The area I seen was just south of the new playground at 41st & RiverSide Drive. They put up a fence and the erroision is undermining the fence. It gets bad at around 100 meters or so south of the playground, farther south the trail moves away from the riverbank. Workmen were putting up those new fancy light poles at the closed section of the trail, they should of been working on the riverbank to shore it up before it all collapses into the river.
I ran that section yesterday and took a good look at the area just south of the 41st/Riverside playground. The rather steep river bank runs roughly parallel to the new trail for about 100-150 yards. The "dropoff"...so to speak...is generally about 7-10 yards from the concrete border of the trail. There is a small section...marked by an orange construction fence...that comes a bit closer to the trail. Here...a dirt path is found that is obviously being using by trucks to haul the huge boulders for reinforcement. It's being worked on.