Recharge

10.863 kilometers off the highway, good gravel all the way - over the bridge then creep along to spot the stream where it crosses the road.  According to the map I was going to see an unharvested alluvial fan channel (colluvial really - some note), but the stream at this location was tiny - barely a half-meter wide flowing through thick forest at the road edge.  I followed it up.

After a few minutes the young forest gave way to open old-growth, a sloping forested wetland.  The channel meandered up, sometimes disappearing briefly under tree roots but always emerging to twist a and babble a bit more.  Eventually I ended up in a bog - the stream split to drain a few ponds.  Disappointing.  I walked out into the clearing and listened.  To my right I heard the sound of water - more water than I'd left and I understood, the channel was there - close by but not quite mapped correctly.

As I stepped into it I knew I was in the right place - 4 meters or more wide, large cobbles and vertical eroding banks - I turned upstream and followed it - sometimes in the stream sometimes on the bank looking at the deposition and the age of the trees.  I walked it for a half hour or so until it went vertical - a waterfall - then up and around it as well to see another set of jagged falls and steep valley walls containing the channel.  Back down below the first falls I rested, filled my water bottle and reveled in the location.  It felt good to be there - working - mapping - being there - not thinking about anything else but the creek, how it looked, how it developed, how it behaved.  Beautiful.

An alluvial fan channel as narrowly defined here in southeast alaska encompasses a fair range of behavior with several points in common.  At some point in its history - perhaps recently after the glaciers relinquished their grip on the valley - rocks high up on the steep erodible hillslope began to be funneled down the mountain to rest at the toe of the slope.  The incised upper high-gradient portion of the channel acts as a sediment pump - pushing pulses of stone down until the gradient breaks and they come to rest.  Large cobbles bound in a matrix of gravel and sand pile up as lobes forcing the stream this way and that - around and down.  Over time the forest takes hold on these deposits - big spruce, devils club.  On large systems the telltale triangle of giant spruce is a dead giveaway and always attractive to loggers.  Sometimes if the pump stops - either when the substrate is held up by dams of wood high up in the notch or perhaps when the slopes reach some sort of equilibrium state - and the stream begins to downcut through its own deposit.  That was the case here - As I moved downstream I looked at the downcutting - a meter or more - and wondered.  If it's not here then where - I kept on going.

Near the toe slope I found the active portion of the fan.   A split channel, gravel all over the place in all directions, live trees dying as they stood buried centimeters deep in gravel.  I followed the lefthand channel at the major breaks - the newer channel and wound down and down until it dumped me out on the side of the main channel, a beautiful low gradient salmon stream.  Then I went back up and followed out the other channel - the original one down to where it intersected as well.

I'll fix the mapping of it - and maybe I'll come back and make some measurements - but not today.  I'm headed home - happier - recharged.