Steve, here's the best way to visualize the main Bonneville Landslide - this is the view looking north toward the Table Mountain/Greenleaf group, and the main landslide is the lobe of terrain that extends into the river, between Bonneville Dam and Rock Creek - you can see the bend that it created in the river, and the powerline corridor marks roughly the halfway mark in the length of the slide from Table Mountain to the river:
Here's another view, this time showing the "profile" of the slide, plus the very obvious bend in the river that the slide created:
An interesting factoid in this view of the slide is that the river basically cut through the low point in the debris to form the current channel, but many believe that the river was completely dammed for as much as a week before the "Bridge of the Gods" was cut through. Another factoid that you can appreciate in this view is that the hummocky terrain on the Oregon side (roughly the area located between the powerline corridor and the river) is "slop-over" (a technical geologic term) debris that was pushed up the far side of the river by the force of the slide. If you've hiked to Dry Falls from BOTG, then you've seen this odd terrain, complete with dry ravines and hollows.
The most interesting new thinking on the Bonneville Slide is just when it occurred: the original theories placed the slide at about 1100 or 1200 AD, but more recently, the thinking is that it occurred as a result of the 1700 AD Cascadia Earthquake, a massive 9.X quake that sent a recorded tsunami to Japan. The fact that it was well documented on that side of the ocean allows geologists to place it quite specifically to the morning of January 26, 1700, at about 9 AM! This more recent date helps explain the existence of the "submerged forest" that still exists below the Bonneville Pool, but was once visible along the Oregon shore, opposite Wind Mountain, and the very specific Native American accounts, via mythology.
A final factoid: the designers of Bonneville Dam were well aware that they were building on unstable land, so the design is a "floating" structure that rides like a raft on the debris, as opposed to being anchored like Grand Coulee or Hoover Dam. So it's very unlikely to be compromised by a geologic event.
Tom