Items left on public side of my fence

Am I able to take items left on the public side of my fence? My property backs up to a busy street. So going toward the street is my fence, then grass space, the side walk, more grass, then the busy street. Someone has been placing items up against my fence such as fence boards (those were actually screwed into my fence) and a trellis. Can I dispose of these items as they are unsightly and on public land maintained by the city? Side note: Not sure why someone keeps doing this. We’ve been here for years and it’s only been the last few months that it’s happening.