New Orleans Outfall Canals

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 17th Street Canal extends 13,500 feet (4,100 m) 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 (3,400 m) from Pump Station 7 to Lake Pontchartrain. The London Avenue Canal extends 15,000 feet (4,600 m) north from Pump Station 3 to Lake Pontchartrain about halfway between the Orleans Avenue Canal and the Inner Harbor Navigation Canal (also known locally as the Industrial Canal).

Before August 29, 2005, the three outfall canal levees operated with little attention. The larger and longer Mississippi River system, which faces annual flood stages of ten to twenty feet lasting for four weeks at a time, garnered significantly more engineering attention.

When Hurricane Katrina made landfall on August 29 along the Louisiana and Mississippi coasts, storm surge from the Gulf of Mexico flowed into Lake Pontchartrain. The levees along the south shore of Lake Pontchartrain (including both Orleans and Jefferson Parish) withstood the elevated lake levels as designed. However, the floodwall structures along the three outfall canals failed in multiple locations.

The floodwall along the 17th Street Canal’s east bank breached just south of the Old Hammond Highway Bridge. In addition, two major breaches occurred on both sides of the London Avenue Canal – one on the west side near Robert E. Lee Boulevard and another on the east side near Mirabeau Avenue. The Orleans Avenue Canal’s floodwalls did not breach.

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Wikipedia