Look to the land

I’m riding in a helicopter over a city and a river of brown water snaking between the city, highways and trees. Then I am walking down an empty riverbed. I keep seeing clumps of weeds and moss that looks like seaweed. The clumps are stuck in bushes on the ground, tree branches higher up and even way up hanging from the steel beams of a high voltage power line tower. The grass and ground all around is still damp or soggy. I take these all as signs that the river has recently flooded and quickly dried up.