The main point of this enquiry was to find out how landscapes and processes change in a river valley. To see how rivers change as they flow downstream.

                   Speed = Distance travelled/Time taken.

Our Results from the River Bollin.

Site 1 – Mottram St. Andrews.

Furthest downstream.

• Depth and width of the river and the river channel.

Channel – 12.2 metres wide.

River – 8.7 metres wide.

Height of river cliff – 0.91 metres.

These figures allowed me to form the cross section below.

• Field sketches. 

These are my field sketches - 

        

• Bed Load.

We measured 10 stones from the riverbed. These are the results.

Here is a stone, drawn using the average measurements from the 10 stones.

• Speed of Flow.

Here are our results.

TOTAL AVERAGE = 20.31 secs.

Speed = distance/time

           = 20 metres/20.31 secs

           = 0.98 metres per second.

Our Results from the River Bollin.

Site 2 – Sutton.

Nearest the Source.

• Depth and width of river and river channel.

Channel – 5.4 metres wide.

River – 4.1 metres wide.

Height of River Cliff – 0.6 metres.

These figures allowed me to form the cross section below -

        

• Field Sketches.

These are my field sketches –

• Bed Load.

We measured 10 stones from the riverbed. These are the results.

Here is a stone, drawn using the average measurements from the 10 stones.

• Speed of Flow.

Here are our results.

TOTAL AVERAGE = 34.89 secs

Speed = Distance/Time

          = 20 metres/34.89 secs

          = 0.57 metres per second.

Analysis of Results.

“How do landscapes and processes change in a river valley?”

Do river valleys become wider further downstream?

Yes, they do. This is proven by our measurements of the river channels. Mottram St. Andrews is the site furthest downstream and the width of the channel there is 6.8 metres wider then that in Sutton.

Does a river get bigger downstream?

Yes they do. This is proven by overlaying the two cross sections of the river. As shown in the diagram below. They get bigger because as they go further downstream, small tributaries join with the river and the volume of water increases.

Does the size of material in the riverbed change downstream?

Yes it does. This is proven by the average volumes of the stones found at each site –

Site 1 – 14.9 cubic cm.

Site 2 – 348.3 cubic cm.

That is a difference of 333.4 cubic cm.

As Site 1 is the furthest downstream, this shows that as you go downstream the size of material in the decreases. This could be because the water is flowing faster, which causes the stones to be eroded and to hit against each other, and chip bits off each other.

Where does the river erode and deposit material?

The most hydraulic erosion occurs on the outside edge of a meander. This is because the water flows fastest on the outside of a bend, and the faster the water, the faster the erosion. Deposition occurs on the inside bend of a meander because the water is flowing slowly and it drops the load it has carried from upstream. The field sketches of both of the sites can prove this.

Does a river flow fastest upstream?

No. A river flows fastest downstream, where the volume of water is larger. This can be shown by the speed of flow tests we did. The orange at Site 1 (downstream) travelled at 0.98 metres per second, whereas the orange at Site 2 (upstream) travelled at 0.57 metres per second. That is a difference of 0.41 metres per second.

Is the deepest part of the river in the middle?

Not necessarily. In the cross section of Site 1, the deepest part of the river is clearly 7 metres across. This is more then half way across the river. However, at Site 2, the deepest part of the river is 2 metres across, which is nearly half way across. This is because, as it is just a small river at this stage, the meanders are not very pronounced so the water flows straighter. When you go further downstream, the volume of the river has increased, more erosion has occurred, and very pronounced meanders have been formed. On a meander, the water always flows fastest on the outside curve, as proven by the results from Site 1.

Conclusion.

From my study of the different sections of the River Bollin, I found that river landscapes and processes do change as the river moves downstream. The main changes were the width and depth of the river, the speed of flow and the size of the bed load.

This investigation gave me a greater, more in-depth knowledge and understanding of river formations and processes.

I also learned how important it is to listen to instructions. Also to take accurate measurements and to do an activity more than once to get an average.

We had some difficulty collecting the depth data from Site 1. The river had risen by 30 centimetres because of recent rainfall, so it was too dangerous for Miss Longman to get into the river and collect the data.

The investigation would have been made clearer if we had gone to the sites in the opposite order. Sutton, near the source first and then Mottram St. Andrews, further downstream second. This would have lessened any chances of confusion.

It would improve my knowledge further, to do some further study of sites further down the river, nearer to the mouth, so we could do some further comparisons.

Overall, the investigation went well and we acquired all of the data we needed, even though my feet did get wet!!