridges on which the state highways and communities are located (Figure 53). The parish, state and USACE have partnered to develop a more comprehensive and enhanced levee for this

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region. This project is termed “Morganza to the Gulf of Mexico Hurricane Protection Project”, and included a USACE Feasibility Study completed in March 2002 and a Chief’s Report submitted to Congress three years before Hurricane Katrina in August 2002. The state and local residents have requested levee improvement for more than a decade. Based on the Feasibility Study, the project cost for the initial recommended plan is $680 million. Considering the aftermath of Hurricanes Katrina and Rita, including the lessons-learned, the federal financial limitations, and the specter of greater storm surge threats, it is necessary to re-assess the Morganza to the Gulf project. It is inappropriate for this Pre-Katrina project to be effectively “grandfathered” in. Those that might think the hurricanes are de facto proof of the need for Morganza to the Gulf misunderstand the lessons the storms provided. In New Orleans, it was an inadequate flood protection system that resulted in the disastrous consequences of Hurricane Katrina. The recent Team Louisiana report issued by the La DOTD (2007) and the report released by the American Society of Civil Engineers (ASCE, 2007) makes this abundantly clear. At this time, none of the knowledge from the failures of the New Orleans levee system has been incorporated into the design of the Morganza to the Gulf levee, which has had no engineering or design modifications since the initial report in 2002. We must ask if the current Morganza to the Gulf levee design would create, like New Orleans’ levees, a false sense of security which ultimately leads to disastrous consequences. The Morganza to the Gulf was conceived in a different time when less surge and more coastal restoration were anticipated. To the contrary, restoration has not been adequate and greater storm surge due to more frequent and higher category hurricanes is now anticipated. Figure 52 dramatically illustrates the proximity of the alignment to the Gulf, the adjacent historic land loss and the potential of future land loss. Morganza to the Gulf places a regional levee alignment too far south with too little land separating the levees from the Gulf of Mexico. The proposed levee alignment would impound wetlands and reduce the storage for storm surge. Of the 253,100 acres to be protected, 63% (159,000 acres) are wetlands (USACE, 2002). The concern for these wetlands is now even greater since enclosure of these wetlands removes area for storm surge to occupy and disperse. As implied by this high percentage of wetlands, much of the protected area has low population, especially the southern half of the region which is dominated by typical rural bayou communities strung thinly along small bayous. A particular challenge with the alignments by either the Lafourche Parish is the possible amplification of surge level between the Bayou Lafourche back levee and the east flank of the Morganza to the Gulf alignments (Figure 51). The levee heights would be at least 20 feet high creating an efficient side to the funnel. The Bayou Lafourche levee extends for 12 miles, and the eastern flank of Morganza to the Gulf for 18 miles. This funnel geometry is approximately 50% larger than the size of the now infamous MRGO funnel east of New Orleans (9 miles & 12 Miles). The alignment, if built, would create a new storm surge problems while producing a false security for the region that would encourage more development.

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Figure 54: 2005 Imagery and Proposed Morganza to the Gulf Levee Alignment. Various proposed levee alignments around Houma and the Morganza to the Gulf of Mexico Hurricane Protection Project on 2005 CIR imagery. State’s Master Plan includes both Morganza to the Gulf (Parish or USACE alignment) and a 500 year levee alignment south of Houma (GIWW). This report recommends a modified 500 year levee alignment and ring levees in lieu of a continuous Morganza to the Gulf alignment.

In reviewing the Morganza to the Gulf project, it was found that levees are being proposed in the 2002 USACE Feasibility Study were for a 100 year level of protection, yet there is no plan for armoring the levees or protecting the communities from overtopping of the levees. Evacuation planning elements are not included in the Morganza to the Gulf study, nor does Morganza to the Gulf include any wetland restoration, although it is very clear that the coastal buffer for this levee alignment is severely degraded. The proposed levees do follow some of the bayou ridges and existing hydrologic barriers, but the alignment jumps across several ridges resulting in enclosure of extensive wetlands. In addition, many of the existing hydrologic barriers that are being utilized for the proposed alignment are only one to six feet above marsh elevation and will continue to allow the attenuation of storm surge into the wetlands. The construction of large-scale levees will diminish the capacity of wetlands to absorb the storm surge.

