1. Lesson 9 Channel characteristics
Drawing a river cross section

2. What are these students doing?
What are measurements are they recording?
What errors might they make?
What problems might they encounter?
How could you use their data?

3. 5 November 2013
How can primary data be used to create a river cross sectional profile?
Learning Objectives:
To draw, label and interpret a river cross sectional profile.
Learning Outcomes: C
Essential – you will draw an accurate river cross sectional profile.
Stretch – you will identify and label all the key river channel characteristics. B A*
Challenge – you will apply your understanding of how river processes influence the cross sectional profile.

4. Measuring River Cross Sections
Producing a cross-section of a river channel is a basic river fieldwork skill.  The first stage is to measure the width and depth of the river. The data gathered can then be plotted to create a scale diagram of the cross-section, or used to find the cross-sectional area and wetted perimeter of the river.
Year 12 Hanham students measuring the cross sectional profile of the River Harbourne in South Devon.

5. Depth Measurements(cm)
How to draw a river cross section
Use the readings below to plot a cross section of the stream.
Key information
Width of stream: 6.40 metres
Distance from the water surface to the top of bank was 1.25 metres
Readings taken at 30 cm intervals
Depths
Depth Measurements(cm)
Depth 1
6cm
Depth 2
8.5cm
Depth 3
9cm
Depth 4
10cm
Depth 5
Depth 6
16cm
Depth 7
12cm
Depth 8
8cm
Depth 9
7.5cm
Depth 10
Depth 11
7cm
Depth 12
Depth 13
14cm
Depth 14
16.5cm
Depth 15
17cm
Depth 16
19cm
Depth 17
Depth 18
15cm
Depth 19
Depth 20
Depth 21
Before you start - pause for thought
What scale will you use for the width and depth?
Where is the bank full line?
In which direction must the depths be measured?

6. TASK 2: Label the cross section with the following key words;
Shallow water, Fast flow, Slow flow, Deep water, Deposition, Steep bank

7. TASK 3: Hydraulic Radius
In full write the equation for hydraulic radius in your book.
For your channel cross-section, calculate the hydraulic radius.
TASK 4: Check your understanding
Answer the following questions in full sentences in your book;
What three main things is velocity influenced by, and how does this affect the processes working within a river channel?
How does an Asymmetrical channel vary to a symmetrical channel?
Why does the hydraulic radius vary throughout the year?
What can affect the channels efficiency?
How does channel shape effect velocity and efficiency of the channel?