1. Greetings from the researchers

We sincerely hope that you found our workshop useful and educational.  We want to thank all of you for participating with us in this project.  Since the last first meeting, we have developed the project website, http://www.lsu.edu/cei/research_projects/davis_pond_stakeholders.html 

Currently, the website has the following information:

1) The two presentations we did for the first meeting

2) The first volume of newsletter

3) A relevant article

4) Multiple relevant websites

We will add more information to help you develop a better understanding of the David Pond diversion.  Please check the website and let us know what you think. 

We hope that the newsletter and the project website will be useful in helping you become a more informed stakeholder concerning the operation of the Davis Pond diversion structure.  If you think of additional information that you would like to see, please let us know.  This can include information on scientific, fisheries, historical, legal, and other socio-economic issues that we can include in our bi-weekly newsletter, and the project website.

This second volume of the newsletter includes the following information:

            1) Why the current site, David Pond, was chosen for the river diversion

            2) Impacts of the diversion in Barataria basin so far

            3) Estimation of the amount of sediment needed to keep coastal wetlands sustainable

We’d like to say again how much we appreciate your participation. 

Thank you.

Dr. John W. Day

Dr. Paul H. Templet

Dr. Jae-Young Ko

Ms. Emily Hyfield

2. Why Freshwater Diversion at Davis Pond

The US Army Corps of Engineers, New Orleans District released the revised draft Environmental Impact Statement (EIS) (title: Louisiana Coastal Area, Louisiana: Feasibility Study On Freshwater Diversion to Barataria and Breton Sound Basins) in 1984.  The EIS report recommended the Caernarvon and the Davis Pond diversions, based on benefit-cost analysis, least potential adverse impacts, and the public’s responses, after reviewing 16 plans for the two basins, (See Table 1).  In operating the diversion facilities, the report recommended that the river diversions should happen from January to April, due to a concern in which cool river water after April might adversely affect sensitive juvenile organisms, like shrimp, migrating into the estuaries.

The report forecasted that increasing nutrients and sediment in the Barataria basin would increase the plant growth in marshes and slow the rate of land loss.  Increased plant growth then would produce more organic detritus (or decaying vegetation), which is an important food to fishes.  Further, phytoplankton (microscopic one-celled plants floating in the water) and zooplankton (microscopic animals living in the water) would increase in the area, and resulting in more commercial and sports fishes and increased harvest of shellfishes such as oysters.

Specifically, the report estimated the impacts of the David Pond diversion as follows:

1) The river water would be dispersed through the Davis Pond overflow area;

2) The river water would warm and, after mixing in Lake Cataouatche, and the water temperature would be nearly the normal temperature of the lake;

3) About 5 to 20 percent of the nutrients (nitrogen and phosphorus) and 60 to 90 percent of the sediment would be deposited in the overflow area;

4) The remaining material would be carried in suspension through the basin;

5) Over a 50-year period, a delta would form in the overflow area covering about 4 square miles of water bottoms;

6) Flooding of the overflow area January through May could have some minor impacts on vegetative growth;

7) Drawdown of the overflow area in June will allow ample time for regeneration of most marsh species;

8) About 39 percent of the fecal coliform bacteria would be removed in the overflow area, 57 percent in Lake Cataouatche, and the remaining 4 percent would die off in Lake Salvador;

9) The flows could raise water levels in lake Cataouatche 3 to 4 inches and lake Salvador about one inch but would have an insignificant impact on mean high water levels;

10) Thus, the David Pond diversion would not adversely affect Lac Des Allemands and would have the least water quality impact on the estuarine nursery areas (p.64).

After analyzing various alternatives, the Davis Pond diversion was recommended, because the Davis Pond diversion would cause the lease adverse environmental and social impacts while keeping a higher benefit-cost ratio, when compared with the other fifteen plans (p.65 & 67).

