Sitges Coastal Management Hypotheses

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.

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.

ITEM	METHODOLOGY	REASON	LOCATION	SAMPLE SIZE
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.

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.

ITEM	METHODOLOGY	REASON	LOCATION	SAMPLE SIZE
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.

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.

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