**As we said in the preface, "we do not recommend living on barrier islands and we definitely would not want our loved ones to live there. The hazards are numerous and are difficult to avoid by evacuation. Development on them is destroying a critical and limited ecosystem. Read on, however, if you are a risk taker willing to take your chances. This book will help you reduce your risk. We want to convince you to live by the rules of the sea."
Hazard mitigation in the coastal zone must be guided by coastal type, which is a function of geologic and oceanographic setting (processes, materials, landforms), as well as climate (processes, vegetation). Stability, elevation above flood levels, and protective vegetative cover are commonly associated with low-risk mainland coasts. Rocky coasts and cliffs in stable, consolidated rock not subject to landslide processes or seismic instability, and at high elevations, are less likely to experience coastal hazards than low-lying, unconsolidated shores. The latter includes bluffs, plains, dunes, and other coasts developed in erodible sediments. Most would agree that it is foolhardy to develop a subsiding delta or mangrove swamp. Those same persons, however, regularly purchase and develop property on barrier islands (fig. 2.1), the most common and one of the least stable of coastal types on the USA eastern seaboard and Gulf of Mexico coast.

Barrier Islands: Built-in Hazards

**The most dynamic of coastal types are the low-elevation sandy barriers that typically develop along coastal plains, deltas, or as detached sand bars (spits) off of headlands. The high-risk barrier islands of the United States of America are the primary geomorphic features of the USA Atlantic and Gulf of Mexico coasts forming an almost unbroken chain extending from the tip of Long Island to the Mexican border (fig. 1.2).

**The coastal landscape is an evolving, dynamic balance between sediment supply, wave energy, and sea-level change. The building blocks of barrier islands are woven into an intricate, but ever-changing pattern. Coastal processes act on materials, the stuff of which barrier islands are built. Beaches, dunes, island ridges, terraces, tidal deltas, marsh platforms, mudflats--every barrier island landform--are constructed of sediment, usually sand, shell debris, and mud. Add plant cover to the formula and the sediment can be trapped, anchored, and allowed to build up as grasses build dunes and marshes, and grasses give way to shrub thicket, and then to forest in the plant succession (fig. 2.2). The same basic environments are also found in many non-barrier coastal locations. An idea of the physical processes active in each environment, their intensity and frequency, and resulting hazard ratings are shown in (fig. 2.3).
**Barrier islands act as the interface between ocean and land, between terra firma and the relentless power of the sea. Barrier islands bear the full impact of atmospheric and oceanographic energy including winter storms, hurricanes, storm-surge flooding, and waves. The global sea-level rise is also adding to the instability of these islands, inducing landward migration. Barrier islands are unconsolidated masses of gravel, sand, and mud, surrounded by ocean and sound waters, and characterized by low elevation, narrow width, and fragile vegetation cover. As a result, such islands are highly susceptible to wave erosion, overwash, longshore drift, flooding, flood scour, wind damage, and dramatic sand movement during storms. These hazards are often exacerbated by human alterations to the system such as construction of jetties and bulkheads, dredging of channels and finger canals, flattening of dunes, removal of protective vegetation, and unwise siting of buildings, roads, and utilities (fig. 2.4). When the processes are ignored and natural protection removed the vulnerability to hazards is increased (fig. 2.5).

**Storms are the most dramatic of island hazards and receive most of our attention. Each big storm brings property damage and changes in the coastal landscape, and sometimes causes loss of life. During the past 100 years, an average of two major hurricanes have crossed the USA coastline every three years (Nuemann et al., 1989). Typically two or three dozen winter storm systems (northeasters) impact the USA mid-Atlantic coast each year (Davis and Dolan, 1993), and similar storms affect the western USA coast.

**The point is that living on a barrier island is like living on an active volcano; very scenic and very risky. You never know when it's going to blow. We do know how barrier islands formed, how they evolve, and how they respond to changes, both natural and artificial. Shouldn't we apply this knowledge as we locate in these high-risk areas in order to reduce the loss potential from hazards?

Playing by the Rules

**Nature is not subtle in trying to teach us of the dangers of coastal living. Every hurricane and northeaster (Ash Wednesday, 1962; Camille, 1969; Lincoln's Birthday, 1972; Gilbert, 1988; Hugo, 1989; Halloween, 1991; Andrew, 1992; the "Storm of the Century", 1993; Emily, 1993) is a lesson that we should be living by the rules of the sea. We must recognize the principles from these lessons and put the rules into practice.

