Precarious Seagull nests

I've had seagulls nesting on a roof connected to mine for the last couple of years & each time a young or 2 has come to grief. 1 very young one slid down the roof & got stuck in the gutter/downpipe & perished, eventually taken by some carrion bird I think, 2 very young ones have fallen right down into my garden, luckily not injured, I let them out the gate but they were way off old enough to fly so probably got eaten by something. Now I have have another bigger one, fully grown but not flying yet, with an injured right leg from it's fall. I heard it slide, scrabbling down my roof about 3.45 this morning. It seems happy at the moment, I have fed it a couple of sardines & given it a water supply but it cannot move very far. I am awaiting a call from someone who rescues them. I know this is all nature/survival of the fittest etc but it is distressing to witness at such close quarters & a housing development is not exactly a natural habitat. It is also perilous helping them as the parent gulls can get very aggressive & have attacked people when their young are on the ground.
My Question is... is there anything we can do to stop them nesting in such precarious places which put their chicks in such danger & causes such stress to we who have to deal with the fall out? This parent nests in the right angle V of 2 roofs not a flat surface in sight so the whole site is precarious!
The noise at dawn, 3.40 this morning it started, from the various nests nearby (5 I think) is huge too & very disruptive of sleep.