A Study on Coastal Erosion and Sedimentation Problems along the Coastline of Teluk Senangin, Perak

Tuan Nurul Shakira Bt Tuan Mohd ShukriDepartment of Civil Engineering,Universiti Teknologi PETRONAS,

Bandar Sri Iskandar, 31750 Perak, Malaysia

Abstract - This work presents the assessment of coastal erosion and sedimentation problems occur in Teluk Senangin, Seri Manjung, Perak. Approximately 30% of the Malaysia coastline is having erosion. This has cause negative effects on visual amenity, biodiversity and recreational values. Visitors place high value on useable sandy beaches and reserve areas behind the beach. To achieve an efficient method of coastal rehabilitation, further mitigations need to be carried in for long-term where coastal associated with erosion be retreated. This will improve ecological and socio-economic aspects if coastal areas which have positive impacts to local communities and authorities.

Keywords - coastal erosion, sedimentation, Teluk Senangin.

1. INTRODUCTION

Malaysia has a long coastline of about 4800 km which is valuable as national asset for coastal tourism, marine and wildlife. Apart from that, Malaysia coastal provides gateways for inland trade, port facilities, oil and gas industries, power plant, residential areas besides it has aesthetic value.

Malaysian coastline varies from scenic bays with rocky headlands to shallow mud flats covered with mangrove forest. Peninsular Malaysia has high sediment yield from river discharge and harsher wave environment and create hook-shaped sandy bays coastline, meanwhile on the west coast, the mild climate from Malacca Straits are suits for mud shores and coastal forests to be rich in biodiversity.

However, according to the National Coastal Erosion Study or known as NCES (1985), of 4809 km of shoreline in Malaysia, about 1390 km (27%) are subjected severe degree of erosion. The average rate of shoreline ranges from less than 1 m per year to more than 10 m per year in eroding area. About 132 km of shore are seriously threatened by coastal erosion and fall under critical erosion areas or Category 1. Another 236 km of shoreline fall under significant erosion or Category 2 and Category 3 or acceptable coastal erosion area experienced by 962 km shoreline. Coastal erosion can be classified as follow based on Department of Irrigation and Drainage Malaysia (DID):

i) Category 1 - Critical Areas suffering from coastal erosion where shore-based facilities are in imminent danger of loss

ii) Category 2 - SignificantAreas where shore-based facilities are expected to be endangered within 5 to 10 years if no remedial action is taken

iii) Category 3 - AcceptableErosion areas generally undeveloped with consequent minor economic loss if erosion continues unabated

Coastal areas provide significant particular ecosystem services, native primarily protection of coastal or tidal flooding. A coastal retreat as a result to coastal erosion may affect these services and could lead to loss of land economy and the ecology of human life and property. However, coastal erosion in one area can provide ecosystem services further along the coast, for example where coastal erosion created cliffs provide a natural protection from tidal.

Coastal processes can be defined by extreme variability and high levels of activity which includes waves, tides, current and wind. As results, with the constant equatorial monsoon climate, these processes create sedimentation along the coastline and may also cause erosion, and thus, influence the beach profile and plot. Coastal erosion is naturally occurring due to the response of the beach to the nature effects. Activities done by human also may affect the natural system causing erosion to accelerate. Coastal erosion also may caused by storm waves where sand is transported offshore, but in most of the cases, the material is lost in offshore permanently, while waves erode the beach and scour the bank. Another cause of coastal erosion is by long shore sediment transport by waves breaking at an angle to the shore. Peninsular Malaysia is having most erosion due to major cause of erosion due to deprivation of sediment.

2. DESCRIPTION OF STUDY AREA

Fig. 1. Map of Seri Manjung, Lumut and Pulau Pangkor areas

There are many extensive and relatively new tourist attractions especially in coastal area in Malaysia. The best exposed is selected for coastal erosion and sedimentation is Teluk Senangin. Based on SeaMap (2014), Teluk Senangin is approximately situated 4°18’ Northern latitude and 100°34’ Eastern longitude. Teluk Senangin is located from 30km from the town of Sitiawan, Perak in northwest of Peninsular Malaysia is to be designated as Tourist Development Zone according to the Manjung district local plan.. Teluk Senangin is open to Andaman Sea and Malacca Straits and is protected by Pangkor Island where Dinding Straits separates both Pangkor Island and Teluk Senangin. The geomorphology of the coast can be characterized by a long and wide sand beach and dunes.

However, the development of Teluk Senangin as a tourist attraction can be categorized as slow development progress.The population here is relatively small where about 30 houses are built here.

