Date 03 December 2020 Hydrographs Complete the multiple

Date: 03 December 2020 Hydrographs Complete the multiple choice quiz on rivers Learning Objectives: To be able to describe what a hydrograph is To be able to explain how precipitation links to discharge To be able to evaluate how hydrographs differ

How does precipitation link to discharge? What is discharge? Discharge is the volume of water passing a particular point in a river in a given time. It is measured in cubic metres per second (cumecs). Discharge = Cross section x velocity A river’s discharge can depend on many factors, including the amount, type and intensity of precipitation. A hydrograph shows how a river’s discharge changes in response to a precipitation event.

PEAK RAINFALL=highest rainfall Discharge (m 3/s) 3 Rainfall shown in mm, as a bar graph 2 mm 4 1 3 2 0 12 24 36 48 60 Hours from start of rain storm 72

PEAK DISCHARGE / FLOW=highest discharge of the river Discharge in m 3/s, as a line graph Discharge (m 3/s) 3 2 mm 4 1 3 2 0 12 24 36 48 60 Hours from start of rain storm 72

Rising limb Rising Discharge (m 3/s) 3 The rising flood water in the river 2 mm 4 1 3 2 0 12 24 36 48 60 Hours from start of rain storm 72

Falling limb Peak flow limb b lim 2 g Rising llin Fa Discharge (m 3/s) 3 Falling flood water in the river mm 4 1 3 2 0 12 24 36 48 60 Hours from start of rain storm 72

lag time limb Time difference between the peak of the rain storm and the peak flow of the river ion ss Rising ce lim 2 Peak flow Re mm b Discharge (m 3/s) 3 Lag time 4 1 3 2 0 12 24 36 48 60 Hours from start of rain storm 72

lag time limb Normal discharge of the river ion ss Rising ce lim 2 Peak flow Re mm b Discharge (m 3/s) 3 Base flow 4 1 3 2 0 Base flow 12 24 36 48 60 Hours from start of rain storm 72

How might hydrographs differ? Brainstorm reasons why these hydrographs look different. Think of human and physical factors that will affect the discharge. Learning Objectives: To be able to describe what a hydrograph is To be able to explain how precipitation links to discharge To be able to evaluate how hydrographs differ

Assess your learning- did you get these factors? • • Prolonged rainfall Impermeable soil/ rock Steep sided valley Small river basin Little vegetation Urban area Poor farming practices Learning Objectives: To be able to describe what a hydrograph is To be able to explain how precipitation links to discharge To be able to evaluate how hydrographs differ Read the hand out to find out more

B Discharge A Time A ‘flashy’ hydrograph has a short lag time and a high peak discharge Other hydrographs have a longer lag time and a lower peak discharge

Factors affecting the shape of a hydrograph Factor Flashy, rapid Flat, slow Relief Steep slopes rapid runoff Gentle slopes, slow down water transfer Rock type Impermeable rock, encourage rapid overland flow Permeable rock, allowing water to soak into rocks where transfer is slow Soil Very thin soil, saturated leads to run off Deep soil, absorb water Natural vegetation Thin grass, moorland encourages rapid transfer to rivers Forest, water is intercepted and evaporates Land use Urbanisation, impermeable surfaces encourage rapid overland flow Rural area, water absorbed Use of river Limited use of river Used for industry, dam built Drainage density Higher density Lower density

Extended Writing You are looking to move home. However, you are worried it may be an area that is prone to flooding. You need to do your research. Compose an email to the local council, putting forward your concerns. Include: àHow 2 physical factors cause flooding àHow 2 human factors cause flooding àYour knowledge on hydrographs and how they can look flashy! Learning Objectives: To be able to describe what a hydrograph is To be able to explain how precipitation links to discharge To be able to evaluate how hydrographs differ

Plenary Quick fire definitions: 1. Lag time 2. Rising Limb 3. Peak discharge 4. Base flow 5. Flashy hydrograph 6. Slow response hydrograph Learning Objectives: To be able to describe what a hydrograph is To be able to explain how precipitation links to discharge To be able to evaluate how hydrographs differ

Homework Question Explain the factors affecting river discharge. (6 marks) Mark Scheme: L 1 (1 -2) There is a basic statements of some factors L 2 (3 -4) develops and links statements together. L 3 (5 -6) detailed statements, more than one type of factor (human/physical)

WAGOLL How many marks would you give this? Why? The amount of water will be high if the river is in an area with steep slopes. This will cause the water to run quickly over the surface due to gravity, before it has time to soak in. It will reach the river quickly and the amount of water will increase. The previous weather can also cause changes. If it has been dry, rain will soak into the ground and will be slow to reach the river. However, if it has been wet, the water will flow over the surface reaching the river quickly. Mark Scheme: L 1 (1 -2) There is a basic statements of some factors L 2 (3 -4) develops and links statements together. L 3 (5 -6) detailed statements, more than one type of factor (human/physical) How could you improve this answer?