I am sure some clever hydrologists are estimating the volume of water that has been held back by the landslide. Based on the graph of the discharge at Arlington it appears the river was backed up for approximately 30 hours so I came up with 2,727 acre feet.
The good news it that it sounds like the river is finding a new path and the held back water will draw down in a steady manner, but will require the river to erode downward. Given the loose material and distance it was deposited over, I am optimistic there will not be a huge flood surge. The communities and public safety and public workers on the Stilly need a break. Weather wise things look not too bad either with weather models indicate the organized storm tracks will be well to the south.