A coupure is a means of closing an opening in a wall, floodwall or levee (dike). The word comes from the French verb couper which means "to cut". In historic times a coupure was a location where a breach in the city walls or the walls of a fortress was closed. In more modern times a coupure is a way of allowing traffic to pass a flood protection structure.
During a siege, a coupure is a ditch or an earthwork or wooden palisade built behind a breach made by the attacker's guns in the walls of a fortress or a city. Its purpose is to hinder and frustrate an attack made by the forlorn hope.
This was a strategy used many times by defenders of fortifications, for example, by the Irish defenders during the Siege of Clonmel (April - May 1650).
It can also be a passage through a glacis to create a sally port, so that the defenders can launch a sortie against the attackers.
When a road or railway crosses a floodwall or levee the road or railway can either be laid on a grade or through a cut in the floodwall or levee. In case of expected flooding the cut can temporarily be closed. This type of coupure is also known as vehicle gate, floodwall gate or similar names. The closure can be accomplished by various means.
The most basic means of closing a coupure is with soil or sandbags. More sophisticated means of closing a coupure consist of wooden or metal beams or doors. Older coupures are usually brick structures with provisions for placing two stacks of beams between them. Between the stacks of beams, which form two walls, horse manure or other animal faeces mixed with straw is dumped and compacted. This type of material swells when wet, thus providing additional waterproofing. Modern coupures can consist of only one wall and can be made watertight with the help of rubber flaps or other materials.
Medieval fortification refers to medieval military methods that cover the development of fortification construction and use in Europe, roughly from the fall of the Western Roman Empire to the Renaissance. During this millennium, fortifications changed warfare, and in turn were modified to suit new tactics, weapons and siege techniques.
A siege is a military blockade of a city, or fortress, with the intent of conquering by attrition, or by well-prepared assault. Siege warfare is a form of constant, low-intensity conflict characterized by one party holding a strong, static, defensive position. Consequently, an opportunity for negotiation between combatants is common, as proximity and fluctuating advantage can encourage diplomacy.
A battering ram is a siege engine that originated in ancient times and was designed to break open the masonry walls of fortifications or splinter their wooden gates. In its simplest form, a battering ram is just a large, heavy log carried by several people and propelled with force against an obstacle; the ram would be sufficient to damage the target if the log were massive enough and/or it were moved quickly enough. Later rams encased the log in an arrow-proof, fire-resistant canopy mounted on wheels. Inside the canopy, the log was swung from suspensory chains or ropes.
A levee, dike, dyke, embankment, floodbank, or stop bank is a structure used to keep the course of rivers from changing and to protect against flooding of the area adjoining the river or coast. It is usually earthen and often runs parallel to the course of a river in its floodplain or along low-lying coastlines.
A defensive wall is a fortification usually used to protect a city, town or other settlement from potential aggressors. The walls can range from simple palisades or earthworks to extensive military fortifications such as curtain walls with towers, bastions and gates for access to the city. From ancient to modern times, they were used to enclose settlements. Generally, these are referred to as city walls or town walls, although there were also walls, such as the Great Wall of China, Walls of Benin, Hadrian's Wall, Anastasian Wall, and the Atlantic Wall, which extended far beyond the borders of a city and were used to enclose regions or mark territorial boundaries. In mountainous terrain, defensive walls such as letzis were used in combination with castles to seal valleys from potential attack. Beyond their defensive utility, many walls also had important symbolic functions – representing the status and independence of the communities they embraced.
A siege engine is a device that is designed to break or circumvent heavy castle doors, thick city walls and other fortifications in siege warfare. Some are immobile, constructed in place to attack enemy fortifications from a distance, while others have wheels to enable advancing up to the enemy fortification. There are many distinct types, such as siege towers that allow foot soldiers to scale walls and attack the defenders, battering rams that damage walls or gates, and large ranged weapons that attack from a distance by launching projectiles. Some complex siege engines were combinations of these types.
The Sieges of Nagashima, taking place in 1571, 1573, and 1574, were part of Oda Nobunaga's campaigns against the Ikkō-ikki, arguably among his greatest enemies. Nagashima, in Owari Province along Japan's Pacific coast, was the location of a string of river island fortresses and defensive works controlled by the Ikkō-ikki, which surrounded their Ganshō-ji monastery. This string of defenses included Nagashima Castle, which they had captured previously. Oda Nobunaga attacked three times over the course of four years, before finally destroying the entire Nagashima complex. These sieges were executed concurrently with Nobunaga's eleven-year siege against the Ikki's primary fortress of Ishiyama Hongan-ji.
