blockage of rainwater flow by neighbour

You have to make a complaint to the local civic body about this and if the occurrence recurs then you can file a suit for esement rights against the neighbor seeking the relief of removal of the obstruiction he has created which not only is a hinderance to your easement but also a continuous disturbance for your peaceful living, you can file an application for mandatory injunction in the same suit to remove the obstuction

You are welcome.

It is better to seek permanent and mandatory injunction against the neighbour through a local prudent lawyer.

Yes, you need to take up the issue with the Grampanchayat and further escalate the issue by serving legal notice and initiating a civil action, if so required.