Vol. 9, No. 12 December 1999 INSIDE Section Meetings • Northeastern, p. 14 GSA TODAY • Southeastern, p. 18 A Publication of the Geological Society of America • South-Central, p. 22

Hurricanes Dennis and Floyd: Coastal Effects and Policy Implications

Robert S. Young, Department of Geosciences and Natural Resources Management, Western Carolina University, Culhowee, NC 28723, [email protected] David M. Bush, Department of Geology, State University of West , Carrollton, GA 30118, [email protected] Andrew S. Coburn, acoburn@alumni. duke.edu, Orrin H. Pilkey, opilkey@geo. duke.edu, Program for the Study of Developed Shorelines, Division of Earth and Ocean Sciences, Nicholas School of the Environment, Duke University, Durham, NC 27708 William J. Cleary, Center for Marine Science Research, UNC—Wilmington, 601 South College Road, Wilmington, NC 28403-3297, [email protected]

ABSTRACT Tropical systems Dennis and Floyd impacted eastern in Figure 1. Erosion on Oak Island, North Carolina by in 1999. Pilings on the house and 1999, the fourth and fifth storms in exposed, broken septic tanks lining the beach indicate that the beach profile was lowered approximately three years to make landfall in this area. 1 m during the storm. Septic tanks are emplaced with drain fields above the water table, which limits All five storms were very similar in their location in nearshore environments. As an example of the range of impacts of human development in the coastal zone, before Floyd the recreational beach was situated directly above these septic systems. strength (wind speed); however, the effects on the coast were quite different. In addition to absolute storm strength, morphological changes to the natural INTRODUCTION meteorologists and the popular media environment were controlled by the for- described the first of these (Bertha) as a The probability that a hurricane will ward speed of the storms, orientation of 50-year storm—a storm that would be make landfall at any given point along the the shoreline relative to storm track, expected to recur once every 50 years. All coast in any one year is low, and the even underlying geology, impacts of recent five storms in this three-year period were lower probability of a great hurricane storms, and associated rainfall. Damage of comparable strength and had varying (category 3, 4, or 5) makes such an event to buildings was a function of the place- coastal impact. Obviously, our concept of seem extremely unlikely. But low probabil- ment of structures with respect to the a 50-year storm may need some adjust- ities give a false sense of security, because shoreline and the removal of weaker ment. It is also clear that despite recent the lesson of hurricane history tells us that buildings by previous storms. On the improvements in hurricane forecast mod- in the lifetime of a building such a storm basis of these observations, we recom- els, long-term forecasting is still difficult if is almost a certainty. Furthermore, the mend a new Hurricane Impact Scale, not impossible, as demonstrated by both occurrence of a hurricane one year does which will allow prediction of possible 1999 storms. We describe here the geologi- not reduce the likelihood that a similar storm impacts and comparisons of cal impact of these two storms in North storm will strike again the next year. coastal impacts in other hurricanes. Carolina, and we discuss our views on the The coast of North Carolina was Each additional hurricane demon- coastal zone management lessons to be struck by two hurricanes in 1996 (Bertha strates that our society does not have a learned and the need for a new scale to and Fran). It happened again in 1999. forward-looking plan for dealing with communicate predicted and observed Hurricane Dennis impacted the coast for coastal storms. Instead, we typically coastal storm impacts. several days, from August 30 to September repair and rebuild in place, and con- 4. Hurricane Floyd made landfall on tinue the upward spiral of property HURRICANE DENNIS September 16, causing record flooding damage in storms. Although the dollar across most of eastern North Carolina and Dennis tracked up the U.S. East Coast amount of property damage will be low damage to shoreline structures in some as a category 3 hurricane on the Saffir- from these storms, the public must bear places (Fig 1). These were the fourth and Simpson scale of hurricane intensity, the cost of cleanup and repair of infras- fifth storms to strike the North Carolina stalling off the of North tructure. coast in the past three years (Fig. 2). Local Hurricanes continued on p. 2 IN THIS ISSUE GSA TODAY December Vol. 9, No. 12 1999 Hurricanes Dennis and Floyd: Toward a Stewardship of the Global Coastal Effects and Policy Commons ...... 25 GSA TODAY (ISSN 1052-5173) is published monthly by The Geological Society of America, Inc., with offices at 3300 Implications ...... 1 Penrose Place, Boulder, Colorado. Mailing address: P.O. Box Call for Applications and Nominations 9140, Boulder, CO 80301-9140, U.S.A. Periodicals postage Dialogue ...... 3 for GSA Bulletin Editor ...... 26 paid at Boulder, Colorado, and at additional mailing offices. Postmaster: Send address changes to GSA Today, Member- Washington Report—Trouble at State . . . 8 2000 GSA Section Meetings ...... 26 ship Services, P.O. 