Phases 1 and 2 reclamation and was subsequently applied to Phase 4 reclamation. The concept works on the basis that a sedimentary shoreline will be sculptured into J-shaped bays between the headland breakwaters. This scheme was the first large-scale application of such a breakwater system for stabilizing the coast as well as forming sandy beaches for recreational purpose.
Systematic study and monitoring of beach development between breakwaters were carried out over a period of several years. The following conclusions have been established:
(a)Headland breakwaters constructed in series are successful in stabilizing the shoreline.
(b)J-shaped sandy bays with a curved portion upcoast and a long straight section downcoast are formed between the headland breakwaters.
(c)Headland breakwater system provides an economic solution for the protection of the coast and for the formation of beaches for recreational purposes.
Since its construction in mid 1970, the performance of the headland breakwaters, in particular the sandy beaches created, have been stabilized in most of the locations along the East Coast Park. (Silvester and Ho, 1973; Chew et al, 1974)
3. RECLAMATION AT TUAS FOR THE MALAYSIA-SINGAPORE SECOND CROSSING
3.1 General
To complement the existing causeway link to West Malaysia at Woodlands to the north of Singapore, a second link has been planned to be constructed to the west of Singapore connecting Tuas to Tanjung Kupang on the Malaysian side. The road link will take the form of a 2 km long bridge supported on piers positioned in the West Johor Straits at approximately 70 m c/c with 3 navigation channels, one on the Singapore side (75 m wide) and 2 on the Malaysian side (75 m and 50 m width). At the Singapore end of the second link about 20 ha of land is to be reclaimed from the foreshore at Tuas to accommodate the Custom, Immigration and Quarantine (CIQ) complex and the bridge support structures.
The reclamation extends about 360 m into the West Johor Straits into waters upto -14 m Chart Datum. The reclaimed land is formed to +8.7 m CD; this is dictated by the required elevation of the high level bridge and is well above the minimum required to satisfy the wave run-up or overtopping considerations. The outline of the reclamation profile resembles that of a mushroom to provide smooth hydraulic flow. The reclamation profile is constrained to the north by the existing Tengeh Dyke (impounding the Tengeh Reservoir) to the west by the Singapore Port Limit and to the south by the Raffles Marina (Fig. 2).
3.2 Hydraulic Model Studies
It was expected that the proposed reclamation and the supporting structure of the bridge (artificial islands and piers) would result in a constriction to the waterway. To assess the impact of these developments on the hydraulic and sedimentary regimes in the West Johor Straits, numerical and physical model simulations were carried out. Details of hydraulic model studies are reported in Cheong et al (1994).
3.2.1 Mathematical Hydrodynamic Model
A mathematical hydrodynamic model was carried out using a suite of three numerical nested models which included a Regional model (grid size 1 kin x 1 kin), a Western model (grid size 250 m x 250 in) and a Local Fine Grid Model (gird size 75 m x 75 in).
The hydrodynamic modelling is based on the application of 2DTIDFLO which is a finite difference numerical model utilizing the vertically integrated equations of motion and continuity for shallow water flow problems (Jothi Shankar et al, 1991). The numerical scheme is based on the work of Stelling (1984). The equations are solved numerically using an alternating direction implicit method based on a fully staggered grid.
The Regional model comprising the Singapore and West Johor Straits was calibrated and validated using extensive field data on tidal water levels and current measurements carried out in 1978, 1987 and 1990. For the second crossing at Tuas study it was used to generate the boundary conditions for the mid-size western model. The fine grid nested Local model covering Tuas and part of West Johor Straits (covering approximately 90 km x 14 km) was operated with boundary conditions transferred from the western model.
