Geography river study coursework - Why do channel characteristics vary downstream at a number of sites along the Mulunguzi river?

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The question I have been asked to answer is:

Why do channel characteristics vary downstream at a number of sites along the Mulunguzi river?”

The aim of the investigation is to find out how and why the river Mulunguzi’s characteristics change from its source to its middle course. Some of these characteristics include: the width and depth of the river, velocity, bedload size and shape etc.

I decided to come up with 3 hypotheses of which will help me to answer the question. They are:

  1. “The width of the river channel will increase with distance downstream.”

I would expect this to be true because as we move downstream, there is a greater volume of water at a faster velocity. This causes more hydraulic power erosion in the river channel downstream, which makes the channel wider. More lateral erosion also occurs downstream, causing the river to erode sideways, increasing in width.

  1. “The bedload shape( smoothness and roundness) should increase with distance downstream”

This would be because as the velocity of the river increases with distance downstream, there will be more attrition as the rocks collide, causing the rocks to become rounder.

  1. “The cross-sectional area of the river channel increases with distance downstream.”


I expect to find this because I expect the width and depth of the river to increase downstream and these results will influence the cross-sectional area. I would expect the channel to be larger because of the increased velocity causing more hydraulic power erosion.

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Location description

The study will take place at the Mulunguzi river in Zomba. Zomba is a small town in which a plateau is located—it is on this plateau, at 15▫ south and 34▫ east, where the source of the river Mulunguzi is found. The river is perfect to carry out this investigation as it enables us to examine a number of its features including: meanders, waterfalls, rapids, tributaries and so on. Zomba plateau is also easliy accessible for us, being only an hour away from our school in the city of Blantyre. The location of Zomba Town and the ...

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