ACCESS NUMBER: 30660-19911b 

STUDY TITLE: Wave Climate and Boundary Layer Dynamics with Implications for 

Offshore Sand Mining and Barrier Island Replenishment, South-Central Louisiana 

REPORT TITLE: Wave Climate and Bottom Boundary Layer Dynamics with 

Implications for Offshore Sand Mining and Barrier Island Replenishment in SouthCentral Louisiana 

CONTRACT NUMBER: 14-35-0001-30660-19911b 

SPONSORING OCS REGION: Gulf of Mexico 

APPLICABLE PLANNING AREA: South-Central Louisiana Coast 

FISCAL YEARS OF PROJECT FUNDING: FY 1994 through FY 1999 

COMPLETION DATE OF REPORT: 2000 

COSTS: FY 1994, $93,897: FY 1995, $83,102; FY 1996, $94,363; FY 1997, $91,138; 

FY 1998, $31,171: CUMULATIVE PROJECT COST: $393,671 

PROJECT MANAGER: Gregory W. Stone 

AFFILATION OF PROJECT MANAGER: Coastal Studies Institute, Louisiana State 

University 

ADDRESS: 331 Howe Russell, Louisiana State University, Baton Rouge, Louisiana 

70803 

PRINCIPLE INVESTIGATORS: Gregory W. Stone, J.P. Xu, K. Henderson, and J.M 

Grymes 

KEY WORDS: Numerical models, sediment transport, hydrodynamics, Ship Shoal 

BACKGROUND: In an earlier MMS-funded project conducted by the PI of the current 

report, three numerical modeling objectives were undertaken: (1) to develop a numerical 

model of wave energy transformation and decay across the inner shelf encompassing 

Ship Shoal and the nearshore adjacent to the Isles Dernieres; (2) to develop a 

nearshore sediment transport model along the Isles Dernieres; and, (3) to quantify 

changes in (1) and (2) due to removal of various sediment quantities based on likely 

scenarios provided by MMS. 

OBJECTIVES: The current project included three additional field measurement 

objectives: (1) to procure and fabricate an additional bottom boundary layer 

instrumentation system; (2) to obtain direct field measurements of temporally- and 

spatially-varying directional wave spectra at two locations; and, (3) to obtain direct field 
ACCESS NUMBER: 30660-19911b 

measurements of bottom boundary layer hydrodynamic processes and suspended 

sediment transport. All experiments were conducted at Ship Shoal. 

DESCRIPTION: Instrumentation was deployed on the Louisiana inner shelf during two 

winter periods, between November 24, 1998 and February 2, 1999, and February 9 and 

March 25, 2000. The three instrumentation packages consisted of two types of framemounted systems, both of which included a self-contained data recorder module. 

System 1 was a unique multi-sensor package nicknamed WADMAS, which consisted of 

a Paroscientific pressure sensor, a sonar altimeter, and a vertical array of three colocated Marsh-McBirney electromagnetic current meters and Seapoint optical 

backscatter sensors (OBS’s). This instrumentation enabled WADMAS to measure 

water level, directional wave parameters, and seabed elevation, as well as current 

velocity and suspended sediment concentration at heights of 20, 60, and 100 cm above 

the seabed. Systems 2 and 3 each consisted of a pressure sensor and a SonTekTM

downward-looking Acoustic Doppler Velocimeter (ADV) that measured seabed 

elevation, relative particulate concentration and three-dimensional currents at an 

elevation of approximately 20 cm above the bed. During the first deployment, Systems 

1 and 2 were deployed in approximately 8.5 m of water on the seaward side of Ship 

Shoal, while System 3 was deployed in about 7 m of water on the landward side. 

During the second deployment, Systems 1 and 3 were deployed in the same locations 

as previously, while System 2 was placed at a 3.5 m water depth in the middle of the 

Shoal. During each deployment and retrieval, divers collected sediment from the bed, 

and water samples from the water column, and observed and measured any visible bed 

forms. Data were then processed and analyzed using conventional methods found in 

the literature. 

STUDY RESULTS: Hydrodynamic, bottom boundary layer, and sedimentary processes 

on the Louisiana inner shelf during the winter are characterized by episodic variability, 

largely as a result of the quasi-periodic cycle of recurring extratropical storm passages 

in the region. Extratropical storms are generally characterized by increases in: wave 

height, near-bed orbital, and mean current speed, shear velocity, suspended sediment 

concentration, and sediment transport. Decreases in wave period and apparent bottom 

roughness are also apparent. Despite these regularities, considerable variability 

between storms, as well as during storms themselves, is reflected in hydrodynamic, 

bottom boundary layer, and sedimentary processes. During strong storms, some 

indices were several orders of magnitude greater than during fair weather, while during 

weak storms they were lower. 