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Written permission is required from GSA for all other forms of capture, reproduction, and/or distribution of any item in this publication by any means, including posting on authors’ or organizational Web sites, except that permis- sion is granted to authors to post the abstracts only of their science articles on their own or their organization’s Web site providing the posting includes this reference: “The full paper was published in the Geological Society of America’s news- Hurricanes continued from p. 1 island. Barrier island migration is a com- magazine, GSA Today [include year, month, and page num- plex process primarily driven incremen- ber if known, where article appears or will appear].” GSA provides this and other forums for the presentation of Carolina on Monday, August 30. The tally by storms during times of rising sea diverse opinions and positions by scientists worldwide, storm then reversed course, remaining off level (Leatherman et al., 1982; Nummedal, regardless of their race, citizenship, gender, religion, or polit- ical viewpoint. Opinions presented in this publication do not North Carolina until it made landfall 1983; Leatherman, 1983a, 1983b). Pilkey reflect official positions of the Society. across Core Banks on Saturday, September et al. (1998, p. 44–47) described barrier 4 (Fig. 2). By that time Dennis had weak- island migration with North Carolina SUBSCRIPTIONS for 1999 calendar year: Society Members: GSA Today is provided as part of membership ened to a tropical storm (sustained winds examples as a three-step process. Barrier dues. Contact Membership Services at (800) 472-1988, less than 119 km/h). islands migrate landward by: (1) shoreline (303) 447-2020 or [email protected] for member- Hurricanes usually move ashore retreat on the open ocean side, (2) eleva- ship information. Nonmembers & Institutions: Free with paid subscription to both GSA Bulletin and Geology, quickly, minimizing the time available to tion of the island by the addition of over- otherwise $50 for U.S., , and Mexico; $60 else- erode beaches, but Dennis stayed offshore wash sand, and (3) movement of the where. Contact Subscription Services. Single copies may be requested from Publication Sales. Also available on an for several days, producing large waves island’s soundside shoreline landward by annual CD-ROM, (together with GSA Bulletin, Geology, GSA much like a stalled winter storm or extension of the overwash fans into the Data Repository, and an Electronic Retrospective Index to nor’easter. In this century, the storm that sound. All of these processes were evident journal articles from 1972); $89 to GSA Members, others call GSA Subscription Services for prices and details. Claims: caused the most damage on the Outer on Core Banks following Hurricane Den- For nonreceipt or for damaged copies, members contact Banks was the Ash Wednesday storm of nis. In this fashion, Core Banks took Membership Services; all others contact Subscription Ser- 1962, a nor’easter that remained station- another small step landward and up the vices. Claims are honored for one year; please allow suffi- cient delivery time for overseas copies, up to six months. ary for three days at the time of spring coastal plain during the current sea-level tides. Tidal amplitude on the Outer Banks rise. STAFF: Prepared from contributions from the GSA staff and membership. is small (less than 1 m) but large enough Along (Fig. 2), within Chief Executive Officer: Sara S. Foland to cause increased dune erosion and the National Seashore, sev- Science Editors: Suzanne M. Kay, Department of inland penetration by overwash when eral small communities are connected by a Geological Sciences, Cornell University, Ithaca, NY 14853; Molly F. Miller, Department of Geology, Box 117-B, Vanderbilt storms arrive at high tide. Waves from lone road, the two-lane, blacktop NC Hwy University, Nashville, TN 37235 Dennis impacted the shoreline of the 12. Overwash sand covered the road in Forum Editor: Bruce F. Molnia, U.S. Geological Survey, North Carolina Outer Banks through at many places and was quickly cleared by MS 917, National Center, Reston, VA 22092 Director of Publications: Peggy S. Lehr least a dozen high tides, a major factor in highway crews following the storm; most Managing Editor: Faith Rogers island response to the storm. Even though of it was moved to the nearby beach. A Production Manager: Jon Olsen Production Coordinator: Gaynor Bloom damage to structures along the shoreline <0.5 km section of the road north of Bux- Graphics Production: Gaynor Bloom was not extensive, the long duration of ton that was entirely destroyed during the Dennis may have caused as much coastal hurricane was rebuilt within three days. ADVERTISING: Classifieds and display: contact Ann Crawford, (303) 447-2020; fax 303-447-1133; acrawford@ erosion and shoreline retreat as a category We are trying to convince the North Car- geosociety.org. 4 or higher hurricane. olina Department of Transportation to Issues of this publication are available as electronic Acrobat On narrow and undeveloped Core leave the overwash sand in place and files for free download from GSA’s Web Site, http://www. Banks (Fig. 2), part of the Cape Lookout rebuild the road, perhaps with gravel. This geosociety.org. They can be viewed and printed on various personal computer operating systems: MSDOS, MSWin- National Seashore, large numbers of nar- would allow the island in the National dows, Macintosh, and Unix, using the appropriate Acrobat row overwash fans were produced as storm Seashore to function naturally, and the reader. Readers are available, free, from Adobe Corporation: surge flooded parts of the island and storm road elevated by the addition of overwash http://www.adobe.com/acrobat/readstep.html. waves rolled ashore and across the island would be subjected to less frequent storm GSA ONLINE: www.geosociety.org through dune gaps and eroded dunes. In flooding, reducing damage in future This publication is included on GSA’s annual this way, sand was actively deposited on storms and saving taxpayer dollars. CD-ROM, GSA Journals on Compact Disc. 50% Total Call GSA Publication Sales for details. Recoverd Fiber the island (Fig. 3). A few of the overwash In the 1930s, as part of a Civilian Printed in U.S.A. using pure soy inks. 10% Postconsumer fans extended into the sound behind the Conservation Corps project during the

