Someone's home is on a public street. A homeless man likes to feed bread to the birds that are in the nests and on the person's lawn. Sometimes, the man just dumps a pile of bread crumbs on the lawn and leaves it there and birds aren't the only ones that stop by.
Besides having to deal with the mess on the lawn, the crumbs encourage geese that leave their poop all over the lawn, and the owner's kids can't play on the lawn.
Moving the chametz aside doesn't solve the problem. As it will still be on his lawn - subject to the wind and geese / other animals. He can't sweep it into his trash can, as then he will be owning chametz until the sanitation dept. disposes it. He also can't sweep the trash onto the street or down a storm drain, as this is unlawful.
Perhaps, the only way would be to dispose of it in some public trash can in another neighborhood, as the street he is in has no street corner trash bins. However, doesn't he acquire ownership of the chametz once he picks it up?
So, how can he properly dispose of the chametz, or does he have to live with the mess for the week?
(Assume that a friendly sign, "No chametz allowed on my lawn this week", isn't doing the trick :-)
Related question - Are the rules different if either an animal or the wind deposited the chametz from a public area onto private property?