(from Zac, aged 4)
Why doesn't G-d make a flood to take away all the yucky people like He did for Noah?
Zac, I know you are a very good boy. But have you ever been naughty? Did you ever hurt your little brother, or say something rude to your mummy?
G-d wants us to be good all the time. But we don't always get it right. Even good boys like you can sometimes do the wrong thing.
It is a pity that we are naughty sometimes, but the most important thing is that we stop being naughty and say sorry. Then it's ok again, and we can start being good and doing what's right.
If a flood would come every time someone did something bad, then no one would get the chance to say sorry and change. So G-d has patience. He is waiting for the yucky people to realise that they are wrong and to start behaving.
In the times of Noah, G-d waited 120 years before He brought the flood. Only because no one changed their naughty ways in all that time did the flood happen. They even watched Noah building the ark, so they knew the flood was coming, but they still didn't start behaving themselves. From that story we learn how silly it is to keep on being yucky.
Even if you have been naughty, you can change and say sorry and be good from now on. G-d is waiting for you, because even when you do something bad, He knows how good you can be.