*Each barrier island and coastal community presents unique challenges with respect to assessing hazards and evaluating vulnerability and risks for coastal property damage (Tables 9.1, 9.1B and 9.2). Variations along the Atlantic and Gulf coasts in geologic setting (e.g., sediment supply and type), climate (e.g., temperature range, rainfall, and type, frequency, and intensity of storms), and oceanographic setting (e.g., tidal range and average wave energy), translate into a wide variety of barrier island morphologies, vegetation cover, shoreline types and hazards. Added to the complexity of these natural variations is a wide range of development types and densities. Communities ranging from light developments of a few single-family dwellings to dense high-rise condominium and hotel rows require a like range of management and property damage mitigation strategies.
 *Based on our experience and case studies in hazard risk mapping and mitigation recommendations, the previous chapters have presented a set of general or universal principles of property damage mitigation. General principles serve only as a guide and each location must be evaluated on its own merit in order to make property damage mitigation recommendations that are site-specific (Table 9.2). These principles were illustrated and their application implied in specific examples drawn from the variety of areas hard hit by Hurricane Hugo (e.g., South Carolina's Charleston area islands, particularly Folly Beach; the mainland coast of Myrtle Beach and the Grand Strand; and North Carolina's Sunset Beach), and North Carolina's wide range of barrier islands and associated communities (Tables 9.1, 9.1B and 9.2). Two areas, in particular, were included to show the range of community mitigation responses, namely the northern Outer Banks (e.g., Kill Devil Hills and Nags Head, NC), and the communities on Bogue Banks, NC. The examples are dispersed throughout Chapters 5, 6, and 7, but Table 9.1and 9.1B provides a short recap, and Bogue Banks is presented again here for overview and comparison.
*Assessments of hazards and property damage mitigation recommendations for several selected coastal communities whose wide geographic spread is intended to broaden the scope and applicability of this concept. Figure 9.1 highlights the locations referred to in this chapter, and Table 9.3 provides a quick overview of the sample communities.
*Keep in mind that the risk mapping criteria are based on the property damage risk potential from a low Category 3 hurricane. For almost any community, everything is at extreme risk in a larger hurricane, especially a Category 5.
Southhampton, Long Island, New York
*The township of Southampton, NY is located on the south shore of Long Island in Suffolk County, approximately 80 miles east of New York City. Southampton Township includes the villages of Westhampton Beach, Quogue, Hampton Bays, Southampton, and Bridgehampton which occupy the western half of the south fork of Long Island: covering a total of 25 miles of the Atlantic shoreline.
*The northern half of the town lies on the Ronkonkoma terminal moraine, deposited during the most recent glacial episode. The moraine consists of till, a poorly sorted mixture of clay, sand, and gravel, which is highly erodible. The area has relief of over 200 feet at its highest points. This glacial moraine is well forested and is an important groundwater recharge area. The area between the moraine and the Atlantic Ocean is a glacial outwash plain. The outwash consists of well-sorted sand derived from the Ice-Age glacial melt waters, and slopes gently seaward. The rich agricultural soils of the outwash plain led to early rural development. Peconic Bay lies north of the moraine.
*The nature of the Atlantic shoreline changes significantly from east to west in the area (fig. 9.2). The eastern half of the township is a headland or mainland shoreline which extends past the eastern town boundary to Montauk Point at the eastern tip of Long Island.
*Within the village of Southampton the shoreline changes to a barrier coastline which extends westward to New York City. Two stabilized inlets, Shinnecock and Moriches, divide the barrier islands in Southampton (fig. 9.2). Because of the low tidal range and high wave energy environment, the barriers exhibit a wave-dominated morphology. The islands are long and narrow with few tidal inlets. Moriches Inlet marks the western boundary of Southampton.
*Very narrow stands of salt marsh grow in the lagoons between the barrier islands and the mainland. The two lagoons in Southampton (Shinnecock and Moriches Bays) are extremely shallow and several miles wide. Salt marsh vegetation only grows in two general regions: on overwash fans on the backside of the islands, and in small protected coves within the bays.
*The net littoral drift in Southampton is from east to west. Most of the sediment in the system is derived from the eastern headlands, but there also is evidence of an offshore source (the continental shelf) because the volume of sand transport on the beach increases to the west.
*Numerous ponds and small embayments have formed in the eastern part of the town where former outwash streams were closed off by the development of baymouth bars. In fact, before Moriches Inlet formed in 1931, the south shore extended unbroken by inlets from Montauk Point to Fire Island Inlet. However, Mecox Bay and Sagaponack Pond are frequently inundated by storm tides. As sea level continues to rise, permanent inlets will likely form at these locations.