**The need to establish a means of effectively and routinely evaluating (1) the potential risks from coastal processes to development, (2) disaster preparedness, and (3) disaster response (e.g., evacuation), becomes increasingly important.Reducing property damage is a national imperative. Deaths from coastal storms have decreased significantly over the past decades, thanks mostlyto improved prediction and monitoring of storms, better evacuation, and sheltering; but the potential for increased death tolls is very real. The costs from property damage are out of control (fig. 2.6).

**The following chapters bring to light some new approaches to both coastal risk assessment and property damage mitigation that reverse the growing disregard for the important protective role of island environments and, where possible, suggest the enhancement of the natural protective features of islands. The fundamental first step for a community seeking to reduce property damage potential is to determine and map the risks. A simple, qualitative approach to risk mapping and evaluating the relative importance of coastal hazards is presented. Mapping is at the reconnaissance level, defining broad hazard zones within coastal communities based on geologic and oceanographic setting. The principles presented apply to most Atlantic and Gulf Coast barrier islands. Many of the examples presented are drawn from the Carolinas, the focus of our specific pilot and demonstration studies, but any barrier island community can apply this mapping approach. The first step for an individual buying property is to evaluate the specific homesite using the same parameters used in risk mapping. In the past, if such an evaluation was considered at all, it was the first and last step. Experience calls for broader risk assessment at the community and island-wide levels.

**The objective is to promote a new attitude about living in the coastal zone, particularly on barrier islands. The ultimate goal of property damage mitigation can be viewed as a four-step process:
(1) understanding/recognizing hazards and vulnerability,
(2) mapping zones of risk,
(3) developing site-specific mitigation techniques including preservation, augmentation, and restoration of natural environments (PAR), and
(4) implementation of mitigation recommendations.

Island Risk Assessment

**Very large differences exist in property damage risk exposure between different islands, between different segments of the same island, between the front and back sides of an island (fig. 2.3), and even between adjacent buildings. Thus a relative level of risk can be determined for a given structure, a property, a community, or an entire island with respect to the potential for damage from hurricanes, other coastal storms, and ongoing erosion.

**Our approach to risk assessment is from a geologically-based understanding of coastal processes and from observations of impacts of storms on coastal development. Coastal hazards, from a geological point of view, include both the intense, short-duration physical processes associated with storms as well as the intermediate-term cumulative effects of such events (e.g., continuous coastal erosion and shoreline encroachment). Longer-term processes (e.g., subsidence of a delta) also may be important. Storms come in all shapes and sizes, from modest tropical depressions to Category 5 hurricanes, from passing cold fronts to immense winter storms (nor'easters). Table 2.1 gives an idea of the frequency, intensity, and duration of several types of natural hazards which impact coastal areas, and compares their overall severity and impact with some other common natural hazards that have affected the USA in recent years. Obviously the recognition and mitigation of coastal hazards is an important concern facing our nation as we prepare for the 21st Century.

**The assessment technique and property damage mitigation recommendations presented here are from a conservative perspective. That is, the following two major considerations are the basis of the text's recommendations:

~120 mph winds, essentially the eye wall of a Category 3 hurricane or the more distant portions of a stronger hurricane are the maximum conditions; these evaluations are too low for Category 4 and 5 hurricanes, or equivalent.
oHousing sites recommended are those with which we would feel comfortable recommending to our parents or grandparents (assuming they were imprudent enough to want to build on a barrier island).

Property Damage Mitigation: Regulatory, Structural, Natural

**Property damage mitigation is the term for collective efforts to reduce the potential for storm damage to buildings, roads, utilities, and infrastructure. The goal is to offset some of the danger in the rush to the shore which has resulted in more and more property and people at risk. The current sea-level rise, plus predictions of an acceleration in that rise, and increased frequency and intensity of storms, all add greatly to the urgency of taking measures to assess coastal hazards and to reduce property vulnerability.

**Observations of several barrier island communities after Hurricanes Gilbert (1988) and Hugo (1989) indicate that property damage potential can be lessened by prudent site selection, and location of buildings. Likewise, post-storm observations also indicate that reliable means exist by which property damage can be mitigated (e.g., dune construction and road reorientation). The recent passages of Hurricanes Gilbert (1988), Hugo (1989), Bob (1991), Andrew (1992), Iniki (1992), and Emily (1993) have demonstrated the need for a new approach to mitigation in order to stem the tide of ever increasing property damage from storms.

