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Maa Works with Local Business toTest Breakwater

It might be the last thing on theirminds as they relax on the beach, shopin nearby stores, or enjoy an evening con-cert, but visitors to Yorktown’s newRiverwalk Landing are direct beneficia-ries of a long-term collaboration betweenYork County officials and scientists atVIMS.

The collaboration, which beganwith the construction of a small break-water in 1985, hashelped the historicriverfront communitystem shoreline erosion,weather HurricaneIsabel and severalpowerful nor’easters,and maintain a popu-lar swimming beach.

VIMS’ lead inthe project is ScottHardaway, head ofthe Shoreline StudiesProgram at the Institute and a recentelectee to the National ResearchCouncil’s Study Committee on Mitigat-ing Shore Erosion Along ShelteredCoasts.

Hardaway says that VIMS’ primaryrole in the revitalization project has beento provide technical advice concerningthe size, shape, and placement of the 12breakwaters that now line the York Riverwaterfront.

Two floating breakwaters, whichserve as piers for commercial and recre-ational vessels, were designed by theWilliamsburg office of civil engineeringfirm VHB Inc. VHB prepared the fi-nal design and plans for all phases ofthe Yorktown project.

The Yorktown work is part ofVIMS’ larger Chesapeake Bay Break-water Database Project, a partnership

with the U.S. ArmyCorps of Engineers todevelop guidelines andtrack breakwater per-formance at 40 sitesaround the Bay.

Breakwaters areelongate structures,typically of stone, thatare emplaced just sea-ward of the shorelineto be protected. Theywork by damping,

bending, and otherwise disruptingwaves before they reach land.

To ensure that a breakwater systemwill per form most effectively,Hardaway’s group uses a combinationof field measurements, mathematicalequations, and computer models to iden-tify the particular conditions underwhich the system will operate. They char-acterize the prevailing wind and wavedirection, predicted wave heights and

A Tale of Two BreakwatersEditor’s note: This pair of articles highlights two parts of VIMS’ multi-faceted role in helping to guide shoreline management in Chesapeake Bay.

Shoreline Program Aids Yorktown Revitalizationwater levels for 50- or 100-year storms,the seafloor bathymetry, and the shore-line profile.

They then use this information tospecify the many interacting factors thatgovern a breakwater’s shape and place-ment (see figure). “While we try to con-sider all of these factors, they rarely carryequal weight,” notes Hardaway. “In fact,

satisfying all objectives for any givenproject is unlikely, as some may be mu-tually exclusive.”

The magnitude of the sand supplyis another important design factor. His-torically, Yorktown Beach was fed by ero-sion of sandy banks nearby. However,the beach began to narrow as the natu-

Many interacting features govern the shape and placement of elements in a break-water system. These include orientation, length, and height of individual breakwa-ters; the gap between adjacent breakwaters; the distance between a breakwater andthe shore; the width and elevation of the beach; and the system’s possible effects onother shorelines up- and downriver.

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In its first year of operation,the $10 million RiverwalkLanding drew more than65,000 visitors to specialevents in Yorktown and

countless more on an everydaybasis. The development

pumped millions of dollarsinto the local economy.

VIMS researcher Dr. Jerome Maahas been funded by a local company totest the efficiency of floating breakwa-ters in protecting marinas and othercoastal structures from wave action.

The company, Coastal Design andConstruction, Inc. (CDCI) ofGloucester County, recently awardedMaa a 4-month contract to study the ef-ficiency of a floating breakwater they’veemplaced outside the Hyatt Hotel’sRiver Marsh Marina. The marina abutsthe Choptank River near Cambridge,Maryland.

Test results will help the companyprovide its customers with more realisticestimates of breakwater performance—and help explain a discrepancy betweenobservations of breakwater performancein the laboratory and the real world.

“The marina had asked for a float-ing breakwater that could reduce waveheight by 75%,” says Maa. “Lab stud-ies done by a Spanish institute severalyears ago showed that a floating break-water would be unable to meet this re-quirement, but CDCI’s experience withreal world breakwaters suggests other-wise.”

To help the company test breakwa-ter performance in the field, Maa willdeploy three separate wave gauges in thevicinity of the Hyatt Hotel’s River MarshMarina—one outside the structure andtwo in the protected waters within. Thegauges, built by VIMS instrumentmaker Wayne Reisner, employ a bottom-mounted sensor that records the rise andfall of water pressure as wave crests andtroughs pass above. In addition to mea-suring wave height, the external sensoremploys a trio of pressure gauges that

together provide data on wave direction.Maa, along with team members Bob

Gammisch and Ho Kyung Ha, willtravel to the site once a month betweenDecember and March to download thewave data for analysis. The four-monthstudy was scheduled for winter in orderto sample the larger waves that typicallyroil Chesapeake Bay and its tributariesduring that time.

Maa suspects that his study will con-firm that the Choptank breakwater meetsthe performance requirements requestedby the marina. Concerns about break-water performance, he thinks, are likelya result of the methods used in the origi-nal laboratory tests of breakwater effi-ciency.

“The original experiments with thefloating breakwater didn’t distinguishbetween wave diffraction and transmis-sion,” explains Maa. “They thus prob-ably underestimated the effectiveness ofthe device.” Results of Maa’s study willbe provided in a report to CDCI thisspring, just after the wintertime experi-ment ends.

Floating breakwaters are a relativelyrecent innovation in wave-managementtechnology. Because they float on thesurface, they are more environmentallyfriendly, and typically cheaper, thanmore traditional designs that require thecostly and oftentimes destructive em-placement of stonework on the seafloor.

