Make a model for investigating channel efficiency

To follow up the popular Juicy Geography Flume, try making a really simple model to investigate channel efficiency. The idea came from Gyles Morris of the Magdalen project. The project is much cheaper to make than the full-on flume, and making time could be reduced to seconds for the really determined. With the help of the Juicy Geography part-time staff I present a short photo-gallery of the project:


Go to HomeBase. You'll need to spend about £20.00



Purchase a 4m section of gutter - the wider size. Optionally, for the luxury version, you might also purchase a downpipe and end section. You might also purchase a few bargeboard attachments to stop the gutter from rolling around while in operation, though other materials can be used instead.



Finally some white spray paint will complete the look.



Now it's time to make the model. Step 1 is to spray the gutter white.



Then cut the gutter in half. Note that this is an optional step and obviously rather committing.



Nip out to get some gravel. Our council tax is one of the highest in the country so personally I'm happy to rob it.



Place some gravel in the gutter.



and spread out roughly.



Locate some dye. I use proper drain tracer dye as there is a problem with the stream in my garden. (The story is really too disgusting to relate)



Set the model up with a water source (ideally a constant head) and a drain.



Mix up some dye and add it to the river to measure water velocity.


Various experiments can be carried out using the dye to measure the velocity of the water. Try using different size bedload, adjusting the gradient and comparing two rivers directly. If you retain a long section of gutter you could use two or three grades of bedload and time the dye to pass each section. There are lots of possibilities; I'd like to get students to to explain the concept of channel efficiency after playing with the model. It would be possible to carry out micro-measurements to calculate hydraulic radius. The model might form part of next year's GCSE coursework.

I haven't used the model in the classroom yet, but I'll update the article when I do.