Hydrodynamic modelling for mangrove afforestation at Haji Dorani, west coast peninsular Malaysia

Following the Indian Ocean tsunami disaster of 2004, which increased recognition of the importance of mangal for coastal protection, the Malaysian Government changed its‟ Policy in relation to mangrove and coastal vegetation. Since 2005, considerable effort had been made to establish mangroves in areas affected by the tsunami and rapid coastal development. Mangrove growth is affected by numerous coastal processes such as tides, waves, currents, the type of sediment, nutrient availability, and sediment erosion, transport and deposition. Therefore, a careful assessment of the multiple factors is necessary to facilitate successful replanting. In this thesis, a study has been carried out to determine whether the tidal flats at Sungai Haji Dorani are suitable for mangrove afforestation. The specific objectives are to establish tidal current velocities and flow patterns from hydrodynamic modelling in order to identify the likely sediment transport pathways, and investigate wave shoaling and their role in sediment transport. Sungai Haji Dorani is a low gradient muddy shoreline, consisting predominantly of silt and clay, over which occurs a fluid mud layer of about 0.3-0.5 m thick. There are three river sources of predominantly fine sediment, namely: Bernam, Haji Dorani and Selangor rivers. The existing mangal belt is very narrow (~20 m width) in the study area, and there is no natural mangrove regeneration to replace mangroves lost due to the tsunami and coastal development. Simulations of tides, currents and waves were carried out using the 3DD hydraulic modelling suites. Results were calibrated and validated against measured conditions to facilitate an accurate representation of the study area, and provide a high level of confidence in the model outcomes. The calibrated models were used to simulate the impact of a proposed mangrove replanting project on waves, currents and sediment transport pathways. Modelling results indicate that without mangroves, the average velocity over Haji Dorani is 0.14 ms-1 and peak velocities varied from 0.1-0.4 ms-1, which is high enough to transport fine sediments. The wave model predicted that at highest offshore spring tide and during storm conditions, waves of 0.2-2.0 m are transformed into 0.2-1.0 m high waves at the Haji Dorani shoreline, which will initiate fluidization of the bed sediment. These high waves, combined with tidal currents, can entrain the bed and transport sediment away. Results from the POL3DD Particle Tracking Model indicate little sediment is deposited close to the Haji Dorani shore and any deposited would not permanently consolidate. High waves will erode the bed and re-suspend the sediment while strong tidal currents will transport it into deeper waters offshore. Modelling of simulated mangrove replanting suggests a large reduction in current velocities and storm wave heights due to the increased friction provided by the mangrove roots and trunks. The particle tracking model shows that fine sediment from the Bernam and Haji Dorani rivers will accumulate along the adjacent coasts in response to the reduced transport capability and reduced potential to re-suspend sediment. These sediments will be trapped by the mangal, which may result in the long term build-up of islands around the trees. Increased sedimentation will also provide habitat and nutrients for mangroves to reproduce and regenerate new trees naturally. At the same time, the mangrove trees will provide nutrients and shelter for marine life and terrestrial animals, as well as behave as a wave breaker, reducing incoming wave heights and tidal currents and thereby protecting the coast from high waves and storm surge

Historical Storm Surges: Consequences on Coastal Resources and Shoreline Protection in East Coast of Peninsular Malaysia

Most of the storm surge event affected the East Coast of Peninsular Malaysia has produced significantly high water levels thus caused severe flooding and destruction to coastal mitigation structures. Analysis of 28 years span of recorded water level data (1986 to 2013), from southern coast of Thailand to south-eastern coast of Peninsular Malaysia, show that the surge level is higher in the 80’s and started to decline in late 90’s and slowly increasing later in the twentieth century. Maximum surge is recorded in 1988 at Paknam Bangnara station in southern region of Thailand (max. storm surge, SSmax = 1.42 m) and Geting (SSmax = 0.93 m) in the north-eastern region of Peninsular Malaysia which resulted in high erosion rate along these coasts. This paper explores the consequences of storm surge increment on the vulnerability of present coastal resources and shoreline protection structures along the East Coast of Peninsular Malaysia. The study reveals an increasing magnitude of storm surge and mean sea level increment in all the stations over the years which conform with the sea level rise assessment in IPCC AR5. Storm surge trends and the correlation between the stations are also investigated. A storm surge return levels corresponding to various return periods are derived as a guideline for engineers and developers to determine the optimum level in their design

Sea Level Rise Impacts and Adaption Measures for Sandakan, Sabah

Mini-Symposium: Impacts of Climate Chang

Beach morphodynamic classification in different monsoon seasons at Terengganu beaches, Malaysia

International audienceWave climate, topography and sediments are the main forcing factors that influence beach morphodynamics. This paper characterise beach morphodynamic classification along the Terengganu coast during seasonal monsoons (the onset of southwest monsoon in June 2009 as calm conditions and northeast monsoon in December 2009 as storm conditions). Two main morphodynamic characteristics are used to define a reflective, intermediate and dissipative beaches such as the surf similarity index (ξb) and the dimensionless fall velocity (Ω). In order to estimate morphological changes, repetitive beach profiles were acquired and averaged. The morphodynamic characteristics are also supported with wave data collected from the European Centre for Medium-Range Weather Forecasts (ECMWF) database and modeled in Spectral Wave Flexible Mesh of Mike-21 module, in order to investigate the wave propagation along the Terengganu coast. According to the beach morphodynamic classification scheme, the southern Terengganu coast showed a reflective beach state with high wave energy and coarser sand. In contrast the northern part with low wave energy, due to sheltering by many islands, demonstrated an intermediate beach state and finer sediment. However, the trend of sediment mean grain size (D50) reveal finer to coarser during southwest and northeast monsoons respectively. The results of this study are helpful in formulating and preliminary observation on effective coastal zone management plan for monsoon-dominated coast especially in sandy beach

The strategic establishment of the Malaysian Mangrove Research Alliance and Network (MyMangrove)

The Malaysian Mangrove Research Alliance and Network (MyMangrove) was established in recognition of the needs for a collaborative effort to significantly influence the management and conservation of mangrove forests through research and education. MyMangrove brings scientists and researchers together, to join forces in exploration and enhancement of scientific knowledge on mangroves and their connecting habitats and ecosystems. The goal of the establishment of MyMangrove is chiefly to close the gap and create a functional and efficient scientific networking among scientists and researchers. It also anticipates at improving public communications on mangrove-related issues and to influence the landscape of policies and regulations pertaining to mangrove management and conservation, particularly in the context of Malaysia. Ultimately, MyMangrove aims at being a strategic platform for the local communities, NGOs, students, corporate sectors and government agencies to collaborate with the multi-and inter-disciplinary group of scientists and researchers from universities and agencies on all matters concerning mangroves and their interconnectedness with other coastal and marine habitats