*Southampton has endured a long record of brutal hurricanes and northeasters. The most destructive storm of this century was the hurricane of 1938 which wiped out development along the entire barrier coast and opened Shinnecock Inlet. The inlet was subsequently maintained by dredging, and later by jetties.
*The village of Southampton was founded in 1640 and became the first English settlement on Long Island, and the first European settlement on the eastern end (the Dutch had previously settled in what is now Brooklyn). The indigenous Shinnecock Indians showed the early settlers the value of the region's rich coastal resources---shellfish, fishing, and even whaling. Until this century the local population consisted largely of baymen who depended on the sea for their living.
*Since World War II the population on Long Island has exploded as New York City's suburbs sprawled eastward. Southampton has resisted the suburban development that has enshrouded the rest of Long Island. Today it depends more on its reputation as a wealthy, exclusive resort area than on its coastal resources. The development pattern on the oceanfront consists primarily of large, expensive, secluded homes. Commercial development on the beach is largely absent.
*The barrier island between Shinnecock and Moriches Inlets is all classified as extreme risk (fig. 9.2). The elevation of the island is mostly below 10 feet, and the V-zone covers the entire width of the island. Erosion is severe due to two prominent structures: (1) the jetties at Shinnecock Inlet, and (2) the groin field in Westhampton Beach.
*The Shinnecock jetties block most of the littoral transport to these beaches. Storm overwash occurs frequently within 2 miles of the jetties. Increased erosion rates in Westhampton Beach after the construction of the jetties prompted the construction of a groin field which terminates 3 miles east of Moriches Inlet. The 21 groins were completed in 1977. A devastating scenario has unfolded to the west of the groins as erosion accelerated even more. While the groin field has stabilized the beach and protected homes within its limits, almost 200 homes have washed away within a mile of the last groin and a new inlet formed! This portion of the island is now almost barren of houses and vegetation, and is a mere sand bar separating the Atlantic from Moriches Bay. Development is coming back, however, as the citizens of West Hampton Dunes successfully sued the Corps of Engineers, forcing them to return the shoreline to its original position through beach replenishment. The effects are encroaching further and further westward, and every storm season sees more homes disappear.
*East of Shinnecock Inlet a 3-mile long barrier spit extends from the headland area. Because sand is impounded on the east side of the jetties, the beach within a mile and a half of the inlet is stable, but is still rated as extreme risk. Continuous dune ridges range from 15 to over 30 feet high, greatly reducing the risk of overwash, but a few gaps do exist and these should be avoided. Secondary dunes add width to the island, but elevations on the back side of the island are low. The remainder of the barrier spit is eroding and has no secondary dunes, so it too falls into the extreme risk zone (fig. 9.2).
*The mainland portion of the town's shoreline is eroding at a considerable rate which increases from west to east. Although the dune crest is over 20 feet in some areas the dunes are severely scarped. In many areas, however, the dunes are low and do not have enough width to withstand a high storm surge. The bars blocking Mecox Bay and Sagaponack Pond are particularly vulnerable. They overwash during most storm tides and will very likely become permanent inlets as sea level rises. Beachfront property is at extreme risk and should be avoided (figs. 9.3 and 9.4).
The margins of inland bays and ponds are floodable and are high-risk zones. Areas shown as moderate risk are generally open fields which are agricultural lands, but some are occupied by recently built subdivisions. The remainder of the town is low risk. Because of the slope of the mainland, low-risk sites can be found close to the ocean, but as erosion continues, these areas will be subject to increased risk.
*The area of the town north of Montauk Highway was not mapped, but is virtually all low risk. Likewise, the mainland portion of the town which is separated from the barrier island is also low risk, except for low-lying land adjacent to the bay.
Bogue Banks, North Carolina
*Bogue Banks is over 25 miles long and over 1 mile wide at its widest, and is oriented essentially east-west. The island is bordered on the east by Beaufort Inlet, and to the west by Bogue Inlet (fig. 9.1). High elevations characterizes island in places, with dunes reaching over 35 feet high on the western end. Even the relatively narrow, lower central part of the island is higher in elevation than most other North Carolina islands (fig. 3.7). These positive elevations are less vulnerable to hazards as reflected in Figure 9.4. The storm surge from a category 5 hurricane would flood only about one-half of the western end of the island, though all of the eastern half would be covered (ENCHES, 1987).
