Bonnet Carre Spillway Research Articles

Impacts of a Major Mississippi River Freshwater Diversion on Suspended Sediment Plume Kinematics in Lake Pontchartrain, a Semi-enclosed Gulf of Mexico Estuary

MODIS satellite imagery and in situ water measurements were used to quantify inorganic sediment concentration (ISC) and, subsequently, sediment plume motion and evolution during the 2016 diversion of the Mississippi River through the Bonnet Carre Spillway (BCS) within Lake Pontchartrain (LP) estuary in Louisiana, USA. Satellite images revealed that sediment plume areal distribution was closely linked to BCS discharge rate. The plume flowed eastward along the southern LP coastline at an average speed of ~ 0.3 m s−1 during the first week of the event and attained its maximum areal extent (~ 1117 km2; 68% of the total LP area) on 23 January. In an attempt to examine the plume kinematics and potential sediment resuspension impacts, wind information was also assessed. Following BCS closure, the prevailing wind direction, but not wind speed, corresponded to significant differences in LP ISC. LP was further subdivided into four separate quadrants to assess relationships between ISC within each quadrant to BCS discharge rate and winds. While the BCS was open, the plume’s eastward motion was associated with a high correlation (r2 = 0.93) between BCS discharge and ISC in the southeast quadrant. However, the weak relationship (r2 = 0.42) between BCS discharge and ISC in the northwest quadrant was attributed to influences from other tributaries. These results will benefit future research regarding impacts of freshwater diversions on coastal and estuarine processes that are sensitive to sediment influx by providing a satellite-based sediment map time series that can be used to help validate numerical circulation and sediment transport models.

Numerical Modeling of Sediment Transport and Its Effect on Algal Biomass Distribution in Lake Pontchartrain Due to Flood Release from Bonnet Carré Spillway

In order to protect the city of New Orleans from the Mississippi River flooding, the Bonnet Carre Spillway (BCS) was constructed from 1929 to 1936 to divert flood water from the river into Lake Pontchartrain and then into the Gulf of Mexico. During the BCS opening for flood release, large amounts of freshwater, nutrients, sediment, etc. were discharged into Lake Pontchartrain, and caused a lot of environmental problems. To evaluate the environmental impacts of the flood water on lake ecosystems, a two-dimensional numerical model was developed based on CCHE2D and applied to simulate the flow circulation, sediment transport and algal biomass distribution in Lake Pontchartrain. The effect of sediment concentration on the growth of algae was considered in the model. The numerical model was calibrated using field measured data provided by USGS, and then it was validated by the BCS Opening Event in 1997. The simulated results were generally in good agreement with filed data and satellite imagery. The field observation and numerical model show that during the spillway opening for flood release, the sediment concentration is very high, which greatly restricts the growth of algae, so there is no algal bloom observed in the lake. After the closure of BCS, the sediment concentration in the lake reduces gradually, and the nutrient concentration of the lake is still high. Under these conditions, numerical results and satellite imagery showed that the chlorophyll concentration was high and algal bloom might occur.

Rangia cuneata clam decline in Lake Pontchartrain from 2001 to 2014 due to an El Niño Southern Oscillation shift coupled with a period of high hurricane intensity and frequency

The clam, Rangia cuneata, occurs in low salinity zones of Atlantic and Gulf of Mexico estuaries. Prior to 2001, it was abundant in Lake Pontchartrain, a large and shallow oligohaline estuary, located north of New Orleans. However, density abruptly decreased by 96% after an extreme drought from an El Nino Southern Oscillation (ENSO) shift (1998—2000). Stable higher salinities resulted in the establishment of higher salinity communities. The hooked mussel, Ischadium recurvum, increased abruptly and colonized live R. cuneata. Competition from I. recurvum and the R. cuneata decline occurred at the end of the drought, despite a decrease in salinity. After the drought, there was a period of high hurricane intensity and frequency which stifled clam recovery. Their densities remained relatively low due to declines from hurricane disturbances in 2005, 2008 and 2012. In 2014, after two years without severe hurricane effects, density and biomass recovered to baseline years (1954 and 1997). Barrier island erosion caused by Hurricane Georges in 1998 and adverse effects of the ENSO drought on wetlands may have set the stage for increased effects of subsequent hurricanes. High relative sea level rise, wetland loss and erosion of barrier islands, which occurred with each successive storm, potentially increased the size of surges. Surges resuspended sediments which buried clams and abruptly increased salinity and lowered dissolved oxygen. Salinity stratification persisted after storms and caused hypoxia in bottom waters. Storm surge interactions with discharges from the Bonnet Carre Spillway, a Mississippi River flood diversion structure, and the MRGO, a ship channel, also exacerbated hurricane effects.

