Coasts 3.1 3.2 3.3 3.4

• Backwash: The action of water receding back down the beach towards the sea
• closed system: a system that transfers energy, but not matter, across its boundary to the surrounding environment.
• constructive waves: Waves with a low wave height, but a long wavelength and low frequency. Swash is more powerful than its backwash resulting in a buildup of material on the beach.
• destructive waves: Waves that are high, steep and have a high frequency. Backwash stronger than swash. So sediment is removed.
• Dynamic equilibrium: A state of balance where inputs equal outputs in a system that is constantly changing.
• Fetch: The distance of open water over which the wind blows.
• Global ocean currents: An ocean current flows for great distances and together they create the global conveyor belt, which plays a dominant role in determining the climate of many of Earth's regions.
• High-energy coast: Where the rate of erosion exceeds the rate of deposition
• Longshore currents: When a wave reaches a beach or coastline, it releases a burst of energy that generates a current, which runs parallel to the shoreline
• Low energy coasts: Where the rate of deposition exceeds the rate of erosion.
• Neap tide: Moon at right angles to sun when in first quarter or last quarter. Gravitational pulls act against each other to create lower high tides and higher low tides.
• Negative feedback: Where a flow/ transfer leads to a decrease or decline.
• North Atlantic drift: an ocean current that brings warm, moist air across the Atlantic Ocean
• Open system: allow energy and mass to pass across the system boundary
• Positive feedback: Where a flow/ transfer leads to an increase or growth
• rip currents: a relatively strong, narrow current flowing outward from the beach through the surf zone and presenting a hazard to swimmers.
• Spring tide: Sun and moon in line at full moon or new moon. Gravitational pulls act together to create higher high tides and lower low tides.
• Swash


  when a wave washes up onto the shoreline
• Tidal bore: A long wave or bore caused by the constriction of the spring tide as it enters a long, narrow, shallow inlet.
• Wave crest


  Highest point of a wave
• Wave frequency: the number of waves that pass a point in a certain period.
• Wave height: the vertical distance between the crest and the trough of a wave.
• Wave length: the distance between two successive crests or troughs of a wave.
• wave refraction: When waves approach a coastline that is not a regular shape, they are refracted and become increasingly parallel to the coastline. The overall effect is that the wave energy becomes concentrated on the headland, causing greater erosion. The low energy waves spill into the bay, resulting in beach deposition
• wave trough


  the lowest point of a wave
• sources of sediment: rivers, cliff erosion, longshore drift, wind, glaciers, offshore
• Rivers estuaries (sources of sediment): sediment transported in rivers accounts for the vast majority of coastal sediment. esp in high-rainfall environments where active river erosion occurs.
• cliff erosion (sources of sediment): can be extremely important in areas of relatively soft or unconsolidated rocks. cliffs comprising of sand and clay have very high rates of erosion whereas cliffs made of tough, igneous granites erode at very slow rates.
• longshore drift (sources of sediment): Strength and direction of the wind. sediment is transported from one stretch of coastline (as an output) to another stretch of coastline (as an input)
• wind (sources of sediment): Direction of wind and presence of fine sands.
• glaciers (source of sediment): Areas where ice, with sediment in it, break off (clave) ice sheets.
• offshore (source of sediment): Rise of Standard Level at the end of the last ice age brough huge volumes of sediment onshore, also storm surges, tsunamis, tropical cyclones.
• sediment cell: a conceptual way of describing sediment movement from a source, through various transfers to a sink or output. This movement is usually cyclical
• the sediment cell in the form of a conceptual systems diagram has: inputs (sources)

  transfers (flows)

  stores (sinks)
• Inputs (sources) of a sediment cell: these are primarily derived from the river, coastal erosion and offshore sources
• Transfers (flows) of a sediment cell: Involve longshore (littoral) drift together with onshore and offshore processes such as rip currents.
• Stores (sinks) of a sediment cell: include the beach, sand dunes and offshore deposits (bands and bars)
• Sediment budget: the balance of sediment volume entering and exiting a particular section of the coast.

  material in a sediment cell can be considered in the form of a sediment budget with losses and gains.
• what do losses in the system involve: Deposition - beaches, salt marshes, offshore bars.
• what do gains in the system involve: Cliff erosion

  Rivers

  Offshore sources