Potential Effect of Sea Level Rise on Rambai River, Malaysia

Sea level rise could alter the boundary conditions of tidal rivers. This in turn would modify the hydrodynamic behaviour of coastal rivers and consequently their backwater rise. This paper presents the effect of modified boundary conditions on river peak stage and flow resulting from probable levels of sea level rise on the west coast of Peninsular Malaysia. The study site is a tidal affected river in Penang, i.e. Rambai River (main tributary of Juru River). Channel flows under different probable sea level rise projections compared to 1999 mean sea level are routed along Rambai River using complete one dimensional Saint Venant equations. Catchment inflows into the river are computed using an enhanced Rational Method, i.e. transformed Rational Method developed by the author. The effect of sea level rise on peak stage and flow for a set of scenarios that combined different outlet boundary conditions affected by sea level rise and urbanization extent is compared. On the whole, modeling results indicated that a 1.0m sea level rise combined with the impact of further urbanization could cause the peak stage and flow to increase by 20% compared to initial conditions (1999 tidal levels and urban extent) at the outlet of Rambai River. In consequence, the percentage of Rambai River catchment area susceptible to flooding could increase by 21%.