The coastal environmental profile of Singapore

: This report presents empirical relationships available in the literature for design and prediction of beach response to single, segmented, headland, pocket beach, and reef breakwater systems for the primary purpose of shore protection. The data set used to develop each design method is discussed, and the empirical procedures are evaluated based on available Corps-built breakwater project data, An existing US detached break-water project is used to intercompare design relationships and further assess their validity. Several empirical methods are shown to predict prototype response fairly well. These relationships may be useful in conjunction with detailed studies to quickly assess prototype response to various design alternatives. Keywords: Literature surveys; Detached breakwaters; Pocket beaches; Segmented breakwaters.

Functional Design of Breakwaters for Shore Protection: Empirical Methods

Beach nourishment and particle size effects

Crenulate‐shaped bays are ubiquitous, with a large spectrum of sizes on coasts, enclosed seas, lakes, and rivers. They exist where waves arrive persistently from an oblique direction to the general coast. They thus indicate to man nature's way of maintaining beaches that are in dynamic or static equilibrium. This phenomenon can be utilized to retain beaches in locations where erosion was previously encountered. Such a process has been termed “headland control.” It is applicable to any shapes of coastline, be it straight, bayed, or convex. The headlands can be designed to minimize the effect of storm waves on them. It must be accepted that such waves will still remove the beach berm almost annually to form an offshore bar that affords protection to facilities landward of it. Their direction of arrival dictates the volume of material so demanded, which can vary around the periphery of a bay.

Applications of headland control

One of the function of the offshore breakwater is to protect the coast from wave action. By dissipating the wave energy along its entire length, the breakwater causes sediments in its lee to deposit and a shore salient is formed. If the offshore breakwater are placed in a series along a coast with a gentle offshore slope and a substantial littoral drift tombolo will form behind the breakwaters between which bays will be sculptured by waves to form stable shapes (1). These attached breakwater would thus form a series of artificial headlands. In nature, beaches between headlands are influenced by the position of the headlands. Where the headlands are closely spaced and a limited sediment supply exists, small pockets beaches are formed. Where the headlands are far apart and an adequate sediment supply exists, long and wide beaches are formed. Generally, between these two extremes most beaches between natural headlands take a shape that is related to the predominant wave approach; on the downcoast sector is a long and straight beach, while on the upcoast end is curbed beach. Silvester (2) in his model study established a relationship between the logarithmic spiral constant ( °^ ) and the angle of predominant wave approach ( & ). A quasi-permanent shape was reached when waves broke simultaneously around the model bay. As it is difficult to measure the curve sector in nature, Silvester and Ho (3) suggested the use of an indentation ratio to relate the bay's shape to wave approach.

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Beach development between headland breakwaters in a low wave energy environment, pasir ris, singapore

Breakwaters in a series can be employed to protect sedimentary coasts. They are used to protect newly reclaimed land along the southeast coast of Singapore; they act as headlands between which sand beaches are formed. The development of these beaches takes place under conditions of low energy waves, a predominant wave direction from the southeast and an east-west littoral drift. The characteristics and development of three beaches over a one-year period are presented. Surveys of the reclaimed land show various beach types between the headland breakwaters. A relationship exists between berm orientation and headland breakwater orientation. Beach stability is tentatively indicated by the formation of a wide berm.

https://icce-ojs-tamu.tdl.org/icce/index.php/icce/article/download/2977/2642

K.K. Chin

Papers

Beach development between headlakd breakwaters