2 GSA TODAY, December 1999 Dialogue Sara Foland, CEO

The Year Past To tend, unfailingly, unflinchingly, towards and the Year Ahead a goal is the secret of success. —Anna Pavlova We are completing an exciting year at GSA and looking forward to a new year, a new century, and a new millennium. Here, I review what GSA has accomplished A new budgeting process and tell you about some of my goals for the next 12 months and the was reviewed with the Invest- © Paul Abdoo next several years. ment and Budget committees At Dinosaur Ridge near Morrison, Colorado. In July, the headquarters staff completed a significant reorgani- at the 1999 GSA Annual Meet- zation, to align our human and fiscal resources with the annual goals ing and will be used in the preparation of our fiscal year 2000 bud- that were defined from the five-year strategic plan. In the next sev- get. This new model balances growth of our investment portfolio eral issues of GSA Today, we will discuss the strategic plan with you in with prudent spending. Growth of the portfolio will be ensured first, greater detail and highlight progress and new directions. The four to protect the long-term future of GSA. To provide program review new functional areas at GSA headquarters are Science, Education, and prioritization, a new committee, the Programmatic Overview and Outreach—focused on education and public policy; GSA Enter- Committee (POC), was formed. At the committee’s first meeting, prises—our revenue-generating activities; Member Services—the the GSA staff reviewed the 166 current programs. This review interface and service center for members; and Infrastructure Services allowed our leadership to look at GSA as a whole, not just piece by and Support—for all our in-house needs in Boulder. piece. The overall success of the first program review led to the POC With the reorganization of our Science, Education, and Out- becoming a standing committee, which will meet annually at the reach group, we envision a new direction in education. We are spring Council meeting. expanding our focus to include K–12, undergraduate, and graduate To accomplish the array of objectives in our strategic plan, GSA levels. A new Education Science Officer position has been approved, must pursue strategic partnerships. These joint ventures will enlarge and a national search committee is being formed. Robert Ridky, GSA’s sphere of influence and help us to reach our goals in more University of , will chair this committee. timely and cost-effective ways. Currently, we are investigating joint All programs and services that directly support members are ventures for global meetings, online publications and digital archive located within Member Services. A new Member Service Center will creation, integrative science, and student programs. Strategic provide real-time service for all our members and our customers. On alliances have been formed with the USGS, National Park Service, January 3, 2000, you can reach this team at our new toll-free num- National Forest Service, AGI, and the Geological Society (London). ber, 1-888-443-4472, to buy a book, change your address, register All 23 of our associated societies are reviewing new partnership for a section or annual meeting or get a question answered. To opportunities for 2000 and beyond. gather more information about members, we initiated a comprehen- In the next year, I look forward to shifting my perspective from sive general membership survey in November 1999. A sample set of internal operations to external partnerships. Adopting a more exter- 3,300 was selected from our total membership of 16,000. nal view will allow me to work on strengthening our existing partner- At this year’s annual meeting we received 85% of the 2,942 ships and exploring new ones—aiding in the expansion of GSA’s abstracts electronically; this is the highest electronic submission rate sphere of influence. I am excited about the future and very pleased and the largest number of abstracts ever for GSA. We had 6,389 with the progress to date. To get a chance to chat with you in 2000, registrants at our meeting in Denver, making it one of the three I will attend all the section meetings in the spring. Roundtable dis- largest GSA annual meetings. Planning is now underway for the first cussions will be scheduled to discuss GSA and gather your insights GSA global meeting, scheduled for June of 2001. This joint venture and hopes for the future, and to learn how GSA can help you attain with the Geological Society in London will be held in Edinburgh, your goals. Scotland. Meetings are one part of GSA Enterprises; publications are the other part. In 2000, a feasibility study on electronic publishing Enjoy the New Year! options will begin.

