Shea Penland

Shoreface translation and the Holocene stratigraphic record: Examples from Nova Scotia, the Mississippi Delta and eastern Australia

Abstract Classic descriptive models of barrier sedimentation have been developed with data from the Atlantic and Gulf coasts of the United States. These models are dominated by low to moderate rates of relative sea level (RSL) rise and wave energy. Barriers respond by landward recycling of sediment through the mechanism of shoreface retreat. Sedimentation processes on the central coast of New South Wales (N.S.W.), Australia, consist of rapid RSL rise in early Holocene times followed by a stillstand since 6500 B.P. Wave energy is relatively high year-round and sand sources for barrier formation are only found on the inner shelf. Barrier sedimentation on the central coast of N.S.W. exhibits a thick, composite sequence composed of a basal marine transgressive sand overlain by regressive beach and dune facies. The Louisiana coast surrounding the Mississippi delta is underlain by compacting deltaic muds which generate very rapid rates of RSL rise. The Louisiana coast experiences low wave energy punctuated by high-energy tropical and extra-tropical storm events. Barrier sediments accumulate from the erosion of deltaic headlands and undergo a transformation from subaerial barrier island systems to subaqueous shoals located on the inner shelf. Drumlins experience coastal erosion on the Eastern Shore of Nova Scotia and provide a sediment source for compartmented estuary mouth barriers. An ongoing, moderate rise of RSL results from the passage of a glacial forebulge. Wave energy is intermediate between Louisiana and N.S.W. and displays a seasonal pattern dominated by frequent winter storms. Coastal barrier sedimentation is episodic, consisting of a period of beach ridge progradation followed by barrier destruction and re-establishment further landward. The three contrasting sedimentary sequences found in examples from Louisiana, N.S.W. and Nova Scotia indicate that presently available sedimentation models from locations such as the middle Atlantic or Texas coasts of the United States may only represent well-documented regional case studies. A true generalised coastal sedimentation model is required which can identify the parameters controlling vertical and horizontal translation of the depositional surface and provide relationships between these parameters which quantitatively predict the genesis, distribution and geometry of coastal sedimentary facies.

Impacts of Rising Sea Level to Backbarrier Wetlands, Tidal Inlets, and Barrier Islands: Barataria Coast, Louisiana

The Barataria barrier system within the Mississippi River delta plain, is experiencing some of the highest relative sea-level rise (SLR) rates in the continental USA (0.94 cm/yr). This has led to substantial wetland loss in Barataria Bay (16.9 km 2 /yr, from 1935-2000). This conversion of wetlands to intertidal and subtidal environments results from several linked processes including subsidence, marsh front erosion, and catastrophic scour during large magnitude hurricanes. Increasing open water within Barataria Bay has amplified tidal exchange with the ocean. Between 1880 and 2006, an increase of 400% took place in the combined cross-sectional areas of the major tidal inlets of Barataria Bay, associated with the enlarging tidal prism. This expansion of the inlets has been at the expense of the adjacent barrier islands, evident in the concomitant progradation of the ebb-tidal deltas. Since the 1880s the ebb delta at Barataria Pass built seaward more than 2.0 km, sediment cores show that sand constitutes the upper 1-2 m of the ebb delta. Movement of sand offshore, regional subsidence and increasing bay tidal prism produce segmentation of the barriers, forming new inlets such as Pass Abel. Acceleration in eustatic sea level rise will lead to further wetland loss and thus ultimately barrier disintegration. The Barataria barrier chain will be transformed into an island-only system similar to the Isle Dernieres and Timbaliers.

IMPLEMENTING THE SHORELINE CLEANUP ASSESSMENT TEAM PROCESS IN THE GULF OF MEXICO

ABSTRACT Louisiana State University (LSU) and Woodward-Clyde Consultants are working with state and federal agencies, and industry through the LSU Gulf of Mexico Oil Spill Research and Response Program to establish a shoreline cleanup assessment team program (SCAT) in the Gulf of Mexico. Each SCAT team consists of a coastal geomorphologist and ecologist (and archaeologist when appropriate), as well as representatives from the responsible federal, state, and private agencies. This cooperative effort is aimed at identifying oil spill impact and interagency coastal resource concerns and recommendations, and developing a cleanup strategy based on interagency cooperation and concurrence within a systematic and standardized framework. The SCAT program provides interagency coordination, SCAT preparedness, spill drill participation, interagency training, geographic information systems services, monitoring, and routine aerial videotape surveys. It also offers technical support to the decision-making process within...

SEDIMENTATION PROCESSES ALONG THE EAST FRIESIAN ISLANDS, WEST GERMANY

This report will update the coastal zone practitioner on the National Flood Insurance Program (NFIP) as it affects the implementation of manmade changes along the coastline. It is our intent to place in proper perspective this fast-changing and often difficult to interpret national program. Readers will achieve an overall understanding of the NFIP on the coast, and will be in a position to apply the programs requirements in their efforts. We will begin with a history of the application of the NFIP to the coastal zone. The history of the problems encountered will lead into current regulations, methodologies, and the changes the Federal Emergency Management Agency plans for the future.The spatial variability of the nearshore wave field is examined in terms of the coherence functions found between five closely spaced wave gages moored off the North Carolina coast in 17 meters depth. Coherence was found to rapidly decrease as the separation distance increased, particularly in the along-crest direction. This effect is expressed as nondimensional coherence contours which can be used to provide an estimate of the wave coherence expected between two spatial positions.Storm surges from hurricanes have even more devastating effects on human lives and property than the high wind velocities associated with such storms. Storm surge forecasts are necessary as a guide for emergency action to prevent disasters due to coastal flooding caused by tropical storms. The design and evaluation of coastal structures are also dependent on estimates of storm surge levels. Several numerical models have been developed that appear to reasonably predict the surge from storms of given size and intensity, but they sometimes differ significantly among themselves. A comprehensive data set is needed to quantitatively evaluate these models. These data will also provide a better understanding of coastal processes during periods of severe wave activity and high water levels, and will better define coastal and inland water elevation time histories, high water marks, and water velocity fields caused by tropical storms and hurricanes. The U. S. Army Engineer Waterways Experiment Station (WES), Coastal Engineering Research Center (CERC), under the sponsorship of the Office Chief of Engineers (OCE), has been involved for several years in a project entitled Hurricane Surge Prototype Data Collection Work Unit, the primary objective of which is to collect such a data set. In addition to the work being performed by CERC personnel, a cooperative program has been established with the Nuclear Regulatory Commission (NRC) and the University of Florida to collect surge data along the coast of Florida. A cooperative program has also been established with the National Ocean Service (NOS) to harden tide stations in the Gulf of Mexico and along the Atlantic Coast of Florida to survive hurricane forces and record the full range of anticipated surge levels. This paper describes CERCs long term, ongoing Hurricane Surge Prototype Data Collection project, as well as the data collected.Prediction of depositional patterns in estuaries is one of the primary concerns to coastal engineers planning major hydraulic works. For a well-mixed estuary where suspended load is the dominant transport mode, we propose to use the divergence of the distribution of the net suspended load to predict the depositional patterns. The method is applied to Hangzhou Bay, and the results agree well qualitatively with measured results while quantitatively they are also of the right order of magnitude.