Survivors of Libya's deadly floods describe catastrophic scenes and tragic losses

Libya 's Red Crescent estimates 11,300 people have died; mayor says death toll could reach 20,000 .

Derna is a Mediterranean coastal city bisected by a seasonal river that flows south from the highlands.

The amount of rain from Storm Daniel was extraordinary, and two dams collapsed.

For those living by the Wadi Dern a valley, there was barely any warning before the floodwaters swept in, tsunami-like.

Taha Muftah , a photojournalist living on the west side of Derna , spent Friday morning walking around the center and taking stock of the devastation.

"The damage is huge, unfathomable. We are begging with the world to send help, to listen to our plea," he says.

Tarhoni , a doctor in Benghazi , warns that the most difficult weeks lie ahead.