What are levees in geography?
Levees are natural embankments which are formed when a river floods. Smaller material is deposited further away and leads to the formation of gently sloping sides of the levees. High pressure, caused by a river meeting its bank-full capacity, can cause a levee to burst.
What are the characteristics of levees?
The banks form levees made of sediment, silt, and other materials pushed aside by the flowing water. Levees are usually parallel to the way the river flows, so levees can help direct the flow of the river. Levees can also be artificially created or reinforced.
What are levees GCSE geography?
Levees. Levees occur in the lower course of a river when there is an increase in the volume of water flowing downstream and flooding occurs. Sediment that has been eroded further upstream is transported downstream. When the river floods, the sediment spreads out across the floodplain.
What is the purpose of levees?
Levees are designed to reduce flood risk from flooding events; however, they do not eliminate the risk entirely. It is always possible that a flood will exceed the capacity of a levee, no matter how well the structure is built.
How long do levees last?
The average age of levees in the U.S. is 50 years and many are showing their age. While there are newer or reconstructed levees, a large number of levees were built in response to the widespread flooding on the Mississippi River in 1927 and 1937, and in California after catastrophic flooding in 1907 and 1909.
What are levees 7 geography?
Levees are the raised banks of the rivers. The streams which distribute the waters of a river are known as distributaries. The triangular deposits at the mouth of a river from the delta, which is very fertile. The erosion and deposition of the sea waves give rise to coastal landforms.
What are advantages and disadvantages of levees?
Floodwalls and Levees Advantages and Disadvantages
|In some cases, costs less than elevating or relocating the structure||May be expensive depending on height, length, availability of materials, and other factors|
|Allows the structure to be occupied during construction||Requires periodic maintenance|
What is natural levees in geography?
Natural levees are embankments formed naturally after a river floods and recedes. The deposits in natural levees contain mud, sand, and stones and are formed such that they slope away from either side of the river or flood plain.
What are the advantages and disadvantages of levees?
Why are levees bad?
Levees have been the nation’s most common method of flood control for much of US history, despite a major drawback: Levees protect the land immediately behind them, but can make flooding worse for people nearby by cutting off a river’s ability to spread over the floodplain—the flat, low-lying land beside the river …
Why do levees fail?
Sometimes levees are said to fail when water overtops the crest of the levee. Levee overtopping can be caused when flood waters simply exceed the lowest crest of the levee system or if high winds begin to generate significant swells (a storm surge) in the ocean or river water to bring waves crashing over the levee.
Where does the geography of Greece take place?
Greek Geography. Greece is a land of mountains. They begin in the north-west of the country, and run south-east until they slip beneath the waves of the sea; their peaks periodically breaking the surface to form the thousands of islands for which the Greek waters are renowned.
Which is the largest natural lake in Greece?
Lake Trichonida is the largest natural lake in the country and occupies an area of 38.1 square miles. Lake Trinonida is situated in the eastern region of Aetolia-Acarnania near the city of Agrinio. The lake’ length stretches a maximum 12 miles and is 190 feet at its deepest part.
Which is the longest river in the country of Greece?
Greece has numerous rivers that make up the country’s drainage system. Many of the rivers originate from the many mountain ranges that characterize the country’s geography. The Haliacmon River is the longest river in the country and flows 185 miles in Greece.
Where are the most of the Greek islands located?
Most of them are located in the Aegean between the mainland and Turkey. The largest Greek island is Crete and the second largest is Evia. Lesvos and Rhodes come next. Some of the most famous islands are Santorini, Mykonos, Rhodes, Crete, Zakynthos, and Corfu.