Tree-ring records of variation in flow and channel geometry

We review the use of tree rings to date flood disturbance, channel change, and sediment deposition, with an emphasis on rivers in semi-arid landscapes in the western United States. As watershed area decreases and aridity increases, large floods have a more pronounced and sustained effect on channel width and location, resulting in forest area-age distributions that are farther from a steady-state exponential relation. Furthermore, forests along three major snowmelt rivers in the northern Rocky Mountains, USA, have smaller than expected areas of young trees, suggesting that high flows and channel migration have decreased since the late 1800s.