A Process Based Assessment of Engineered Structures on Reef Islands of the Maldives

Abstract: This paper examines the use and environmental consequences of engineered structures on reef platform islands in the Maldives. The Maldives comprises 1 500 islands which are mostly low-lying sand cays. These cays are inherently unstable, changing their size, and position on reef platforms in response to short-term and seasonal adjustments in wind, wave and current patterns. Island instability combined with high population densities has resulted in the proliferation of engineered structures to combat erosion and to provide boat access. In many instances introduction of hard engineered structures has exacerbated island erosion and degraded reef productivity. Reasons for the negative environmental consequences are twofold. First, the design, materials used in construction and the mode of construction contravene most standard measures of sound engineering design. Constraining sound design is a total lack of environmental information, particularly wave and current data. Second, structures are often inappropriate with respect to natural coastal processes. This is illustrated by wave and current measurements on Hulhudhoo Island in Baa Atoll. Results show the nearshore process regime is dominated by strong alongshore current gradients. Furthermore, seasonal shifts in monsoon winds produce reversals in wave, current and sediment transport