The following extratropical storm classification, consisting of two storm types, is 

proposed on the basis of their influence on the Louisiana inner shelf. Type 1 storms are 

characterized by weak southerly pre-frontal and strong northeasterly post-frontal winds 

that cause strong post-frontal responses including high, short-period, southerly waves, 

strong, southwesterly currents, and moderately high southwesterly sediment transport. 

Type 2 storms include periods of both strong southerly pre-frontal winds, which 

generate high, long-period northerly swell waves, and strong northerly post-frontal 

winds, which cause energetic southerly storm waves. Rotational, net southeasterly 
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currents and high shear velocity occurs during both the pre- and post-frontal phases, 

while sediment transport occurs predominantly during the post-frontal phase, when it is 

southeasterly. Local extratropical storms are apparently not the only cause of highenergy responses on the Louisiana inner shelf. Distant storms apparently cause high, 

long-period waves, accompanied by moderate rotational currents that can create high 

sediment transport. Results suggest that resuspension and transport of bottom 

sediment may sometimes occur during winter fair weather conditions, although it has 

previously been considered unlikely. 

SIGNIFICANT CONCLUSIONS: Differences between the seaward and landward sides 

of Ship Shoal are apparent. Waves tend to be higher and longer in period on the 

seaward side, while mean currents are generally higher landward, where they are 

directed onshore, unlike the offshore site, where seaward currents predominated. It is 

apparent, therefore, that Ship Shoal exerts a significant influence on regional 

hydrodynamics, reducing wave energy and modulating current velocity. The short-term 

evolution of Ship Shoal appears to be the result of a balance between fair weather 

influences, which cause erosion and landward migration, and winter storm influences 

(particularly Type 2 storms), which cause accretion and seaward migration. 

STUDY PRODUCTS: Stone, G.W. and J.P. Xu. 1995. Wave Climate Modeling and 

Evaluation Relative to Sand Mining on Ship Shoal, Offshore Louisiana, for Coastal and 

Barrier Island Restoration. Report prepared for Minerals Management Service, OCS 

Study, MMS 96-0059. 

Stone, G.W. and J. P. Xu. 1995. Wave and nearshore transport modeling Louisiana 

coast. Coastal Morphodynamics Laboratory Technical Paper 95-5, 18 pp. 

Stone, G. W., J. P. Xu, and X. P. Zhang. 1995. Estimation of the wave field during 

Hurricane Andrew and morphological impacts along the Louisiana coast. In: Stone, 

G.W. and C.W. Finkl, eds. Impacts of Hurricane Andrew on the Coastal Zones of 

Florida and Louisiana: Journal of Coastal Research Special Issue 21:234-253. 

Stone, G.W., J. P. Xu, and X. P. Zhang. 1995. Wave climate modeling and evaluation 

relative to sand mining on Ship Shoal, offshore Louisiana, for coastal and barrier island 

restoration. U.S. Minerals Management Service International Transfer Meeting, New 

Orleans, LA. (invited). 

Xu, J.P., G. W. Stone and X. P. Zhang. 1995. Impacts of Ship Shoal on storm wave 

propagation across south-central Louisiana shelf, a simulation study. Geological 

Society of America Annual Meeting, New Orleans, LA. 

Stone, G.W., J. P. Xu and X. P. Zhang. 1996. Ship Shoal wave climate modeling and 

evaluation. Transactions, International Transfer Meeting, Minerals Management 

Service, Gulf of Mexico OCS Region, New Orleans, LA. 
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Stone, G.W., J. P. Xu and X. P. Zhang. 1996. Physical and environmental studies 

within the Ship Shoal area: wave climate study and ongoing physical field study. U.S. 

Minerals Management Service International Transfer meeting, New Orleans, LA. 

(invited). 

Xu, J.P. and G. W. Stone. 1996. Wave climate modeling and evaluation relative to 

sand mining on Ship Shoal, offshore Louisiana, for coastal barrier island restoration. 

American Geophysical Spring Meeting, Baltimore, MD. 

Zhang, X.P. and G. W. Stone. 1997. Application of GIS to assist in wave modeling for 

the central Louisiana coast. 13th. Louisiana remote Sensing and Geographical 

Information Systems Conference, Lafayette, LA. 

Pepper, D.A., G. W. Stone and P. Wang. 1998. A preliminary assessment of wave, 

current, and sediment interaction on the Louisiana shoreface adjacent to the Isles 

Dernieres. Recent Research in Coastal Louisiana, Lafayette, LA. 

