Factchecks timeline of events says about 5 hours after Katrina hits land; "Late Morning (exact time uncertain) - The vital 17th Street Canal levee gives way, sending the water from Lake Pontchartrain into the city in a second, slower wave of flooding. A full day will pass before state or federal officials fully realize what is happening. —John McQuaid, " Katrina trapped city in double disasters ," New Orleans Times-Picayune , 7 Sep 2005. Eventually, engineers will find five separate places where concrete floodwalls gave way. They will still be debating and studying the causes of the failures two weeks...