When Hurricane Harvey hits Houston, Texas, in 2017, the city is overwhelmed by four feet of rain in four days, causing catastrophic flooding and billions of dollars in damage; experts use cutting-edge tech to discover what went wrong and how it can be fixed.

Boston's Big Dig was one of the most ambitious engineering projects in history, but in 2006, a fatal collapse in one of its tunnels put the ambitious project in doubt; experts reveal what caused this engineering disaster and how it was fixed.