*Some of the highest sand dunes on the east coast and the largest in North or South Carolina south of Jockey's Ridge, North Carolina can be found on Bogue Banks. The large dunes on Bogue Banks are testimony to the large volumes of sand moving ashore in this area, although the exact reason for such extensive sand movement in unknown. Part of the answer is certainly the east-west orientation of the island, making it perpendicular to the predominant wind directions. This orientation favors proceses which bring a lot of sand onshore, compared to a very low-elevation island such as Core Banks which is oriented north-south, parallel to dominant wind directions (Godfrey and Godfrey, 1976). The total answer is almost certainly more complex than that, as Jockey's Ridge, Nags Head, NC is an enormous sand dune and it is located on a north-south trending shoreline.
*Bogue Banks has five separate municipalities on the island (fig. 9.5), each with a different philosophy about "Living with the Shoreline". In addition, the island can be divided into three distinct parts geologically. The eastern one-third is low-to-moderate elevation and wide. The central one-third is low elevation and narrow. The western one-third is extremely high elevation (by barrier standards) and very wide.
*Bogue Banks Hazard Assessment and Mitigation Recommendations.-- Bogue Banks is important to the study because it provides the best example of reduced risk attributable to natural island character (e.g., high elevation, large amount of sand in the system, and good forest cover) resulting in more moderate to low-risk sites than other islands studied. Hurricane Hazel, a Category 4 storm, visited Bogue Banks in 1954, the last Hurricane of that magnitude to hit this portion of North Carolina. Hazel opened several new inlets along Bogue Banks, which, though they were artificially closed, can still be recognized today in the form of small tidal deltas in the sound and low-elevation spots along the main island road (fig. 7.9). Hazel's impact on specific sites should have served as a warning. It did not!
*Overall, Bogue Banks has one of the lowest hazard ratings along the east coast United States. Of course, no island is completely secure from the ravages of a major storm. A great deal of the natural protective capability of Bogue Banks has been destroyed by development, making even this lower-risk island an invitation for disaster in some places. For example, Bogue has a significant sand volume, one of the keys to reducing property damage. A large sand volume means a wide and high island. Island elevation and width allow siting of development back and up from the water, two of the best ways to mitigate against storm damage. Unfortunately, in some places, much of the sand was removed, compromising the protective capacity. A study by Stanczuk (1975) documents some of the early effects of development on Bogue Bank's natural environment. The impact of development on the maritime forest resources on Bogue Banks is discussed by (Lopazanski, 1987) and (Lopazanski, et al, 1988). Recommended mitigation repairs for such damage are given in the generalized mitigation map for Bogue Banks (fig. 6.2 and 6.2B).
*Numerous other examples of the destruction of the islands' natural protective qualities exist on Bogue Banks. Very large dunes protected the community of Atlantic Beach, but they were totally removed from the heart of the city for ease of construction of buildings and for roads. Other high dunes were removed and dunes were notched for roads. Extensive protective maritime forest still exists on the island, but in many places the forest has been completely cleared for development. Locations of historic inlets are documented, yet development is continuing in these locations which are likely to be sites of future inlets. And although modern building codes allow structures to withstand high winds and modest waves, many older buildings on Bogue Banks were built before building codes were established. The list of trouble spots goes on. The response must be to repair the damage, encourage restoration of natural dynamics, and prevent further loss of dunes and forest (fig. 6.2 and 6.2B).
*Atlantic Beach (fig. 7.8) represents the portion of the island most modified by man. The natural contours and environments have been highly altered or obliterated. Marsh fill, finger canals, and septic tanks further detract from the island's natural character. The lagoon side of Atlantic Beach is mostly marsh fill. Several finger canals were dredged and the spoil dumped on the marsh to fill for home sites. These locations are very low in elevation and certainly will be flooded even by a modest storm. Little can be done to improve these sites except for elevating the houses on stilts above potential flood danger. Elevation will protect these buildings from rising water, but not from wind and wave damage or storm-surge ebb scouring of the stilts.
*The far eastern end of Bogue Banks is occupied by Fort Macon State Park which will not be developed much beyond its present status. The park's dunes, beach, and forest will remain in a relatively natural state. The actual fort area has been damaged by past storms. In fact, the earlier stone Fort Hampton, which protected the inlet during the War of 1812, was destroyed by a severe hurricane of the early 1800's. Private property between the park and the Atlantic Beach town limits has also suffered in past storms. This area of relatively low elevation is susceptible to overwash, a high rate of shoreline erosion, storm-surge flooding, and active sand dune migration, which minimizes the number of sites of even moderate risk for development. Lower-risk sites are located near the center of the island where shrub stands and maritime forest indicate island stability. Any structures along this stretch that are above the 100-year storm surge level are not likely to be flooded.
