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Geography A Level > 3. Hydrographs > Flashcards

3. Hydrographs Flashcards

1
Q

What is a Hydrograph?

A

A hydrograph is a means of showing the discharge of a river at a given point over a short period of time (an individual rainfall event)

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2
Q

Cumecs

A

Cubic Metres per Second

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3
Q

Peak Flow / Peak Discharge

A

The highest level of water reached during a flood

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4
Q

Bankfull Discharge

A

When the river is completely full - if it rises further there will be flooding!

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5
Q

Rising Limb

A

Measures increasing discharge over time. Steeper limb = flashier flood!

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6
Q

Falling Limb / Recession

A

Measures discharge after peak discharge / heavy flow.

  • Decreasing in steepness
  • Less steep than rising limb because of throughflow now reaching river (to increase water level).
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7
Q

Runoff / Storm Flow

A

Stream discharge after a rainstorm, produced by a combination of overland flow and then throughflow (overland makes greatest contribution).

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8
Q

Base Flow

A

(Normal flow ) - stream discharge produced by water seeping from bedrock

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9
Q

Lag Time

A

The difference between peak rainfall and peak discharge.

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10
Q

Rainfall Peak

A

The maximum volume of rainfall that occurrs in a storm event.

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11
Q

Approach Segment

A

The discharge before rainfall

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12
Q

Infiltration Capacity

A

The maximum rate at which the soil will absorb water

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13
Q

Rainfall Intensity

A

Amount of rain in a given time

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14
Q

If infiltration capacity is greater than rainfall intensity…

A

…the stores (capacity of the soil to store water) will fill up before overland flow occurs. This is typical of many locations in the UK.

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15
Q

If infiltration capacity is lower than rainfall intensity…

A

…then rapid runoff occurs (known as Hortonian flow). Water cannot enter the ground so it runs straight off.

This often occurs in hot arid and seri-arid environments.

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16
Q

What does a steeper / more peak-like rising limb represent?

A

A steeper / more peak-like rising limb represents a more rapid response to rainfall with a shorter time of rise / lag time.

17
Q

Which physical factors (catchment area) lead to steeper rising limbs?

A

Catchment area factors leading to steeper rising limbs:

  • Impermeable rock in (most) of catchment area
  • Extensive bare rock with little soil
  • Cold climates with little vegetation
  • Large, dendritic drainage basin (catchment area) with a high drainage density
  • Basin with steep valley sides
  • Thin soil with limited infiltration capacity
18
Q

Which physical factors (weather) lead to steeper rising limbs?

A

Weather factors leading to steeper rising limbs:

  • Major intensive thunderstorm
  • Saturated soil following prolonged rainfall (Aberfan)
  • Fast snow melt
19
Q

Which human factors lead to steeper rising limbs?

A

Human factors leading to steeper rising limbs:

  • Rivers without dams
  • Urbanised river basins
20
Q

What does a flatter / gentler rising limb represent?

A

A flatter / gentler rising limb represents a slower response to rainfall and a longer lag time

21
Q

Which physical factors (catchment area) lead to gentler rising limbs?

A

Catchment area factors leading to gentler rising limbs:

  • Catchment area contains permeable rock (porous or pervious)
  • Large areas of vegetation / forest
  • Humid climate and denser vegetation
  • Small, linear drainage basin / drainage basin with a low drainage density
  • Basin with gentle valley sides
  • Thick / deep soil with a large infiltration capacity
22
Q

Which physical factors (weather) lead to gentler rising limbs?

A

Weather factors leading to gentler rising limbs:

  • Long period of gentle rain
  • Dry, thick soil (less prolonged rainfall so less saturated)
  • Slow snow melt
23
Q

Which human factors lead to gentler rising limbs?

A

Human factors leading to gentler rising limbs:

  • River with dams
  • Rural river basins (not urbanised)
24
Q

What factors affect a river’s regime?

Very similar to factors affecting flashiness of flood

A

Factors affecting a river’s regime:

Climate - amount and distribution of rainfall e.g. seasonal
Snowmelt patterns
Geology - permeable / impermeable rock
Rates of evapotranspiration (vegetation)
Steepness of land
Human factors - abstraction for domestic water supply / dams / irrigation

Some factors not included here can be added from ‘factors affecting rising limb’

25
Q

Why is it useful to know about the river’s regime?

A

Why is it useful to know about the river’s regime?

  • Irrigation
  • Shipping
  • Sewage disposal
  • Recreation
  • Water supply
  • Seasons with increased flood risk
  • Rice planting
26
Q

Why might humans build dams to regulate a river’s regime?

A

Reasons for dams:

  • Hold back high flow to prevent flooding
  • Hold back high flow as a water source e.g. for irrigation
  • Hold back high flow to generate HEP evenly throughout the year

Geography A Level (33 decks)

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