Dan, Lisa, and I just drove through this area when we did the Park county tornado survey. There were numerous locations along Highway 67 where a combination of water, gravel, sand, and debris had washed onto and over the roadway. The worst location was about 2 1/2 miles south of Deckers along Highway 67. This is where Wren Gulch empties into Horse Creek (see images below - These are also in Z:2009 Severe WeatherHayman Flash Flood Pics).
At this location, a tremendous amount of sediment in the form of rocks, gravel, sand, and trees piled up several feet deep at the bottom of the gulch where it empties into Horse Creek, effectively damming up the creek and forcing it to spill out across Highway 67. I have no idea how deep the water was over the Highway, but probably more than enough to wash vehicles off the road. There was also significant damage along Six Mile Creek (North of Deckers) that Treste spoke of below. What was very interesting is that there must have been a tremendous amount of rainfall during this or a later event, as even where the forest was NOT burned there was evidence of erosion and small alluvial fans at the bottom of ravines.
As a result, I think our criteria seems pretty good since we were probably approaching flash flood criteria even in non-burn areas. Do we have that case(s) stored on the WES so we could all take a look at it and see the observed storm totals and compare it to our FFG? With regard to the Oxyoke site, we did not see much evidence of any flash flooding at that location. If you want to take a personal tour of that area via Google Earth, open the program and do a search for 39.22926, -105.19859 which will take you to the location where Wren Gulch empties into Horse Creek. What's really neat is if you pan up/down the numerous gulches, ravines, streams along the route (Hold down the middle mouse button and slide the mouse up/down/left/right to get different perspectives of the drainage basins).