Hurricanes continued from p. 2 prone to flooding because the interior of An aerial flyover of the impacted area the island is at a lower elevation than the after the storm indicated that the amount depression, a large frontal dune line for oceanfront and because the primary of dune and beach erosion varied consid- erosion control was constructed from the dunes, which would have afforded some erably along various shoreline reaches. We North Carolina– line to the west- measure of protection from believe that the differences in shoreline ern end of Ocracoke Island (Stick, 1958, and waves, have been eroded. The sea- impact may have been strongly controlled p. 250). The presence of the dune encour- ward-facing part of the island communi- by offshore geology; in particular, Kinna- aged beachfront development in areas pre- ties is a landward-sloping surface of coa- keet and Wimble shoals partially protected viously routinely overwashed during lesced overwash deposits. Storm surge and the towns of Avon and Salvo, respectively. storms. Now the artificial dune line has waves easily overtop the overwash and Geologic framework and barrier island large gaps due to shoreline retreat, and flood the island interior. Thus, for the fifth dynamics are discussed by Riggs et al. hundreds of buildings are exposed to time since 1990, the seaward-most, three- (1995). Overall, only a small number of storm processes, especially north of Ore- block area of the towns was flooded by buildings were destroyed by Dennis, gon Inlet in the old towns of Nags Head, ocean water trapped behind the higher because the winds were sub-hurricane Kitty Hawk, and Kill Devil Hills (Fig. 2). In elevation beachfront. Because the old strength and storm surge was probably these communities, Dennis covered the dune cannot be replaced without removal only about 0.5–1 m. Sand was eroded from roads with sand and debris and eroded of the first row of houses, a politically dif- beneath many buildings, and some, partic- beneath numerous houses elevated on pil- ficult thing to do, these communities face ings. These communities are particularly more flooding from future storms. Hurricanes continued on p. 4

GSA TODAY, December 1999 3 VA NC

North Carolina

Kitty Hawk of Cape Lookout as a strong category 2 Kill Devil Hills Nags Head storm with maximum winds around 150 km/h. The hurricane dumped more N Oregon Inlet than 50 cm of rain on parts of eastern Greenville d Rodanthe North Carolina where the ground was 0 25 Waves Salvo miles already saturated from the passing of 0 25 kilometers N atteras Islan Hurricane Dennis. Floyd followed a clas- H Avon Buxton Frisco sic path, curving up the U.S. East Coast, Pamlico Sound Cape Hatteras New Bern Ocracoke I. leading to the largest evacuation in U.S. history, more than 2 million people in s k cean n a Beaufort B , Georgia, , and Morehead City e r tlantic O o A North Carolina. Track forecast models C fared much better than in Dennis, but Cape Lookout nd la model uncertainty allowed for possible il Is Onslow sa Bay op landfall in Florida, Georgia, and South

