Rivers 2

Question 1

what can we use to show the relationship between precipitation and discharge?

Answer 1

hydrographs

Question 2

discharge

Answer 2

the volume of river water flowing per second, measured in cumecs

Question 3

Why is discharge not measured from 0?

Answer 3

Due to base flow

Question 4

peak discharge

Answer 4

the highest discharge in the period of time you’re looking at

Question 5

lag time

Answer 5

the delay between peak rainfall and peak discharge

Question 6

Why does lag time happen?

Answer 6

Most rainfall doesn’t land directly in the river channel. It flows quickly overland (surface runoff) or soaks into the ground (infiltration) and then flows slowly underground to the river channel.

Question 7

rising limb

Answer 7

the increase in river discharge as rainwater flows into the river.

Question 8

falling limb

Answer 8

the decrease in river discharge as the river returns to its normal level.

Question 9

a v shape where contour lines cross the river points…

Answer 9

uphill to the river’s source.

Question 10

What are the three main factors that affect flood risk?

Answer 10

-precipitation
-geology
-land use

Question 11

When does flooding occur?

Answer 11

When a river’s exceeds its maximum capacity (‘bank full’)

Question 12

A shorter lag time means…

Answer 12

peak discharge is higher and flooding is more likely to occur.

Question 13

Physical factors affecting flood risk

Answer 13

-Heavy rainfall
-prolonged rainfall
-geology
-relief

Question 14

How does heavy rainfall increase flood risk?

Answer 14

Water arrives too quickly to infiltrate to ground. This means a lot of surface runoff, which increases discharge.

Question 15

How does prolonged rainfall increase flood risk?

Answer 15

Saturates the soil meaning any further rainfall can’t infiltrate, increasing surface runoff into river channels, which increases discharge.

Question 16

How does geology increase flood risk?

Answer 16

Clay soils and some rocks e.g. granite are impermeable, increasing runoff, increasing discharge.

Question 17

How does relief of the land increase flood risk ?

Answer 17

If a river is in a steep sided valley, water will reach the river channel quicker because it can flow faster down the steep slopes. This rapidly increases discharge.

Question 18

Relief

Answer 18

Changes in land height.

Question 19

Human factors affecting flood risk

Answer 19

-land use
-(man-made drains)
-(removing trees)

Question 20

How does land use increase flood risk?

Answer 20

Buildings made from impermeable materials (like concrete), and surrounded by roads made from impermeable surfaces (like tarmac) increases surface runoff, which increases discharge.

Question 21

How do man-made drains increase flood risk?

Answer 21

They quickly transport runoff to rivers, increasing discharge.

Question 22

How does removing trees increase flood risk?

Answer 22

Trees intercept rainwater on their leaves, which then evaporates. Trees also take up and store water from the ground. This means that cutting down trees increases the volume of water that enters the river channel.

Question 23

Hard engineering

Answer 23

Man-made structures built to control the flow of rivers and reduce flooding.

Question 24

Soft engineering