The correct answer is - Frequent rains caused rivers to flood.
Panama is a country that has wet tropical climate. This basically means that the country is warm throughout all of the year, and also has rainfall throughout all of the year.
Now those are nice conditions for the nature, so the animals and plants thrive there, but it is not good at all for performing a large-scale construction project. The constant rains were making the terrain muddy all the time, and as if that was not bad enough, the rivers were flooding very often, and the construction had to be stopped, people evacuated, and after the floods, clean up the terrain again and continue with the work.