Wilmington T Dennis 1999

C

R ape Fear iver Carolina before the storm went ashore near Cape Fear, North Carolina (Fig. 2). Long Beach The beachfront damage, the pri- Oak Island mary focus of this paper, has received Cape Fear Bonnie 1998 relatively little attention in the North Carolina and national media because the most damaging aspect of Floyd was

Bertha 1996 Fran 1996 Floyd 1999 riverine flooding in eastern North Car- olina and . Flood levels in several North Carolina counties exceeded the 100-year recurrence inter- Figure 2. Eastern North Carolina and tracks of the five hurricanes affecting the North Carolina coast val level and were the highest ever from 1996 to 1999. Notice the similarity in landfall locations, especially of Fran, Bertha, and Floyd, and recorded. Two interstate highways (I-40 the erratic path of Dennis. The Outer Banks of North Carolina stretch over 280 km from the Virginia line and I-95) were blocked for several days to below Cape Lookout. and two universities (University of North Carolina at Wilmington and East Carolina University in Greenville) were closed Hurricanes continued from p. 3 energy here due to a narrow continental because of power loss, emptying students shelf (Hayes and Sexton, 1989). In addi- from dorms into communities cut off in ularly in Rodanthe, were left stranded sea- tion, high storm frequency and ongoing all directions by river waters. This type of ward of the high-tide line. sea-level rise will mean that maintenance storm presented major difficulties for Immediately after the storm, North of the shorefront in its current location those who evacuated from the Outer Carolina Governor Jim Hunt declared that will prove ultimately impossible. Banks, which turned out to be largely federal funds for a beach nourishment One building, the six-story Comfort unaffected by Floyd. One person left Ocra- project, long in the planning stage, were Inn at Whalebone Junction in Nags Head coke Island (Fig. 2) only to require rescue needed immediately. The project as (Fig. 2), now resides on the beach, having off an inland roof top by helicopter. planned is a small one, however, and lost its swimming pool. This is an old On the coastline, Long Beach, North probably would not have prevented flood- structure, probably the first high rise built Carolina, on Oak Island (Fig. 2), was hit ing and other damage. The speaker of the on the Outer Banks. The hotel was origi- the hardest. This old community has a his- North Carolina State Senate, in whose nally built well back from the beach. tory of disruption by hurricanes. It was district most of the hurricane damage Shoreline retreat of about 1 m/yr has thriving prior to 1954, when 300 out of occurred, stated that the shoreline was in caught up with the hotel. Because seawall 305 buildings, properly built well back the “worst erosive shape possible” prior to construction is illegal in North Carolina, from the beach, were destroyed or moved the storm, and that beach and road-build- a politically difficult situation faces the off their foundations by category 4 Hurri- ing money was needed immediately. His state’s coastal managers. We believe that cane Hazel. The buildings were rebuilt, view is undoubtedly shaped by the fact this building represents a landmark in the and the shoreline, in its inexorable, 0.5–1 that more buildings than ever were state’s efforts to preserve beaches for future m/yr landward creep, caught up with the exposed to the storm, the inevitable con- generations. If a variance in the regulation buildings. During Hurricane Floyd, about sequence of decades of shoreline retreat is granted, North Carolina’s anti-shoreline 240 beachfront homes (more than half of occurring simultaneously with intensive armoring regulation is doomed, as is the the oceanfront homes in the community) beachfront construction of cottages and future quality of recreational beaches. were destroyed or made uninhabitable, motels. The Outer Banks are perhaps the largely due to wave action on top of a most naturally dynamic developed barrier HURRICANE FLOYD 1.5–2.5 m storm surge. Before the storm, it island chain in North America, but as is Hurricane Floyd was a much larger was clear that the extensive damage was true everywhere, politicians respond with and more powerful storm than Hurricane entirely predictable, because this was a crisis-driven maintenance of the status Dennis, although it was not as strong and highly vulnerable community (Pilkey et quo, thereby treating beachfront develop- was smaller than Hurricane Hugo, which al., 1998). A large vertical scarp was ment in similar fashion to inland develop- struck the South Carolina Coast in 1989. formed in many places at the back of the ment at higher elevations. Our view is that After causing serious wind damage in the beach on Long Beach. The scarp cuts into due to a lack of planning for sensible post- northern Bahamas, the storm threatened old wetland sediments imbedded with tree storm action, an opportunity is missed to the east coast of Florida with maximum stumps—another clue that this barrier relocate buildings and roads back to safer sustained winds of 249 km/h (category 5 is island was sand-poor and vulnerable locations following storms such as Dennis. >249 km/h). As it tracked to the north, it before the storm. Previous work has The Outer Banks are a high-hazard setting gradually lost wind velocity, coming shown that the age of tree stumps exposed for development. There is high wave ashore in southern North Carolina, south on the beach varies along Oak Island,

