Location and landscape

Because many coastal hazards involve flooding by ocean water, people and property that are located closer to the shore and at lower elevations will generally be more exposed to hazards than people and property located farther inland and at higher elevations. Landforms and human structures can interact with coastal hazards to raise or lower this exposure. This is rarely a simple relationship. The same feature of the natural or human landscape that decreases exposure to one hazard may simultaneously increase exposure to another. For example, steep, rocky shores and cliffs may reduce exposure to flooding (compared to low-lying, gently sloping shores), but they may also increase exposure to a storm's winds and erosion. Landscape features can also cause significant differences in the intensity of hazards from place to place – even over distances as small as several hundred meters. Bays and inlets may funnel and trap storm surge, increasing exposure to flooding in areas at the ends of the bay (particularly when the winds of coastal storms blow parallel to the bay's length). Human structures such as levees and breakwaters can reduce the exposure to flooding of communities that they protect. However, by deflecting water away from these communities, they can also increase exposure in adjacent areas. They can also trap water behind them, as in the case of Hurricane Katrina.

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Figure 10.11: Oblique aerial photographs of Long Branch, New Jersey from before and after Hurricane Sandy. Note how the flood control structures (groins) have shaped the exposure to storm surge and beach erosion.
Credit: USGS: St. Petersburg Coastal and Marine Science Center