A Paddlefish Entrained by the 2011 Mississippi River Flood: Rescue, Recapture, and Inferred Swim Speed

Abstract We observed a large adult Paddlefish entrained from the Mississippi River through the Bonnet Carre spillway, south Louisiana, which was injured and underweight. We captured, measured (23 metrics), and tagged the fish. After it had spent a week at large on the floodway, we recaptured and released it back into the Mississippi River. The specimen was re-captured eight months later in northern Mississippi, 627 km upriver from where it was released. Distance traveled and water velocities in the river indicate that the fish was traveling at least 90–197 cm/s for prolonged periods, equivalent to gross speeds of 77–170 km/d. This incident suggests that a large entrained fish, trapped for several days in a hyperthermic and hypoxic habitat, can be viable when returned to the river. It also demonstrated that rescue efforts could reduce impacts of spillway operations to fish populations, and that comprehensive field assessment of fish morphology can be benign t o fish.

Abundance and Distribution of Vibrio cholerae, V. parahaemolyticus, and V. vulnificus Following a Major Freshwater Intrusion into the Mississippi Sound

In response to a major influx of freshwater to the Mississippi Sound following the opening of the Bonnet Carre Spillway, water samples were collected from three sites along the Mississippi shoreline to assess the impact of altered salinity on three pathogenic Vibrio species. Salinity readings across the affected area during the 2011 sample period ranged from 1.4 to 12.9 ppt (mean = 7.0) and for the 2012 sample period from 14.1 to 23.6 ppt (mean = 19.8). Analyses of the data collected in 2011 showed a reduction in densities of Vibrio parahaemolyticus and Vibrio vulnificus with a concurrent increase of Vibrio cholerae numbers, with V. cholerae becoming the only Vibrio detected once salinity readings dropped to 6 ppt. Follow-up samples taken in 2012 after recovery of the salinity in the sound showed that the relative densities of the three pathogenic vibrios had reverted back to normal levels. This study shows that although the spillway was open but a few weeks and the effects were therefore time limited, the Mississippi River water had a profound, if temporary, effect on Vibrio ecology in the Mississippi Sound.

Mitigating land loss in coastal Louisiana by controlled diversion of Mississippi River sand

The Bonnet Carre Spillway diverts floodwaters from the Mississippi River to Lake Pontchartrain, and was opened for 42 days during the 2011 flood. According to measurements of the newly deposited sediments, at least 31–46% of the river’s sand load was diverted into the spillway at this time, suggesting that such diversions can help mitigate coastal wetland loss.

Effects of freshwater input on nutrient loading, phytoplankton biomass, and cyanotoxin production in an oligohaline estuarine lake

Pulsed river water events can increase nutrient levels potentially translating into enhanced primary production, phytoplankton community shifts, and bloom formation. The Bonnet Carre Spillway is a managed river diversion which can be used to redirect a significant amount of Mississippi River water into Lake Pontchartrain, reducing the risks of flood in the downstream communities during runoff seasons. We investigated nutrient enrichment and consequent changes in phytoplankton biomass, including toxic species in Lake Pontchartrain during and after a 1-month Bonne Carre Spillway opening in 2008. Water samples were collected along a 30 km transect. A freshwater plume was found to have formed by the strong river input that had limited mixing with the lake during the opening. The plume and lake water gradually mixed together after the Spillway was closed, indicated by the reduction of the horizontal salinity gradient. The river pulse increased the lake nitrate and dissolved reactive phosphorus concentrations to more than five times the lake background in the plume stations. Nutrient concentrations decreased rapidly after the Spillway closure as the plume dissipated. Diatoms and chlorophytes dominated the system during the opening. After the Spillway closure, there was a shift over time from diatom dominance to toxic cyanobacteria dominance that corresponded to more stable, warmer, and nutrient-limited water conditions. Associated toxins were present and varied over time and space. Further research on the phytoplankton assemblages on the lake is needed in subsequent, non-Spillway opening years to evaluate the impact of river water pulses on the development of these toxic cyanobacterial blooms.

