The cover page of this USGS report has a picture of Racehorse Creek Falls.
Page 15 has a map showing the Racehorse Creek subbasin. This illustrates the area carved out by the stream.
Page 16 has a satellite map of the subbasin and a description of the Racehorse Creek Landslide. The text below is copied from the report.
Page 17 has two pictures of Racehorse Creek near the logging bridge downstream of the landslide and waterfall.
The Racehorse Creek subbasin is about 11 mi2 in size, and is located in the northeastern part of the Nooksack River basin on the northern slope of Slide Mountain in the North Fork Nooksack River basin. This mountain stream subbasin is carved through a mantle of glacial sediments and into bedrock composed of massive sandstone, conglomerate, and shale (Easterbrook and others, 2007). The subbasin has a history of landslide occurrence and is in a part of the Nooksack River basin that remains seismically active (Linneman and others, 2007). The subbasin is predominantly forested, and interspersed with areas of clear-cutting and logging roads. Most recently, the subbasin was affected by a landslide that occurred on January 7, 2009, during a period of intense rainfall. The material from this failure temporarily dammed the flow on Racehorse Creek (which already had large flows due to heavy rains) about 1 mi upstream of the gaging station, and after giving way caused an outburst flood downstream that significantly modified the stream channel in the lower part of the subbasin (fig. 4).
Racehorse Creek is a low-order stream that drains into the North Fork of the Nooksack River about 4 mi upstream of the confluence of the Middle and North Fork Nooksack Rivers. The main channel is about 7 mi long and runs westward from Slide Mountain at an elevation of about 4,000 ft to its confluence with the North Fork Nooksack River at an elevation of about 400 ft. The USGS streamflow-gaging station (12206900) is 0.7 mi upstream of the mouth of the creek and just downstream of a single-span bridge used for logging traffic. At flows less than about 20 ft3/s, the stage of the stream is controlled by a series of gravel/cobble bars, and at higher flows (greater than about 200 ft3/s), the stage is controlled by channel geometry and slope. The bankfull width of the channel (post-January 2009 flood) is about 75 ft in the reach just downstream of the gaging station and the top of bank elevations are about 6.0 ft above the gage datum (a reference datum for measuring river stage only). The reach is fairly uniform in channel shape but has been significantly altered by the January 2009 flood event, which both widened the channel and armored its banks with large woody debris (fig. 5).
The following references are cited:
Easterbrook, D.J., Kovanen, D.J., and Slaymaker, O., 2007, New developments in late Pleistocene and Holocene glaciations and volcanism in the Fraser Lowland and North Cascades, Washington, in Stelling P., and Tucker, D.S., eds., Floods, Faults and Fire: Geological Field Trips in Washington State and Southwest British Columbia: Geological Society of America Field Guide 9, p. 31-56.
Linneman, S., Pittman, P., and Vaugeois, L., 2007, Lively Landscapes: Major Holocene Geomorphic Events in the Nooksack –Sumas Valley, in Stelling P., and Tucker, D.S., eds., Floods, Faults and Fire: Geological Field Trips in Washington State and Southwest British Columbia: Geological Society of America Field Guide 9, p. 99-119.