Entire neighborhoods on the south shore of Lake Pontchartrain were flooded. The extensive flooding stranded many residents who were forced to stay in place long after Hurricane Katrina had passed.

What happened to Lake Pontchartrain during Katrina?

When the pumps were finally reactivated, the bulk of contaminated water from the city was jettisoned for many days directly into the southern portion of Lake Pontchartrain with a discharge estimated at 2–3 percent of the volume of the lake, or approximately 30–50 billion gallons (100–200 billion liters) (fig. 3).

What lake flooded New Orleans?

A federal judge in New Orleans ruled in 2009 that the U.S. Army Corps of Engineers' failure to properly maintain and operate the Mississippi River-Gulf Outlet was a significant cause of the catastrophic flooding during Katrina. Levee failures near Lake Pontchartrain also flooded New Orleans neighborhoods.