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 built 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 a well-prepared assault. This derives from Latin: sedere, lit. 'to sit'. 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 not uncommon, as proximity and fluctuating advantage can encourage diplomacy. The art of conducting and resisting sieges is called siege warfare, siegecraft, or poliorcetics.
A siege tower or breaching tower is a specialized siege engine, constructed to protect assailants and ladders while approaching the defensive walls of a fortification. The tower was often rectangular with four wheels with its height roughly equal to that of the wall or sometimes higher to allow archers to stand on top of the tower and shoot arrows into the fortification. Because the towers were wooden and thus flammable, they had to have some non-flammable covering of iron or fresh animal skins.
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 stopbank is an elongated naturally occurring ridge or artificially constructed fill or wall that regulates water levels. It is usually earthen and often 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 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 fortification is a military construction or building designed for the defence of territories in warfare, and is also used to establish rule in a region during peacetime. The term is derived from Latin fortis ("strong") and facere.
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.
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 and landfall in Mississippi. The levee and flood wall failures caused flooding in 80% of New Orleans and all of St. Bernard Parish. Tens of billions of gallons of water spilled into vast areas of New Orleans, flooding over 100,000 homes and businesses. Responsibility for the design and construction of the levee system belongs to the United States Army Corps of Engineers; the responsibility of maintenance belongs to the local levee boards. The Corps hands components of the system over to the local levee boards upon completion. When Katrina struck on August 29, 2005, the project was between 60–90% complete. Four major investigations were conducted by civil engineers and other experts in an attempt to identify the underlying reasons for the failure of the federal flood protection system. All concur that the primary cause of the flooding was inadequate design and construction by the Corps of Engineers.
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.
Tunnel warfare is a general name for war being conducted in tunnels and other underground cavities. It often includes the construction of underground facilities in order to attack or defend, and the use of existing natural caves and artificial underground facilities for military purposes. Tunnels can be used to undermine fortifications and slip into enemy territory for a surprise attack, while it can strengthen a defence by creating the possibility of ambush, counterattack and the ability to transfer troops from one portion of the battleground to another unseen and protected. Also, tunnels can serve as shelter for combatants and non-combatants from enemy attack.
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.
The Walls of Dubrovnik are a series of defensive stone walls surrounding the city of Dubrovnik in southern Croatia. With numerous additions and modifications throughout their history, they have been considered to be amongst the great fortification systems of the Middle Ages, as they were never breached by a hostile army during this time period. In 1979, the old city of Dubrovnik, which includes a substantial portion of the old walls of Dubrovnik, joined the UNESCO list of World Heritage Sites.
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 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.
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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