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The conclusion to be drawn is that Morganza to the Gulf Project is not just a Pre-Katrina design; it is a design not utilizing a Multiple Lines of Defense approach or utilizing the higher safeguards for levee design. Morganza to the Gulf project is truly a project molded from an era of incomplete integration and inadequate engineering, permitted by the outdated notions that levees alone are adequate and that traditional levee designs will not fail. The tax payers who might pay for this project and the residents who might choose to live within this levee alignment deserve more than an outdated and ineffective flood protection system design. Recommendations for Planning Unit 2 start with a new levee alignment to protect the greater Houma region including Montegut and Chauvin with 500 year protection (Figure 54). Ring levees with 100 year protection are proposed around Dulac and Theriot. Additional modeling is being completed to further evaluate this recommendation.

Figure 55: Planning Unit 3a recommendations near Houma. Base is USACE land loss map (Britsch & Dunbar, 2006). Red line indicates the recommended levees (500 year protection for Houma; 100 year for ring levees). 4, 5 & 6 are recommended areas for marsh creation.

Wetland restoration by marsh creation is focused on the wetlands adjacent to the proposed levee alignments. The perimeter marshes around Terrebonne and Timbalier Bays should be restored to a brackish habitat. Oyster productivity and oyster reefs should be actively promoted and developed here. Reefs should be located around the peninsular ridges extending into the bays. Freshwater introduction is to be increased in three ways. The proposed spillway from the Atchafalaya River (near Lake Palourde) will increase freshwater input from the northwest. Freshwater input from the east should be increased by directing Bayou Lafourche flow west into Terrebonne Basin. The

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spillway located south of Cutoff should be utilized during a major flood pulse event to allow flow across Bayou Lafourche into Terrebonne Basin. The barrier islands are recommended for restoration with the addition of offshore breakwaters at Cat Island Pass.

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Table 7: Planning Unit 3a (Terrebonne Basin) – Lines of Defense Measures

PU-3a # line

color Location Measure Description New/Existing

Maximum Discharge

Controlled div

Maximum Discharge

Flood year- pulse events w/spillways

1 red Greater Houma, including Chauvin, Montegut, and Crozier

New levee - 500 year protection provided by the Flood Protection System including lock on HNC new

2 red Theriot Ring levee - 100 year protection provided by Flood Protection System new 3 red Dulac Ring levee - 100 year protection provided by Flood Protection System new

4 lt green Lake Boudreaux Basin Restore marsh to 1978 extent with marsh creation (5000 acres), restore hydrologic connections & restore canals, existing

5 lt green W. Pointe au Chien WMA (Madison Bay)

Restore marsh to 1978 extent with marsh creation (3000 acres), restore hydrologic connections & restore canals, existing

6 lt green E. Pointe au Chien WMA (Madison Bay)

Restore marsh to 1978 extent with marsh creation (7000 acres) & restore canals, existing

7 lt green Caillou Lake to Upper Timbalier Bay

Aggressive oyster reef restoration and restore marsh with marsh creation (5000 acres) existing

8 Yellow Houma Navigation Canal Construct multi-purpose lock structure including salinity control new structure

9 Yellow Hwy 57 and other artificial hydrologic barriers Restore hydrology with additional culverts to Lake Boudreaux Basin new structures

10 lt green Isle Derniers Barrier Island Maintain barrier islands w/ Ship Shoal sand existing BI

11 lt green Cat Island Pass Construct offshore breakwaters to trap sand of terminal ends shoreline drift new structure

12 lt green East & West Timbalier Islands Maintain barrier islands w/ Ship Shoal sand existing BI's

13

dk blue and lt blue

South of Cut Off, Bayou Lafourche

Controlled hurricane surge relief spillway: east to west or west to east across Bayou Lafourche, also used for flood year pulse events east to west discharge freshwater new structure 10000

14 lt blue

Lake Mechant/ Lake Decade region (East Atchafalaya Restoration Spillway)

