Set on the northeastern side of Mount St. Helens, just north of Johnston Ridge, Coldwater Lake was formed as a byproduct of the May 18th, 1980 eruption of Mount St. Helens. The bulk of the mud and ash from the explosion instantly flowed down the drainage basin of the North Fork Toutle River and created a natural dam at Coldwater Creek. As the once-glaciated valley began to fill from snow melt and rain, concerns arose regarding the strength of the new silty dam. Geologists predicted that the lake would be full by November of 1980 (at a depth of 200 feet), and if the dam were to break, communities downriver would suffer a second catastrophic flood. Officials quickly decided to create a semi-natural outlet for the lake using bulldozers and explosives. At first the lake was a muddy, brown pool full of sediment, ash and debris, but after three years of bacteria and microorganisms naturally inhabiting the site and feeding on the organic matter, the lake/natural reservoir was as clear as it is now.
Evidence of the 1980 eruption can still be witnessed today, with broken trees standing like tooth picks on the ridges that flank both sides of the lake, and these remnants aren't the only mark of the area's unique history. Washed out stumps of giant western red cedars dot the lake's shore and bottom, acting as reminders of the valley's logging past before the notorious explosion.
For the paddlers who bring their fly rods, there is a one fish, 16" minimum limit per person in order to maintain the lake's now healthy population of cutthroat and rainbow trout.
Note: Internal-combustion motors are not permitted.