Land Owner/Developer Duty of Care

Hi! I have bought a new build house, where there is an open green space (with a dug storm drain outside a fence) on a hill over looking out car parking spaces. Unfortunately my car has twice been hit by rocks thrown from the hill, beyond knowing it is children I don't know where they live. After the first time I asked the developer to please remove a pile of stones from the drain, as well as a few piles of building waste such as metal pipes and bricks. However this has not been does and my car has now been hit a second time, once denting the door and once smashing the windscreen. Each repair has been the same price as my excess so I have paid out of pocket. I was wondering what Duty of Care they would have over the cars? I would assumed as the land owner there would be one to ensure the land is well maintained as well as clear of debris, which they have not done. I would like to both not be out of pocket and have them sort this out!