(1) The owner of land in any county containing more than 250,000 population through which a nonnavigable stream has its natural outlet, or through which ditches or drains have been constructed and other ditches have their outlet, shall keep the same free from driftwood, trash or any obstruction which would stop the free flow of water.
(2) The county engineer shall inspect such streams, ditches and drains and see that they are free from obstructions. If he finds any obstruction, he, or one of his deputies or ditch inspectors, shall notify the owner of the land abutting on the stream, ditch or drain in writing to remove the obstruction.