*The eastern end of Bogue Banks, including the town of Atlantic Beach, has been the beneficiary of two beach replenishment projects at no cost to the community because the sand was obtained from navigation channel dredging (see Chapter 5; fig. 5.22).
*Mitigation recommendations for Bogue Banks rely on the PAR approach: preserve, augment, and restore. The dense maritime forest, still extensive in places, should be preserved as much as possible. The same goes for the high dunes.
Fernandina Beach, Florida Atlantic Coast
 *The community of Fernandina Beach is located on Amelia Island, the northernmost island on the eastern coast of Florida and the southernmost of the "Sea Islands" (fig. 9.1). Amelia Island is located about 11 miles (18 km) northeast of Jacksonville, and is bounded by the St. Mary's Inlet to the north, and St. George Inlet to the south. The island is some 8 miles (13.5 km) long, with an average width of roughly 1.8 miles (3 km). Elevations at the back of the island can exceed 50 feet (16 m) while the majority of the island's interior is well above 15 feet (4.5 m) with an average elevation between 10 and 16 feet (3-5 m). The highest dune on the island rises more than 54 feet (16.5 m) above mean sea level. These unusually high elevations are found entirely on the northwestern portion of the island. The present Amelia Island represents the merging of the modern barrier island with its more ancient predecessor (Parchure, 1982). The majority of the island is composed of reworked Pleistocene sediments which made up the ancient barrier island. Atop this Pleistocene core is a sliver of modern Holocene sediment (Parchure, 1982).
*The oldest development in Fernandina Beach dates to 1567 and is located on the back side of the island along the Amelia River (Parchure, 1982). Elevations there typically exceed 40 feet (12 m), an elevation generally safe from flooding. The city of Fernandina Beach grew outward toward the beach extensively since the passage of Hurricane Dora in 1964.
*The northern portion of Fernandina Beach (north of Atlantic Ave.) is composed mainly of single family dwellings, most of which are not elevated on stilts. The base flood elevation in this area ranges from 10-16 feet (3-5 m) along the beach itself. The first row of houses sit behind a low (5 feet, 1.5 meter-elevation), unvegetated dune ridge, often less than 10 feet (3 m) wide. There are as many as eleven rows of houses and as few as two rows between the ocean and the densely forested dune ridges. The southern portion of Fernandina Beach (south of Atlantic Ave.) is composed of single family dwellings, two to seven-story condominiums, and small stores and businesses. Most of these buildings are not stilted, and are located directly behind, or on top of the first row of dunes. The majority of this development lies along Highway 105. For this reason, there are typically only two to four rows of buildings between the ocean and the densely vegetated dune ridges. The base flood elevation in this area also ranges from 10-16 feet. The central region of the island hosts the Fernandina Beach municipal airport which occupies approximately 0.6 square miles.
*Amelia Island exhibits a highly engineered shoreline. The earliest coastal engineering projects began in 1881 with construction of five spur groins around Fort Clinch (Parchure, 1982). In 1882, The U.S. Navy began work on a 11,000 feet-long jetty with a height of 6 feet above mean low water. The jetty stabilizes the St. Marys entrance. A year later, in 1883, two additional groins were added in the Fort Clinch area (Parchure, 1982). Once the jetties were completed, dredging programs were necessary to keep the inlet open. Sediment removal ranged from about 22,000-200,000 cubic yards (17,000-150,000 cubic meters) per year (Parchure, 1982). In 1953, the City of Fernandina constructed eight groins at intervals of about 425 feet extending north of Atlantic Avenue (Stevens, 1960). In 1964, funds were provided for 3.4 miles of revetment (Pilkey et al., 1984). In the years 1978, 1982, 1987, and 1988, sands dredged from federal navigation projects were placed on the beach in an effort to replenish them (Hobbs, 1988), though no record of the total volume of material emplaced is available.
*Fernandina Hazard Assessment and Mitigation Recommendations.--The coastal hazard zones for Fernandina Beach are shown in Figure 9.5 which divides the community into several areas. Blank areas on the figure represent undevelopable lands which have therefore been left unranked (Fort Clinch State Park, the airport, industrial areas, and marsh). Low-hazard areas include two small areas south of town, distinguishable by high elevation dunes, dense forest, and shrub thicket. Moderate-hazard areas include the older developed section of the town. High-hazard areas include most of the state park area and a large section of the southern portion of town parallel to the coast. Extreme-hazard areas are confined basically to the oceanfront. Three distinct portions of Fernandina Beach are rated as extreme hazard (fig. 9.6), which include the public beach and one zone each to the north and south of the public beach as discussed below.
