Coastal Environments Sand Dune Systems Coastal environments are very important ecologically, especially in the UK as we live on a small island with nowhere being more than a few hours away form the coast. In this presentation, I will try to first explain a little about their formation. This needs to be understood in order to understand the processes that follow. Classification is needed to identify specific types of dunes as each has differing characteristics and therefore different properties.

Coastal Dunes Temperate latitudes. Accumulation of windblown sediment needed in backshore zone. UK - around 7-8% of coast has vegetated dunes. The UK provides ideal conditions for the formation of sand dunes which is why they are relatively abundant. It is because they are so common that they are important in ecological and geographical terms. Examples of coverage: Ynyslas near Aberystwyth - spit dunes. Needs vegetation, low rainfall, strong winds and abundant sand. Lindsey Wood, liw2, 022423830

Sand Movement Saltation sand blown downwind. Transfers energy through other grains. 75% of sand moved by this method. Surface Creep By product of saltation. Pushed along sand surface Must be dry In order to fully understand the dune formation, the reasons of how and why they form need to be outlined. Saltation - grain is 2000 times heavier than the equivalent volume of air and so becomes bouncy. When a grain bounces, it transfers energy to adjacent snad grains which are lifted and bounce etc. See “An Introduction to Coastal Geomorphology” for further details. Surface Creep - started by the descending saltating grains. As saltating grain hits a larger grain, it is too heavy to be lifted upwards so the impact makes it roll forwards instead. Relatively Small amount of sand moved this way, around 25% although significant as it sorts the grain sizes out. Saltating grains move faster and further, surface creep grains move slower and shorter distances. Lindsey Wood, liw2, 022423830

Formation Embryo dunes Foredunes Grey dunes obstacle forces deposition of sand Embryo Fore Grey Foredunes embryo dunes coalesce laterally Embryo Dunes - Needs obstacles for sand to accumulate, e.g. some driftwood or a bottle. The obstacle changes the natural path of the wind and they pass around the object. Wind increases to the sides and in its lee wind speeds decrease to zero and slowly rise downwind. As wind speed governs sand deposition, sand transport rates change. Sand is eroded from the sides and deposited in its lee. It forms a long streamlined ridge, parallel to the wind direction, sometimes known as a shadow dune. Foredunes - An extension of embryo dunes. As embryo dunes grow they extend laterally and therefore coalesce to form longer ridges. Growth is exaggerated due to a change in vegetation . As the dunes get taller, they are further away from the water table so the pioneering species can not grow as well, giving way to marram grass. This traps more sand so growth rates increase. Grey Dunes - growth is due to a combination of changes in wind velocities in the windward and lee directions. The beach profile gives a diagrammatic guide to the transition of dunes in a landwards direction. Grey dunes includes 1st, 2nd, 3rd dune ridges etc. Growth of foredunes Lindsey Wood, liw2, 022423830

Classification Lindsey Wood, liw2, 022423830 A summary of appearance of dunes. Dunes get increasingly larger landwards, shown in diagrammatic form in the next slide. Lindsey Wood, liw2, 022423830

Further Classification Bay Dunes eg. Studland Spit Dunes eg. Ynyslas, see right Hindshore Dunes eg. Merthyr Mawr Ness or Forland Dunes eg. Tentsmuir Offshore Island Dunes eg. Scott Head Ynyslas Dunes dunes Although all the dunes have the same basic kind of formation and overall appearance, some have more specialised forms and only appear in specific places. These are summarised in the slide. http://www.bbc.co.uk/wales/mid/fun/wallpaper/pages/ynyslas_sand_dunes.shtml Lindsey Wood, liw2, 022423830

This powerpoint was kindly donated to www.worldofteaching.com http://www.worldofteaching.com is home to over a thousand powerpoints submitted by teachers. This is a completely free site and requires no registration. Please visit and I hope it will help in your teaching. Lindsey Wood, liw2, 022423830