Rivers Flashcards
What are the feature of the river?
Watershed Source Tributaries Confluence Estuary Delta Mouth Course Basin Distributaries
What is a water shed
The line dividing the waters of a river and its tributaries (river basin) from those of another river and its tributaries (another river basin)
What are tributaries
Smaller rivers that join a larger river
What is a confluence
The place where tributaries join the main river
What is an estuary
The tidal mouth of a river
What is delta
Land that forms at the mouth of rivers
What is the mouth of a river
Where the river enters the sea or lake
What is a source
Where the river begins
What is a course
The path of the river from the source to mouth
What is a basin
The area drained by the river and its tributaries
What are distributaries
Small rivers that break of from the main reason I we as it enters the sea
What is erosion
The wearing away of rock, the transport of that rock and its deposition. This is carried out by rivers, moving ice and the sea
Material transported by a river is called its load
What is hydraulic action
This is the erosion carried out by the force of the flowing water in the river
What is abrasion
When the river uses it’s load to erode the bed and banks (channel of the river)
What is attrition
The rivers load is worn down when the pieces collide so that the stones are smoothened and made smaller
What is solution (erosion)
Some rocks, such as limestone, are dissolved in the river.
What is solution (transport)
Rock minerals are dissolved in the water and carried away
What is saltation
Small stones are bounced along the bed of the river
What is suspension
Light material, such as silt, is transported in the water
What is traction
Larger rocks are rolled along the river bed
What is deposition
When a river slows down, it loses energy, so it deposits some of its material or load
This happens when a r ver enters a lake, or on the inner bend of a meander
What is the youthful stage of a river
Erosion ; most active during this stage (upper course). River rushes along and wears away the bed of the river, this is called vertical erosion .
Forming - V shaped valleys, steep sides and narrow valley floor, Gravity causes regolith on the valley sides to move downslope
Waterfalls
How are waterfalls formed
1) a band of hard rock lies next to softer rock
2) the river erodes the softer rock faster than the hard rock, creating the water fall
3) a plunge Poole develops at the base of a waterfall, caused by hydraulic action and abrasion, the river undercuts the harder rock, creating an overhang
4) the rock overhead collapses
5) the water fall retreats upstream
E.g. Powerscourt waterfalls
What is the mature stage of a river
Valleys in the mature stage are wider, with gentler valley sides. The river erodes laterally (on the sides or banks), widening the valley, and vertically (on the bed of a river), deepening the river channel
Forming - floodplain, a flat area along the river course that is flooded by the river. As the river floods, it lays down alluvium on the valley floor
Alluvium - a mixture of clay, silt, sand, gravel and other materials
How are meanders formed
1) water flows faster on the outer bend. The river erodes the bank of the river here by undercutting the bank and causing it to collapse (erosion)
2) the water flows slower on the inner bend. The river deposits some of its load here
This makes the inner bend more prominent
What is the old-age stage of a river
In the old age stage, the river slows down and meanders. It deposits its loaf either because it is losing energy or because the load is too great
Forming - Ox - bow lakes, when a river cuts through a bend in the meander leaving a C like shape of a lake separate to the river as the river deposits it load there blocking it of. levees
What are the causes of flooding
Usually occurs during the winter months and is often caused by extreme weather conditions, such as a number of days of heavy rainfall. But the way people manage rivers can also contribute to the flooding
E.g poorly constructed bridges, weirs and failure to dredge the riverbed can all force the extra water out onto the land
Effects of flooding include….
Deaths
Ruined farmland
Food prices increase
Higher tax
What is a dam
A dam is a barrier to hold back the flow of a river. The main dams in Roland were built to produce electricity. They also act as reservoirs to store water