Geochemistry of Surficial Sediments from Lake Pontchartrain Resulting from the 1997 Opening of the Bonnet Carré Spillway

Abstract The Bonnet Carre Spillway is a flood-control structure that diverts Mississippi River water into Lake Pontchartrain during exceptionally high river stages. Because of elevated water levels in the Mississippi River in the spring of 1997, the Bonnet Carre Spillway was opened on March 17 and fully closed on April 18. The total volume of water discharged into Lake Pontchartrain was approximately 11.8 km3, or two times the volume of the lake, and the total mass of sediment discharged into the lake was approximately 7.1 × 108 kg (780,000 US tons). In 1996, 757 surface sediment samples were collected in Lake Pontchartrain and were analyzed by x-ray fluorescence spectroscopy for major cation constituents. These same sites were revisited following the 1997 Mississippi River discharge event. Analysis of the 1996 and 1997 lake-bed sediment samples was accomplished utilizing fundamental statistical and graphical methods. Element concentration contour maps and variograms for the major cations illustrate meani...

Lessons Learned from a Decade of Assessment and Restoration Studies of Benthic Invertebrates and Submersed Aquatic Vegetation in Lake Pontchartrain

Abstract Studies of Lake Pontchartrain benthic invertebrates and submersed aquatic vegetation (SAV) from 1996 through 2005 provided the opportunity to determine community responses to severe disturbances including: recovery from shell dredging; effects of anoxia and hypoxia from saltwater intrusion; the 1997 Bonnet Carre Spillway opening; a prolonged drought resulting from an El Nino Southern Oscillation; and effects of Hurricane Katrina. We included reviews and updates of our recently published work, an integrated analysis of findings, and restoration recommendations. During this decadal study there were no prolonged periods of “normal” conditions. Instead, benthos and SAV were experiencing or recovering from significant temporal disturbances. This made it difficult to use the abundance of a particular set of organisms at a point in time to evaluate habitat quality or restoration success without considering past disturbance effects. Benthos species diversity and the relative abundance of stress tolerant ...

Water quality and phytoplankton communities in Lake Pontchartrain during and after the Bonnet Carré Spillway opening, April to October 2008, in Louisiana, USA

The Bonnet Carre Spillway, located 28 miles northwest of New Orleans, was constructed in the early 1930s as part of an integrated flood-control system for the lower Mississippi River system. From 11 April to 8 May 2008, Mississippi River water was diverted through the spillway into the 629-square-mile Lake Pontchartrain, which is hydraulically connected to the Gulf of Mexico. On 8 April, prior to the opening of the spillway, water-quality instruments were deployed and recorded hourly measurements of water temperature, dissolved oxygen, specific conductance, pH, and nitrate. Discrete water-quality and phytoplankton (algae) samples were collected in Lake Pontchartrain from 8 April to 3 October 2008 to assess the water-quality nutrient enrichment effects of the diversion on the lake. The maximum influence of river water in the southern portion of the lake was captured with continuous (hourly) monitoring of nitrate concentrations, and field measurements such as of specific conductance during the critical period in late April to early May. By late May, the deployed instruments had recorded the arrival, peak, and decline of selected constituents associated with the freshwater influx from the Mississippi River/Bonnet Carre Spillway diversion. The continuous monitoring data showed the short-term interactions of high-nitrate, low-specific conductance river water and low-nitrate, high-specific conductance lake water. The phytoplankton community composition, as an indicator of water quality, illustrated an extended response from the river water evident even after the continuous and discrete samples indicated that the lake had returned to pre-diversion conditions. The initial phytoplankton community response to nutrient increases was related to accumulations of diatoms. During periods of low nutrient concentrations, accumulations of blue-greens occurred by July and August. As blue-green algae cell densities and biovolumes increased in the summer, so did the species richness of blue-green algae, particularly the harmful algae bloom taxa. Cell densities and biovolume of the phytoplankton lake indicator taxa Skeletonema costatum, Anabaena sp., and Cylindrospermopsis raciborskii were highest and dominated the diatom and blue-green algae communities during the period of most river water influence on the lake and immediately following the freshwater inflows. The dominance and recession of these indictor taxa reflect the dramatic changes that occurred in the phytoplankton community in response to an increase in nutrient-rich freshwater from the diversion into the lake, and not normal seasonal phytoplankton compositional differences. Water-quality data indicated a gradual reversion to pre-diversion lake conditions by June to July, but shifts in the phytoplankton composition were still evident through August 2008. Observations from this study were similar to results from previous studies of Mississippi River/Bonnet Carre Spillway diversion opening in 1997.

