River Regimes And Flood Hydrographs

Question 1

What is a river regime?

Answer 1

The annual variation in the discharge of a river, the amount of water that travels through a river and how this changes throughout the year

Question 2

What might influence the river regime?

Answer 2

Urbanisation
Deforestation
Slope/ gradient
Intensity/type of weather event
Rock type

Question 3

What is a perennial channel?

Answer 3

Continuous flow in parts of its bed all year round during years of normal rainfall

Question 4

What is an intermittent channel?

Answer 4

Normally ceases flowing for weeks or months each year

Question 5

What is an Ephemeral channel?

Answer 5

Only flows for hours or days following rainfall

Question 6

What type of river regime is the river wye?

Answer 6

Perennial as it has continuous flow all year around

Question 7

Where is the river wye drainage basin would you expect to find intermittent or ephemeral channels?

Answer 7

Some tributaries in the mountains of mid wales near the source of the Wye will be ephemeral because of the extreme variations in the mountain climate

Question 8

What is common in hydrograph’s in areas with snow cover?

Answer 8

In the summer months there will be an increase in discharge because of snowmelt

Question 9

In warmer climates around India what in the cause for an increase in rainfall in the summer months?

Answer 9

Monsoons

Question 10

What is the main geology of the River Wye?

Answer 10

Predominantly characterised by old red sandstone

Question 11

What are the characteristics of sandstone?

Answer 11

It is permeable
Which means it increases the lag time reducing the peak discharge

Question 12

How does building new houses affect the river regime?

Answer 12

It creates impermeable surface and drainage systems with reduce lag time and increase peak discharge

Question 13

How does damming affect the river regime?

Answer 13

Prevents the natural flow of the river so discharge/flow downstream in reduced

Question 14

What are flood hydrographs?

Answer 14

Graphs that show how a drainage basin responds to a period of rainfall

Question 15

What is peak discharge?

Answer 15

The highest recorded discharge following a rainfall event

Question 16

What is peak rainfall?

Answer 16

The highest amount of rainfall per unit of time

Question 17

What is the rising limb?

Answer 17

Shows how quickly the discharge rises after a rainstorm

Question 18

What is lag time?

Answer 18

The time difference between peak rainfall and peak discharge

Question 19

What is the falling limb?

Answer 19

Shows the reduced discharge once the main effect off run-off has passed

Question 20

What is base flow?

Answer 20

The normal flow of the river when its water level is being sustained by ground water flow

Question 21

What is the bank full discharge?

Answer 21

The level of discharge above which flooding will occur

Question 22

What will the drainage basin of a flashy hydrograph be like?

Answer 22

Small circular basin as the water reaches the channel rapidly as it has a shorter distance to travel
Steep slopes
Impermeable surfaces

Question 23

What will the basin size of a typical hydrograph be like?

Answer 23

A large basin that means water will take longer to reach the channel as it has a greater distance to travel

Question 24

What will the basin shape be of a flashy hydrograph?

Answer 24

Circular basin will take less time for the water to reach channel as the extremities are equidistant

Question 25

What will the basin shape of a flatter/ typical hydrograph be?

Answer 25

Elongated basin Water will take longer to reach the channel format he extremities

Question 26

What will the slopes be like for an area with a flashy hydrograph?

Answer 26

Steep slopes Water flows down hill rapidly and reaches the channel quickly

Question 27

What will the slopes be like in an area with a typical hydrograph?

Answer 27

Gentle slopes water can infiltrate into the ground and travel slowly to channel through soil/ rock.

Question 28

What the hydrograph of an area with clay and thin soils look like?

Answer 28

Flashy hydrograph As clay soil has a low porosity So water infiltrates slowly Thin soils are saturated easily

Question 29

What will the hydrograph look like in an area with sandy soils and thick soils?

Answer 29

Flatter as sandy soils have a: High porosity meaning water can infiltrate Deep soils allow infiltration

Question 30

What will the hydrograph look like in an area with impermeable rocks?

Answer 30

Flashy Percolation wont occur Increased surface run-off

Question 31

What will a hydrograph look like in an area with permeable rock?

Answer 31

Flatter Percolation can occur

Question 32

What will the hydrograph look like in an area with a high drainage density?

Answer 32

Flashy Many streams per km2 means water will reach the channel quicker

Question 33

What will a hydrograph look like in an area with low drainage density?

Answer 33

Flatter Small number of streams per km2 means water travels slowly back to the channel

Question 34

What will a hydrograph look like in an area with thin grass?

Answer 34

Flashy Little water intercepted Little loss by evapotranspiration More water reaches channel

Question 35

What is a flashy hydrograph?

Answer 35

When there are sharp vertical increase sin river discharge

Question 36

What will a hydrograph look like from an area with forest and woodland?

Answer 36

Flatter/ typical More water intercepted High evapotranspiration rates Less reaches the channel and more slowly

Question 37

What will the hydrograph look like in an urban area?

Answer 37

Flashy More impermeable surfaces (road and drains) mean water gets to the channel quicker

Question 38

What will a hydrograph in a rural area look like?

Answer 38

Vegetated surfaces intercept water and allow infiltration so water travels slowly to the channel

Question 39

What will the hydrograph look like after high intensity rainfall?

Answer 39

Flashy Rain falls faster then infiltration capacity so surface run-ff occurs water reaches the channel quicker

Question 40

What will a hydrograph look like after low intensity rainfall?

Answer 40

Flatter/ typical Water can infiltrate into soil where it travels slowly to river channel

Question 41

What will a hydrograph look like after prolonged rainfall?

Answer 41

Flashy Water table rises Soil becomes saturated Increased surface runoff Water reaches channel faster

Question 42

What will a hydrograph look like after short duration rainfall?

Answer 42

Flatter Most water infiltrates into soil Slower travelling through soil and rock

Question 43

What will a hydrograph look like in an area with fast snowmelt?

Answer 43

Flashy Water can’t infiltrate the frozen ground Flows rapidly to channel

Question 44

What will a hydrograph look like with slow snowmelt?

Answer 44

Flatter Ground thaws is melt water can infiltrate into soil so moves slower to the channel

Question 45

What will a hydrograph look like in an area with low evapotranspiration rates?

Answer 45

Flashy Fewer losses from the drainage basin Increased discharge

Question 46

Hat will a hydrograph look like in a area with high evapotranspiration rates?

Answer 46

Flatter Increased form drainage basin Reduced discharge