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How do changes in the mean occupied channel width and channel depth of the River Lyn compare with the Bradshaw model?

Consolidate your thinking – fieldwork to calculate changes in the mean occupied channel width and depth of the River Lyn

The Bradshaw model states that both mean occupied channel width(distance across a river channel measured at the surface water i.e. not the wetted perimeter) and mean channel depth (height from water surface to the stream or river bed) will increase with distance from the source to the mouth of a river.  In both cases this will happen as additional water volume (discharge input) is contributed from tributary streams and rivers as well as surface runoff from a larger land catchment area as a river progresses downstream.  

To test this assumption against the real world example of the River Lyn measurements can be taken of its occupied channel width and depth at sample points along the course of the river and then tested statistically to ascertain whether the changes identified are significant.  

 

 The film and narration on this page shows clearly how to measure the width and depth of a river and further guidance is available at

http://www.geography-fieldwork.org/rivers/river-variables/2-fieldwork.aspx and http://www.rgs.org/OurWork/Schools/Fieldwork+and+local+learning/Fieldwork+techniques/Rivers.htm

The width and depth of a river needs to be measured through systematic sampling e.g. at every 10 m interval and the following sites along the river are suggested as possible locations to take the sets of measurements required:

Assessing risk and identifying control measures to manage risk

Please refer back to guidance on this page and use the template with regard to fieldwork above.

Secondary data sets

If access to these locations is not possible for primary data collection then the following tables provide sets of secondary data obtained from the sites for the students to test statistically:

SITE1234567891011
Dist. From Source (m)100011501375287033603725664071907630839010330
Avg Width (m)1.551.071.932.851.804.007.144.5015.0012.6818.60
Avg Wetted Perimeter (m)1.661.872.513.052.354.157.284.7816.2014.1021.30
Average Depth (m)0.090.290.230.170.120.180.120.340.430.330.33