*At the beginning of the 1995 hurricane season, an Associated Press news article noted that two major hurricanes striking USA populated areas (e.g., Atlantic and/or Gulf coasts; California) in a single year could cause $50 to $80 billion in insured losses. Adding in a moderate earthquake could bankrupt the American insurance industry. A series of big storms in successive years could have the same effect. Such multiple events have occurred over the short term in spite of probability statistics to the contrary (e.g., multiple hurricanes in the Carolinas during the 1950's; Hurricanes Camille and Frederic in an 11 year interval; the floods along the Missouri and Mississippi Rivers in 1993 and 1995).
*The probabilities of natural hazards and economics do not mix. As noted in Chapter 1, the growth in population and capital investment in the coastal zone has passed a critical point in terms of risks from natural hazards and probable future property damage and loss. Hurricanes Hugo and Andrew clearly demonstrated the magnitude of the problem, and illustrate the necessity for all communities to establish programs to reduce future property losses.
*The several representations of our fictional island named "Pandora's Island" are used as a recurring theme throughout the book (fig. 10.1). It would be well for property owners and planners to review them (figs. 10.1 and 10.2). It is seen first in its natural state, and then as development comes to the island (Chapter 2, figs. 2.1 and 2.4). Next, a drawing of the zones likely to be affected by various storm processes on Pandora's Island and Pandora's Island after the big one (Chapter 3, figs. 3.1 and 3.2). Using our risk mapping technique, the risk zones for Pandora's Island are drawn based on elevation, vegetation and secondary factors such as land forms, inlet position, cover, sites of new inlet potential, potential ebb focus, etc. (Chapter 4, fig. 4.1). Placing development in hazard zones leads to the need for mitigation, but typically, mitigation has meant doing something structural to the front of the island (walls, groins, beach replenishment) (Chapter 5, fig. 5.1). Our mitigation recommendations consider the larger coastal-zone system and we thus present a whole-island hazard mitigation plan for Pandora's Island (Chapter 6, fig. 6.1). Finally, Pandora's Fantasy Island represents a lower-risk ideal development, preserving natural landforms and vegetation (Chapter 8, fig. 8.1).
Lessons for Coastal Management
*Post-storm observations of the impact of Hurricanes Gilbert (1988), Hugo (1989), Bob (1991), Andrew (1992), Emily (1993), and several winter storms on developed shorelines helped define several principles or "lessons learned" regarding property damage mitigation. These generalized conclusions are the basis of the rules of the sea presented earlier and related concepts that are restated here.
(1) Wide beaches protect property. The more beach available to absorb and dissipate storm wave energy, the greater the possibility for mitigating damage to structures. The greater the distance between the zone of wave action and fixed construction the better. When beaches narrow, replenishment or soft stabilization is a means of widening beaches and increasing their "storm buffer" capacity. Beach replenishment is, however, expensive and temporary. As erosion threatens, a better alternative may be to move buildings.
(2) Dunes protect property. Sand dunes are often referred to as the "barrier" in barrier island, or "nature's shock absorber." The mass of dune sand may absorb and dissipate storm-wave energy, thus protecting buildings located behind dunes. Where dunes, rather than buildings, are available to absorb the impact of waves and storm surge, post-storm beaches are markedly wider. Dunes are the sediment reservoir, banked for a stormy day, which provide sand to the beach profile as it readjusts to storm-wave energy. Dune systems reduce overwash potential. In addition, interior dunes provide elevation for homesites, reducing flood damage potential. Building placement can take advantage of larger dunes to afford wind protection. Remember that dune width (and dune-field width)is as important as dune height.
*Ideally, no dune on any portion of a barrier island should ever be removed. In most states, frontal dunes are protected, but you can have your way with interior dunes. Removal of interior dunes may lead to property loss and damage that could have been prevented if these dunes had remained intact. Killing or removing dune vegetation leads to reactivation of dunes by wind, creating blowouts and blowing sand that will be a nuisance, if not a hazard. Conserve sand resources. Add sand to island interiors, and vegetate to stabilize and trap moving sand. Don't lose a grain of sand!
