Rivers

Waterfalls

• F= In a waterfall a river falls over a vertical slope. This happens where a sudden drop occurs in the course of the river.
• E= Powerscourt Waterfall on the River Dargle in Co.Wicklow, Angel Falls Venezuela, Victoria Falls Zimbabwe.
• E= 1) A band of hard rock lies over an area of soft rock.
• 2) Using the process of hydraulic action + abrasion the The river erodes the soft rock more quickly than the hard rock so that a vertical drop develops where the hard and soft rock meet. The river flows over this drop as a waterfall.
• 3) Falling stones and water wear away a hole called a plunge pool in the soft rock.
• 4) Hard rock is left hanging over the edge of the waterfall. This is called an overhang. The hard rocck above the plunge pool is undercut and collapses into the plunge pool. As this continues the river slowly erodes its way upstream.
• https://www.youtube.com/watch?v=AhiL2HJzhxc (Einbetten)

Meanders

• F= Meanders
• E= 1) When a river has developed a winding course, the curves in the river become more pronounced until they form meanders.
• 2) Meanders are developed by both erosion and deposition.
• 3) The river flows faster on the outside of each bend. Erodion happens here.
• 4) The river flows more slowly on the inside of each bend deposition happens here.
• E= Mature stage of the River Shanonn and the Boyne.
• https://www.youtube.com/watch?v=_JcbQV30gBw (Einbetten)

Ox-Bow Lakes

• F= Ox-Bow Lakes.
• E= 1) They are horseshoe shaped lakes.
• 2) Erosion takes place on the outer banks of meanders.
• 3) The neck of land between meanders becomes very narrow.
• 4) It is eventually worn away during times of flooding.
• 5) The river now flows straight through instead of folowing the meander.
• 6) Deposits then seal off both ends of the abadoned meander which is now called an Ox-Bow Lake.
• E= River Moy, Co.Mayo.
• https://www.youtube.com/watch?v=ykKl79lSylU&index=16&list=PLPyIFM6OV7iug6YWAjXNjvsbCj9o7kkEC (Einbetten)

Floodplains

• F= Floodplains.
• E= 1) In times of heavy rain, river water may rise and flood surrounding flat ground .
• 2) As the floodwaters subside, they deposit thin layers of alluvium on the land.
• 3) These build up covering the floodplain in fertile alluvial soils.
• E= Old age stage of River Boyne.
• https://www.youtube.com/watch?v=WSw6Uh_4-vI&index=21&list=PLPyIFM6OV7iug6YWAjXNjvsbCj9o7kkEC (Einbetten)

Deltas

• F= Deltas
• E= Deltas are triangular shaped areas of land which form at the mouth of rivers. They are made up of alluvium.
• 2) When a river enters the sea it loses its energy and it deposits what remain of its load. If the sea cannot wash away these deposits they will build up to form a Delta at the river mouth. Soon the river channel chokes and causes the river to break up into a number of smaller chanells called distributaries.
• E=
• * The River Nile, Egypt.
• * The Mississippi River in Louisiana, USA.
• * The River Shanonn in Limerick, Ireland.
• https://www.youtube.com/watch?v=XorJptywI_8&list=PLPyIFM6OV7iug6YWAjXNjvsbCj9o7kkEC&index=18 (Einbetten)

Levees

• F= Levees
• E= 1) Levees are long narrow ridges of alluvium found along the banks of old rivers due to deposition.
• 2) Each time a river floods, its floodwater deposits most of its load close to a riverbank.
• 3) After numerous floodings these deposits build up to form levees.
• 4) some levees are man-made to prevent flooding of farmland or urban areas.
• E= Lee Fields, Cork City.
• https://www.youtube.com/watch?v=IuR0LQEBw98&index=20&list=PLPyIFM6OV7iug6YWAjXNjvsbCj9o7kkEC (Einbetten)

Case Study: New Orleans.

• * Where?: New Orleans, USA.
• * Location?: Low ground on the Delta of the Mississippi River.
• * When?: 29th August 2005.
• * What Happened?: New Orleans is protected from flooding by levees. When a violent hurricane crashed into the coastline. A great surge of seawater swept up the Mississippi. Some of the Levees which protected New Orleans gave way. The city was invaded by a wall of water. As many as 100,000 poor people had neither the transport nor the money needed to leave. They became trapped in what was sonn to become a stinking wasteland of polluted floodwater. Almost two thousand people drowned. Government and emergency services was inadequate and slow to arrive and many people died of thirst and the baking heat.
• 

Hydroelectric Dams

• Benefits of Hydroelectricdams:
• * They enable hydroelectric powerbto be generated for our homes, schools, etc.
• * Artificial lakes can be used as reservois (storage areas) for urban water suppliers.
• * Artificial lakes can be used for fishing and other water sports.
• Disadvantages of Hydroelectric dams:
• *Artificial lakes flood settlements and valuable farmland.
• * The survival of salmon and other river creatures may be threatened if their natural habitat is interferred with.
• * It is difficult and expensive to dam ariver.
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