MMS ENVIRONMENTAL STUDIES PROGRAM: ONGOING STUDIES
MMS OCS Region: Headquarters
Title: Biological Characterization/Numerical Wave Model Analysis within Identified Borrow Sites Offshore the West Coast of Florida/Physical Implications of Sand Dredging on the Topography of the West Florida Shelf (NT-05-06)
Total Cost:

$518K

 Period of Performance:

FY 2005-2007
Conducting Organization: Scientific Environmental Applications, Inc
MMS Contact:

Colleen Finnegan
Description:
Background
Sand resources in Federal waters are actively being investigated for long-term use on the west coast of Florida (Sarasota, Charlotte, Lee, and Collier Counties). Offshore Collier County, Florida, two large sand ridges located in Federal waters approximately 10 miles southwest of Sanibel Island are being examined for use as future beach nourishment material. Geological and geophysical surveys are being conducted for the county by Coastal Planning and Engineering, Inc. Many of the other communities along the southwest Florida coast, such as Fort Myers and Naples are also in critical need of sand for beach nourishment and their economy largely depends on the beach habitat and tourist industries. Requests from the State and local jurisdictions to use sites in Federal waters is expected in the near-term, particularly if storm events continue to impact the coastline. The level of detail regarding the biology and physical characteristics of these areas is not adequate at this time to make reasoned decisions regarding the environmental consequences prior to actual dredging of the areas. Of particular importance is the impact of dredging on the local wave climate offshore the west coast of Florida given the shallow water depths likely to be encountered at many of the borrow sites. Given the frequency of severe storms which traverse this part of the Gulf of Mexico, any significant increaser in wave height could result in increased coastal damage or accelerated beach erosion. In addition, there are many sensitive biological communities and hard bottom areas which may be susceptible to impact from dredging.
Objectives
The purpose of the study is to address environmental concerns, prior to actual dredging of potential sand resource areas identified offshore the west coast of Florida, the likelihood of adverse environmental impacts on resident biological organisms and on the local wave climate and sediment transport regime from sand dredging for the purposes of beach renourishment. The information provided from this study will be used to prepare environmental analyses to meet the requirements of current environmental laws and legislation and incorporate results, as appropriate in lease requirements for the dredging of OCS sand
Methods

Biological: To evaluate the possible biological impacts associated with dredging, the present condition of benthic and fish assemblages will be characterized and interpretations will be developed to assess those impacts. The characterization of benthic communities will be done using existing literature, collection of field data and laboratory analysis. Grab samples, trawls, sediment profiling cameras, water column profiles and other current sampling techniques will be used to characterize the benthic biology in the field.  The structure of benthic communities and fish assemblages will be analyzed for diversity, evenness, species richness, biomass, taxonomic composition, gut content, and secondary production, etc.  Community cluster analysis will be performed as well. An evaluation of the potential environmental impacts to the biological community will be conducted by making inferences and interpretations based on the field data, laboratory analysis, historical information, past studies and the most recent scientifically accept theories and models.

Physical: To evaluate the possible physical impacts associated with dredging of identified borrow sites, and to examine on a generic basis, the possible effects of dredging along the west Florida shelf, wave transformation modeling and sediment transport potential calculations will be performed for 1) present existing conditions, and 2) present conditions with the proposed excavations sand from the identified borrow sites. Comparison of computations for existing and post-dredging conditions illustrate the relative impact of borrow site excavation 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.

Importance to MMS
The State of Florida and local jurisdictions on the west coast of Florida will certainly be requesting negotiated agreements from the MMS for the use of OCS sand resources for beach nourishment, especially as resources in State waters run dry. Environmental concerns, such as impacts on endangered manatees, have also put many areas in State waters on the west coast of Florida off-limits to dredging. The information gathered from this study is crucial in properly undertaking the required environmental assessments for proposed site-specific beach nourishment projects and will be used in developing/incorporating environmental stipulations in negotiated leases to protect the environment.
Current Status:

The initial biological cruise has been completed and benthic and fish samples and surveys were successfully completed.  The second biological sampling cruise will take place in Summer 2006. Numerical modeling has commenced with the preparation of the modeling grids.
Final Report Due:

September 2007
Publications:
Affiliated WWW Sites: http://www.mms.gov/sandandgravel/Floridastudies.htm
Revised date:

February 2006
ESPIS

ESPIS - All completed ESP Studies:
Full Text, Online, Right Now!
 Environmental Studies Program Information System