(3) Vegetation protects property. Overwash penetration and storm damage is noticeably greater where maritime forest is removed for development. This protective effect was well illustrated on Pawleys Island, SC, where neighboring houses suffered vastly different degrees of damage from Hurricane Hugo depending on the degree of vegetation cover. Many houses located within the maritime forest were essentially untouched, except for some cosmetic damage. Many houses built in cleared areas were destroyed. Similar effects were noted on the coast of the Yucatán Peninsula of Mexico after Hurricane Gilbert in 1988. As much forest as possible should always be retained (a practice exemplified by Pine Knoll Shores on Bogue Banks, NC), and, where appropriate, reforestation of areas where trees were removed should be carried out. Once newly built dunes are stabilized with grassy vegetation, shrub, and forest growth could be encouraged. Stabilizing cover of dune grass, marsh grass, maritime thicket, and mangrove is important to each respective environment.
(4) Shore-perpendicular roads act as overwash and storm-surge ebb conduits. Elevating and curving roads so they approach the beach at an oblique angle will reduce the extent and amount of overwash. Obliquely angled and elevated roads also provide a more difficult return path for storm-surge ebb flow, reducing scour potential. Simply putting a hump in the road at its beach terminus may help dramatically. A more effective method is a road-blocking scheme such as outlined for Folly Beach, South Carolina. Blocking these conduits in the interior of the interior of the island may be as important as plugging dune gaps. Roadbed material should never be obtained from the beach or the dunes.
(5) Notches in dunes create overwash passes. Notches cut in dunes for beach access, views, or construction sites are naturally exploited by waves and storm surge, and by storm-surge ebb flows. Such notching can be avoided by constructing walkovers, elevating structures, and taking particular care during construction to avoid creating artificial passes. Where present, notches should be plugged, or equipped with storm barriers that can be used to close these conduits prior to storms.
(6) Overwash and storm-surge ebb is intensified when funneled by structures. As storm surge waters overwash an island and then return to the sea, driven either by gravity alone or in combination with onshore/offshore winds, existing structures may constrict the flow and reduce the cross-sectional area through which the water must pass. This tends to increase flow velocity, resulting in scour. This effect was well demonstrated by the storm-surge ebb channels observed the Grand Strand shoreline after Hurricane Hugo, and along the Yucatán coast after Hurricane Gilbert. Impermeable roads, drives, parking lots, and similar hard surfaces in constricted spaces between buildings prevent infiltration and add to the storm-surge ebb current effect.
(7) Seawalls can protect buildings, but they also can cause narrowing of the beach reducing both recreation and storm protection value. Large seawalls are effective in protecting shorefront buildings from wave attack. But seawalls, as a rule, cause degradation and even eventual loss of beaches. Loss or narrowing of beaches reduces their storm buffering role and also may damage the tourist economy. Low seawalls on the Yucatán Peninsula and in South Carolina were, without exception, overtopped by the storm surge associated with recent hurricanes. Low seawalls in particular may serve to inhibit gradual shoreline retreat, but they afford minimal storm protection for property. Given such minimal tradeoff, seawalls are a poor choice for even short-term protection of property from storm surge, associated waves, storm-surge ebb scour, and flooding. Some coastal states now restrict or prohibit seawall construction on open ocean shorelines in order to prevent the loss of recreational beaches.
(8) Setbacks protect. Choosing a beachfront building site well back from the sea is the easiest and least costly method of property damage mitigation. As erosion threatens, structures can be moved. Most coastal states have some form of building setback regulations designed to reduce storm damage potential. Setbacks work over the short term because the beach storm buffer remains wide and wave energy from major storms is typically reduced by friction on land between the beach and the normal shoreline. If a shoreline is retreating due to long-term erosion, setback requirements are a short-to-intermediate-term solution to property damage mitigation. However, federal and state programs provide incentives for relocation, either moving back on property or demolition and rebuilding in another location.
(9) Elevation protects. Elevation, whether achieved by natural land elevation, infilling of a construction site, or by building on pilings, may be the single most important site-specific factor in property damage mitigation. Combined elevations of published FEMA 100-year flood elevations plus predicted storm wave heights are incorporated into building codes for habitable first floor elevations on virtually all United States barrier islands. Building codes, however, represent minimum requirements, and property owners may want to elevate even higher. The advantage of elevation increases may be offset by the hazard of increased wind velocities in the "big one."
(10) Proper community governance offers a degree of self protection. Development where building codes are enforced, and barrier island environments and processes allowed to operate, is less susceptible to property damage than development where failed structures become agents of additional destruction. Something as simple as keeping the subfloor area of stilt houses free of obstructions allows overwash to take place without damage to the building. In contrast, ground-level enclosures are smashed by storm-surge floods and waves directly damaging that building and possibly others with the debris from the damaged/destroyed enclosure. Know your building codes and see that they are followed for new construction. A home inspection of a previously-built home will give insight into the quality of construction and adherence to codes.
