| Summary: | Coastal defence structures play a critical role in safeguarding the underlying coast from wave action under both storm and normal conditions. Sea level rise due to global warming continues to place more coastal cities under increasingly harsh wave conditions that threaten their stability.
In Singapore, the Urban Redevelopment Authority announced the development of a “Long Island” along Singapore’s East Coast. Using traditional hard engineering structures like sea walls would not be ideal as it limits access to East Coast Park and alter the aesthetics of the beach permanently. Thus, a soft engineering solution such as a Beach Drainage System (BDS) can be used to promote accretion of sand and stabilise the beach profile without sacrificing the aesthetics. Traditionally, Beach Drainage Systems pump out seawater from the beach which might have higher operational costs than hard engineering solutions. However, in Singapore, it is possible to use the pumped, sand filtered seawater as an input for its desalination plants to facilitate cost sharing such that it is as economically feasible as other hard engineering solutions
This paper uses XBeach to numerically simulate and assess the impact of a Beach Drainage System under overseas extreme storm wave conditions, Singapore storm wave conditions and normal Singapore wave conditions. Using XBeach, different beach drainage locations are tested to test the impact of location on the efficacy on such a system and different discharge volume conditions that mirror the intake volume of a typical desalination plant in Singapore can also be simulated. The results are then processed to check the cumulative impact on the beach erosion or sedimentation and the impact on the variance in bed level for the beach.
The results from the XBeach simulation show that the BDS is effective at promoting beach stability under extreme storm conditions, although the results are mixed on what is the optimal location and discharge volume to cause accretion of sand or increased beach stability. The results for overseas extreme wave conditions showed decreased mean cumulative erosion and decreased bed level variance.
However, under Singapore localised conditions, the Beach Drainage system did not seem to have such a significant impact. This might be evidence that under the milder wave conditions of Singapore, a Beach Drainage system requires a longer time scale to be effective. Since the Beach Drainage system has shown to operate somewhat effectively under more extreme storm wave conditions, it should also operate effectively under milder wave conditions, but the effects might require more time to show. Thus, this paper provides further evidence to suggest that a Beach Drainage System might be effective at countering the effect of wave action to promote beach accretion and overall stability.
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