Search

Coastal restoration in Louisiana requires clean sands for beach and dune restoration, whereas mixed sediments are required to rebuild marshes. The Louisiana coastal erosion problem is especially dire because it occurs on several fronts with the narrowing and overtopping of barrier islands and loss of back barrier bay and interior marshlands. Coastal restoration efforts in Louisiana depend on emplacement of sediment to build up barrier island and deltaic systems. Discovery of usable sediment is thus a vital factor in restoration efforts because up to 80% of some restoration project budgets can be allocated to exploration, exploitation, and emplacement of sediment. Because this cost is directly proportional to the distance of borrow sources from the project area, the cost-effectiveness of barrier island restoration and marsh creation depends on locating sufficient sediment volumes that are suitable for placement on beaches and dunes and for creating marshes. The restoration of Louisiana's barrier islands and the creation of coastal marshes are critically dependent on the availability of suitable modern marine and riverine sediments and other buried fluvio-deltaic deposits. It is thus imperative that a comprehensive sediment management plan be developed to systematically and efficiently identify and allocate suitable sediment resources. At present, coastal and barrier island restoration projects are included in regional planning efforts, and the restoration project is decided before sediment sources are considered. The new approach proposed here is based on planning projects around locations of dredgeable sedimentary deposits in order to optimize sediment resources. Centralization of voluminous historical geoscientific and oil and gas infrastructure data is being accommodated in a new data management system called the Louisiana Sand Resource Database (LASARD). Managing sediment resources more strategically optimizes regional planning strategies and reduces construction costs. The Louisiana Sediment Management Plan (LASMP) conceptualizes systematic planning and better coordination of essential components of the huge restoration and protection effort currently undertaken in Louisiana. [ABSTRACT FROM AUTHOR]

Coastal land loss in the Mississippi River delta region, related to degradation of wetlands and erosion of barrier islands, contributes to loss of valuable habitat, endangerment of infrastructure and socioeconomic systems, and coastal flooding hazards. Restoration of these ecosystems is thus a primary activity that requires large volumes of sand to rebuild beach-dune systems and restore wetland habitats. Sand sources have traditionally been sought offshore in the marine environment, but there are problems associated with setbacks from oil and gas infrastructure, presence of muddy overburden, and limited reserves of beach-quality sediments. Fluvial sand sources in channel and point-bar deposits become an attractive alternative for barrier island restoration because of large volumes of relict deposits and because active sand waves are renewable. Results of preliminary geophysical and geotechnical investigations in the lower Mississippi River (south of New Orleans) along a 32-km stretch of the river indicate the presence of at least 23 million cubic meters of usable sediments in seven potential borrow sites. Caveats to assessment and exploitation of river sands include interpretation of vibracores and seismic reflection profiles that include evidence of lateral translation-type bank failures along bendways, lateral slumps, and postdepositional disturbance of strata above -30 m. Reliable extraction of good quality sediment should occur down current from bendways. [ABSTRACT FROM AUTHOR]

Because of the large volumes of sand required for beach renourishment, dredging from offshore borrows is the preferred method of sediment supply. As easily accessible and previously known (obvious) deposits are exploited, apparent sand reserves are seen as a dwindling resource that becomes more precious over time. Because economically exploitable offshore sand sources are limited in many regions, renewed efforts are underway to locate additional offshore sand sources that can supply sand and mixed sediments (sand, silt, and clay) to harrier-island restoration efforts in Louisiana. Sediment volumes required for beach renourishment and marsh restoration are variously estimated on the basis of numerous assumptions to range in the extreme from 14 × 106 m³ to 71 × 106 m³, respectively, for one complete restoration of the entire barrier island chains. Although estimates of required volumes are controversial, significant new borrow sites must he located on the continental shelf off Louisiana to restore the barrier islands. The search for new sand sources must he focused on logistical procedures that are economical and efficient in order to cover large areas of the shelf in a timely manner. Sand search protocols developed for US East Coast sedimentary environments are broadly applicable in a conceptual sense hut need to he adapted to deltaic coastal frameworks in Louisiana. Procedures and protocols for the Delta Sand Search Model (DSSM) are thus based on bathymetric, geophysical, and geotechnical survey recommendations for the identification of targets that will he proven out by detailed studies and cultural resource investigations. Development of a DSSM has advantage because it is specifically adapted to coastal marine morphosedimentary units in different-aged lobes of the Mississippi Delta that have fine-grained (muddy) deposits interspersed by sandy deposits of paleodistributaries and interdistributaries. [ABSTRACT FROM AUTHOR]

Reports on the 44th issue of the Journal of Coastal Research which contains a collection of papers that reflect stages in the development of reconstruction plans for Louisiana.

This paper reviews physical, geologic and environmental parameters of Louisiana barrier islands to support the definition of regional strategies and management practices for long-term coastal restoration. For management purposes the barrier island systems of Louisiana are divided into a series of coastal segments to be maintained over the long term. Recommendations are drawn for each coastal segment on the basis of biophysical properties. Two separate design approaches for barrier island restoration are elucidated (stable location design and retreat design including sediment volume requirements for the restoration of specific barrier islands. In order to maintain long-term stability, intensive restoration programs require barrier island nourishment, vegetative plantings, and coastal structures in some cases. Restoration strategies, practices, and design approaches are refined by employing monitoring data in an adaptive management process. [ABSTRACT FROM AUTHOR]

In this paper, we review physical, geological, and environmental parameters of the Louisiana Chenier Plain to support the definition of regional strategies and management practices for long-term coastal restoration along this coastal segment. For management purposes, the Chenier Plain of Louisiana is divided into three main coastal segments that could he maintained over the long term. Recommendations are drawn for each coastal segment on the basis of biophysical properties. Approximate volumetric requirements for coastal restoration based on historical rates of shoreline change are presented. Discussions of potential sand resources are based on data published in the professional literature. Compared with the Louisiana barrier islands, the Chenier Plain is less well known; consequently, there is significantly less data related to shoreline change, sedimentology, beach profiles, and large-scale geomorphological evolution. Future restoration projects in this coastal region must direct attention toward obtaining essential coastal data that is lacking for many coastal segments along the Louisiana Chenier Plain. [ABSTRACT FROM AUTHOR]