Fig. 2 Map of Seri Manjung, Lumut and Pulau Pangkor areas

Malaysia with its tropical climate with two monsoonal seasons: the northeast during middle October to March and the southwest during May to September. Based on NCES (1985), the wave from the southwest during Southwest Monsoon period rarely exceeds the height 1.8 m with period less than 6 seconds. Since Teluk Senangin is located at the northwest of Peninsular Malaysia, it is hardly affected by the monsoon. The fetch length is limited to approximately 40 km to 130 km in the Malacca Straits as the Sumatera Island provides shelter to the west coast, with the range of wave height from 0.5 m to 1.0 m and maximum to 3.0 m during southwest monsoon. The predominant wave condition along the northern part of west coast has the longer period waves which propagate to the coast from Andaman Sea. During Southwest Monsoon, Andaman coast experience highest waves due to peaks in wind and wave intensity caused by the passing cyclones frequently accompany the retreat of the monsoon during October to November (Thampanya et al., 2006). Based Malaysian Meteorological Department the winds seldom exceed 15 knots and the significant wave height is lower than 1 m about 89% of the time.

3. OBJECTIVES

During this assessment, the author needs to achieve few objectives in order to fully analyze on coastal erosion and sedimentation problem that happen in Teluk Senangin. The objectives are as follow:

i) To determine the possible reasons of erosion and sedimentation problem ii) To study the effect of coastal erosion and sedimentation problem on beach characteristics, socio-economy and others iii) To come out with mitigation measures to reduce and control the rate of erosion in Teluk Senanginiv) To justify which category of coastal erosion Teluk Senangin coastline falls

4. DISCUSSION

4.1 Factors of coastal erosion and sedimentation problems

The main reason of the erosion in the coastline of Teluk Senangin is high tides which relates with sea level rise..

Tides play an important role in the beach processes and profiles. The tide on the west coast is generally between 2 m to 2.5 m, but can reach 4.1 m. Neap tidal ranges vary from 0.5 m to 1.6 m on the west coast. Based on interview with fisherman who lives here, high tides happen twice a day and the erosion was worst happen during Tsunami 2004 because high tides happened every 2 to 3 minutes. According to Natural Resources and Environment Ministry Deputy Secretary-General, Datuk Aziyah Mohamed at Intergovernmental Panel on Climate Change (IPCC), there has been increasing significant wave heights in the South China Sea and eastern parts of Andaman Sea, which had direct impacts on Malaysian coastline for the last 50 years. The wave height increase may be the result of increasing storm activities in this region. IPCC also stated that projections need to be assessed future impacts of sea-level rise on coastal area and the sustainability of coastal settlements in the future. The impact of sea level rise has increased the frequency and depth of tidal flooding. It accelerates the coastal erosion where a sea lever rise will deepen the nearshore waters and allow larger waves to break on the coastline. Sea rise level cause stable or accreting beaches to be eroded. The size and frequency of waves is naturally very variable with no clear pattern evident.

Fig.3. Maximum Wave Height data from Malaysia Meteorological Department

Based on the Fig 3 above, the maximum wave height at coastline of Perak falls between 0.6 m to 0.9 m which can contribute to coastal erosion.

Longshore net sediment transport also plays an important role in coastal process. Although comprehensive long-term baseline oceanographic data such as wave, wind and current of this region are limited, the longshore net sediment transport can be analyzed. It is mainly driven by waves rather than tides and ocean currents. Erosion occurs when carrying capacity of the long shore current generated by waves exceed the quantity of sediment supplied to the beach. From observation seen at site, the sedimentation at high rate only occur at particular area, meanwhile the other part receive less sedimentation. However, the parts where the coast erodes more have their natural forest as natural coast protection.

Another reason that can be considered as a factor of coastal erosion is global warming. Global warming with has increase the rate of sea-level rise began in nineteenth century with a global mean ocean levels rising about 0.15 m to 0.2 m in twentieth century but significantly greater amount are expected in another present century (Komar, 2012).

Development of building and resorts along the coastal area has clearing some parts of the forest that should be coastal natural protections. Parts of forest have been taken down to build chalets and houses to accommodate the population and tourist here.

4.2 Effects of Coastal Erosion and Sedimentation Problems

The erosion in Teluk Senangin has caused some houses to be in unstable condition.

Fig.4. Sand erosion in front of a chalet

From the Fig. 4 above, coastal erosion is slowly happen. Based on Komar (2012), the erosion has decreases the volume of sand and gravel that reach the beach ocean. At particular sites along the coastal area, the lengths of the backshore are differed. The longest length measured is 25 m. Therefore, only certain parts of the beach are available and safe for human activities such as swimming. This has reduced the limit of number of tourists and may affect the tourism of this place.

