Potential hazards from floodflows in Grapevine Canyon, Death Valley National Monument, California and Nevada

Delineation of flood-inundation areas in Grapevine Canyon near Scotty’s Castle, Death Valley National Park, California

“…At Scotty's Castle, flood waters from the October 18 flood rose to the 1-percent annual exceedance probability (AEP) flood water level delineated from a flood-inundation map for the area (Bowers, 1989), with an estimated streamflow of 12,000 cubic feet per second (cfs). However, a post-flood streamflow measurement using surveyed high-water marks, cross sections, roughness, and other channel characteristics (hereafter referred to as an indirect measurement) made approximately 2,000 ft upstream of Scotty's Castle computed a streamflow of only 3,200 cfs.…”

“…The difference in streamflow between the indirect measurement and the estimated streamflow from Bowers (1989) suggests that the previous flood-inundation mapping is no longer applicable, and a new analysis, based on current (2016) conditions, is needed to document current channel conditions.…”

“…Several USGS studies have examined and mapped flood-inundation areas at Furnace Creek (Crippen, 1979), Wildrose Canyon (Crippen, 1981), and Grapevine Canyon (Bowers, 1989) in Death Valley National Park. In 1983, the National Park Service (NPS) completed a more geographically diverse analysis of flooding using single channel cross-sections near major infrastructure (Overzet and others, 1983).…”

“…Flood-inundation areas in Grapevine and Tie Canyons (including Scotty's Castle) were mapped after the July 1976 flood by Bowers (1989). Eighteen cross sections were surveyed along the entire length of Grapevine Canyon and the downstream end of Tie Canyon.…”

“…However, the area delineated for the 4-percent AEP flood (3,500 cfs) was generally verified by an estimated streamflow of 2,900 cfs from the July 1976 flood, which was calculated based on depth and width observations made by the NPS. The July 1976 flood reportedly incised a channel into the parking lot (Bowers, 1989).…”