A ravelin is a triangular fortification or detached outwork, located in front of the innerworks of a fortress. Originally called a demi-lune, after the lunette, the ravelin is placed outside a castle and opposite a fortification curtain wall.
A bastion fort or trace italienne is a fortification in a style that evolved during the early modern period of gunpowder when the cannon came to dominate the battlefield. It was first seen in the mid-fifteenth century in Italy. Some types, especially when combined with ravelins and other outworks, resembled the related star fort of the same era.
The 17th Street Canal is the largest and most important drainage canal in the city of New Orleans. Operating with Pump Station 6, it moves water into Lake Pontchartrain. The canal, along with the Orleans Canal and the London Avenue Canal, form the New Orleans Outfall Canals. The 17th Street Canal forms a significant portion of the boundary between the city of New Orleans and Metairie, Louisiana. The canal has also been known as the Metairie Outlet Canal and the Upperline Canal.
The London Avenue Canal is a drainage canal in New Orleans, Louisiana, used for pumping rain water into Lake Pontchartrain. The canal runs through the 7th Ward of New Orleans from the Gentilly area to the Lakefront. It is one of the three main drainage canals responsible for draining rainwater from the main basin of New Orleans. The London Avenue Canal's flood walls built atop earthen levees breached on both sides during Hurricane Katrina in 2005.
Though Hurricane Katrina did not deal the city of New Orleans a direct hit on August 29, 2005, the associated storm surge precipitated catastrophic failures of the levees and flood walls. The Mississippi River Gulf Outlet ("MR-GO") breached its levees in approximately 15 places. The major levee breaches in the city include the 17th Street Canal levee, the London Avenue Canal, and the wide, navigable Industrial Canal, which left approximately 80% of the city flooded.
On Monday, August 29, 2005, there were over 50 failures of the levees and flood walls protecting New Orleans, Louisiana, and its suburbs following passage of Hurricane Katrina. The failures caused flooding in 80% of New Orleans and all of St. Bernard Parish. In New Orleans alone, 134,000 housing units—70% of all occupied units—suffered damage from Hurricane Katrina and the subsequent flooding.
A floodwall is a freestanding, permanent, engineered structure designed to prevent encroachment of floodwaters. Floodwalls are mainly used on locations where space is scarce, such as cities or where building levees or dikes (dykes) would interfere with other interests, such as existing buildings, historical architecture or commercial use of embankments.
A scarp and a counterscarp are the inner and outer sides, respectively, of a ditch or moat used in fortifications. Attackers must descend the counterscarp and ascend the scarp. In permanent fortifications the scarp and counterscarp may be encased in stone. In less permanent fortifications, the counterscarp may be lined with paling fence set at an angle so as to give no cover to the attackers but to make advancing and retreating more difficult.
Sapping is a term used in siege operations to describe the digging of a covered trench to approach a besieged place without danger from the enemy's fire. The purpose of the sap is usually to advance a besieging army's position towards an attacked fortification. It is excavated by specialised military units, whose members are often called sappers.
There are three outfall canals in New Orleans, Louisiana – the 17th Street, Orleans Avenue and London Avenue canals. These canals are a critical element of New Orleans’ flood control system, serving as drainage conduits for much of the city. There are 13 miles (21 km) of levees and floodwalls that line the sides of the canals. The 17th Street Canal is the largest and most important drainage canal and is capable of conveying more water than the Orleans Avenue and London Avenue Canals combined.
The Walls of Nicosia, also known as the Venetian Walls, are a series of defensive walls which surround Nicosia, the capital city of Cyprus. The first city walls were built in the Middle Ages, but they were completely rebuilt in the mid-16th century by the Republic of Venice. The walls are still largely intact, and are among the best preserved Renaissance fortifications in the Eastern Mediterranean. They are a major tourist attraction.
Siegecraft originated in Ancient Greece. This type of siege originated from the moment in which the stage of the mere siege was surpassed by an exceptional development of military techniques, which were hardly taken any further during the Middle Ages, until the invention of firearms. The importance of siege techniques was due to the increase in the strategic role of the city to the detriment of the territory in the overall defense of the polis.
Stephen Francis Wyley A Dictionary of Military Architecture Fortification and Fieldworks from the Iron Age to the Eighteenth Century , Drawings by Steven Lowe
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