When I see stuff like that, I'll go to the pile and check if there are any packing, PO# or a delivery slip; anything that might show an address or name. Either way I'll call the cops and give them the location; eventually a road crew will show up and clean the mess up.
Then there's my garbage dumpster here at the shop; people think it's a free for all to use. Get here some mornings and its all but full. I've tried locking it closed; but they'll just throw the garbage on the ground beside the dumpster. I get so pissed that I'll open the bags and look for a name and address. When I find one, it is usually only a few blocks away. I'll then bag the crap back up put it my truck and go for a ride. Bang on their door, when they answer, I ask is this the residents of such and such. If they answer yes; I drop the bag at their feet and ask if they misplaced their garbage. If I get any flak, I'll wave my phone and ask if they'd like me to call the cops; that usually shuts them up.
Dan.