Trees also fall, where the number of tree falls at a node is exponentially distributed and depends on the ratio of storm intensity to root strength. Tree fall re-distributes wood among neighboring nodes, e.g., to channel nodes from valley nodes. Line color represents deposit composition, and line thickness represents deposit thickness. Each line is associated with the node at its upstream end and connects that node to its downstream neighbor. For youngest stand, thickest deposits are near the outlet.
Older stands result in thicker, woodier deposits further upstream along the channel network.
Outputs with the 200 yr.-old stand are lowest of all. The sensitivity of the failure threshold to root strength is a large part of that coupling, but the effect of the forest on debris flow runout is also important. Forest age affects the landslide frequency and, thus, the volume of debris entering the channel network through greater root strength with age. Forest age also affects debris flow runout length and composition. More wood in the system leads to shorter runout lengths and, thus, greater storage and woodier composition of deposits higher up in the network.