Sarah Fearnley

The Soil Physical and Chemical Properties of Restored and Natural Back-Barrier Salt Marsh on Isles Dernieres, Louisiana

Abstract Isles Dernieres is a transgressive barrier island arc in southeast Louisiana associated with the Bayou Grand Caillou headland of the Lafourche delta complex, which was abandoned 600 to 800 years ago. During the past two decades Trinity and Whiskey Islands have been eroding at rates of >18 m/y, and East Island has been eroding at a rate of 11.8 m/y. The Isles Dernieres Barrier Island Stabilization Project, implemented in 1998, dredged material from various sites in the bay behind the barriers for dune and marsh restoration of East, Trinity, and Whiskey Islands. The 1998 restoration increased the overall height and width of the islands but marsh habitat has not developed on the restored material behind the barriers. This study characterizes the physical and chemical properties of soil from restored and natural back-barrier salt marsh on Isles Dernieres to determine the restoration timeframe in which restored marsh soils develop to conditions more similar to natural marsh soils. Additionally, the goal is to identify the soil properties in restored marsh that could be modified to enhance back-barrier marsh habitat. Laboratory analyses of 60 cores from four different vegetation density classes in restored marsh and nine cores from natural marshes included bulk density, soil moisture content, grain size, sorting, pH, conductivity, total carbon, and total nitrogen. Vegetation density in restored marshes had no significant effect on soil properties, with the exception of bulk density. Marsh type had a significant effect on all measured soil properties. Variations in the soil properties of restored and natural back-barrier salt marsh are primarily the result of differences in soil texture and elevation.

Ecological Aspects of Coastal Sediment Management in the Gulf of Mexico

Abstract Water and sediment resource planning is a vital facet of natural resource management. There have been many ecologically disruptive consequences from conventional resource management plans. In the northern Gulf of Mexico (GOM) nearby communities depend on water and sediment resources both ecologically as well as economically. The value of these resources is determined by habitat structure and ongoing sediment dynamics. This article explores how human activities have changed sediment dynamics in relation to the ecology of the habitats present in the northern GOM. It further presents ideas to prevent future problems through sediment management plans that account for natural processes. The northern GOM contains several habitats that are affected by sediment/water resource management plans such as the shoreface (beaches and dunes), barrier islands, hardbottom (coral and oyster reefs), bays, marshes, and forested wetlands. Many common techniques for water/sediment resource management have been used in these areas such as dredging, hard structures (jetties, groins, sea walls, and breakwaters), dams, diversions, levees, and coastal development. The implications of these different management techniques can lead to extensive changes in coastal habitats. Dredging causes disturbances to both borrow and placement sites and can change natural community structure at both sites. The installation of hard structures can cause severe changes in habitat structure that can lead to losses of species diversity. The impacts of river management structures (dams, levees, and diversions) alter the delivery of sediment needed by coastal habitats for growth and sustainability. Anthropogenic development in coastal regions prevents those areas from maturing naturally. Because of the importance of sediments to the ecology of the northern GOM coast and its vulnerability to natural and anthropogenic disturbances, several recommendations are made for holistic future sediment management plans.

Mapping the Geomorphology and Processes of Coastal Land Loss in the Pontchartrain Basin: 1932 to 1990 and 1990 to 2001

Abstract The geomorphology and processes of land loss in the Pontchartrain Basin for the period 1990–2001 are mapped and the results of the classification presented. This data set is compared to an earlier classification, which covered the period 1932–1990 to determine the status and trends of wetland loss in the Pontchartrain Basin between 1932 and 2001. Results of the land loss classification indicate land loss rates have remained steady between the two periods (13 km2/y between 1932 and 1990 and 12 km2/y between 1990 and 2001). The geomorphology and processes of loss have shifted from primarily interior loss as a result of direct removal and submergence in the first period to primarily shoreline loss as a result of erosion in the second period. Three areas of concentrated land loss between 1990 and 2001 represent portions of the upper, middle, and lower basin. Land loss at all three locations shifts from interior to shoreline loss between the two periods. In the second period, interior loss through the process of submergence is still occurring but at much reduced rates at locations 1 and 2. Interior loss through the process of direct removal is only occurring at location 1 during the second period and accounts for less that 2% of the loss. At location 3, land loss is completely in the form of shoreline erosion during the second period.