Most residents of Kerr County, Texas, would have been asleep when flood alerts flashed up on their phones in the early hours of Friday.

A few hours later, many of them were woken by neighbours hammering on their door or their dogs frantically barking. Others would not have woken up until flood water engulfed their beds. For many, it was already too late.

The Kerr County towns that lie along the Guadalupe River, which surged more than 20 feet in less than an hour on Friday morning, bore the brunt of the floods and suffered most of the deaths.

The story leading up to this tragedy is one of grave mistakes.

It is not about what happened when the Guadalupe burst its banks, or the immediate aftermath, where rescuers frantically tried to save lives.

It is about how officials – in a Texan disaster hotspot known as Flash Flood Alley – failed to act years before.

The disaster is one of the most lethal floods in US history, with a death toll of more than 100 and climbing - including 28 children. Dozens are still missing, with ten girls among them.