(11) Property damage mitigation must be applied island wide. The forgoing principles are inadequate if applied singly or only in one island subenvironment or one development. Traditional mitigation techniques that focused on the shoreline have not reduced damage to island interiors, or, in some cases, shoreline property. A community that nourishes its beach, but levels interior dunes has yet to grasp that a barrier island is an integrated system. Although recommended actions may be site specific, the total set of mitigation actions must be compatible and applied over the entire island.
The Coastal Processes Approach
8Although the traditional approaches to property damage mitigation (legal regulation, construction requirements, and protective engineering) must continue to be applied, the main purpose of this book is to promote recognition of mitigation approaches based on the physical processes active within coastal environments. The theme is to develop a "coastal processes approach" to property damage mitigation; the basis for recognition and mapping of hazard areas. Again, the following points are central to this concept:
(1) Hazards must be evaluated based on an understanding of coastal physical processes from a geological point of view. The barrier island, its dunes, beach, and offshore are all part of one large geobiological system impacted by several different types of processes (e.g., wind, waves, currents, storm surge).
(2) Recognition of hazard areas is imperative. By doing so, development can be directed away from inlet hazard areas, potential overwash zones, low elevation areas, backside flood zones, and so forth.
(3) Approaches to property damage mitigation must be taken in recognition of the fact that sea level is rising. The present interglacial period is resulting in a world-wide shoreline migration as sea level rises over a sloping land surface. The sea-level rise is likely to continue in the foreseeable future and may accelerate over the next 50-100 years due to the greenhouse effect. Storms are a common natural phenomenon and should not be considered as "unexpected catastrophes." Storms are the major driving force moving beaches landward. As sea level rises the impact area of storms (hazard zones) moves in a landward direction. Because barrier islands exist only on very flat coastal plains, a small sea level rise can result in a large horizontal shoreline retreat. Risk analysis must be updated to take sea-level rise into account.
(4) Alterations of island environments due to development should be repaired and restored to the natural setting, especially where the natural protective qualities of the island are reduced. In many cases this will entail little more than restoring relatively small areas to its pre-development state by rebuilding dunes or replacing maritime vegetation.
(5) Island sand volume should be augmented or at least maintained. Emplacing new sand from an off-island source is better than moving sand from place to place on an island. The same is true for native vegetation. Don't lose a grain of sand!
(6) Potential for property damage must be recognized as both site-specific and regional in character. Each area presents a unique set of circumstances that require unique solutions, although general principles can be drawn from all of the coastal zone.
(7) The entire coastal zone (an entire island, for example) must be considered when applying mitigation plans. Property damage mitigation can no longer be considered as only appropriate for the first one or two rows of houses. Likewise, the coastal zone will continue to move landward as the sea level rises. The storm-to-storm crisis approach should be replaced with a search for long-term solutions to a long-term problem.
Hazards, Economics, and Politics
8Nature is not the only arena of the coastal zone, and hazardous processes are not the only performers. Property owners, planners, and public officials can mitigate the impact of hazards, but their theater is one of politics and economics; usually governed by their own set of rules. Our survey of coastal communities reveals as great a diversity of attitudes and responses to hazards as the variability in nature. Nevertheless, enough similarity between communities exists to make the following generalizations:
1) Development sites are chosen on the basis of market forces, not nature's forces. Most town sites came into existence without hazard planning. Plantations, port facilities, church camps, hunting clubs, and ultimately the resorts they became, evolved haphazardly with a few exceptions (e.g., Kiawah Island, SC; Sanibel Island, FL). Such sites on the barrier island shores, along estuaries, on deltas, floodplains, or in seismic zones (e.g., the Boston, MA area, the Charleston, SC area), were often the most hazardous. Barrier-island towns, in particular, were platted in traditional grids over fragile, dynamic, environments, rather than developing with site stability, suitability, and low risk in mind.
2) In old developments residents learned from experience, low- risk sites tended to be developed first, leaving high-risk sites/areas to accommodate growth (e.g., the New Jersey Shore; Nags Head, NC; Pawleys Island, SC; Dauphin Island, AL). Such development, when threatened, often opted for engineering "solutions" rather than relocation. These stabilization projects are increasingly expensive, and often ineffective. For the oldest resorts (e.g., the New Jersey shore; western Long Island, NY) the end results were large walls, little or no beaches, and a kind of coastal urban blight.
