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Coastal Zones and Attributes

In Europe, the USA, Asia, and Australia, more than 50% of the coastline has been modified with hard engineering. Hard engineering is a permanent hard structure in a fixed position. Soft engineering is the use of reinforcements on an existing structure rather than creating a whole new project. Engineering takes place in several distinct regions on the shoreline. These regions are very specific to the environmental and physical constraints placed on the creation of a structure in each zone. The coast is the edge of the water to the next prominent change in terrain inland. Structures are commonly constructed in the region of the coast because of the slight contact with the ocean elements.  The next region is the back-shore, which is the body of land that goes from the coast to the surf line. In this region tides, surf, and temperatures are constantly changing. These factors are threats to the durability and sustainability of structures in the back-shore region. Like the back-shore, the surf-zone is an uncommon place for construction. In this zone, structures must be able to sustain constant contact with waves, erosion, and other ocean factors that lead to the degradation of the structure. The final region in regard to coastal engineering is the offshore region. The offshore region is from the end of the surf-zone outward to sea. Outside the surf line, the offshore serves as a common place for coastal engineering. Offshore drilling platforms are considered to be a mechanism of coastal engineering due to their location. The urban sprawl is the increase in artificial coastal engineering that is a result of environmental side effects.

Prominent factors addressed when considering coastal engineering are corrosion, moisture, and weathering. Corrosion is the most common side effect when building in wet, salty, and windy conditions. The coastal environment oxidizes metals, so a building alternative to certain metal alloys that easily oxidize is stainless steel. Stainless steel, with its strength and corrosion resistance, is able to be used in harsh sea conditions and does not degrade at the rate other metal counterparts would. Joints and unions for the foundation of the building generally deteriorate early on. With their constant exposure to the elements, other preferable choices would be galvanized joints or unions. The zinc coating of galvanized alloys allows for protection for 7 to 20 years, shielding the metal from corrosion. Oxidation corrodes and effects all exposed metal structures like air conditioner units, electrical outputs, light fixtures, and vents. After being exposed to air, water, and the outside world these apparatuses deteriorate and ultimately need to be replaced. Moisture that becomes trapped within objects or absorbed into materials causes decay, mildew, and deterioration of that material. Decaying and mildewing wood near the coast is a prime habitat for termites to build colonies. Termites are common in the coastal region because of their diet of decaying wood, which is battered by sun, water, and other coastal weathering.

Examples of Breakwaters

Core-Loc Structure used in the rebuilding of the Kaumalapau Harbor.

The purpose of breakwaters is to provide protection for coastal areas and harbors from wave action . Breakwaters are used for reducing breakwater in areas with poor soil and sand characteristics, reducing wave loads, and protecting the breakwater structure toe from damage. A structural component of breakwaters is called structure toes. Concrete structure toe units are small devices that are placed alongside concrete berms to aid against the movement of the shifting sea floor. Berms are laid in front of structure toes to reduce the settling of bottom sediment, increasing the sturdiness and stability of the concrete armored toes.  Kaumalapau Harbor is located on the southern corner of Lanai, HI. In 1925 the original breakwater for the harbor was created by the Hawaiian Pineapple Company, today known as Dole. The breakwater stood 10 feet tall and extended out 350 feet into the ocean in order to prevent swell and crashing waves from destroying the surrounding waterway. The water depth around the breakwater was measured to be 21 meters deep and with hurricane storm conditions the breakwater would protect form thirty-foot-high waves that would crash on the breakwater. Constructed out of quarried stone, many repairs were necessary, leaving engineers wondering if the creation of the breakwater was planned or by accident. After several recent hurricanes, the Army Corps of Engineers decided to reconstruct the original breakwater into something more efficient that will not have to be repaired as often. Tests were conducted in a wave flume, a scientific tool used to model the movement of waves, in addition to calculations to determine the stability formula for the design of the breakwaters. The rebuild consisted of using newly designed 35-ton Core-Loc concrete armor. Completed in 2007, the Kaumalapau Harbor breakwater project costed a $21,299,000.