*The extreme-hazard north of the public beach lies behind an unsubstantial man-made dune ridge ranging from less than 3-5 feet (1-1.5 m) in height. The majority of these residences have not been constructed on stilts, although some structures utilize the first floor as garage space only. The artificial dunes in this stretch are small, unstable, and not continuous. In addition, low lying roads are perpendicular to the shore and encourage overwash and storm-surge ebb. Several houses are located too close, less than 130 feet (40 m), from ocean. The sparse vegetation offers no protection (fig. 9.7).
*Mitigation recommendations for this area are limited. There is little or no space to build dunes in front of houses, so relocation becomes a more reasonable alternative. If houses are not relocated, the volume of the artificial dune must be augmented, increasing its height and width so that it will offer more protection during storms. But who will pay for this? Dune gaps must be plugged and the dunes vegetated for increased stability. In addition, a program should be initiated to plant and encourage native vegetation, especially shrubs and forest vegetation. Some streets (for example, 7th and 9th streets) can be completely closed off, filled in and revegetated. No private drives are located in these areas so access is of no concern. Other streets (for example, 1st, 2nd, 3rd, 5th, and 8th streets) can be blocked with sand at their ocean terminus.
*Fernandina public beach is also an extreme-hazard area (fig. 9.6). Here the road perpendicular to the shore will allow overwash penetration and storm-surge ebb. The rock revetment will cause beach narrowing over time. Sparse vegetation offers no protection. The corresponding mitigation recommendations for this area are to block the road gap, begin planning for replenishment in the future to maintain the recreational beach, and develop a planting program.
*South of the public beach is another extreme-hazard area. Development in this area is distinguishable from development north of the public beach in that it lies on top of, or directly behind a lightly vegetated natural dune ridge of moderate size. The development consists mainly of 1-2 story, non-stilted, single family dwellings. The only beach front condominiums in Fernandina Beach are located along this strip of Highway A-1-A. Dunes in this area are sparsely vegetated and are therefore less stable. Where houses are built on top of the dune or directly behind it, the dune offers no protection, except for some elevation. Driveways and roads perpendicular to shore encourage overwash and storm-surge ebb. Many houses are located less than 200 feet (60 m) from ocean. On-beach parking encourages erosion and creates a dune gap.
*Mitigation recommendations for this area include planting and encouraging native vegetation, especially along the dune ridges for stabilization and removing beach parking access and filling the dune gap.
Venice Beach, Florida Gulf Coast
*Venice Beach is located approximately 60 miles (100 km) south of Tampa Bay, facing the Gulf of Mexico (fig. 9.1). Venice is bounded by Venice Inlet (jettied) to the north and Stump Pass to the south (fig. 9.8). Elevations reach as high as 40-50 feet (12-15 m) above mean sea level, with a majority of the land between 10-20 feet (3-6 m) above mean sea level.
*The entire Venice area is heavily developed and few areas with dense vegetation remain. The first row of buildings nearest the shore varies as follows: buildings from the jetty (Tarpon Center Drive) to just south of Whitecap Circle are 1-3 story, apartments and condominiums built at grade (without stilts); south of this area, to the public beach (the Esplanade), is a variety of high-rise hotels and apartments, most ranging from four to eleven stories; and just south of the public beach is a variety of single-family dwellings, bounded at the south by an eleven story high rise. The second row of buildings consists primarily of one to two story apartments and condominiums, with the exception of a three block area with low rise (3-6 story) apartment buildings. Most of the other development in Venice consists of one-to-two story single family dwellings or businesses, all of which are built at grade, not elevated on stilts or pilings. Several trailer parks are located about one mile inland. The Venice municipal airport, just south of Venice, occupies approximately one square mile.
*Shoreline engineering began in Venice in 1937 when two 650-foot (200-meter)-long jetties were constructed to stabilize Venice Inlet. In 1963, 19,000 cubic yards (14,500 cubic meters) of sediment dredged from the inlet was used in a replenishment program (Dixon and Pilkey, 1991). Three finger canals were cut into the bayside of the northernmost tip of Venice and seawalls and rock revetments were constructed almost the entire length of the beach (dates unknown). Beaches were again replenished in the years 1971-75 as well as in 1979 and 1980 and into the 1990s (Dixon and Pilkey, 1991).
*Venice Beach Hazard Assessment and Mitigation Recommendations.-- The coastal hazard zones for Venice Beach are shown in Figure 9.8. Low-hazard areas include a few small high-elevation, forested hummocks well back from the shoreline. Moderate hazard areas dominate the community and comprise the bulk of the developed areas. Although there are no areas in Venice Beach rated as high hazard, extreme-hazard areas border the oceanfront and the area around Roberts Bay in the northern part of the community.