The plan for the Davis Pond diversion was presented at a number of public meetings beginning in November 1968.  The draft EIS of the Davis Pond was released to the public in May 1982 and public meetings were held in Baton Rouge, Des Allemands, Destrehan, Hahnville, Lockport, New Orleans, Vacherie, and additional places in St. Charles parish from June 1982 to 1984.  The major concerns expressed by the public were:

1) Possibility of flooding and poor water quality

2) Local drainage

3) Possible adverse effects of diversion on fish and wildlife

4) Jobs associated with fishing, hunting, and trapping industries, especially in the area around Lac Des Allemands

According to the feasibility study of the revised draft EIS, the following benefits and adverse impacts were expected from the Davis Pond diversion for the Barataria basin:

2. A. Benefits

1) $9,450,000 per year from increased catch of commercial fish and wildlife

2) $260,000 per year from increased sport fishing and hunting

3) Increased oyster production by 100 percent

4) Improved habitat for wildlife

5) Increased recreation potential

6) Increased plant species diversity

7) Positive effects on local businesses for commercial and recreational fishing

8) Reduced marsh losses

9) Increased wetlands as a buffer zone for protection against hurricanes

10) Increased wetlands as a medium to improve water quality

2. B. Adverse impacts

1) Conversion of some wetland habitat area into open water

2) Destruction of habitats which would be used for channel and structure building (688 acres for the diversions at Caernarvon and the Davis Pond)

3) Destruction of benthic population (animals that live on the bottom) in water bodies which will be dredged

Currently, the operational objective of the diversion structure is to divert the Mississippi River water at 10,500 cfs (cubic-feet-per-second) for 90 days to shift the 5 ppt (parts-per-thousand) line 12 km south and the 15 ppt line 5-7 km south (Figure 1) (Annual report 1998-2001; p.11).  Then, salinities in Lakes Cataouatche and Salvador are expected to be reduced to the 0-1 ppt range during the discharge period (Annual report; p.11).  (The average Gulf salinity is 35 ppt, while freshwater salinity is less than 0.5 ppt.).

Source:

US Army Corps of Engineers, New Orleans District. 1984. Louisiana Coastal Area, Louisiana: Feasibility study on Freshwater Diversion to Barataria and Breton Sound Basins.

LA Dept. of Natural Resources. 2002. Davis Pond Freshwater Diversion Project: Annual Report 1998-2001. Available from http://www.dnr.state.la.us/crm/coastres/project.asp?id=BA-01

LA Dept. of Natural Resources. 2004. Davis Pond Freshwater Diversion Project: Annual Report 2002-2003. Available from http://www.dnr.state.la.us/crm/coastres/project.asp?id=BA-01

3. Impacts of the Davis Pond Diversion in the Barataria Basin

According to the two monitoring reports published by the Louisiana Dept. of Natural Resources, the following changes have been observed;

3. A. Discharge

Since opening of the structure in July 2002, river water was diverted up to 1,000 cfs during the periods of 7/18/2002 - 9/5/2002 and 12/5/2002 - 12/18/2002 for the year 2002.  The structure was closed frequently due to tropical storms, back-flow, maintenance in the ponding area, oil spills in the Mississippi River, and other reasons.  In 2003, the structure was open during the period of 1/15/2003 – 1/28/2003, 3/24/2003 – 4/27/2003, and 8/14/2003-8/26/2003, at a discharge of 1,000 cfs.  Additionally, 5,000 cfs discharge happened on 9/16/2003, and 4,500 cfs on 5/14/2003.

3. B. Salinity

Mean monthly salinity levels for Lakes Cataouatche and Salvador stayed under 1 ppt and 1.5 ppt respectively for 2002 and 2003.  Salinity levels at Bayou Dos Gris and Barataria Bay Waterway, which are located at the 5 ppt line (Figure 1), showed a greater variability.  Lower salinity generally occurred after high rainfall events such as tropical storms and high river discharge.  Mean monthly salinity at the 5 ppt line ranged from 0.7 ppt to 11.8 ppt, with a maximum of 26 ppt, and minimum of 0.3 ppt.  The average for the two stations prior to the diversion was 8.5 ppt and the average salinity dropped to 6.4 ppt after the diversion.