Outfall management to enhance freshwater movement from Lake Palourde diversion (in Planning Unit 3b) to central Terrebonne Parish new structures 10000 10000

15 lt blue Bayou Lafourche Bayou Lafourche diversion Maximum design discharge 1000 cfs new structure 1000 1000

Total discharge 21,000

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Figure 56: Planning Unit 3a Lines of Defense Measures Map (excluding evacuation, drainage and non-structural measures)

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Specific Recommendations Planning Unit 3a

1) 500 Year Hurricane Protection for Houma and Vicinity The greater Houma region has significant concentration of assets and population and should be provided a high level of flood protection. A levee and flood gates are proposed to provide 500 year protection. The alignment extends slightly south of Houma near Highways 56 and 55 to include the towns of Chauvin and Montegut, which now have minimal protection. The proposed 500 year protection levee alignment would provide a higher level of protection for these towns than the proposed Morganza to the Gulf alignment (100 year protection). The proposed 500 year levee does cross some small segments of the marsh, such as between Highways 56 and 57 to reduce local funneling effects by the levee. The western end of the alignment terminates near the proposed Lake Palourde spillway. This spillway may be used to disperse surge as well as to divert Atchafalaya River water (see #10 & 11). The eastern end of the alignment is near the proposed spillway across Bayou Lafourche. The overall alignment is intended to disperse surge laterally and into adjacent basins. The release of the storm surge into adjacent basins is critical due to the condition and extent of wetlands between the levee alignment and the Gulf of Mexico. Although this levee alignment is entirely within the habitat goal of intermediate wetlands and is historically marsh habitat, restoration of sustainable wetland forests outside and adjacent to the levees may be possible locally adjacent to the levee at stormwater or treated wastewater outfall. A very narrow buffer of cypress forests may still yield additional protection to the levee and should be pursued by municipal water management to benefit local wetland forests adjacent to the levee. The treated wastewater from locally protected communities can also be used to rejuvenate local forests. 2) 100 Year Protection for Theriot (Ring Levee) 3) 100 Year Protection for Dulac (Ring Levee) Since the “Morganza to the Gulf” levee project is not recommended, ring levees are proposed for Dulac and Theriot to provide 100 year protection for these communities. The levees should be designed to be overtopped without failure of the levee. Concentration of assets or population in these small communities is not vast. Nevertheless, a levee protection is recommended because these small settlements can support the much larger highway corridors of Highways 315 and 57. Protection will allow commercial viability to continue for a much larger area. The ring levee will encourage future concentration of commercial assets which are not very desirable or amenable to being elevated (such as gas stations, grocery stores, drive-through businesses, etc.) within the ring levees. Non-structural measures, such as flood proofing businesses and elevating residences, will need to be required within the levee to provide a level of protection greater than the 100 year protection of the levee system. 4) Restoration in Lake Boudreaux Basin Significant wetland loss has occurred in the Lake Boudreaux Basin and the adjacent basin to the west. These wetlands can provide critical protection benefits to the proposed 500 year protection system south of Houma (see #1) and to local residents dependent on non-structural protection. It is recommended that the marsh extent be restored to the ~1978 extent, which is approximately 5000

