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Research about Louisiana

Source-linked reports with geographic coverage including Louisiana.

At least 505 records · Page 28Linked to original sources
USGS2007

Assessing functional equivalency of nekton habitat in enhanced habitats: Comparison of terraced and unterraced marsh ponds

A primary goal of many coastal restoration programs is to increase nekton habitat in terms of both quantity and quality. Using shallow water ponds rehabilitated with a technique called marsh terracing, we examined the quality of nekton habitat created, using and comparing several metrics including nekton density and diversity, functional group composition, and weight-length relationships as indirect measures of habitat quality. We examined three paired terraced and unterraced marsh ponds in southwest Louisiana. Nekton, submerged aquatic vegetation (SAV), and soil and water quality variables were sampled bimonthly from April 2004 through April 2005 at four subtidal habitat types: terraced nearshore, terraced open water, unterraced nearshore, and unterraced open water. Results indicate that terraced ponds had increased the habitat value of degrading unterraced ponds over open water areas for estuarine nekton; nekton density and richness were similar between terraced and unterraced nearshore habitat types, but greater at all nearshore as compared to open water sites. Analysis of the distribution of nekton functional groups and weight:length ratios indicates the terraced and unterraced pond habitats were not functioning similarly: distribution of nekton functional groups differed significantly between habitat types with greater percentages of benthic-oriented species at unterraced open water habitats and higher percentage of open water species in terraced ponds as compared to unterraced ponds, and two of the six numerically dominant fish species had greater weight-length relationships in unterraced ponds as compared to terraced ponds. This lack of functional equivalency may be attributed to environmental differences between terraced and unterraced ponds such as water depth or SAV biomass, or the relatively young age of the terraces studied, which may not have allowed for the development of some critical habitat variables, such as soil organic matter that was found to be significantly lower in terraced versus unterraced ponds (p < 0.05). To properly assess the ecological equivalency of restored or rehabilitated sites for nekton requires that we move beyond measures of nekton density, biomass, and diversity and incorporate measures of functional equivalency, including habitat measures.

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USGS2007

Bacteriological water quality in and around Lake Pontchartrain following Hurricanes Katrina and Rita

Following the Louisiana landfalls of Katrina on August 29 and Rita on September 24, 2005, the local population and the American public were concerned about the effects the hurricanes might have on water quality in Lake Pontchartrain. The lake is a major recreational resource for the region and an important fishery. Contamination carried by the storm surge—along with runoff and water pumped from flooded areas of New Orleans—was considered a serious threat to the water body. The USGS, in collaboration with the LDEQ, monitored the sanitary quality of water at 22 sites in and around Lake Pontchartrain, La., for 3 consecutive weeks from September 13 to 29, 2005 (fig. 1). A subsequent multipleagency survey of 30 sites within Lake Pontchartrain was undertaken by the U.S. Environmental Protection Agency (EPA), the USGS, and the National Oceanic and Atmospheric Administration during the week of October 11–14, 2005, to evaluate the effects of the hurricanes and overall levels of fecal contamination on the water quality of the lake (see Heitmuller and Perez, this volume). In addition, the EPA monitored fecal-indicator concentrations at a variety of sites in New Orleans, surrounding areas, and the Mississippi River between September 3 and October 22, 2005 (U.S. Environmental Protection Agency, 2006). This article describes fecal-indicator bacteria concentration results collected by USGS in the context of other existing data.

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USGS2007

Restoring resilience to the Gulf of Mexico coast

Hurricane Katrina and its destructive aftermath in 2005 were unprecedented. Hurricanes Dennis, Rita, and Wilma were also powerful hurricanes affecting the Gulf of Mexico that year. These storms highlighted the need to integrate science that supports restoration of natural landscapes with intelligent coastal planning. The following essay describes both the value and vulnerability of the Gulf of Mexico's northern coast before the storms and the current need to connect science to the human dimension of restoring the coastal landscape. Readers are invited to ponder these concepts as they read the rest of the articles in this report that describe the scientific activities that the U.S. Geological Survey performed in late 2005 and early 2006.

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USGS2007

Analysis of the Interstate 10 Twin Bridge’s collapse during Hurricane Katrina: Chapter 3D in Science and the storms-the USGS response to the hurricanes of 2005

The Interstate 10 Twin Span Bridge over Lake Pontchartrain north of New Orleans, La., was rendered completely unusable by Hurricane Katrina. The cause of the collapse of the bridges generated great interest among hydrologists and structural engineers as well as among the general public. What made this case study even more important was the fact that two nearby bridges sustained the effects of the same storm surge and suffered only light damage. Lessons learned from this investigation are invaluable to maintaining the safety of many of the Nation's coastal and river-crossing bridges.

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USGS2007

Topography-based analysis of Hurricane Katrina inundation of New Orleans

The ready availability of high-resolution, high-accuracy elevation data proved valuable for development of topographybased products to determine rough estimates of the inundation of New Orleans, La., from Hurricane Katrina. Because of its high level of spatial detail and vertical accuracy of elevation measurements, light detection and ranging (lidar) remote sensing is an excellent mapping technology for use in low-relief hurricane-prone coastal areas.

