Hydrographs date today i will be able to construct and understand flood hydrographs
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Higher Geography Hydrosphere. Hydrographs [Date] Today I will: - Be able to construct and understand flood hydrographs. Higher Geography Hydrosphere.

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Hydrographs date today i will be able to construct and understand flood hydrographs

Higher Geography

Hydrosphere

Hydrographs [Date]Today I will:- Be able to construct and understand flood hydrographs


Higher Geography

Hydrosphere

What is a hydrograph?A hydrograph is a graph showing the rate of flow (discharge) versus time past a specific point in a river. The rate of flow is typically expressed in cubic meters (m3).They are used to show how rivers respond to a flood.

Hydrographs are used to help predict flooding events therefore influence implementation of flood prevention measures.


Higher Geography

Hydrosphere


Higher Geography

Hydrosphere


Higher Geography

Hydrosphere


Basin lag time

Peak flow

3

Rising limb

Overland flow

Recession limb

2

Discharge (m3/s)

mm

4

Through flow

1

3

2

Base flow

0 12 24 36 48 30 72

Hours from start of rain storm


3

Discharge (m3/s)

2

1

0 12 24 36 48 30 72

Hours from start of rain storm

The discharge of the river is measured in cumecs - this stands for cubic metres per second


Rainfall expressed in mm

3

2

mm

Discharge (m3/s)

4

1

3

2

0 12 24 36 48 30 72

Hours from start of rain storm


Discharge in m3/s, as a line graph

3

2

mm

Discharge (m3/s)

4

1

3

2

0 12 24 36 48 30 72

Hours from start of rain storm


The rising limb is when the normal (base) flow of the river starts to rise when run-off, ground and soil water reaches the river.

3

Rising limb

2

mm

Discharge (m3/s)

4

1

3

2

0 12 24 36 48 30 72

Hours from start of rain storm


Peak flow

3

Peak flow is when the Maximum discharge in the river, the time when the river reaches its highest flow

Rising limb

2

mm

Discharge (m3/s)

4

1

3

2

0 12 24 36 48 30 72

Hours from start of rain storm


Peak flow

The recession limb shows that water is still reaching the river but in decreasing amounts

3

Rising limb

Recession limb

2

mm

Discharge (m3/s)

4

1

3

2

0 12 24 36 48 30 72

Hours from start of rain storm


The basin lag time is the time it takes for the water to find its way to the river

Basin lag time

Peak flow

3

Rising limb

Recession limb

2

mm

Discharge (m3/s)

4

1

3

2

0 12 24 36 48 30 72

Hours from start of rain storm


Basin lag time

Base Flow is the normal discharge of the river

Peak flow

3

Rising limb

Recession limb

2

mm

Discharge (m3/s)

4

1

3

2

Base flow

0 12 24 36 48 30 72

Hours from start of rain storm


Overland flow

Basin lag time

+

Peak flow

Through flow

3

=

Rising limb

Overland flow

Recession limb

Storm Flow

2

mm

Discharge (m3/s)

4

Through flow

1

3

2

Base flow

0 12 24 36 48 30 72

Hours from start of rain storm


Higher Geography

Hydrosphere

Read the information on page 230 and 231 of the NWW Textbook. Copy the table below into your jotter and fill in the information gathered.

Reasons for Differences in Flood Hydrographs


Higher Geography

Hydrosphere

Can you label 1 to 8 accurately?

7.

1.

6.

8.

5.

4.

2.

3.


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