*Hard stabilization structures (jetty, seawalls, and revetments) along the Venice Beach shoreline will lead to beach narrowing or create a need for replenishment with time (figs. 9.9 and 9.10). Dunes are low or absent, and vegetation is generally sparse or nonexistent. Finger canals and the marina allow further inland incursion of storm waters. Many buildings are located less than 200 feet (60 m) from ocean, and roads perpendicular to shore will allow overwash and storm-surge ebb funneling. Large commercial high rise structures may be more resistant to damage during storms, but damage to the buildings' contents and to windward and lower floors will be extensive (fig. 9.11).
*Mitigation recommendations for Venice Beach are to add sand volume to dunes (frontal and interior), vegetate with native plants, and encourage shrub and forest growth. Relocation will be a necessity at some point. The community should be evaluating the possibility of demolishing and rebuilding if the economics of moving intact aren't feasible. Block some shore-perpendicular roads with sand to inhibit overwash and storm-surge ebb.
*The Venice public beach area is a valuable natural resource. However, low dunes and sparse vegetation offer little protection. No mitigation recommendations are made for this basically undeveloped shoreline stretch. However, consider future replenishment to maintain the recreational beach.
Wakulla County, Florida "Zero-Energy" Coast
*Wakulla County is located about 21 miles (35 km) south of Tallahassee on Florida's panhandle (fig. 9.1), and is home to Wakulla Springs Lodge, a well known resort. Wakulla County has no barrier beaches. This mainland coast (fig. 9.12) occupies a setting on the low-energy reentrant section of Florida's Gulf of Mexico coast. The region is distinguished by a very broad and gently sloping continental shelf, the overall concave shape of the shoreline, and the local embayment of Apalachee Bay. The very gentle slope contributes to the low wave energy conditions due to frictional damping of the waves as they travel across the shelf. The gentle slope and the embayed shape of the coastline allow for maximum potential storm surge heights. Storm surges here theoretically can exceed 30 feet (9 m). In addition, extremely low energy shoreline settings prevent formation of barrier islands. Little sandy beach property exists in Wakulla County, as most of the coastline consists of coastal marshes grading into swamps. The large influx of fresh water from Wakulla Springs and other sinking streams maintains a freshwater marsh ecosystem along portions of the shoreline in addition to the expected salt-water marsh ecosystem.
*Wakulla County is sparsely developed; the entire county's 1990 population was approximately 15,000 residents. Due to the large quantity of land held by St. Mark's wildlife refuge, development along the coast is not extensive. The main coastal communities of Wakulla County are Shell Point, Oyster Bay, and Live Oak Island. In general, houses in all areas are found at three physical levels: (1) nonelevated, which were built prior to the FEMA-regulated coastal development, (2) elevated 10-12 feet, built to original FEMA flood standards, and (3) elevated 30 feet, which meet present FEMA flood regulations. It is not uncommon to see houses at all three elevations right next to each other (fig. 9.13). Obviously the lower-elevation houses are at higher risk for property damage and, if damaged or destroyed, debris could be carried by wind or water and damage nearby properly elevated buildings.
*The community of Shell Point is comprised almost entirely of single family dwellings. The first row of houses are mostly stilted. Approximately half of the buildings in the community however, are trailer homes, located along canals in the central portion of the developed area. The community of Oyster Bay is a small community made up entirely of single family housing units; mostly elevated on stilts as is the first shore row of houses. Several mobile home units are interspersed among the permanent structures. Live Oak Island is also a residential area. The houses on the first row are stilted, but Live Oak Island differs from the other communities in that there are few mobile homes.
*Shell point displays the highest degree of engineering with its numerous finger canals both parallel and perpendicular to the coastline. Oyster Bay has a series of finger canals parallel to the coastline, but to a lesser extent. The roads here are also parallel to the coast. Live Oak Island is the only community of the three that boasts a seawall. The seawall is approximately three feet high. The landward side of the island has individual docks which are kept operable by the use of a revetment. Live Oak Island also maintains a series of canals.
8The reconnaissance evaluation shows that the low elevation, numerous finger canals, and high potential for storm surges combine to place the entire area at extreme-risk from coastal hazards.
Galveston Island, Texas
*Galveston is one of the oldest cities located on a Gulf of Mexico barrier island. Early Galveston grew as a prominent port city and was a profitable location for merchants and entrepreneurs. By l900 the population was about 40,000. But in September of that year disaster struck. The deadliest hurricane ever to strike the United States took more than 6,000 lives; the worst natural disaster ever to strike the USA in terms of death toll.
