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Hypothesis 1: That some sections of beach 18 are more
liable to erosion than others.
Assumption: That wave energy changes and longshore drift occurs
along the beach
Methodology: Annotated sketches showing evidence of
erosion and management. Worksheet sketch can be provided for annotation. |
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Hypothesis 2: That longshore drift operates in a NE-SW
direction along the coast.
Assumption: That pebble long axes decrease in size towards the
SW |
| ITEM |
METHODOLOGY |
REASON |
LOCATION |
SAMPLE SIZE |
| Pebble long axis |
Measure pebble long axes, randomly selected using
random numbers and a quadrat, or with a marked pebble dropped at random. After
being dropped, the pebble it touches at its marked end should be selected for
measurement. |
To ascertain average pebble size. Pebble size is
related to both wave energy and longshore drift direction. The smaller material
is carried by the process of longshore drift to be deposited down-drift. On the
contrary, high-energy waves will remove all but the largest and heaviest beach
material. |
Swash zone |
A minimum sample size of 58 pebbles to a
confidence level of 68%, with a mean pebble long axis +/- 0.5 cm. |
|
Hypothesis 3: That storm beach pebble long-axis size and
alignment will be related to changes in wave energy
Assumption: That some sections of the beach will be more
liable to erosion than others. |
| Pebble long axis and orientation |
Measure orientation in degrees using a compass.
Long axes also to be recorded. Sampling to be random. |
To ascertain dominant wave direction. The pebble
long axis is aligned to the dominant wave direction. |
Storm beach. |
Minimum sample size 58 pebbles. |
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Hypothesis 4: That beach profiles will change along
beach 18 related to changes in wave energy and longshore drift.
Assumption: (a) that longshore drift occurs and that
some sections of the beach are more prone to sediment accumulation than others;
(b) that some sections of the beach are subjected to high energy (destructive)
rather than low energy (constructive) waves. |
| Beach profile |
Three profiles to be selected. Measurements at 1
metre intervals.
Profiles to be recorded using an abney level, ranging pole, calibrated pole
and measuring tape. The total width measurement is very important.
|
To ascertain minimum beach width and the degree of
sand accumulation. Analysis of the degree of sand accumulation should point to
the nature of the processes operating on the beach, particularly dominant wave
direction and longshore drift. |
At either end and in the middle of the beach,
perpendicular to the shoreline. |
Minimum of three profiles to be selected. |
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Hypothesis 5: That sandy beach profiles in the main town
will reflect the processes operating on the shingle beach
Assumption: (a) that longshore drift occurs and that
some sections of the beach are more prone to erosion than others; (b) some
sections of beach may be aligned with a longer fetch and more prone to erosion
from high energy waves.
Method: Measurement of three profiles on each of the
sandy beaches as per Hypothesis 3. It is very important to record the total
beach width at the three profile locations. |
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Hypothesis 6: That sand accumulation will be greater on
the up-drift side of the Sitges groynes.
Assumption: that groynes will interrupt the movement of
sediment by longshore drift
Method: Measurement of beach depths either side of the
groynes |
