Wave refraction the bending of wave fronts as they

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Wave refraction : The bending of wave fronts as they approach shallow water near the shore. Longshore current : A current of water that travels parallel to the coast. This occur when waves break on the shore at an angle. Longshore drift : Refers to sediment that is transported parallel to the shore through longshore current. Coastal Structures Since the coast is a high-energy environment, deposition and erosion continuously form a variety of geological features (Fig. 2). Accumulated sand that builds a ridge off a point of land is called a spit . The spit usually points in the direction of sediment transport along a shore. In the instance where a sand spit connects two land masses (e.g. an island and the main land), it is referred to as a tombolo . If a sand ridge builds up to form a bar that closes off a bay from the open ocean, it becomes a baymouth bar . Rocky points of land that protrude seaward, and are often made of resistant rock types, are called headlands . Remnants of eroded headlands are known as sea stacks . When a horizontal bench forms through wave erosion and cliff retreat it is called a wave-cut platform . When a cliff forms through wave erosion and mass wasting, it is called a sea cliff . Sea cliffs occur in regions of high relief. Figure 2. A diagram illustrating coastal landforms.
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Lab #6: Streams, Coastlines & Groundwater 88 Coastal Disaster Prevention The structures listed below are placed to prevent coastal erosion or sedimentation. However, many of these stuructures frequently fail due to catastrophic natural events (Fig. 3). Jetties : Walls built to protect harbor entrances from sediment deposition and storm waves. Jetties are often built in pairs. Groins : Structures built perpendicular to the shore. Groins are meant to trap sediment and widen the beach in the up-current direction. Breakwater : Off shore structure built to absorb energy of breaking waves and provide quiet water near the shore. Bulkhead/seawall : Structure built at the base of a slope parallel to the shore. It is designed to protect the shoreline from energy of breaking waves and prevent erosion. Groundwater Groundwater is a critical part of the hydrologic (water) cycle that results from the infiltration of rain or surface water. Water seeps downward through the soil and cracks in rocks to restore the groundwater supply. A recharge area is where water soaks into the ground from the surface (e.g. rainy spots, lakes, etc.). A discharge area is where water leaks out of the groundwater system (e.g. streams, springs, etc.). Groundwater flow rates depend on the porosity and permeability of the subsurface material, as well as the hydraulic gradient (the slope of the water table). Porosity is the volume of pore space in soil, sediment, and rock, and is often reported as percentage (%) of open space in a rock. Permeability is the ability to transmit fluid, and how easy fluids travel through the pore space.
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