*After the Great Storm, the city of Galveston undertook one of the largest engineering projects ever on the USA shoreline. By 1902 a four-mile (6.4 km) long, 17-feet (5 m) high seawall was in place to protect the city from future storms (fig. 5.3). In addition, 12 million cubic meters (16 million cubic yards) of sand were pumped into the city to increase the elevation of the island (fig. 6.3). The project lasted until 1906 and required tremendous sacrifices of the city's residents. Since the original wall was constructed, an additional 6 miles (10 km) of concrete wall has been added, along with lines of riprap at its base to protect the wall.
*Despite these costly efforts, Galveston remains extremely vulnerable to hurricanes. Although the wall has been successful against most of the subsequent storms of this century, a storm with the same magnitude as the 1900 hurricane would still demolish much of the city.
*Two glaring hazards plague Galveston Island. First, the highest elevation on the island is less than 15 feet (4.5 m). The only high ground available is behind the seawall, in the old city where the grade was artificially built. Second, dune heights on the entire island are less than 10 feet (3 m), and secondary dune development is virtually absent. These elements combine to create a giant flood hazard from any significant storm surge (fig. 9.14).
*Galveston Island is almost 30 miles (about 50 km) long and is entirely incorporated as the city of Galveston, although the city proper covers only the eastern one-third of the island. The island's two-mile (3-km) width, unusually wide for a barrier island in a microtidal environment, is due to the fact that in the past few thousand years the island has had a large sand supply and has widened in a seaward direction.
*The eastern end of the island is mostly moderate to high risk (fig. 9.14). Due to the seawall and the artificial grade built early this century, the land immediately behind the seawall is where the highest elevations are found, and so is classed as moderate risk. The lower elevations are found toward the back side of the island, where the risk is high.
*To the west, the island is flat and has a rural flavor complete with cattle ranches. Many low-lying interior areas are covered by fresh-water marsh. The dunes are low and narrow and vegetation consists of small shrubs and grasses typical of the semiarid climate; no developed forest has ever existed on the island. This half of the island is all rated as extreme risk or high risk (fig. 9.14). The delineation is made at the boundary of the V-zone and A- zone (from FEMA Flood Insurance Rate Maps). The area is easily flooded, easily overwashed, and has no dense vegetative protection. Hurricane Alicia passed over Galveston in 1983, leaving destruction of many homes in her wake (figs. 9.15 and 9.16).
*A potential problem with the seawall and fill is that both water washed over the wall and rain water is forced to drain to the back of the island because of the graded fill. This backside flow adds to the flooding potential. And, as with most seawalls, Galveston has no beach in front of the wall. The western terminus of the wall is a fine place to observe the loss of beach. The beach is now displaced about 100 feet landward of the seawall, where it used to be several hundred feet seaward.
*The positive result of the seawall has been property protection and halting shoreline retreat. In this respect, the wall is one of the most successful seawalls in the USA. The city probably would never have regained its footing without its protection. Still, major hurricanes such as Beulah, Carla, Celia, and Alicia have done significant damage. Additional protection is afforded to property because development is set back behind Seawall Boulevard, a four-lane highway. Fortunately, the loss of beach in front of the wall has been partially offset by sand impoundment behind the jetty at the east end of the island. This area of sand fillet provides a wide, flat, public recreational beach.
*In 1995 the city's $4 million beach replenishment project rebuilt an artificial beach along the 4-mile (6.4 km) stretch between 10th St. and 61st St. This project was the first public renourishment attempted in Galveston, and took more than 2 years to be approved. The borrow site is less than a mile (1.6 km) offshore and could have a large impact on sediment transport along the nourished beach, or adjacent beaches. In June of 1995, Hurricane Allison churned by Galveston and according to television reports, the beach replenished up to that time largely disappeared.
*Table 9.1 and 9.1B: A quick sampling of salient property damage risk attributes of islands in the Carolinas reveals that large differences may exist between adjacent islands and even on the same island. Hence the principles of hazard risk mapping and property damage mitigation must be applied in the context of recognition that no two barrier islands or coastal zones are alike.
