rivers

Question 1

when does surface run off occur

Answer 1

urban places - tarmac etc

when soil is saturated

Question 2

what is infiltration ?

Answer 2

when surface water soaks in soil

Question 3

what is the difference between through flow and ground water flow ?

Answer 3

through flow is when water flows through the soil, under the influence of gravity, towards a river

ground water flow is a very slow flow that occurs in rocks and feeds rivers and springs

Question 4

what is percolation ?

Answer 4

water moves downwards through the soil into permeable rocks

Question 5

drainage basin system order from precipitation down to ground water flow and to evaporation

Answer 5

precipitation 
interception 
surface storage 
infiltration 
soil moisture 
percolation 
groundwater 
groundwater flow 
river channel
evaporation

Question 6

water shed

Answer 6

the boundary between two drainage basins marked by a ridge of high land

Question 7

drainage basin

Answer 7

the area which is drained by a river and its tributaries

Question 8

drainage density

Answer 8

the total length of all the streams in the basin divided by the total length of the basin

Question 9

what are the processes of transportation?

Answer 9

traction

saltation

suspension

solution

Question 10

traction

Answer 10

The largest rocks in the river are slowly rolled along the bottom of the river by the force of the water. This primarily occurs in upper reaches of the river.

Question 11

saltation

Answer 11

smaller rocks are bounced along the river bed. this occurs in the upper and middle sections of the river in general

Question 12

suspension

Answer 12

The water carries smaller particles of material. This process occurs throughout the course of the river, but increases the closer you get towards the mouth.

Question 13

Solution

Answer 13

material is dissolved within the water and carried along by it. Primarily this occurs in the middle and lower reaches of the river

Question 14

different types of erosion / meanings

Answer 14

abrasion (thrown against bed / banks)

attrition (crashing together)

hydraulic action (water forces air to be trapped - pressure eventually causes rocks to crack and break)

corrosion (chemical erosion of rocks along river over bank by slightly acidic water)

Question 15

v shaped valleys

Answer 15

• river erodes downwards (abrasion)
• as river cuts down the steep sides are attacked by weathering (abrasion/corrosion/hydraulic action)
• this breaks up and loosens the soil and rock. The loosened material slowly creeps down the slope because of gravity or is washed into the river by rainwater. The river carries it away. The end result is a steep sided valley that has the shape of a V

Question 16

waterfalls and gorges

Answer 16

• river meets band of softer, less resistant rock.
• erosion such as abrasion cause undercutting
• softer rock is eroded more quickly
• more resistant left unsupported and overhangs
• hydraulic action helps create deep plunge pool
• more resistant collapses onto river bed, causing abrasion of river bed
• repeats and waterfall retreats upstream. steep sided river valley is created called a gorge