Flooding due to construction?

I live in a rural area. The neighborhood is generally peaceful and Hindu and Muslim families live in harmony here. Early this year, a plot of land , which is a few metres away from our house, was bought by a Hindu family. They deny that they are constructing a building on that piece of land for business activites, (which doesn't ring true to us) It isn't exactly clear what the purpose of their endeavour is and they haven't bothered to clarify the matter either. They've built very tall walls all around their plot of land. The elders of our gaon had reminded the family beforehand that our state is one that has to suffer heavy rains and had asked them to give up a foot of their land (like everybody else in the community) to make a drainage for diverting any rainwater. They refused to do so and this has led to flooding of the village even in the case of a moderate amount of rainfall, which was unimaginable until they built their walls. This has angered the muslim families of the community as their properties lie very close to theirs and are thus in danger of erosion and flooding in case of heavier rainfall. We've already spoken to the Muslim familes concerned and they've confirmed that the construction has altered their daily lives and their land has been eroded and decayed due to the stagnant water that has no way out, creating lake where it shouldn't be. As a result, the vegetation here has grown alarmingly and so have the number of mosquitoes, which has put us at the risk of diseases like dengue or malaria, which were advoidable before these human nuisances turned up at our neighborhood. Please help us. Whom can the community approach for help?