The water's up
When I lived in Clark Fork I always found pleasure in driving home over the Lightning Creek bridge and proclaiming to my girlfriend, now my wife, “Lightning Creek’s up.” Sometimes it would be and sometimes not. Mel didn’t know, nor probably did she care, but I took pride in the fact that I could tell. At least, I thought I could.
This past summer it didn’t take a scientist to tell you that Lightning Creek was not up. In fact it was very low, the lowest I have seen it in my nine years of living here. For the first time I noticed that the stream dried up below the bridge into Clark Fork.
Bob Hays, owner of Hays Chevron, says he recalls that maybe sometime in the early seventies the creek dried up below the bridge. Bob is not certain it went totally dry but, “It was dry enough that the fish were using the footpath through town,” he laughed.
Joe Brashear, a Clark Fork native of 84 years, says that he has never seen Lightning Creek go dry beneath the bridge. “In the driest months Lightning Creek usually goes dry for about a mile just upstream of the confluence with Spring Creek.” Joe also remembered in the 20s when the railroad bridge jammed up with logs and the creek flooded the lower portion of town. Pretty drastic extremes.
The latter events are probably what led to Lightning Creek’s name. I remember December of 1996 when the water was so high that it looked like the bridge might be wiped out.
Flashy is one word used to describe the type of flow variability that Lightning Creek experiences. This is due to several factors. To begin with, the terrain in the drainage is very steep and high in elevation. Secondly, the Lightning Creek drainage receives some of the highest precipitation in Idaho and Montana. And finally, much of the drainage is susceptible to rain-on-snow events. This phenomenon occurs most frequently at elevations between 3,000 and 4,000 feet, where snow accumulates but the elevation is low enough that rain is common during the winter. This produces a tremendous amount of runoff in a short period of time, very fast, maybe even like lightning.
Floods of this nature move a lot of material and those that live near the streambank will attest to this. This material, over time, moves from the upper parts of the creek, i.e., Rattle and Moose Creeks, to the lower parts, down near the town of Clark Fork. Over thousands of years a lot of material has accumulated in the lower portions of the drainage not only from the activity of Lightning Creek but from the Clark Fork River as well.
The reason that Lightning Creek goes dry in the lower sections is that the material is very deep, loose and unconsolidated from being constantly shifted around. During the dry summer months there is not enough water coming out of the drainage to keep the stream flowing above ground because it also flows through the spaces between the coarse rock.
A massive drought has made major impacts on our landscape this summer, as Lightning Creek so eloquently attested to. But autumn rains, almost record-setting in October, have had an impact, especially on one of the flashiest bodies of water in the area. So next time you come across the Lightning Creek bridge into Clark Fork look out the window, give an assuring nod, then lean toward your spouse and say, “Lightning Creeks up.” They’ll be impressed.
Kevin Davis is a hydrologist for the Forest Service, and a long-time fan of the Clark Fork area.