At the 15 ppt line (Figure 1), the average was 16.4 ppt before the diversion.  The average salinity was actually higher, 20.8 ppt, after the diversion.  Salinity change at the 15 ppt line was more impacted by marine influences. 

Two monitoring stations in the Terrebonne basin, away from the influence of the Davis Pond diversion, also had lower salinities during the low salinity period of the Barataria basin.  This indicates that part of the reason for lower salinities in Barataria basin was due to high rainfall.

3. C. Wildlife

Mean alligator numbers during the post-operation period increased by 31%, when compared with those of the pre-operation period.  95% of alligator nests were observed in fresh or intermediate marshes.  It is expected that once the diversion is operating fully the habitat would become more favorable to alligator nesting in the Barataria basin.

Waterfowl numbers show a decreasing trend from the 1998 season through the 2002 season in the Barataria basin.  However, over 80% of waterfowl were reported from fresh and intermediate marsh.  Thus, an increase in waterfowl population is expected in the coming years, because the Davis Pond diversion will increase fresh and intermediate marshes.

3. D. Oyster

The Davis Pond oyster relocation program has relocated or purchased all oyster leases in the area which are located above the target 5 ppt salinity line.  The 1999-2001 droughts did not appear to have any major impacts on oysters. 

3. E. Fisheries

The freshwater species, such as bass and catfish showed below than normal catch during the 1999-2001, due to high salinities.  The catch rebounded to a normal level after the drought.  Saltwater species, such as spotted seatrout and red drum, did not show any clear pattern of change due to the impacts of diversion.  High catches of the saltwater species occurred in the area of below the 5 ppt line.  Blue crabs showed no clear pattern in catch over time, but were caught more above the 5 ppt line. 

Brown and white shrimps showed clear seasonal patterns of catch.  High catch of brown shrimp was occurred from April to June and white shrimp were caught more from August to October.  The catch of brown shrimp was fairly consistent for the years of 1998 – 2003.  Shrimps were mainly caught in the area of below the 5 ppt line.

3. F. Vegetation

No clear changes reported.

4. A Study of Sediment Budget in Restoring Coastal Louisiana

How much sediment is needed to maintain coastal marshes against subsidence?  One team of researchers estimated that about 9.2% of the Mississippi River’s annual suspended sediment load, if spread evenly over the marsh, would be required to sustain the deltaic plain wetlands (Templet and Meyer-Arendt 1988).

Land loss is a consequence of many natural and human-related processes.  Before the European settlement along the Mississippi River, the Mississippi delta grew and was maintained by overbank flooding, crevasses, and the formation of new river channels.  However, beginning in the 18^th century, European settlers begin to build levees along the river to protect themselves from flooding.  Before the 1927 flood, this levee system was discontinuous and maintained by different authorities.  After the 1927 flood, the federal government took over the responsibility of maintaining the levees.  This has protected developed areas from flooding, but it also resulted in most river sediment being discharged directly into deep waters of the Gulf.  Also the amount of sediment in the river has decreased due to retention of sediments behind dams.  This all resulted in a separation of the river from coastal wetlands.  Most scientists agree that this is a major factor leading to coastal wetland loss.  The disruption of wetland hydrology is also a reason for coastal wetland loss.  It is predicted that sea level rise will accelerate due to global warming.  Thus the reason for freshwater diversion is to reintroduce river water into the coastal area to reduce wetland loss and to build new wetlands.

Templet and Meyer-Arendt, first, estimated the degree of sediment shortage in coastal Louisiana by measuring trends of accretion - the heights of accumulated mineral and organic matters on the surface of marsh – for coastal marshes in Louisiana.   According to them, each different type of marshes- fresh, intermediate, brackish, saline and swamp – shows different accretion, and it also depends on backmarsh or streamside of each march, because the streamside marshes are relatively healthy while the backmarsh is deteriorating into ponds and open water.  The difference in accretion between healthy streamside and deteriorating backmarsh accretion rates is called accretion deficit.  According to their calculations, the accretion deficits are 4.1 millimeter (mm) per year for backmarsh area of fresh marsh, 7.1 mm per year for intermediate marsh, 8.1 mm for brackish, 6.0 mm for saline, and 10.3 mm for swamp.  After considering areal extent of the different marshes, the total amount of sediment needed to maintain the deltaic wetlands in coastal Louisiana is about 14.6 million tons (1.32 E10 kg) per year.

