physical geography: rivers Flashcards
(23 cards)
what is the drainage basin
an area of land or catchment area drained by a single river and its tributaries
what is a watershed
an imaginary line that seperates one drainage basin from another. it frequently follows a ridge of high land.
(check book for diagrams)
what are the characteristics of the upper course (source) of a river
- narrow
-shallow
-vertical erosion
(cross profile shows a steep gradient)
what are the characteristics of the middle course of a river
-wider
-deeper
-has vertical and some lateral erosion
-cross profile is wider than the source
what are the characteristics of the lower course (mouth) of a river
-widest
-deepest
-fastest
-lateral and vertical erosion
what can occur at the upper course
v shaped valley
interlocking spurs
what can occur at the middle course
waterfalls and gorges
what occurs at the lower course
meanders, oxbow lakes and flood planes
what are the four methods of erosion
hydraulic action, abrasion, attrition and solution
what are the four methods of transportation
traction, saltation, suspension and solution
define: transportation
how material moves along the river
define: erosion
water breaking down materials
how does hydraulic action work?
(erosion) power of water crashes against material, as they hit the object, air becomes trapped in cracks of the river bank and causes it to break apart.
how does abrasion work
(erosion) when pebbles grind along the river bank and bed in an almost sand papering effect
how does attrition work
(erosion) when rocks that the river is carrying knock against each other. they break apart to become smaller and smaller.
how does solution (erosion) work
when the water dissolves certain types of rock such as limestone.
what is depostion
something that happens when a river loses energy, enters shallow water or when volume of water decreases.
what is a confluence
a point where a tributary joins a larger river
what is traction
transportation process by which larger pebbles/ boulders cannot be picked up due to little energy in the water, they are rolled across the river bed.
what is saltation
a transportation process by which there is a bit more energy than traction, smaller pebbles are present, they are picked up moved then dropped (leaping motion).
what is suspension
a transportation process by which small material is carried or floated
what is solution (transportation)
material is chemical broken down or naturally small and then dissolved and carried
what happens with erosion and transportation in the v shaped valley
erosion- vertical erosion (abrasion)
