Coasts (1/4) Inputs- Energy (Wind, Waves and Tides) and Sediment (detailed notes)


Systems and Processes

Coastline: Coasts are ‘that bit of the land affected by the sea, and the bit of sea affected by the land’. In real terms, this is up to 37 miles inland from where the sea meets land and is up to 200 miles offshore

  • Backshore: Are the area between the high water mark (HMW) and the landward limit of marine activity. Changes normally take place here only during storm activity

  • Foreshore: Is the area lying between the high water mark (HMW) and the low water mark (LWM). It is the most important zone for marine processes in times that are not influenced by storm activity

  • Inshore: Is the area between the LWM and the point where waves cease to have any influence on the land beneath them

  • Offshore: Is the area beyond the point where waves close to impact upon the seaned and in which activity is limited to deposition of sediments

  • Nearshore: Is the area extending seaward from the HMW to the area where waves begin to break. It includes all areas affected by currents due to proximity to land

Characteristics features of coastal landscapes are created by the action of wind, waves, tides and sea currents. To explain how their processes work it is important to understand where the energy comes to drive the various, weathering, erosion and mass movement processes

Input: Energy

  1. WIND

Wind is a vital input into the coastal system as it is a primary source of energy for other processes.

  • Prevailing Wind (SW)

Variations in energy results from variations in the strength and duration of the wind. Most coastlines will have a prevailing wind direction, the wind will generally reach the coast form one direction. It is one factor that controls the direction of the transport of material in the coastal zone and also the waves approach the coastline

  • Fetch

This refers to the distance of open water over which a wind blows uninterrupted by major land obstacles. The length of fetch helps to determine the magnitude and energy of the waves reaching the coast

  • Creation of Waves

Waves are created by the transfer of energy from the wind blowing over the sea surface (referred to as the ‘frictional drag of the wind. The energy acquired by waves depends upon the strength of the wind, the length of time it is blowing and the fetch.

  1. WAVES

Waves of any form- be it ocean waves, sound waves or seismic waves- are a way of transferring energy from point A to point B. There are two types of waves in the universe, electromagnetic (eg. light waves) and mechanical (eg. sound waves). The waves we’re interested in, ocean waves, are a type of mechanical waves. This means they have to travel through something (a medium) which is the case of ocean waves, is water.

Ocean waves are created by the frictional drag of wind, when it blows across an open body of water, giving them the alternate title of wind waves or wind-generated waves.


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