Support systems KQ1- Hydrographs Flashcards Preview

OCR A level Geography > Support systems KQ1- Hydrographs > Flashcards

Flashcards in Support systems KQ1- Hydrographs Deck (16):
1

What do hydrographs show?

Continuous recordings of river discharge

2

What is river discharge?

Volume of water passing a given point in a given time

3

What is river discharge measured in?

Cumecs (m cubed, seconds to the minus one)

4

Why are hydrographs important?

-used to compare drainage basins and how they respond
-speed and scale of the rise in discharge can be worked out
-assess the risk of flooding
-changes in the management can be monitored

5

What is peak discharge?

Maximum discharge recorded after a rainfall event

6

What is the rising limb?

When discharge begins to rise due to overland flow

7

What is the recession limb?

When discharge begins to fall as inputs to the channel decrease

8

What is base flow level?

The level at which the stream maintains in dry spells due to ground water flows

9

What is lag time?

Time between maximum rainfall and peak discharge

10

What is peak rainfall?

Maximum rainfall value

11

What is storm flow?

The area under the graph above base flow level

12

Why is there a lag time?

Water takes time to reach the river

13

What are the features of a 'flashy' hydrograph?

-steep rising and falling limb
-reaches high peak discharge
-shorter lag time

14

What are the features of a 'non flashy' hydrograph?

-flat hydrograph
-reaches lower peak discharge
-longer lag time

15

Give some factors which might produce a 'flashy' hydrograph

-steep relief of area
-small drainage basin
-saturated soil
-heavy prolonged rain
-urban area
-frozen ground

16

Give some factors which might produce a 'non-flashy' hydrograph

-permeable rock
-vegetation
-flat land
-dry soil
-light rain