Regarding harassment involving our pond

A neighbor of our's sold their place to a local promoter/builder who will be building a flat there within a few years....As they started demolishing the building he came to talk to my dad regarding whether or not they could be able to dump the gravels around the edges of our pond.....My father agreed as the badly damaged edges needed the securing and hence told them to level and secure the edges with their gravels only....Btw my father works outside our state and was here for a few days only.... Afterwards they managed to secure a most of the edges and everything was going all well,Until yesterday..When a 2 guys(they were not legal representatives and more like political foot soldiers)showed up suddenly and entered our property without our permission.When we confronted them they flat out told us we can't do what we are doing with our pond...Somehow they thought we were filling up the pond as someone told them that......Then when we cleared the fact we weren't they started making other things,Like we can't secure it without their permission,we must "pile" the pond and a few other very unclear things.....When asked about whether or not it is legally mandatory to "pile" a pond if we are securing it;s edges already,they simply babbled before hesitantly saying that it is.....Then they went away... The thing took a turn for the worse today when my mother went to the market and was told by another one that they will go to the police and the one that complained against us is a dangerous man without stating what laws we were violating.....She was hysteric when she returned and was acting irrationally...when i told her to consult a legal representative she just refused and started a tantrum as i m a 19 yrs old and shouldn't have interfered......I am in a very weird situation right now i want to save our pond and i don;t know what laws we have violated by securing it's edges....Pls help us out regarding What should we do about our current situation???