**Past approaches to property damage mitigation are discussed by Godschalk et al. (1989), and include such broad categories as:
o engineering to armor the coast
o engineering to strengthen buildings
o land use planning to avoid construction in hazard areas.
**These mitigation techniques are primarily applied through regulations (e.g., setback requirements, building codes, permit requirements) and heavy reliance heavily on engineering (structural solutions).

**Property damage mitigation includes specific goals such as:
o reducing damage to structures
o preserving natural environments
o increasing evacuation capacity
o locating new structures out of hazardous areas
o relocating existing structures out of hazardous areas
o providing safe storm shelters
o structurally altering the environment

**For the most part, approaches to property damage mitigation developed in recent decades have focused on the regulatory and structural methods; efforts that may be misplaced. Traditional mitigation approaches are somewhat myopic, focusing mainly on the beach and island front, although some attention has been given to protecting critical environments (e.g., marshes).

**A new, broader approach, viewing the entire barrier island, as well as the adjacent nearshore ocean floor is needed; mitigation that is based on the entire complex system, and applied island-wide. To decrease the risk to lives and property on barrier islands, let's apply the rules of the sea. It is hoped this new approach can be used as a tool by coastal planners and managers in making their mitigation plans and post-storm reconstruction guidelines. For island dwellers, understanding this approach should provide a basis for wiser coastal property purchases no matter where the house or lot is located on an island. And existing communities can identify problem areas where environmental features can be repaired or enhanced to restore natural mitigation.

**The natural coastal environment is quite capable of absorbing the impact of a coastal storm, albeit with some change in the coastal geomorphology. Changes include: raising the island elevation by dune formation or deposition of storm overwash sand; reducing the island elevation by destruction of dunes; changing island width and shape by shoreline retreat on either the ocean or sound side, or shoreline advance (beach accretion on either the ocean or sound side); and steepening or flattening of the beach profile. Such changes may be permanent or temporary, short-term or long-term, depending on the coastal environment in question and its unique geological, oceanographic, and climatic setting. On barrier islands, such changes contribute to the natural long-term processes of barrier island migration. How and to what degree development interferes with these natural coastal changes will determine what steps can be taken in a given area to reduce the potential for damage from future storms. The rule is that mitigation should mimic nature.

PAR: Preserve, Augment, Restore

**The guide to property damage mitigation presented here is based mainly on experience with past storms. Observations were made after several hurricanes, tropical storms, and winter northeasters along the southeastern U.S. coast, and the coasts of Mexico and Puerto Rico (Bush, 1994; Hall et al., 1990; Bush, 1991; Gayes, 1991; Lennon, 1991; Priddy, 1991; Thieler et al., 1989; Thieler and Bush, 1991; Thieler and Young, 1991), as well as studies from the Gulf of Mexico (Penland et al., 1980; Kahn, 1986; Morton, 1985). These studies of hurricane damage indicate that in most cases, useful and economically reasonable steps could have been taken before these storms that would have reduced property damage significantly. These mitigation actions range from preserving natural areas that afford protection (e.g., forest cover), to augmenting such environments or landforms (e.g., frontal dunes), to restoring or repairing such features when altered or damaged (e.g., interior dunes).

**Methods of protecting buildings and other property from coastal storms and erosion range from the simple planting of dune grass and placing of sand-trapping fences for encouraging dune growth, to the costly and complex design of sand emplacement and rebuilding of beaches, roads, and service systems; from efforts costing very little to projects costing millions of dollars per mile of island length.

**The process-oriented perspective (i.e., to mimic nature) presented here provides for identification of hazard areas based on likely processes such as potential overwash zones, and potential inlet formation areas; zones of inlet expansion or migration; and identification of potential flooding problems and flood zones. The inter-relationship of processes, materials, and vegetation is considered. Moreover, a geological perspective allows special insights into repairing damage already done to the natural environment, for example, restoring beaches, rebuilding excavated interior dunes, plugging dune gaps, reestablishing destroyed maritime forest, curving roads around natural island topography, or putting roads and walkways over rather than through such topographic features. In addition to repairing damage done to the island, steps can be taken to enhance the natural protective capabilities of coastal environments, such as planting marsh grass to slow lagoonside erosion, beach replenishment, dune construction, and encouraging maritime forest growth. Planning can avoid hazard enhancement by not creating overwash passes, not interrupting sediment supply, not disrupting stabilizing ground cover, and not creating potential for new inlet formation.