4 GSA TODAY, December 1999 ranging from about 3.8 to 1.8 ka (Griffin sand. The island infrastructure, roads, better job of conveying to the public the et al., 1979; unpublished data of Cleary). power and phone lines, and septic and coastal geomorphological effects of these This is further evidence of the island’s sewer systems were largely destroyed after storms. The public hears about the Saffir- erosive history even before the storm. having been replaced by federal funding Simpson hurricane scale and has a good On heavily developed, low-elevation, after Fran in 1996. In spite of the lack of idea of the relative strength of storms. narrow Topsail Island (Fig. 2), most of loss of private property, the federal recov- Saffir-Simpson is a scale of categories 1 which was extensively damaged by Hurri- ery costs to replace infrastructure on this (120–152 km/h) to 5 (>249 km/h), and canes Bertha and Fran (occurring within island will be large. At least two and possi- was originally developed as a hurricane eight weeks of each other in 1996) build- bly three of the temporary inlets opened damage potential scale (Simpson, 1974). ing damage was much less than on Long by Fran were reopened in Floyd. Some Although the scale is satisfactory for Beach. Local officials attributed this to the houses built after Fran in the throats of describing the absolute strength of a hurri- fact that the poorly constructed buildings the former inlets were washed under but cane in the open ocean, it is less satisfac- had been removed by the earlier storms. survived. Strong evidence was noted of tory in describing the effect of a hurricane In addition, the storm surge from Floyd erosion caused by channelization of on the shore during landfall. Geologists was 0.3–0.8 m less than during Fran. storm-surge ebb (the seaward return of the understand that the actual impacts of any Instead of a dune scarp, the northern part storm surge as the storm moved away; Fig. given hurricane on the coast will vary of the island had the appearance of a large 4). Along much of Topsail Island, the only depending on several geologic and meteo- smooth sandbar, because almost the entire frontal dune was an artificial one, con- rologic factors including, but not limited island was covered by a sheet of overwash structed largely from sand bulldozed from to: (1) the absolute strength of the hurri- the beach. Much of cane (wind speed), (2) the size of the the dune disap- storm (radius of maximum winds), (3) for- peared in Floyd (Fig. ward speed of the storm center (faster 5), making up a equals higher storm surge), (4) track of the large part of the storm relative to orientation of the shore- overwashed sand on line (perpendicular approach means the island. At the higher storm surge, low-angle approach northern end of the means greater area affected), (5) storm island, the dune has duration (relatively short in most hurri- been replaced at canes), (6) offshore and onshore profiles least five times in (major control on storm surge), (7) plan- the 1990s. view shape of the shoreline (major control on storm surge), (8) underlying island NEED FOR geology including sand supply (can con- A NEW trol shoreline erosion and overwash, see HURRICANE Riggs et al., 1995; Cleary, 1997), and (9) IMPACT SCALE recent storm history (one storm removing the protective dunes, setting up the shore- After Dennis line for greater damage to structures in a and Floyd, as well subsequent storm). Because the Saffir- Figure 3. Core Banks, North Carolina, was almost completely overwashed by as several previous Hurricane Dennis as the storm stalled offshore for several days. With each Simpson scale does not consider these hurricanes that high tide, storm-surge flooding and storm waves washed sand onto and, in local and regional controls on coastal have affected North some cases, completely over the island. Storms drive barrier island migration response to hurricanes, we believe that a during rising sea level. Overwash deposits are a primary way in which island Carolina over the new scale emphasizing hurricane impact is elevation is built up and the soundside shoreline is incrementally moved land- past several years, it needed. ward. is clear that coastal geologists must do a Hurricanes continued on p. 6