Floating breakwaters function bestin protected coastal areas where waveheights are generally low and the dis-tance between wave crests is short. Shore-lines exposed to massive, long-periodswells still require the use of solid break-waters that sit on the seafloor.

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ral sediment supply was depleted by“hardening” of the shoreline upstreamdue to emplacement of riprap and bulk-heads.

“By the 1970s and 80s, theYorktown beach was easily overwashedduring storms, and continued to erode,”says Hardaway.

VIMS scientists entered the picturein 1985 after a particularly damagingnor’easter, when they were asked to be-

come technical advisors toYork County ’s PublicBeach board. Hardawayand colleagues havepartnered with the Countyever since, helping to de-sign and monitor all fourphases of Yorktown’s cur-rent system, which now fea-tures 12 separatebreakwaters that rangefrom 80-150 feet long.

VIMS has also ad-vised on nourishing andstabilizing the Yorktownbeach. A common miscon-ception, explains Hard-away, is that breakwaterstrap sand to form the adja-cent beaches. Instead, hesays, the beaches are cre-ated by sand brought infrom upland sources. InYorktown, some of thebeach sands were obtainedduring dredging forColeman Bridge wideningin 1996.

Once created, thebeaches are stabilized byplanting cord grasses in the

sandy ridge, or tombolo, that connectsthe breakwater to the shore.

Breakwater systems at Yorktown andelsewhere around the Bay weathered asevere test when Hurricane Isabel blewashore in 2003. At Yorktown, Isabel pro-duced a 7-foot storm tide topped by 6-foot waves. During the height of thestorm, waves of 4 feet or higher werebreaking across Yorktown’s breakwatersystem and into the adjacent walkway,road, and buildings.

Although Yorktown’s waterfrontsuffered considerable damage fromIsabel, Hardaway notes that the break-waters did provide an important service,by preventing even worse damage.

“The breakwater system significantlyreduced wave action, which likely en-sured the structural integrity of the build-ings on Water Street,” says Hardaway.“The system experienced sand losses andlocal scour but maintained its overallintegrity and performed above expecta-tions. It was designed for a 50-year eventand sustained what many consider a 100-year event in this part of the Bay.”

Hardaway notes that trade-offs be-tween protection and cost are an inte-gral part of any breakwater design. “TheYorktown breakwater system minimizedIsabel’s damage, hastened post-storm re-covery, and provides the benefits of beachand dune habitat. Higher breakwatersand more sand would give more protec-tion, but at what cost?”

Local officials will continue tograpple with that question during the

On December 2nd of last year, In-formation Technology and NetworkingServices Assistant Director Gary Ander-son ran a length of fiber optic cable intothe Customer Service Center at VIMS,thus completing a multi-year project toreplace the campus’ original copper net-work cabling.

The new fiber-optic cabling makespossible high-bandwidth connectionsamong all VIMS buildings, labs, offices,and classrooms. VIMS’ Internet band-width is now 700 times larger than itwas in 1997.

However, the biggest immediate ben-efit of the new network is that fiber opticcable does not conduct electricity. Light-ning will thus no longer damage theVIMS data network and connectedequipment and computers via their net-work connection.

“In addition to providing higherconnection speeds, the network will bemuch more reliable and be much easier

for the ITNS staff to maintain,” saysITNS Director Newt Munson.

The new fiber-optic network willallow VIMS to implement new technolo-

VIMS Sees the Light

In addition to breakwaters, theShoreline Studies group at VIMScan choose from several other alter-natives when advising localities onshoreline protection.

Bulkheads are vertical woodenstructures parallel to shore that reflectthe energy of breaking waves. Theycommonly promote scour on the sea-ward side.

Revetments are inclined pilesof stone riprap that protect the baseof eroding banks. The slope of a re-vetment minimizes wave reflectionand seaward scour.

Groins are built perpendicularto the shore to trap sand for beaches.In areas with insufficient sand sup-ply, they can starve existing beaches“downdrift.”

Sills are elongate, wedge-shapedpiles of rock built near-shore to helpestablish a marsh fringe or “livingshoreline.”

During the last few decades, therehas been a move from traditional“hardened” structures like bulkheadsand revetments toward breakwatersand sills, as shoreline managers pro-mote the benefits of a living shore-line.

Breakwaterscontinued from page 3

gies, such as VoIP, or Voice over InternetProtocol, which brings the power of theweb to telephone systems. The additionalbandwidth will also facilitate more wide-spread use of video conferencing and col-laboration technology.

The next step in VIMS’ ongoing ef-forts to increase Internet access is pursuitof a high-speed connection to Williamand Mary, which will increase externalconnection speed by a factor of 20.

“This will provide access to the Na-tional LambaRail network, which willbetter serve the VIMS community, espe-cially our research faculty and students,”says Munson.

VIMS Dean and Director John Wellsadds that “VIMS now sees the ‘light atthe end of the fiber,’ which is the founda-tion for the future information technologythat we need to remain a world-class re-search, education, and advisory serviceorganization.”

VIMS Information Technology and Networking Services Director Newt Munson(L) and Asst. Director Gary Anderson (C) join Dean and Director John Wells (R)in ceremoniously connecting the final link in VIMS’ new fiber optic network.

An aerial view of the Yorktown waterfront shows thebreakwaters that protect the new Riverwalk develop-ment.

coming years, as many hurricane expertspredict that the current period of en-hanced hurricane activity in the Atlan-tic will continue for a decade or more.