Robert H. Baumann

Mississippi Deltaic Wetland Survival: Sedimentation Versus Coastal Submergence

Seasonal sedimentation, measured with the aid of artificial marker horizons, was markedly different in deteriorating as compared with stable marshes in the Mississippi River deltaic plain. Deteriorating marshes receive most sediment during storm events, whereas stable marshes receive substantial amounts of sediments during the spring river flood. The deteriorating marshes are accreting at a faster rate (1.5 centimeters per year at streamside, 0.9 centimeter per year at inland areas) than the stable marshes (1.3 centimeters per year at streamside, 0.6 centimeter per year at inland areas). However, relative to local apparent sea-level rise as measured by tide gauges in each area, the deteriorating marshes are not maintaining their intertidal elevation as well as the stable marshes. These results indicate the importance of considering accretion relative to submergence.

Influence of hurricanes on coastal ecosystems along the northern Gulf of Mexico

Available literature indicates that hurricanes do not generally produce long-term detrimental impacts to unmodified coastal systems and that they often provide net benefits along the U.S. Gulf Coast. While there is normally initial erosion from hurricanes, they also often result in a large influx of inorganic sediments, creating new wetlands and contributing to the maintenance of existing wetlands. The formation of washover deposits is disastrous where cultural development has occurred, but in natural areas these deposits are part of the natural cycle of shoreline development and contribute to habitat diversity and productivity. Abundant rainfall typically associated with hurricanes often results in large increases of sediment and nutrient inputs into coastal estuaries, leading to both short-term and long-term increases in productivity. Rainfall during tropical disturbances accounts for a significant part of total precipitation along the northern gulf. The immediate impact of hurricanes may be to reduce populations of some species but these populations generally recover rapidly. Overall, productivity in natural systems seems to be increased by periodic hurricanes. Hurricane impacts are often severe and long lasting in wetlands that have been modified by human impacts such as semi- or complete impoundments.

Modeling future trends in wetland loss and brown shrimp production in Louisiana using thematic mapper imagery

Abstract The land-water interface of coastal marshes may influence the production of estuarine-dependent fisheries more than the area of these marshes. To test this hypothesis, we created a spatial model to explore the dynamic relationship between land-water interface and degree of land loss in disintegrating coastal marshes of Louisianas Barataria, Terrebonne, and Timbalier basins. Calibrating our model with Landsat Thematic Mapper satellite imagery, we found a parabolic relationship between land-water interface and marsh disintegration. Aggregated simulation data suggested that the land-water interface in the study area will soon reach its maximum and then decline. We found a statistically significant positive linear relationship between brown shrimp catch and total interface length over the past 28 years. This relationship suggests that shrimp yields will decline when interface declines, possibly beginning about 1995.

Direct impacts of outer continental shelf activities on wetland loss in the central Gulf of Mexico.

The direct impacts of outer continental shelf (OCS) development on recent wetland loss in the northern Gulf of Mexico were quantified using aerial imagery, field surveys, and literature review. The total direct impacts accounted for an estimated 25.6 percent of total net wetland loss within the Louisiana portion of the study area from 1955/56 to 1978. Of the total direct impacts of 73,905 ha, OCS-related activities accounted for 11,589-13,631 ha of the wetland loss during the same time interval. Although this is a substantial areal loss, it represents only 4.0-4.7 percent of the total Louisiana wetland loss from 1955/56 to 1978, and 15.7–18.4 percent of direct impacts.Direct impacts from OCS pipelines averaged 2.49 ha/km, lower than published guidelines, and totalled 12,012 ha. Lowest impacts are for backfilled pipelines in the Chenier Plain of western Louisiana and for small young pipelines built in clustered rights-of-way. Widening of OCS pipeline canals does not appear to be an important factor for total net wetland loss in the coastal zone because few pipelines are open to navigation and, for the examples found, the impact width was not significantly different than for open pipelines closed to navigation. Navigation channels account for a minimum of 16,902 ha of habitat change. Direct impacts per unit length of navigation channel average 20 times greater than pipelines.

BLUFF EROSION OF A MISSISSIPPI RIVER MEANDER AT PORT HUDSON, LOUISIANA

The rate of bluff erosion has been monitored and related processes examined on a Mississippi River meander bend at Port Hudson, Louisiana, from 1971 to mid-1980. The erosion data were analyzed using a stepwise multiple regression analysis to determine the conditions controlling the amount and distribution of bluff erosion. The results indicate a pattern of decreasing bluff erosion that is attributed to downstream migration of the zone of maximum basal scour. Bluff retreat in the period of active basal undercutting (1971 to mid-1975) was 18.9m/year and in the following period of decreased basal scour activity (mid-1975 to mid-1980) was 6.8m/year. Approximately, 61% of the erosion was associated with rising river levels. The data also indicated that 66% of the erosion occurred at bankfull discharge stage or above. Conditions that produce bluff erosion were found to vary between the two eriosion periods and also as river levels rose or fell in each of the periods. During the actively undercutting period, pre...

The potential economic and environmental impact of a Public Benefit Fund in Louisiana

Abstract Public Benefit Fund programs are one approach to provide energy assistance to low-income households placed at risk in a competitive electric industry. The purpose of this paper is to assess the potential economic and environmental impact of a proposed Public Benefit Fund for the state of Louisiana. The “best available” model to estimate the relationship between the cost of Public Benefit Fund programs and the benefits delivered by its implementation would be based on an evaluation of existent energy conservation and weatherization programs in the state, but unfortunately, such an evaluation has not been previously performed and so the “next best” analytic model was employed. The impact of a Public Benefit Fund on energy savings and environmental consequences is assessed through a simulation model and input–output analysis. The model developed is based on publicly available data and infer results under a reasonable assumption set. The model structure and system assumptions of the Public Benefit Fund program are described, realistic policy alternatives are examined—including cost-ceiling, variable funding, and target group strategies—and the limitations of the analysis are outlined.

Oil in Louisiana’s estuarine environments: A development model

Coastal erosion, accelerated by sea level rise, and subsidence are major Louisiana issues. With current sea-level-rise projections, coupled with the state’s eroding barrier islands and coastal wetlands, the region’s estuarine environments are in jeopardy of being lost, redefined, or permanently altered. As the coast erodes, Louisiana is endangered of losing valuable wetland’s habitat. In addition, if the barrier islands disappear, the region’s wetland-oriented oil and gas wells and associated infrastructure will be at risk to open Gulf conditions. If this should occur, each well, pipeline, and storage battery represents a potential environmental catastrophe. From an oil-spill-response perspective, it is much easier to clean a barrier beach than a salt-water or freshwater marsh. The barrier islands represent not only the first line of defense against the combined wind and water forces of a hurricane, but they also serve as pipeline anchor points. More importantly, the islands protect the marshes from an offshore-derived oil spill. Tidal mud flats, shallow grass beds, marshes and swamps are especially difficult to clean. The key, therefore, to an effective oil-spill-response plan is related directly to the viability of these islands, along with detailed pre-existing environmental, ecological, and habitat information. To be useful, this knowledge must be extensive, current, and easily extracted from a comprehensive data base. These data are being developed in Louisiana in the form of an all-inclusive geographic information system (GIS). Data in this system are helping Louisiana manage a vast array of resources. From a historical perspective, analysis of these data can serve as a model on how a deltaic environment can change from hydrocarbon exploration and development. Entering into the 21st century, Louisiana’s comprehensive database can help balance oil and gas activity, while maintaining the viability of the state’s estuarine environments.