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USGS2007

Temporal analysis of floodwater volumes in New Orleans after Hurricane Katrina

Satellite images from multiple sensors and dates were analyzed to measure the extent of flooding caused by Hurricane Katrina in the New Orleans, La., area. The flood polygons were combined with a high-resolution digital elevation model to estimate water depths and volumes in designated areas. The multiple satellite acquisitions enabled monitoring of the floodwater volume and extent through time.

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USGS2007

Land area changes in coastal Louisiana after Hurricanes Katrina and Rita

Comparison of classified Landsat Thematic Mapper (TM) satellite imagery acquired before and after the landfalls of Hurricanes Katrina (August 29, 2005) and Rita (September 24, 2005) demonstrated that water area increased by 217 mi 2 (562 km 2 ) in coastal Louisiana. Approximately 82 mi 2 (212 km 2 ) of new water areas were in areas primarily impacted by Katrina (Mississippi River Delta basin, Breton Sound basin, Pontchartrain basin, Pearl River basin), whereas 117 mi 2 (303 km 2 ) were in areas primarily impacted by Rita (Calcasieu/ Sabine basin, Mermentau basin, Teche/Vermilion basin, Atchafalaya basin, Terrebonne basin). Barataria basin contained new water areas caused by both hurricanes, resulting in some 18 mi 2 (46.6 km 2 ) of new water areas. The fresh marsh and intermediate marsh communities' land areas decreased by 122 mi 2 (316 km 2 ) and 90 mi 2 (233.1 km 2 ), respectively. The brackish marsh and saline marsh communities' land areas decreased by 33 mi 2 (85.5 km 2 ) and 28 mi 2 (72.5 km 2 ), respectively. These new water areas identify permanent losses caused by direct removal of wetlands. They also indicate transitory water area changes caused by remnant flooding, removal of aquatic vegetation, scouring of marsh vegetation, and water-level variation attributed to normal tidal and meteorological variation between satellite images. Permanent losses cannot be estimated until several growing seasons have passed and the transitory impacts of the hurricanes are minimized. The purpose of this study was to provide preliminary information on water area changes in coastal Louisiana acquired shortly after both hurricanes' landfalls (detectable with Landsat TM imagery) and to serve as a regional baseline for monitoring posthurricane wetland recovery.

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USGS2007

Impacts of Hurricane Rita on the beaches of western Louisiana

Hurricane Rita made landfall as a category 3 storm in western Louisiana in late September 2005, 1 month following Hurricane Katrina's devastating landfall in the eastern part of the State. Large waves and storm surge inundated the lowelevation coastline, destroying many communities and causing extensive coastal change including beach, dune, and marsh erosion.

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USGS2007

Impacts of Hurricane Katrina on floodplain forests of the Pearl River

Floodplain forests are an important habitat for Neotropical migratory birds. Hurricane Katrina passed through the Pearl River flood plain shortly after making landfall. Field measurements on historical plots and remotely sensed data were used to assess the impact of Hurricane Katrina on the structure of floodplain forests of the Pearl River.

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USGS2007

Cheniere forest as stopover habitat for migrant landbirds: Immediate effects of Hurricane Rita

It is not known whether en route fall migratory birds (August-October) are likely to suffer more from direct or secondary effects of hurricanes. On September 24, 2005, Hurricane Rita wreaked havoc on Louisiana's coast by toppling trees over vast areas and by stripping away microhabitats that harbor the invertebrates and produce the fruits upon which migrant landbirds depend (e.g., canopy foliage, vine tangles, epiphytes, leaf litter, and thickets of perennial plant species). Such transient effects of a hurricane on wildlife food resources are poorly understood, but these effects may have longterm consequences for some wildlife species.

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USGS2007

Wind damage and salinity effects of Hurricanes Katrina and Rita on coastal baldcypress forests of Louisiana

The frequency of hurricane landfall in a given coastal stretch may play a more important role in the ecology of coastal forests than previously thought because of direct and indirect impacts of fallen trees and the introduction of salt water that lingers long after the storm passes. Findings show that surge events can inundate interior freshwater forests many miles from the coast and elevate soil salinities twofold to threefold. These elevated salinities may contribute to delayed mortality of certain tree species and set the stage for eventual forest decline and dieback.

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USGS2007

Examining offshore sediment-hosted contaminant transport from Hurricane Katrina

A rapid-response expedition was organized after the passage of Hurricane Katrina to investigate potential offshore environmental impacts and storm-induced sediment-transport processes. Both water-column and sediment samples were collected on the Louisiana shelf for a full complement of organic, inorganic, and geochronological tracers. Based on excess lead-210 (210Pb) inventories in cores collected before and after Katrina, the surface sediments and their associated geochemical signatures were considerably affected by the passage of this storm.

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USGS2007

Selected chemical composition of deposited sediments in the flooded areas of New Orleans following Hurricane Katrina

Nearly 4 weeks after Hurricane Katrina passed through St. Bernard Parish, the U.S. Geological Survey's (USGS) Mid-Continent Geographic Science Center and the University of Missouri-Rolla's (UMR) Natural Hazard Mitigation Institute deployed a team of scientists to the region to collect perishable environmental and engineering data. The team collected 149 samples throughout the affected area to chemically characterize the Katrina depositional sediments. Preliminary results of this effort are presented here.

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