Can my neighbor close a ditch and replace it with a water pipe?

Usually this can be done but may in some cases require a local permit (especially if the city built the ditch); the pipe must be of sufficient size, be kept clear of debris, and cannot obstruct the flow of water at any time. Contact the city office and ask for the local rules on permits for these matters. If the new pipe is causing problems for you, you could have a legal action with or without the permit.

See also…

Neighbor Law