Figure 4. When storm surge water flows back to sea, either by the force of gravity alone or when driven by offshore-blowing winds, an erosive ebb cur- rent may be generated with a potential for intense scouring of unconsoli- dated material. Often, structures in the path of such scouring are under- Figure 5. Immediately after Hurricane Fran in 1996, an artificial dune was mined and may topple. In this example from Topsail Island, storm-surge ebb built along the shoreline of North Topsail Beach (the northeastern one-third scouring has eroded a channel at least three feet deep. The house in the cen- of Topsail Island) for protection of the only access road. The dune was almost ter of the photo survived because the scour channel divided and flowed on entirely removed by Hurricane Floyd in 1999, and the sand was redistributed either side of it. as washover deposits on the island.

GSA TODAY, December 1999 5 Hurricanes continued from p. 5 storm investigations will provide a single allowed detailed comparisons over a rela- HIS for a given storm, and allow easy com- tively short time frame in a relatively com- We are developing a Hurricane parisons to other storms. pact geographic area. The need for a new Impact Scale (HIS) that could be used pre- Hurricane Impact Scale grew out of these storm to warn residents of coastal commu- CONCLUSIONS comparisons. A better understanding and nities of potential coastal impacts and ability to predict storm-process interaction post-storm to compare events. The criteria Tropical systems Dennis and Floyd with development, and a greater ability to to be considered for the new HIS are: (1) will not go down in history as significant communicate these predictions to the maximum elevation of the storm surge coastal events. Dennis will be remembered public, will aid in coastal management (the elevated water level associated with for its erratic path, and Floyd will be decisions on zoning and land-use plan- the passage of a hurricane), (2) storm surge remembered for its record-setting and dev- ning. As coastal population continues to spread (how large an area has been astating inland flooding. More significant swell, coastal geologists must take a more impacted by higher water level), and (3) is the opportunity to compare effects of active role in coastal management. Imme- wind speed. these two and three other storms (Bertha diate post-storm observations such as The HIS will reflect the understanding and Fran, 1996; Bonnie, 1998) of similar those presented here will remain an that all storms of the same Saffir-Simpson strengths impacting essentially the same important tool. category do not have the same coastal area in just three years. effects. Even identical storms striking the Hurricanes and other coastal storms ACKNOWLEDGMENTS same shoreline reach may have differing play an integral role in barrier island impacts. For example, storm surge from migration during times of rising sea level. We thank the Public Entity Risk Insti- Hurricane Floyd was predicted and In the larger sense, hurricane-driven tute and the Federal Emergency Manage- reported to be 4.6 m on Long Beach but oceanside erosion and deposition of over- ment Agency for support that allowed us was in actuality between 1.5 and 2.5 m. wash sand on barrier islands and com- to perform immediate post-storm investi- The 4.6 m estimate was based on the pletely over them are important steps in gation of these and several other recent Saffir-Simpson scale for a standard cate- the barrier island migration process and storms. Joe Kelley, Jennifer Tinch, and two gory 4 hurricane approaching perpendicu- were well illustrated by these storms. How- anonymous reviewers made helpful com- lar to the shore across a continental shelf ever, the smaller-scale ocean-shoreline ments on the manuscript. Amber Taylor of known width and shape. Hurricane morphological changes, and especially the drafted Figure 2. Floyd, however, came ashore at Cape Fear, interaction between storm processes and at which point the most deadly northeast human development, varied greatly in REFERENCES CITED quadrant was out at sea and the continen- each of the five storms. This complex Cleary, William J., 1997, Hurricane Fran; Coastwise tal shelf region used to generate storm interaction is dependent on many geo- impacts and recovery in southeastern North surge was different than that of the predic- morphic and geologic factors in addition Carolina: Geological Society of America Abstracts tive model. Because of the uncertainty to the meteorological factors of storm with Programs, v. 29, p. 37. inherent in hurricane track forecast mod- strength, size, and forward speed. Ongoing Griffin, W. T., Cleary, W. J., and Hosier, P. E., 1979, els, it is impossible to predict exactly studies are assessing which factors are the Late Holocene evolution of Oak Island, North Carolina: Geological Society of America Abstracts where a hurricane will make landfall, and more important. with Programs, v. 11, no. 4, p. 180. thus it is impossible to predict exactly There are two important coastal pol- Hayes, M. O., and Sexton, W. J., 1989, Modern what the coastal impacts will be. The Hur- icy lessons to be learned from these recent clastic depositional environments, South Carolina: ricane Impact Scale will provide a larger storms. First, we do not have a forward- Washington, D.C., American Geophysical Union, range of categories than the Saffir-Simp- looking plan for dealing with coastal International Geological Congress, 29th, Fieldtrip son scale, and we envision using the two storms. The typical response is cleanup guidebook T371, 85 p. scales in conjunction. Taking the meteoro- and complete rebuilding, maintaining the Leatherman, Stephen P., 1983a, Barrier dynamics and landward migration with Holocene sea-level logical characteristics of the storm and status quo. Coastal planning must incor- rise: Nature, v. 301, p. 415–417. using the criteria above, we will predict, porate storms as part of the plans. We Leatherman, Stephen P., 1983b, Barrier island for example, that a given storm will have must learn from nature and not rebuild evolution in response to sea level rise: A discussion: an HIS category of 9 if it stayed on one damaged structures and infrastructure in Journal of Sedimentary Petrology, v. 53, p. track but 13 if it veered to another track. place, nor with the same design. Little 1026–1031. Thus, we will predict a range of HIS cate- planning effort goes into learning how to Leatherman, Stephen P., Rice, Thomas E., and gories for a single storm, depending on best rebuild after a storm. Witness the arti- Goldsmith, Victor, 1982, Virginia barrier island the forecast range of landfall tracks. Post- ficial dune line on northern Topsail Island configuration: A reappraisal: Science, v. 215, p. 285–287. or NC Hwy 12 near Buxton which are damaged and rebuilt over and over again. Nummedal, Dag, 1983, Barrier islands, in Komar, Paul D., and Moore, J. Robert, eds., CRC handbook ELECTRONIC The second policy lesson is that even of coastal processes and erosion: Boca Raton, NEW! though none of these storms had a high Florida, CRC Press, p. 77–121. SUBMISSION dollar amount of property damage at the Pilkey, Orrin H., Neal, William J., Riggs, Stanley R., shoreline, and will thus be considered Webb, Craig A., Bush, David M., Pilkey, Deborah F., OF ABSTRACTS largely as non-events, the public still must Bullock, Jane, and Cowan, Brian A., 1998, North pay to repair infrastructure. Even if not a Carolina and its barrier islands: Restless ribbons of You may now submit your abstracts sand: Durham, North Carolina, Duke University to section meetings electronically. single house was lost on Topsail Island, for Press, 318 p. example, the cost to remove all the sand This is fast, easy, and by far the best Riggs, Stanley R., Cleary, William J., and Snyder, way to submit. Visit the GSA Web from the roads, rebuild the roads, repair Stephen W., 1995, Influence of inherited geologic site at www.geosociety.org to find the electrical supply system, and rebuild framework on barrier shoreface morphology and the form. the frontal dune will be great. Insured dynamics: Marine Geology, v. 126, p. 213–234. costs to homeowners is the damage Simpson, R. H., 1974, The hurricane disaster Alternatively, you can download amount typically reported, but the cost of potential scale: Weatherwise, v. 27, p. 169, 186. a PDF version of the paper abstract repairing infrastructure is not an insured Stick, David, 1958, The Outer Banks of North form, or contact one of the cost, and it is borne by the public. Carolina, 1584–1995: Chapel Hill, University of technical chairs if you need paper The legacy of Bertha, Fran, Bonnie, North Carolina Press, 352 p. abstract forms sent to you. Dennis, and Floyd may well be that they Manuscript received October 5, 1999; accepted October 15, 1999.

6 GSA TODAY, December 1999