This leads to the question: where to find the sediments needed.  Templet and Meyer-Arendt calculated that about 9.2 % of the Mississippi River’s annual suspended sediment load would be required to eliminate the deficit and sustain the coastal marshes, given that a total annual suspended sediment load is 159 million tons per year (144 million metric tons per year) in the Mississippi River.  From the sediment record, they find that the months of December through June would provide the highest sediment contribution per unit volume of water distributed over the coastal marshes, and that the water elevation should be slightly above the marsh elevation to distribute sediments in the river water to the coastal marshes.

Assuming the average suspended sediment concentration as 330 mg per liter in the Mississippi River for the months of December through June, Templet and Meyer-Arendt argued for a diversion of approximately 88,000 cfs continuously for six months to maintain the coastal marshes/wetlands.

Finally Templet and Meyer-Arendt suggested policy options for best distribution of sediments in the river into deltaic marshes:

1) A phased diversion of the Mississippi River waters into the Atchafalaya River on an estimated 2% per year basis until 50% is reached

2) Use of the spring flood of the rivers to inundate deltaic wetlands as the major short-period sedimentation event each year.  Regulation of water flows to maximize sediment dispersal and retention, vegetation growth, and to minimize damages to human activities

3) Use of former distributaries of the Mississippi River and current spillways to move water and sediments into deltaic plain wetlands

4) Rerouting navigation traffic out of the lower Mississippi River above Head of Passes and promoting controlled delta building in the lower Barataria, Mississippi, and Pontchatrain basins to offset the trends of deterioration

5) Use of low-level sills in the lower Mississippi levees to move spring flood waters into neighboring wetlands

6) Encouraging delta building in Atchafalaya Bay by relocating the existing navigation channel to a location less detrimental for sediment distribution and delta growth

7) Creation of many small diversions from these main channels to move water efficiently into the sinking wetlands

8) Use of canal acreage reduction, barrier island restoration, and regulatory approaches to complement and increase effectiveness of diversions

9) Use of the existing waterways as channels to move water across and between basins

10) Implementation of the authorized diversions, which should be redesigned to maximize sediment introduction

Source: Templet, P.H., and K.J. Meyer-Arendt. 1988. Louisiana wetland loss: a regional water management approach to the problem. Environmental Management 12:181-192.

5. Your Inputs

Please give us your feedback on this newsletter.  Let us know if there are specific questions or issues you would like to have addressed in future newsletters.  You can contact us by phone, regular mail, or email.  We will do our best to get the information and pass it to all of you as a way to keep you well-informed on the Davis Pond diversion as well as other issues in coastal wetlands protection in Louisiana.

The coming newsletter of volume three will include information on the Caernarvon diversion in Breton Sound, which has been in operation since 1991.  We have studied the impacts of the Caernarvon diversion since February 2000 as part of projects funded by the US EPA (Environmental Protection Agency) and US DA (Dept of Agriculture).  We believe that the information from the Caernarvon diversion will help us understand the potential effects of the David Pond diversion.

Thanks.

Contact Information:

Emily Hyfield                or                     Jae-Young Ko

225-578-2732                                         225-578-6505

ehyfie1@lsu.edu                                   jyko@lsu.edu

Mailing Address:

LSU-Coastal Ecology Institute

Baton Rouge, La 70803

(Source: US Army Corps of Engineers, New Orleans District. 1984. Louisiana Coastal Area, Louisiana: Freshwater Diversion to Barataria and Breton Sound Basins. Vol. 1, pp. 47-58; * cubic-feet-per-second)

** Includes interest, amortization, and operation and maintenance.*** $35.5 million for the Davis Pond only.

Figure 1. Objective for the Davis Pond Diversion