Stone, G.W. 1998. The significance of frontal boundaries, tropical storms and 

hurricanes on the morphodynamics of Gulf Coast barriers, USA.” International Coastal 

Symposium, West Palm Beach, FL. 

Stone, G.W. 1998. Numerical wave modeling of wave energy increases in Louisiana’s 

bays, USA. International Coastal Symposium, West Palm Beach, FL. 

Stone, G.W. and R. A. McBride. 1998. Louisiana barrier islands and their importance 

in wetland protection: forecasting shoreline change and subsequent response of wave 

climate. Journal of Coastal Research 14, 3, 900-916. 

Stone, G.W., X. P. Zhang and P. Wang. 1998. Forecasting wave energy changes 

along the Louisiana coast and implications for accelerated wetland loss. International 

Deltas Symposium, New Orleans, LA. 

Zhang, X.P. and G. W. Stone. 1998. Development of a Louisiana coastal processes 

geographic information system. Recent Research in Coastal Louisiana, Lafayette, LA. 

Pepper, D.A., G. W. Stone and P. Wang. 1999. Bottom boundary layer parameters 

and sediment transport on the Louisiana inner shelf during cold front passages. 

Transactions, Gulf Coast Association of Geological Societies, Lafayette, LA., XLIX: 432-

438.Stone, G.W. and P. 

Wang. 1999. The importance of cyclogenesis on the short-term evolution of Gulf Coast 

barriers. Transactions, Gulf Coast Association of Geological Societies, Lafayette, LA., 

XLIX:478-486. 
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Pepper, D.A., G. W. Stone and P. Wang. 1999. Bottom boundary layer parameters 

and predicted sediment transport. Association of American Geographers, 95th Annual 

Meeting, Honolulu, HI. 

Pepper, D.A., G. W. Stone and P. Wang. 1999. The significance of mid latitude 

cyclones on the inner continental shelf of the northern Gulf of Mexico: the impact of 

Hurricane Camille: A Storm Impacts Symposium to Mark the 30th Anniversary, New 

Orleans, LA. 

Pepper, D.A., G. W. Stone and P. Wang. 1999. Bottom boundary layer parameters 

and sediment transport on the Louisiana inner shelf during cold front passages. Gulf 

Coast Association of Geological Societies, Lafayette, LA. 

Stone, G.W. 1999. The importance of cyclogenesis on the short-term evolution of Gulf 

Coast Barriers. Association of American Geographers, 95th Annual Meeting, Honolulu, 

HI. 

Stone, G.W. 1999. Storm impacts and the importance of subsidence on the Mississippi 

River delta plain, Louisiana, USA. 52nd NGMSO Lecture Series, University of Utrecht, 

The Netherlands. 

Stone, G.W. and P. Wang. 1999. The importance of cyclogenesis on the short-term 

evolution of Gulf Coast barriers. Gulf Coast Association of Geological Societies, 

Lafayette, LA. 

Stone, G.W., P. Wang and D. Pepper. 1999. Importance of hurricanes, tropical storms 

and mid-latitude cyclones on the short-term evolution of Gulf Coast barriers: the impact 

of Hurricane Camille: A Storm Impacts Symposium to Mark the 30th Anniversary, New 

Orleans, LA. 

Stone, G.W., P. Wang and X. P. Zhang. 1999. Development of a wave-current 

information system for Louisiana bay-shelf environments. Estuarine Research 

Federation’99, 15th Biennial International Conference, New Orleans, LA. 

Pepper, D.A., G. W. Stone P. Wang. 2000 A preliminary assessment of wave, current, 

and sediment interaction on the Louisiana shoreface adjacent to the Isles Dernieres. 

Recent Research in Coastal Louisiana: 35-45. 

Pepper, D.A. and G.W. Stone submitted to Geo-Marine Letters, 2001 Atmospheric 

Forcing of Fine Sand Transport on a Low-Energy Inner Shelf: South-Central Louisiana, 

USA 

Pepper, D.A. and G.W. Stone 2001 Extratropical Storms in the Northern Gulf of 

Mexico: Their Characteristics and Importance to Coastal Processes: Presentation to 

the American Meteorological Society: Central Louisiana Chapter, Baton Rouge, LA 

(invited). 
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Pepper, D.A. and G.W. Stone in preparation Hydrodynamic, Bottom Boundary Layer 

and Sedimentary Responses to Two Contrasting Winter Storms on the Low-Energy 

Inner Shelf of the Northern Gulf of Mexico. 

*P.I.'s affiliation may be different than that listed for Project Manager(s).