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acres with marsh creation. The location of the restored wetlands may vary from the 1978 precise extent due to current localized conditions. It is crucial that the restored wetland areas are integrated into the protection system and act as a storm surge buffer for the levee system. It may be desirable to utilize long-distance piping of sediment from offshore. In addition, increasing the natural hydrologic exchange is proposed by using culverts below Highway 57 (see #9) and other artificial hydrologic barriers. Freshwater introduction is proposed through the GIWW and into the Houma Navigation Canal (see #8). The increased hydrologic connectivity and increase in freshwater into the system will aid in sustaining the wetlands restored with marsh creation. It is also recommended that an aggressive program to infill the numerous oil and gas canals and degrade spoil banks is completed. The open canal network contributes to the poor health of this marsh by erosion and an impediment to overland flow and should be addressed to maximize the sustainability of this critical line of defense (Turner, 1997). 5) Restoration in West Pointe Au Chien WMA Significant wetland loss has occurred in the western Pointe au Chien Basin. These wetlands can provide critical protection benefits to the proposed 500 year protection system south of Houma (see #1) and to local residents dependent on non-structural protection. The area for restoration includes the Pointe au Chien WMA, which has experienced dramatic wetland loss and will benefit significantly from restoration. It is recommended that the marsh extent be restored to ~1978 extent which is approximately 3000 acres. The location of the restored wetlands may vary from the 1978 precise extent due to current localized conditions. It is crucial that the restored wetland areas are integrated into the protection system and act as a storm surge buffer for the levee system. It may be desirable to utilize long-distance piping of sediment from offshore. In addition, increasing the natural hydrologic exchange is proposed by installing culverts below Island Road or other artificial hydrologic barriers crossing the basin. It is also recommended that an aggressive program to infill the numerous oil and gas canals and degrade spoil banks is completed. The open canal network contributes to the poor health of this marsh by erosion and an impediment to overland flow and should be addressed to maximize the sustainability of this critical line of defense (Turner, 1997). 6) Restoration in East Pointe Au Chien WMA Significant wetland loss has occurred in the eastern Pointe au Chen Basin. These wetlands can provide critical protection benefits to the proposed 500 year protection system south of Houma (see#1) and along Bayou Lafourche. The area for restoration includes the Pointe au Chen WMA, which has dramatic wetland loss and will benefit significantly with restoration. It is recommended that the marsh extent be restored to ~1978 extent which is approximately 7000 acres. The location of the restored wetlands may vary from the 1978 precise extent due to current localized conditions. It is crucial that the restored wetland areas are integrated into the protection system and act as a storm surge buffer for the levee system. It may be desirable to utilize long-distance piping of sediment from offshore.

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It is also recommended that an aggressive program to infill the numerous oil and gas canals and degrade spoil banks is completed. The open canal network contributes to the poor health of this marsh by erosion and an impediment to overland flow and should be addressed to maximize the sustainability of this critical line of defense (Turner, 1997). 7) Restoration in Caillou Lake to Upper Timbalier Bay The perimeter marshes around Terrebonne and Timbalier Bays should be restored to a brackish habitat. Oyster productivity and oyster reefs should be actively promoted and developed in this region. Reefs should be located around the peninsular ridges extending into the bays. These marshes are relatively stable. Oyster productivity will enhance this stability. Armoring of some shorelines may be necessary for those areas with persistent high rates of shoreline retreat. Shoreline stabilization projects (such as the CWPPRA demo project) in Terrebonne Bay should be constructed to incorporate oysters reefs, allowing for a enhancement of this biological resource as well as providing protection from wave and storm action on the shoreline. These marshes are relatively stable, but some marsh creation is recommended (~5000 acres). 8) Houma Navigation Canal The Houma Navigation Canal (HNC) is a 36.6-mile navigation channel that begins at the Gulf Intracoastal Waterway (GIWW) in Houma and extends southward to the Gulf of Mexico. The Houma Navigation Canal is being impacted by the intrusion of saltwater north through the canal that is threatening the drinking water supply of Lafourche and Terrebonne Parishes. The saltwater intrusion is also contributing to wetland loss in the Lake Fields area. The saltwater wedge caused by the Houma Navigation Canal has been reported as far north as Bayou Lafourche. The construction of a multipurpose lock is recommended near the Canal’s intersection with Bayou Grand Caillou to facilitate the navigational, restoration and flood protection needs of the adjacent communities. The lock would utilize freshwater from the Atchafalaya River, through the GIWW, to restore and maintain wetlands in the Lake Boudreaux, Lake Mechant and Grand Bayou areas. The lock will also prevent the Houma Navigation Canal from acting as a conduit for storm surge. 9) Restore Hydrology at Highway 57 and other Artificial Hydrologic Barriers Highway 57 between Highway 56 and Dulac is on an earthen foundation, impounding the estuary to the north around Boudreaux. This area is targeted for restoration with marsh creation and should be allowed to optimally thrive. Multiple culverts should be constructed underneath Highway 57 to allow a more natural exchange of hydrology and help sustain the marsh buffer to the north. The culverts will also allow drainage of the additional freshwater that will be introduced into the system. 10) Isle Dernieres Barrier Island The Isles Dernieres is a transgressive barrier island arc that has undergone extensive fragmentation and area loss since the mid 1800’s. The entire beach face has migrated landward at an average rate that exceeds 10 m/year (Dingle and Reiss, 1989). The Isles Dernieres, specifically the West Isle Dernieres, should be evaluated for additional restoration needs. Periodic sand nourishment is recommended to maintain the integrity of the islands. Island dimensions should be optimized to minimize the risk of breaching and reduce sand loss from overwash (USACE, 2004).

