Figure 1:
Gradient of the spit
Steep or not
In order to measure the waves’ frequencies, we count the number of waves approaching each side in one minute, which is determined using a stopwatch. Then we repeat the procedure up to the 5th minute. After obtaining the results, we take 2 mean values, which are the waves’ frequencies on both sides. These values can help us deduce about the factors affecting the spit, especially artificial ones. For the waves’ directions, we drop 2 leaves on the water of each side and observe the directions the leaves move. Through these directions, we can evaluate the speed of the longshore drift on each side.
Waves frequencies on 2 sides of the spit
B is affected by both destructive and constructive waves. Since the spit lies on a busy sea route, many boats run past the inlet every day. Each time a boat runs, it will generate strong, high and plunging waves in a short time (Picture 1). Since the inlet is narrow and B has little area of shallow water (Map 1), these man-made waves will only lose a little energy by the time it reaches the shore as it travels a short way without encountering much friction with the seabed. Also, as B has a quite steep gradient (Figure 1) and at the time we measure (2-4pm), the wave frequency is high (30) as it is busy time, B will be eroded a lot during this period. However, B seems to undergo more deposition by constructive waves rather than destructive ones. Firstly, this inlet is blocked by Singapore, Malaysia and Indonesia. Thus, the winds do not travel a long distance at sea to gain energy. Also, they lose energy as they travel through land. Therefore, natural waves do not receive much energy from the winds as they have low wave height and long wave length. Hence, most of the time, at B, the waves are constructive which deposit materials. Also at night, very few ships run into the inlet to generate destructive waves. So on overall scale, more constructive waves hit B than destructive waves. Hence, human interference is the reason which accounts for the steep gradient of B as people might have lifted up the middle of the spit to prevent flooding in the event of storms because this part of Changi beach is a nice and famous tourist attraction. This is why B is steep although it is undergoing deposition.
Picture 1:
Destructive wave at B
Picture 2:
Constructive wave at B
At B, due to longshore drift, materials will move to the East-South East. But there is a sea wall there blocking material’s movement (Picture 3). So at the sea wall’s base, it will be higher as materials accumulate. As materials become higher, it will act like a sea wall which hinders longshore drift and causes its adjacent part to rise. Finally, B will get higher wider and flatter if nature takes its course. However, if we look at Map 1, we can see that the waves approach B at an almost-right angle, so longshore drift at B will dawdle, which means that the above-mentioned process will take a very long time (about thousands of years).
Picture 3:
A sight of B
From map 1, we can see that A has a very large area of shallow water. Therefore, the waves will lose lots of energy if they come to the shallow water as they will be exposed to the air resistance and encounter the seabed’s friction. Also, as explained above, the wind energy here is low and so are the waves’. Moreover, it is the season of the South-West monsoon blowing from the Indian Ocean at the time of records, which also reduces the speed and energy of the waves as the monsoon blows in the opposite direction. These factors explain why the waves here are constructive with low energy, low wave height and spilling breaker if nature takes its course (Picture 4). Therefore, the reason for the high wave frequency of 29.4 at A is because of man-made waves. Again, there are lots of big ships coming here every day. As the ships run, they will generate waves temporarily at a high rate which increase the frequency. These waves have high energy and are destructive waves with plunging breakers at the point they are generated. However, as the ships are too far from A plus this is just a temporary transmission of energy as the ships run past the spit in just a short moment, the waves will lose energy drastically as they approach the shore due to the above-mentioned factors, especially when they run through shallow-water region. This is why the waves at A has high frequency but still, they are constructive.
In the future, for the whole spit has been interfered by humans as explained above, it will not be extended entirely due to longshore drift but each parts will take its own changes. Noting that at A, the longshore drift is from East-South East to West-North West. Because the waves approach A at a very oblique angle, longshore drift there will take place very quickly but will not be effective inwardly. As the middle part has been uplifted by humans and there are quite a lot of greeneries there, these factors will hinder the longshore drift as materials cannot be easily transported to a high point and through obstacles like plants and grass. Therefore, longshore drift will not take place at the whole spit but will only take place at A. Hence, this beach will be extended to the West-North West very fast due to alternate transportation and deposition of materials due to longshore drift if nature is allowed to take its course.
Picture 4:
Constructive wave at A
MAP 2:
Changes of the spit in the future if nature takes its course
However, people will be more likely to change this spit for their aims as it lies on a sea which is important in terms of transportation and tourist attraction. As the spit is still undergoing constant deposition of materials, perhaps no hard measure such as sea wall and breakwater… will be conducted as they can make the coast look ugly and reduce its tourism value. Instead, as part of the spit is being extended tremendously due to fast longshore drift, more greeneries will be grown on the spit as their roots will bind the materials together, which stabilize the new and frail extended part for immediate effect. However, they can also add stress to the extended weak spit and make it sag... So this has to be planned properly. Most importantly, people will be likely to build a bigger port behind the spit. Because it is extended, it will create a larger area of calm water behind itself which means that small and average-size motorboats can come and anchor here for shelter and supply.
Although most of the data collected is quite reliable as they are all collected from dependable sources such as textbook, Google Earth and especially on-site measurements, there is still one weakness regarding data collection. Because the experimental data through the visit to Changi beach is collected in just 2 hours from 2 to 4pm, at the other time, the data may be completely different due to the changing activities of natural factors (tides, winds,…) and man-made factor (movements of the ships) (refers to Map 5).
Map 3:
Thus, there should be a modification to my hypothesis as the spit will be likely to change according to the above-mentioned manner if there is no drastic change in the concerned factors between day and night.
Bibliography:
Google earth
Geography insights