*Bogue Banks, North Carolina:
-Atlantic Beach, Pine Knoll Shores:
-moderate elevation, moderate to wide width
-wide range of development settings
-"free" replenished beach
-Indian Beach, Salter Path, eastern Emerald Isle:
-low elevation, narrow
-historic inlet location
-wide range of development settings
-Central Emerald Isle:
-very high elevation, very wide
-Western Emerald Isle:
-wide, moderate elevation
-inlet hazard area
*Topsail Island, North Carolina:
North Topsail Beach:
-inlet hazard area
-low elevation, narrow island
-high- and low-rise commercial development
Surf City:
-low elevation
-narrow
West Onslow Beach:
-inlet hazard area
-low elevation, narrow
*Southern Brunswick County, North Carolina:
-Ocean Isle Beach
-low elevation
-finger canals
-Sunset Beach, North Carolina:
-high density single family homes
-accreting beach
*Grand Strand Area, South Carolina:
Entire area:
-mainland beach
-high elevations
-very high density high-rises
-high density single family homes in places
-North Myrtle Beach is low elevation
*Litchfield Spit, South Carolina
-very low elevation
-artificial dune destroyed by Hugo
*Pawleys Island, South Carolina:
Southern end:
-very low elevation spit
-moderate density single family homes
Central:
-moderate elevation and well forested
-high density single family homes
Northern end:
-low and narrow
-ocean to lagoon streets
*McClellanville, South Carolina
-not oceanfront
-sits back behind six miles of low marsh
-very low elevation
*Isle of Palms, South Carolina
-high density single family homes
-benefits from being updrift of jetty
*Sullivans Island, South Carolina
-high density single family homes
-benefits from being updrift of jetty
*Folly Island, South Carolina:
Southern end: low elevation spit
Central: high density single family homes
Northern end:
-historic inlet location
-extremely low elevation
-extremely narrow
-low or moderate density single family homes
-military (Coast Guard) property
*Table 9.2 Examples in the Carolinas where property damage mitigation techniques have been applied.
LOCATION ABBREVIATIONS:
FB=Folly Beach, SC
GS=Grand Strand, SC
BB=Bogue Banks, NC
TI=Topsail Island, NC
PI=Pawleys Island, SC
SB=Sunset Beach, NC
SI=Sullivans Island, SC
IOP=Isle of Palms, SC
NH=Nags Head, NC
CH=Cape Hatteras Lighthouse, NC
C=Corolla, NC.
SOFT STABILIZATION
The "Sand Commandments"
Adding Sand to the Beach
"Free" Beach Replenishment-BB, TI
Beach Replenishment-GS, CH
Beach Bulldozing-TI, NH, BB
Increasing Sand Dune Volume
Sand Fencing and Dune Building-BB, SB
Other Examples of Dune Building-SB, PI
Plugging Dune Gaps-C
Adding Sand to Interior of Island
Building Interior Dunes-BB
BUILDING RELOCATION
Relocation Philosophy-CH
Nags Head--Town on the Move-NH
The 10/100-year Relocation Concept-GS
Long Term Relocation Planning-BB, NH
HARD STABILIZATION
Shore Parallel-GS, FB, CH
Shore Perpendicular-FB, PI, CH
VEGETATION
Lagoonside Marsh Planting-BB
Maritime Forest and Hurricane Hugo-PI
Unnecessary Removal of Forest-BB
MODIFICATION OF DEVELOPMENT AND INFRASTRUCTURE
Blocking Beach Access Roads-PI
Re-orientation of Roads-FB
ZONING, LAND USE PLANNING
Recognize Hazard Areas and Avoid
Tidal Inlets
Inlet Hazard Area--Historic Inlet-FB
Inlet Hazard Area--Historic Inlet-BB
Inlet Hazard Area--Modern Inlet-BB, TI
Inlet Hazard Area--Modern Inlet Dynamics-TI
Inlet Hazard Areas--Newly Formed Inlet-PI
"Swashbuckling"-GS
Setback for Protection-BB
Deep Property Lots for Future Relocation-BB, NH
Unwise building location--major structure-FB
Living With an Accreting Beach-SB
Offshore Rubble-GS
Construction Quality and Hurricane Damage-SI, IOP
Dune gaps or breaches increase island interior flooding-NH
Table 9.3. Characteristics of the case study sites used in Chapter 9.
Wave Energy Storm Surge Climatic/ Storm Coast type Engineer/ Structures?
Southampton, NY High Moderate Hurricanes/ NEasters Low/narrow Yes
Bogue Banks, NC High Moderate Hurricanes/ NEasters One island
Wide/high
Dense forests No
Fernandina,
E. Florida Moderate Moderate Hurricanes/ NEasters Wide/very high
Dense forests Yes
Venice Beach,
SW Florida Moderate High Hurricanes/ SWesters Low/narrow Yes
Wakulla Co., FL Zero Energy Extreme Highest Hurricanes Low
Forests No
Galveston, TX Moderate to Low High Hurricanes/ SWesters Low/open/wide Yes
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