Effects of the 1997 Bonnet Carré Spillway Opening on Infaunal Macroinvertebrates in Lake Pontchartrain, Louisiana

Abstract The Bonnet Carre Spillway was constructed in 1931 to divert floodwater from the Mississippi River into Lake Pontchartrain, an oligohaline estuary near New Orleans, Louisiana. The spillway was opened from March 17 through April 18, 1997. Infaunal macroinvertebrate population, surface and bottom salinity, and dissolved oxygen data were examined to determine the effects of this diversion. These data were obtained from November 1996 through November 1998 from five sites on an east-to-west transect across Lake Pontchartrain. A community composed of oligohaline taxa persisted during the freshwater period, but changes in dominance, and to a lesser extent composition, occurred over time and among sites. There was a pronounced spatial effect related to the distance of the sites from the spillway and from tidal passes. Based on decreases in species diversity (H′), abundance, and the number of taxa, it appears that the opening had a deleterious impact on the benthos. The cause of these changes cannot be att...

Nitrogen loading into an urban estuary: Lake Pontchartrain (Louisiana, U.S.A.)

We constructed a nitrogen loading budget for the Lake Pontchartrain watershed located north of New Orleans, Louisiana (U.S.A.). Water quality measurements, discharge estimates, and literature values were used to establish the annual and seasonal variations in loading rates for total nitrogen and nitrate. The relatively stable annual loadings (million kg N) are about 10× that of the pre-settlement nitrogen loading, and come from atmosphere (1.3), the watershed (7.8), pumped urban runoff from New Orleans (1.0), and leakage through the Bonnet Carre flood control structure (0.5–0.9). Relatively minor additional amounts come from nitrogen fixation in the Lake. Occasional openings of the Bonnet Carre Spillway (for flood protection) could triple the annual average loading within 1–2 months. Proposed smaller diversions (for wetland restoration) could raise present N loadings by 50%. The results of water quality management, flood protection and wetland restoration may thus have conflicting effects on the Lake's phytoplankton community, which is primarily nitrogen limited. Lowering the total nitrogen loading, however, seems quite possible, especially given that the present loadings are almost all reducible through existing technology, especially sewerage treatment. The analysis demonstrates that the consequences of ecosystem restoration efforts, continued population growth and flood protection to estuarine nitrogen budgets are intertwined with each other, have a seasonal component, and are changing as policies evolve.