The Rules of the Sea

**Recognition of the physical processes active within coastal environments is the fundamental step toward recognition of hazard areas and forms the basis of a "coastal processes approach" to property damage mitigation. The following points are the central tenets of "Living by the Rules of the Sea:"

(1) The coastal zone is unique and requires unique management strategies. Barrier island environments are far more dynamic than mainland areas. The traditional grid-development pattern and related construction used on the adjacent coastal plain, or the stable interior of the continent, is inappropriate for a barrier island and increases the probability of impact by natural processes, i.e., the type of development often increases the risk from natural hazards.

(2) Coastal physical processes must be identified and understood from a whole-island perspective. Island, marsh, dune, beach, and offshore are all part of one large interrelated geobiological system. Building in the path of the processes creates the hazard.

(3) Property damage potential is site-specific and each site is different. Each area presents a unique set of circumstances that require unique solutions, however, broad general principles can be drawn on to develop these solutions.

(4) Relative risk areas can be recognized on the basis of well- defined criteria. By doing so, development can be directed away from inlet hazard areas, potential overwash zones, low-elevation areas, and so forth. If location out of harm's way is impossible, then mimic the process, e.g., allow overwash to occur, dunes and beaches to migrate, forests to grow.

(5) Property damage mitigation must be from a whole-island perspective. Barrier islands behave as units or systems in terms of process response. Recognize that mitigation can no longer be considered as something for only the first one or two rows of houses. Rather, the whole island and complete processes/materials system must be considered.

(6) All coastal hazard evaluation and mitigation must consider a rising sea level. 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 will likely even accelerate over the next 50-100 years due to the greenhouse effect. Solutions must take into account that barrier islands 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 for a long-term problem.

(7) Repair alterations due to development. Damage to the natural setting reduces the natural protective qualities of the island. Such damage must be repaired in order to mitigate future property damage. In many cases such effort will entail little more than restoring relatively small areas to the pristine state of pre-development by rebuilding dunes, planting grasses, or replacing maritime vegetation. In some cases, the effort will require community spirit, political grit, and adequate financing (e.g., beach replenishment, relocation of roads and services). Augmentation of such environments should be given the same emphasis as repair.

(8) Conserve sand. Sand volume must be maintained or increased. Emplacing new sand from an off-island source is better than moving sand from place to place on an island. Sand, like water and air, is a resource to be conserved.

(9) Conserve vegetation cover. Vegetation is the closest thing to a sign of stability on a barrier island. Vegetation traps and anchors sediment whether it be dune grass building dunes, forest canopy protecting undergrowth, or marsh grass trapping sand and mud and building flats in the lagoon or sound. Removal of vegetation destabilizes the land. raising the hazard potential.

(10) Conserve landforms. This rule follows from those that go before it. The landform (e.g., dune, island terrace, tidal flat, beach) is a sedimentary body that formed in response to processes, sediment supply, and vegetation cover. When the landform is altered, the stability is altered. Stabilization may be augmented by adding and anchoring sediment, planting natural species, or even constructing an artificial landform.

**Hazard assessments, vulnerability determinations, risk estimates, and mitigation recommendations are the realm of scientists and engineers. Implementation, however, falls into the political/legal arena. For example, dune protection ordinances, community mitigation plans, and zoning must be based on scientific principles. Their enforcement and the financing to build dunes, move houses off the beach, and preserve wetlands must be carried out by elected and appointed officials. The rules outlined above provide the basic principles that should underlie and guide such implementation. The impetus to make such mitigation happen must come from the individual property owners whether the motive be continued enjoyment of living in the coastal zone or continued profit from recreational and business property investments.

Table 2.1: Ranking of the world's great natural hazards. The characteristics of a hazard or the importance of its impacts are ranked on a scale of 1 (largest or greatest) to 5 (smallest or least significant). Hazards of the coastal zone are starred (modified from Bryant, 1991).

Grading of Characteristics and Impacts

Overall Rank

Event Degree of Severity Length of Event Total Areal Extent Total Loss of Life Total Economic Loss
Social Effect
Long-term Impact