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In
Starlings may form part of a 
In architecture
Architecture is the art and technique of designing and building, as distinguished from the skills associated with construction. It is both the process and the product of sketching, conceiving, planning, designing, and construction, constructi ...
, a starling (or sterling) is a defensive bulwark, usually built with pilings
A pile or piling is a vertical structural element of a deep foundation, driven or drilled deep into the ground at the building site. A deep foundation is a type of foundation that transfers building loads to the earth farther down from th ...
or brick
A brick is a type of construction material used to build walls, pavements and other elements in masonry construction. Properly, the term ''brick'' denotes a unit primarily composed of clay. But is now also used informally to denote building un ...
s or blocks of stone, surrounding the supports (or pier
A pier is a raised structure that rises above a body of water and usually juts out from its shore, typically supported by piling, piles or column, pillars, and provides above-water access to offshore areas. Frequent pier uses include fishing, b ...
s) of a bridge
A bridge is a structure built to Span (engineering), span a physical obstacle (such as a body of water, valley, road, or railway) without blocking the path underneath. It is constructed for the purpose of providing passage over the obstacle, whi ...
or similar construction.
Starlings may be shaped to ease the flow of the water around the bridge, reducing the damage caused by erosion
Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...
or collisions with flood-borne debris or river traffic. They may also form an important part of the structure of the bridge, spreading the weight of the piers.
The term ''cutwater'' is used for such a structure shaped with water flow in mind, as a pier or starling with a diamond point. A ''starkwater'' is a bulwark against ice floes.
Depending on their shape and location, some starlings may accumulate river debris, mud and other objects, potentially creating navigational hazards or hindering downstream water flow.
Shape
Starlings may form part of a buttress
A buttress is an architectural structure built against or projecting from a wall which serves to support or reinforce the wall. Buttresses are fairly common on more ancient (typically Gothic) buildings, as a means of providing support to act ...
for the vertical load of the bridge piers, so would typically be symmetrical. Other symmetrical starlings may be used on tidal stretches of rivers because of bi-directional flow, requiring dual cutwaters; at low tide, Old Wye Bridge, Chepstow, on the Welsh border, can be seen to have cutwaters on both ends of the piers and their foundations. Cutwaters may also be provided downstream to reduce riverbed scour
Scour may refer to:
Hydrodynamic processes
* Hydrodynamic scour, the removal of sediment such as sand and silt from around an object by water flow
** Bridge scour, erosion of soil around at the base of a bridge pier or abutments via the flow ...
. Other starlings may be asymmetrical, with only an upstream cutwater, the downstream end being flat or rounded.
The starling has a sharpened or curved extreme, sometimes called the nose. The cutwater may be of concrete or masonry, but is often capped with a steel angle to resist abrasion, focusing force at a single point to fracture floating pieces of ice striking the pier. In cold climates, the starling is typically sloped by about 20 to 45° from vertical, so current pushing against part-submerged ice tends to lift and shear it; this can be known as a ''starkwater''. This is distinct from a sloping top to shed the rain.
On a narrow bridge, a cutwater shape can be carried up to the top of the parapet, to provide a pedestrian refuge.
See also
*Dolphin (structure)
A dolphin is a group of pilings arrayed together to serve variously as a protective hardpoint along a dock, in a waterway, or along a shore; as a means or point of stabilization of a dock, bridge, or similar structure; as a mooring point; and a ...
* Breakwater
* Icebreaker
An icebreaker is a special-purpose ship or boat designed to move and navigate through ice-covered waters, and provide safe waterways for other boats and ships. Although the term usually refers to ice-breaking ships, it may also refer to smaller ...
References
{{DEFAULTSORT:Starling (Architecture) Bridge components Hydraulic engineering