FLOOD POTENTIAL IN THE EASTERN GREAT BASIN

The following are generalized discussions of the flood potential due to snowmelt in the Eastern Great Basin drainage as of April 1, 1998. Discussions are segregated by state. It is important to understand that the potential for flooding may increase dramatically if snowmelt accelerates rapidly due to above normal temperatures or if significant rain events occur.

UTAH: The potential for flooding due to snowmelt runoff is higher than usual for this time of year along the western slopes of the Wasatch Mountains from Bountiful north to Ben Lomond Peak and for streams that drain the western slopes of the Oquirrh Mountains above the Tooele Valley. Snowpack conditions in these areas as of early April ranged from 140 to 180 percent of average. High flows are likely and bankfull conditions possible with the onset of the spring snowmelt.

Elsewhere in the Great Basin of Utah the flood potential is not high at this time. Early April snowpack values generally ranged from 80 to 120 percent of average. Above average peaks are expected in some locations, namely City Creek near Salt Lake, the Logan River, Blacksmiths Fork River, Chalk Creek, and Sevier River near Hatch. However, these streams are all expected to remain below the flood levels and well below the peaks of spring 1997. All remaining streams are expected to peak near or below average at this time.

The flood threat can change dramatically over the next few weeks, vanishing altogether or increasing significantly. The biggest threat would be a delay in the snowmelt until late May and an increase in the snowpack. This scenario would leave a large snowpack that would be susceptible to very warm seasonable temperatures.

 

IDAHO:. The potential for snowmelt flooding in the Great Basin of Idaho is lower than usual for this time of year. Currently the snowpack is near to much below average for much of the Bear River Basin of southeast Idaho. Early April values ranged from 75 to near 100 percent of average. Flood problems due solely to snowmelt runoff are not anticipated at this time.