| MMS ENVIRONMENTAL STUDIES PROGRAM: ONGOING STUDIES | ||||||
| MMS OCS Region: | Headquarters | |||||
| Title: | Examination of the Physical and Biological Implications of Using Buried Channel Deposits and Other Non-Topographic Offshore Features as Beach Nourishment Material (NT-05-07) | |||||
| Total Cost: |
$241K |
Period of Performance: |
FY 2005-2007 |
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| Conducting Organization: |
Baird and Associates |
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| MMS Contact: | ||||||
| Description: | ||||||
| Background | ||||||
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The continuing search for new sand borrow sites along the U.S. Atlantic and Gulf coasts has resulted in the identification of potential sand borrow areas in Federal waters which are not associated with raised topographic features such as the offshore shoals which are presently the primary target for local, Federal, and State authorities needing sand for beach nourishment projects. Significant quantities of sand suitable for beach nourishment have been found in surficial deposits, as well as paleochannels. In many instances, these channels are buried under a significant thickness of overlying sediment which must be side-cast or disposed of in some manner before dredging of the borrow material can be accomplished. Like sheet sands, these qualities make channel deposits difficult to dredge. These types of deposits have very different resident biological communities than the shoal-type deposits and may be impacted quite differently during a typical dredging operation. In addition, the taking of the deposits might leave a sizable depression in the seafloor which could result in adverse changes in the local wave climate and sediment transport regime. These factors and the biological and physical impacts associated with the use of these deposits, including the potential effects of the side-casting of any overburden material, must be thoroughly investigated before negotiating leases for planned beach nourishment projects. |
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| Objectives | ||||||
| The purpose of the study is to examine, on a generic basis, the potential for adverse effects on the biology and physical characteristics of areas along the east and Gulf coasts of the United States should dredging proceed in potential borrow sites which are not associated with raised topographic features (surficial sheet sands and buried paleochannels). | ||||||
| Methods | ||||||
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Biological: Existing biological data (infauna, epifanua, fisheries, etc.), where it exists, will be collected from sheet sand areas and paleochannel deposits located on the U. S. east and Gulf of Mexico coasts. The biological characteristics will be compared to those of the sand shoal areas which are currently being used as borrow sites and an evaluation of the possible effects of dredging will be made based on those characteristics. Included in this analysis will be an evaluation of the possible effects of side-casting fine-grained material which might be present in buried channel deposits. Physical: To evaluate the possible physical impacts associated with the dredging of sheet sands and paleochannels, wave transformation modeling and sediment transport potential calculations will be performed for 1) present existing conditions, and 2) present conditions given hypothetical sand extraction volumes. This will be computed for normal conditions and storm conditions. Comparison of computations for existing and post-dredging conditions will illustrate the possible impact of borrow site excavations on wave-induced coastal processes. Nearshore wave heights and directions along the shoreline landward of the proposed borrow site will be estimated using a state-of-the-art spectral wave model (STWAVE or SWAN), which will be used to simulate the propagation of offshore waves to the shoreline. Offshore wave data, available from offshore wave buoys maintained by the National Data Buoy Center (NDBC) will be used to derive input wave conditions for the model used. |
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| Importance to MMS | ||||||
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Sheet sands and palochannel deposits represent viable sources of sand borrow material for beach and coastal restoration along both the east and Gulf of Mexico coasts of the U.S. Prior to any potential dredging in these areas, it is crucial that MMS conduct an assessment of the potential effects of dredging within these zones. The information will be used to properly undertake required environmental assessments for proposed beach nourishment projects, as well as developing/incorporating environmental stipulations in negotiated leases to protect the environment. |
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| Current Status: |
This project is now complete. Please see the final report in ESPIS. |
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| Final Report Due: |
July 2007 |
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| Publications: | ||||||
| Affiliated WWW Sites: | ||||||
| Revised date: |
March 2008 |
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| ESPIS |
ESPIS - All completed
ESP Studies: |
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