Riparian reserve zones in British Columbia have fixed widths, beyond which timber harvesting can take place in a management zone. Buffer width is partly based on the maximum distance from the stream bank that most riparian trees will recruit to the stream channel (Murphy and Koski 1989). It is assumed that buffers of this width will, over the long term, contribute natural levels of Large Woody Debris inputs that maintain channel structure and fish habitat, similar to intact riparian forest. However, this does not take into account the fact that stream channels are active and stream banks naturally migrate through erosion. Over time bank erosion can lead to a significant narrowing of the portion of the buffer with intact forest available to deliver LWD to the stream channel, and therefore cause a significant reduction in future LWD input from the fixed buffer zone adjacent to the stream. This project will model the effects of migration rate of stream channels in different geomorphic contexts on the long-term adequacy of present fixed-width buffers to maintaining natural LWD loadings to streams. Management implications are that present fixed width buffers may not ensure natural/adequate levels of LWD recruitment from riparian zones when erosion rates are high. This model will provide a tool for evaluating the geomorphic contexts (stream size, gradient, and erosion rate) and appropriate buffer widths where this scenario is likely to occur. This will be of significant value to regulators tasked with evaluating the effectiveness of present riparian regulations, and managers evaluating the effectiveness of particular riparian scenarios in the field.
Jordan Rosenfeld, Sandra Nicol.
Martin, Violeta, Trubilowicz, Joel; Carr, David; Rosenfeld, Jordan S.. 2006. Implications of static riparian reserve zones for long-term function of naturally migrating river channels: executive summary/interim annual report. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report