Groynes are suitable erosion control measures where a beach is desirable, and they are compatible with most recreational activities. The beach fed by the sand trapped between the groins acts as a buffer between the incoming waves and the backshore and inland areas: the waves break on the beach and expend most of their energy there. Filled groins provide this protection during normal weather conditions but offer only limited protection against storm-driven waves. Groynes can be found a t Deal.
Seawalls are solid structures built parallel to the beach for two main reasons. One reason for building seawalls is to protect homes on the coastline from the destruction of large storms such as hurricanes or from the large waves they can create. Another reason they may be constructed is to create a distinct definition of the shoreline and to hold it in place which can allow buildings along the coast to stay protected. At Deal Beach, the seawalls are found at the top of the beach.
Fieldwork Method
We call the area between two groynes a groyne box (figure ). Each member of the group stood at the 5 different points showed in figure (they stayed in that position for all groyne boxes studied). Each person, using a plastic tub, scooped up several pebbles and with their eyes shut, in order to attain a random sample, selected a pebble and measured it long axis, measured its angularity and recorded the results in a recording sheet.
We did this for 10 pebbles at each position in the groyne box (in total, 50 pebbles). The group then all moved on and repeated the same process in at least 5 other groyne boxes along Deal beach.
The angularity and size of stones:
This fieldwork method was chosen in an attempt to procure a representation of pebble size and shape over as wide an area of the groyne box as possible. Hence the importance of working as a team.
Limitations
Difficulty of obtaining a random sample:
- Subjectivity of angularity choice
- Difficulty of standing in the same place for each groyne box position for each box studied
- Chance that other factors may have altered pebble accumulation on the beach other than Longshore Drift e.g. beach nourishment
This would have affected our results severely. Beach nourishment, a technique used to restore an eroding or lost beach or to create a new sandy shoreline, involves the placement of sand fill with or without supporting structures along the shoreline to widen the beach. It is the only management tool which serves the dual purpose of protecting coastal lands and preserving beach resources. Beach nourishment is a common management practice on the mainland and several other locations have ongoing beach nourishment projects.
Beach nourishment requires large volumes of beach-quality sand. The initial nourishment project typically requires thousands of cubic meters of sand per kilometre of shoreline, and most beaches need periodic re-nourishment. Beaches should take measures to more effectively manage the limited sources of readily available sand and should build the capacity to tap new, currently unavailable sources of sand.
Sand for nourishment projects is from a variety of environments. Terrestrial sources of sand include coastal dunes, coastal plains, and inland sand dunes. Offshore sources include dredge spoils from harbour maintenance, shallow-water sand fields, medium-depth sand channels, and deeper-water sand banks. Larger sources of sand must be hydraulically dredged with a suction dredge.
This would affect our results because, recording back to the hypothesis, this would not be a fair test as man made is interfering with erosion on the beach, but in this aim, I am only looking at the Longshore Drift affecting erosion on the beach.
Results
(Tables on separate sheets)
Graphs for tables below:
Analyse
By looking at all of the results, it is clear to see that there were not many very angular pebbles in any of the positions in the groyne boxes. The average height are between 2 and 6 with the odd anomalies, which are possibly from putting in the wrong measurement.
Conclusion
I can conclude from my results that longshore drift was taking place on the day of our visit. The longshore drift was shaping and moving the stones between the groynes on the day of the visit, along with the past.
Relation to Hypothesis
The hypothesis was ‘to see if Deal is being shaped more due to the process of L.D (if we found L.D present on our visit) or by human activity on the beach’ and to the fact that longshore drift was moving and shaping the pebbles, then it has been shaping the beach. Due to beach nourishment however, it was hard to see that the pebbles at the back were large and angular and the pebbles at the front were small and rounded, so we couldn’t really tell if the longshore drift was having a large effect on shaping Deal Beach in the past and the day of our visit.
