I saw photos of this in Bournemouth. So sorry you’re having to deal with it.
We get it here when it gets sunny (south Kent coast). And it’s been particularly awful in these warm COVID weeks. Here, it’s a mixture of locals and outsiders flocking to the beach and seaside parks. Considering how many turn up,it’s probably a small percentage who leave their shit (literally sometimes) lying around.
But as someone said above, if the reasonable people would just take their rubbish home, it would be a huge help.
People turn up at 7.30 am laden with tartan plastic bags, gazebos, barbies etc. Then when they leave they say, there wasn’t any room in the bin so I left my rubbish in a bin bag next to the bin. Because obviously there are no gulls, foxes or rats in seaside towns who will tear those bags open.
It’s especially shit here for the garden/ park keeping guys (who are already trying to keep the area and plants looking lovely, and have had their core staff whittled down over the years). So they spend their first 2 hours at work litter picking, including human waste, fielding calls about missing lifebuoys, all the early dog- walkers complaining about buckets of raw marinated chicken left in the bushes, nappies etc.
I think a lot of people, whether local or visiting, think that ‘They’ should have late evening rubbish collections. And thereby absolve themselves from the responsibility of taking their litter home.