I take a cooler on wheels which I carry my tackle box, bait, fishing vest, rod holder, and plastic bags.
I always take home more trash than I create and when fishing with my oldest son (now 14) and he starts not following direction I have him gather a bag or two of trash.
Of course I am in eastern Oregon and not on the Sandy. Part of the problem with the Sandy could be the people going down in air matteresses and just hanging out to party and stay cool (they probably bring a good portion of trash and leave it at the river).