3) Politicians, and/or the political pressures to which they react, are oriented toward giving priority to economic development/management, not protecting the inhabitants. Development is seen as progress, a way to increase the tax base, and like the pioneer days, such progress is still considered our manifest destiny.
4) "Protective" regulations to reduce natural hazards are often viewed as threatening to developers, as well as some property owners (e.g., prohibitions on fill and development of wetlands). Developers often resist regulations designed to protect property owners or building occupants.
5) Politicians are drawn from the economic community. They are often owners of undeveloped acreage, developers, suppliers of materials, lawyers, business people and professionals who benefit from growth and development. Even if no conflict of interest is intended, they have a stake in development to protect. So the approval of a new development may be influenced by the property available from a board member, or the vision of lumber sales or restaurant patrons, rather than an evaluation of the development's hazard-risk potential.
6) Politicians are the employers, while the day-to-day work is carried out by the employees: the hired town manager, planner, and community development personnel. These employees by-and- large do an excellent job for coastal communities. They are knowledgeable, realistic, committed public servants, but they answer to the elected politicians, not the general public.
7) When disasters do strike, we depend on firefighters and police as our first line of defense. The people with the greatest responsibility for public safety sometimes seem to be the least appreciated, e.g., reliance on volunteers rather than a salaried fire-fighting staff; media comments suggesting police are overpaid (the high salaries resulting from overtime due to understaffing). The dedication and fearlessness of these brave people during hazardous and extremely stressful times often means the difference between life and death for hundreds or thousands of persons impacted by natural disasters.
8) Collective community attitudes are widely variable. For example, coastal communities that are suburbs or part of larger urban complexes have a high number of permanent residents. Their perceived planning needs differ from more transient populated communities; the communities where much of the property is "recreational," second homes and only a few of the many property owners are permanent voting residents. Newcomers in the latter communities are not experienced with the surprises of shoreline or coastal living. Their attitude is different with respect to planning; and they are often more likely to locate in newer, higher-risk developments. When they see a need for mitigation programs, they lack the political power to influence planning.
9) Developers are in business to make money, not protect the public. The emphasis is on build and sell, not analysis of site- specific hazard risk, or island-wide hazard mitigation, or future relocation. The construction industry prospers in the post-storm rush to rebuild.
10) Banks and other lenders do have a stake in property mortgages. In some cases, lenders can be a source of information on risk, however, if your credit is good you can get the loan in spite of the risk. You will, however, be required to have federal flood insurance. The post-Hurricane Andrew experience suggests that other forms of property insurance either are going to be more difficult to obtain or more expensive for property in the coastal zone.
11) Catastrophes often set the stage for bigger catastrophes. Post-catastrophe "recovery" is a time of shock and haste to put things right again. Rather than a time of careful relocation and risk reduction, houses and multi-housing units are rebuilt "bigger and better" in the same high-risk zones. Big catastrophes often bring new and/or stronger regulations, e.g., higher insurance rates, upgraded building codes, prohibitions or restrictions on future development, and mitigation against recurrence of the hazard. Expect it.
12) The levels of management regulation and politics are as diverse as the communities and hazards (e.g., towns/cities, counties, state, and federal regulatory agencies, and special regulations for private and public lands such as units of the Nature Conservancy, Heritage Trust, COBIA, Wildlife Preserves, and other restricted lands).
*The individual citizen and property owner is the final decision maker. The foregoing chapters provide a starting point to identify and evaluate hazards in terms of potential risk for both property damage, and human health and safety. Both individual and collective actions are needed to mitigate property damage. The best actions are those that mimic nature, and which address the entire island or coastal zone, not just the shoreline (figs. 10.3 and 10.4). Time is not on the side of the growing investment in property and infrastructure within the coastal zone. Unless systematic mitigation is utilized, losses will escalate in three areas: lives, property, and the coastal environments we originally came to enjoy.
*We do not recommend living on barrier islands and we would not want our loved ones to do so either. The hazards are numerous and are difficult to avoid by evacuation. Development on them is destroying a crucial and limited ecosystem. If you choose, however, to live by the sea, we hope we have convinced you to live by the rules of the sea.
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