The 1994 experimental opening of the Bonnet Carre Spillway to divert Mississippi River water into Lake Pontchartrain, Louisiana

A diversion of Mississippi River water into Lake Pontchartrain, Louisiana, USA by way of the Bonnet Carre Spillway has been proposed as a restoration technique to help offset regional wetland loss. An experimental diversion of Mississippi River water into Lake Pontchartrain was carried out in April 1994 to monitor the fate of nutrients and sediments in the spillway and Lake Pontchartrain. Approximately 6.4×10 8 m 3 of Mississippi River water was diverted into Lake Pontchartrain over 42 days. As water passed through the Bonnet Carre Spillway, there were reductions in total suspended sediment concentrations of 82–83%, nitrite+nitrate (NO x ) of 28–42%, in total nitrogen (TN) of 26–30%, and in total phosphorus (TP) of 50–59%. 3.9±1.1 cm of accretion was measured in the spillway. Nutrient concentrations at the freshwater plume edge in Lake Pontchartrain compared to the Mississippi River were lower for NO x (44–81%), TN (37–57%), and TP (40–70%), and generally higher for organic nitrogen (−7–57%). The Si:N ratio generally increased and the N:P ratio decreased from the river to the plume edge. Nutrient stoichiometric ratios indicate water at the plume edge was not silicate limited, suggesting conditions favoring diatomic phytoplankton.

Euplectrus plathypenae (Hymenoptera: Eulophidae) Reared from Anicla infecta (Lepidoptera: Noctuidae), a New Host Record

Euplectr us plathypenae Howard, a gregarious external parasitoid, is recorded here as the third known hymenopterous enemy of the green cutworm, Anicla infecta Ochsenheimer (Lycophotia incivis Guenee). Thompson (1944) listed Rogas politiceps Gahan (Braconidae) and Teleno2mus minutissimus Ashmead (Scelionidae) as parasitoids of A. infectae in the United States and British Guiana, respectively. Wilson (1933) presented a detailed study of the biology of E. plathypenae. Muesebeck et al. (1951) recorded 12 species of the following genera of Lepidoptera as hosts of E. plathypenae: Cirphis, Diatraea, Heliothis, Laphygma, Leucania, Peridroma, Platlhypena, Prodenia, and Protoparce. A living larva of A. inf ecta was found clinging to a blade of a tall grass in the Bonnet Carre Spillway crossing U.S. Route 61, west of New Orleans, Louisiana on 3 December 1965. A group of 23 light-greenish larvae of E. plathypenae was situated in a mass on a posterolateral surface of the noctuid larva. The larva of A. uinfecta appeared to be of normal color, but it was almost immobile. It was placed in a vial and taken to Ithaca, New York, where it was kept at 20 to 23? C. On 4 December the noctuid larva was still light green but somewhat flaccid, and the eulophid larvae were no longer grouped in one place but had dispersed over the surface of the host. One of the 23 larvae was preserved. On 5 December the noctuid larva was brownish in color and obviously dead. The hymenopterous larvae had spun open networks of threads about themselves, and they had attached the moth larva to the piece of grass by spinning threads between the venter of the larva and the edge of the grass. The larvae did not pupate until 7 December. Twenty-one wasps (2 males and 19 females) emerged on 13 December. One pupa failed to produce an adult. The wasps and noctuid larva were kindly determined by B. D. Burks and J. G. Franclemont, respectively.

The Rational Exploitation of the Sea Fisheries with Particular Reference to the Fish Stock of the North Sea.G. P. Baerends , Jan Hahn , Howard A. SchuckPossibilities for Oyster Culture in Puerto Rico and the Virgin Islands.Walter A. Chipman , Paul E. ThompsonBiological Investigations of the Fishery Resources of Trinity River, California.James W. Moffett , Stanford H. SmithThe 1950 Opening

Previous articleNext article No AccessNew Biological BooksThe Rational Exploitation of the Sea Fisheries with Particular Reference to the Fish Stock of the North Sea. G. P. Baerends , Jan Hahn , Howard A. Schuck Possibilities for Oyster Culture in Puerto Rico and the Virgin Islands. Walter A. Chipman , Paul E. Thompson Biological Investigations of the Fishery Resources of Trinity River, California. James W. Moffett , Stanford H. Smith The 1950 Opening of the Bonnet Carre Spillway: Its Effect on Oysters. Philip A. Butler , James B. Engle Joel W. HedgpethJoel W. Hedgpeth Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 26, Number 1Mar., 1951 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/397967 PDF download Crossref reports no articles citing this article.