Location Name: Mack Creek (Clearcut cross-section reach) - HJAMCC

Parent: Mack Creek - MACKCR

Landform:

The Mack Creek old-growth (MAC) and clearcut (MCC) sites are nearly adjacent, contrasting 320-m long reaches at the downstream end of the undisturbed portion of the Mack Creek watershed. The clearcut reach is somewhat less tightly constrained by the adjacent hillslopes than the old-growth reach. Low areas that appear to be abandoned channels choked with logging debris occur alternately on the right and left sides of the active channel, but the debris and dense vegetation typical of regrowth in clearcuts made detailed mapping of these features impractical. Other than some sand and some possibly rafted deposits of small organic debris, there was little evidence of much recent activity in these suspected former channels. The channel exhibits a bit of a tendency to bifurcate within this reach. Secondary channels active only during moderately high flows are present along the right channel margin in the vicinity of XS 106 to 108 and XS 110 to 112, separated from the main channel by a low surface vegetated with willow and alder. Farther downstream, two channels of nearly equal width (the left channel being somewhat higher and hence not active at very low flows) are present between XS 115 and 117; these channels are separated by a willow-covered bar with one or two mature alders at the downstream end.

Geology:

In contrast, the slopes adjacent to the channel at the MCC site were clearcut in 1964-65, and the reach contains very little woody debris and essentially no large logs. LWD was removed from the channel during the logging operation and by a major flood in December 1964, and regrowth on the streambanks and adjacent hillslopes is not yet capable of supplying much LWD to the channel. Inputs of LWD from the upstream reach (particularly large pieces) were effectively blocked by a culvert at the road crossing at the downstream end of the old-growth site prior to removal of the culvert and its replacement by a bridge in September 1994.

Vegetation:

The riparian zone within the clearcut reach contains abundant willow (Salix spp.) along the channel margins and on mid-channel bars, as well as some vine maple (Acer circinatum) and mature red alder (Alnus rubra). The MCC site, in contrast, may be more representative of many 3rd-order streams on public forest land today.