Based on Sharifah Mastura (1992), as the water table rises, there will be development of new coastal flooding areas where low-lying areas on coastal plain become flooded. In few decades, Teluk Senangin will be flooded and the residential areas will be affected, thus will cause negative effect on the socio-economic of the population over here if no further action will be taken.

4.3 Mitigations Taken

Fig. 5. Natural forest along Teluk Senangin coastline

Historically, the coastline has been protected by natural forest along it. Many species such as Rhizophora mucronata, Ipomoea pescaprae, Casuarina equisetifolia,coconut trees and others which have big sizes, shapes, density of trunks, branches and aerial roots have protected the coast from being eroded. These natural coastal protections can cause sedimentation to take over in longer term, increase surface elevations, and create shallower water and increasing wave shoaling and energy dissipations (Mclvor et al., 2012). The dense structure of roots system provided by the natural forest along the coastline helps consolidate the coastal soil, thus, this will make the coastline more resistant to erosion.

Since wave diverges from Pulau Pangkor, the wave energy receive by Teluk Senangin is less than the wave energy from open sea. Villagers in Teluk Senangin have come out with some mitigation which can slightly reduce the erosion. Zink barriers of a certain height are placed inside the sand few meters from their houses. Barriers mixed with rocks, sands and concrete also are made by the villagers. These little mitigation will reduce at least 10% wave attenuation, thus erosion rate can be deducted.

Mitigation can be proposed in terms of hard engineering and soft engineering. Further study on the coastal area of Teluk Senangin can be continued to suggest better mitigation. Hard engineering for coastal defense such as sea walls and breakwaters physically prevents coastline erosion. However, based on the Marine Climate Change of Impact Partnership Annual Report, it states that these barrier structures may increase the rate of coastal squeeze and steep the intertidal profiles in particular area.

In term of soft engineering, soft approaches can be included for the mitigation. Beach nourishment where sand is added to the beach can raise the height of the beach to raise the beach heights and managed realignment, where the natural rate of erosion can be managed although it is not fully prevented. Beach nourishment refers to bringing in sand from some other location and spreading it on the beach to replace sand lost in storm events. This is a temporary solution and regular replenishment is typically required to maintain the beach. Nourishment can be a cost-effective option for highly utilized beaches (Phillips, 2011).

5. CONCLUSION AND RECOMMENDATIONS

This study suggests that apart from natural phenomena such as exposure to wave attack during monsoon season, anthropogenic activities have had severe impacts on the changing of coastline. The existence of natural forest along the coastline with dense roots systems and continue sediment flux are crucial to maintain coastal stability in the region. This study also has found that Teluk Senangin is still considerably safe and the coastal erosion is still acceptable which falls under Category 3. However, in one or two decades, possible remedial should be taken seriously to maintain the sustainability of Teluk Senangin for tourism, economic and social purposes.

The rapid development of Malaysia economy has been taking place with inadequate safeguards. This has resulted in severe environmental issues and stress on the coastal zone where the resources have been increasingly threatened by conflicting uses in adjacent land and sea areas such as tourism, transportation, industrial, urban development, agriculture and many more. A coastal zone management plan should be immediately and seriously taken by any authorities in Malaysia to ensure no further damage to the Malaysian coastal where all plans must take into accounts all the problems, issues and recommendations.

REFERENCES

Komar, P.D. (2012). Coastal Erosion Processes and Impacts: The Consequences of Earth’s Changing Climate and Human Modifications

of the Environment. Reference Module in Earth Systems and Environmental Sciences Treatise on Estuarine and Coastal Science 2011, Pages 285–308

National Assembly for Wales (2014). Coastal Erosion and Sea Level Rise. Retrieved from http://www.assemblywales.org/QG12-0014.pdf

Philips, Y. Waikato Regional Council (2011). When the Tide is High: Estimating the Welfare Impact of Coastal Erosion Management. Tahuna Conference Centre – Nelson, New Zealand. August 25-26, 2011

Sharifah Mastura, S.A. (1992). The Coastal Zone in Malaysia. Processes, Issues and Management Plan. Background Paper, Malaysian National Conservation Strategy. Economic Planning Unit, Kuala Lumpur.

Thampanya, U., Vermat, J.E., Sinsakul, S., & Panapitukkul, N. (2006). Coastal Erosion and Mangrove Progradtion of Southern Thailand . Estuarine, Coastal and Shelf Science 68, 75-85.