Investigation into the Pebble Ridge at Westward Ho!

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GENERAL STUDIES – MATTERS OF MOVEMENT – MOVEMENT AND THE PHYSICAL ENVIRONMENT

Investigation into the Pebble Ridge at Westward Ho!

Planning and Data Collection

The aim of this study is to see whether pebble length changes with distance from the proximal end of the pebble ridge and along transects up the ridge at Westward Ho! Westward Ho! is located at the Taw Torridge Estuary on the north Devon coast shown by figure 1. The supply of material has come from the south with the aid of wind and longshore drift. However, dissipating wave energy at the mouth of the River Taw has ended any further northward movement and an accumulation of material has built up at the distal end of the ridge. The pebbles are made of hard, fine-grained sandstone, which comes from the cliffs west of Westward Ho! Theory suggests that with distance from the proximal end of the pebble ridge, pebble length should decrease as a result of attrition and the direction of longshore drift. Attrition is when waves cause rocks and pebbles to bump into each other and break up. Longshore drift is the movement of material (ie sand, gravel or shell fragments) along the shore by a current in the area between the high and low water marks known as the surf zone.

I intend to test the following hypothesis:

Longshore drift is occurring when pebble length at three locations along the ridge, the base, the middle and the top decreases with distance from the proximal to the distal end of the pebble ridge.

Figure 1: Location Map of Westward Ho!

In order to test my hypotheses, I shall be recording data at three transects along the pebble ridge at Westward Ho! I shall have one transect at the proximal end with an OS grid reference of approximately 434 298, on at the middle of the ridge with a grid reference of 436 302 and one at the distal end with a grid reference of 437 305. Each transect will be roughly 400m apart. To find if pebble length does decrease with distance I shall measure the length of 10 pebbles every 2m along each transect.

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I have decided to use three transects because then I shall get data which will show clearly the extremes in the different locations. I shall take my data recordings at systematic 2m intervals in order to collect enough data to perform sufficient statistical tests to prove or disprove my hypotheses. I am recording the length of 10 pebbles at each site to get a clear mean.

Before beginning data collection, I visited Westward Ho! to perform a risk assessment, the only risk was the high tide so in order to overcome that problem I collected all my data when ...

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