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11) Cat Island Pass Cat Island Pass has continued to widen for over 100 years. It has become a major sediment sink for sand transported east or west from adjacent islands. Longshore transport form either flank converges toward Cat Island Pass. Offshore breakwaters should be constructed to capture sand. This will create a reservoir of sand for future sand nourishment projects. It is also likely to create a new emergent island. 12) East and West Timbalier Islands West Timbalier Island has had successful restoration completed under CWPPRA. Although the island seems to have not suffered major damage from Hurricanes Katrina and Rita, periodic sand nourishment will be needed to maintain the integrity of the island. Island dimensions should be optimized to minimize the risk of breaching and reduce sand loss from overwash (USACE, 2004). 13) Controlled Spillway across Bayou Lafourche Ridge South of Cutoff It is proposed that a controlled spillway structure be evaluated across Bayou Lafourche just south of Cutoff. The primary purpose would be to disperse surge by allowing flow across the Bayou Lafourche ridge to reduce maximum surge height within the basin most threatened. The spillway structure would replace the flood protection levee locally and would allow flow across the natural elevation of the Bayou Lafourche ridge. This spillway could be critical to reducing surge on the west side of Bayou Lafourche in Planning Unit 3a. In Planning Unit 3a, ring levees and non-structural measures are recommended for regions south of Houma (in lieu of the current Morganza to the Gulf proposal). Reduction in surge by the spillway could reduce expected surge height and therefore the cost of non-structural and structural measures required in the affected region. In addition, during significant pulse events into Barataria Basin during a high water event on the river (see PU-2 # 26, 27 & 28 and the Mississippi River Action Plan), the spillway could be used to divert discharge from the Barataria Basin to the Terrebonne Basin. Even modest discharge may be very beneficial to the Terrebonne area that is generally deprived of riverine influence. Modeling of water levels in the Barataria Basin is necessary to determine if sufficient head would be available to flow a modest discharge (10,000 cfs ) across the spillway during a flood pulse event in which as much as 400,000 cfs is being proposed from the two spillways along the Mississippi River (see PU2 #26, 27, 28). 14) East Atchafalaya Restoration Spillway A new spillway is proposed in Planning Unit 3b just north of Morgan City (see PU-3b #10). A description of this project can be found in Kemp and Hyfield (2006). The purpose of the spillway is to divert Atchafalaya River water into the Lake Penchant area and further east toward Terrebonne Bay. The freshwater is needed to sustain these wetlands and to maintain the salinity of Terrebonne Bay. The proposed discharge is 20,000 cfs, but modeling is needed to determine the correct discharge. Greater discharge capacity should be considered for pulsing events. More information is provided in the project descriptions for Planning Unit 3b.

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15) Bayou Lafourche Diversion The Bayou Lafourche Diversion was initially being designed under the CWPPRA program (LACOAST website) and is currently being developed by the State. The current plans are to divert 1,000 cfs into Bayou Lafourche from the Mississippi River at Donaldsonville. The project is expected to have benefits for both the drinking supply for communities along Bayou Lafourche as well as restoration benefits for wetlands south of the diversion that receive the discharge. The project is recommended and additional discharge is desirable. 19th century reports of discharge in Bayou Lafourche during Mississippi River high water range from 6000 to 11000 cfs (LCA, 2004). However, the feasibility of greater discharge is severely challenged by the intense development along Bayou Lafourche which would be in conflict with further channel improvements. It is recommended that the discharge be preferentially managed into Terrebonne Basin, which has fewer opportunities for freshwater introduction than the Barataria Basin to the west.

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