page_title: New Orleans Outfall Canals
section_title: Early history
hierarchical_section_title: New Orleans Outfall Canals / History of the outfall canals / Early history
caption_attribution_description: English: Image courtesy of USACE.
context_page_description: 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 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 17th Street Canal extends 13,500 feet north from Pump Station 6 to Lake Pontchartrain along the boundary of Orleans and Jefferson parishes. The Orleans Avenue Canal, between the 17th Street and London Avenue canals, runs approximately 11,000 feet from Pump Station 7 to Lake Pontchartrain. The London Avenue Canal extends 15,000 feet north from Pump Station 3 to Lake Pontchartrain about halfway between the Orleans Avenue Canal and the Inner Harbor Navigation Canal.
context_section_description: New Orleans was founded in 1718 by Jean-Baptiste Le Moyne, Sieur de Bienville, along the high ground adjacent to the Mississippi River (about 17 feet (5.2 m) above sea level). The city struggled early on with rainfall drainage because of the topography of the region.
  The Metairie and Gentilly ridges, both about 3–4 feet above sea level and located between the Mississippi River and Lake Pontchartrain, made it difficult for rainwater to move out of the city since the water would have to flow over these ridges in order to be drained northward into Lake Pontchartrain. Bayou St. John, a natural bayou and old navigation channel that ran from the northern edge of the French Quarter north to Lake Pontchartrain (today it runs from the Mid-City neighborhood to Lake Pontchartrain), was not enough to drain the often heavy rainfall that occurred.
  With drainage and rainfall-related flood protection a huge concern, man-made canals were constructed by the mid-19th century. Drainage machines and pumps were built to lift the drained water over the high ridges and into the outfall canals. By 1878, there were approximately 36 miles (58 km) of drainage canals feeding into Lake Pontchartrain to remove rainwater from populated areas. Today there are 90 miles (140 km) of covered drainage canals, 82 miles (132 km) of open channel canals and several thousand miles of storm sewer lines that feed into the system.
  These early primary drainage canals included (from west to east): 17th Street, Orleans Avenue and London Avenue. As the population expanded northward toward the lake, low-lying swamps were reclaimed by constructing shallow drainage ditches that fed into the newly created system of drainage canals. However, the reduction in the groundwater table, as a result of the drainage and reclamation of swamps and marshland, produced significant land subsidence in the drained area. That land subsidence continues today.
  The construction of the outfall canals did have another major consequence. By digging canals through the Metairie and Gentilly ridges, the canals opened up storm surge avenues into the heart of New Orleans via Lake Pontchartrain.
  The New Orleans Sewerage and Water Board, which was established in 1899, became the primary agency that tackled the tough drainage problems facing New Orleans. Flood protection levee upkeep, including those along the outfall canals, was done locally by the Sewerage and Water Board and the Orleans Levee District, the latter of which is a state agency established in 1890 to handle the operation and maintenance duties associated with levees, floodwalls, and other hurricane and flood protection structures surrounding the city of New Orleans.
  In 1915 and again in 1947, devastating hurricanes struck the New Orleans area, causing millions of dollars in property damage and killing hundreds of residents. Water overtopped and breached the levees along the outfall canals and the Sewerage and Water Board and the Orleans Levee District raised the levees an estimated three feet after those hurricanes. However, some of these levees had subsided by as much as 10 feet (3.0 m) during their nearly 100-year existence.
caption: An historical look at the City of New Orleans in 1878. The outfall canals were already constructed and included, from west to east, the 17th Street Canal, the Orleans Avenue Canal and the London Avenue Canal.
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