The layout of the city of Derna, on the northeastern coast of Libya, amplified the extreme damage wrought by flooding there over the weekend. The floods have killed thousands of people, according to local authorities, and thousands more are missing.
Derna lies along the coast of the Mediterranean Sea, at the end of a long, narrow natural valley, called a wadi, which is dry for much of the year.

As the port city was inundated by Storm Daniel, which made landfall in Libya on Sunday, the wadi worked as a funnel, forcing the rushing water into the center of the city. Riverbanks swelled, bridges were washed out and two dams farther up the wadi burst, adding their waters to the deluge.

Rescue efforts are underway, but blocked roads and cut-off bridges posed challenges getting to Derna. It was unclear how much aid had made it to residents as of Thursday.
Libya has an extremely dry climate and rarely experiences heavy rainfall. The storm dumped a record 16 inches, or 400 millimeters, of rain on parts of the area on Sunday, according to Libya’s National Meteorological Center.
Satellite imagery from Tuesday showed miles-wide lakes had emerged in the desert south of Derna in basins that are generally completely dry at this time of year.

Photography from Tuesday showed what remained of neighborhoods in central Derna, where water had swept entire buildings out to sea.


Photos taken in Derna show widespread destruction along what is usually a dry riverbed. Numerous bridges were washed out, with only the support structures remaining in place.
Originally published by The New York Times