On 29 August 2005, as the eye of Hurricane Katrina passed to the northeast of New Orleans, heavy rain and a storm surge raised the water level in Lake Pontchartrain, which lies directly north of the city. The powerful anticlockwise winds drove water in the lake southwards, barrelling into three outfall drainage canals at the northern edge of the metropolitan New Orleans protected basin. The canals were lined by earthen levees, themselves topped with concrete floodwalls. Although the water was several feet below design levels, the 17th Street and London Avenue Canals breached in multiple locations, as the floodwalls and parts of the levee broke and gave way.
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