TAKING ECOLOGICAL ADVANTAGE OF HEADWATER DYNAMICS

Geomorphic processes in headwater environments are controlled by four key components; the eco-geomorphic landscape, the dominant physical processes prone to act in that landscape, the energy distribution imparted by these processes, and the distribution of materials affected by this energy. Between each of these ‘nodes’ of activity lie many variables that are directly and indirectly affected by dynamic responses. Predictive models may be invaluable tools for decision support at the site scale (where constraints may be minimized). Yet, the reductionist approaches needed to accurately model these relationships at the watershed scale requires an intractable array of isolated variables, a condition which is highly unlikely to occur in nature, and logistically difficult to achieve in a laboratory setting. However, many watershed-scale trends can be observed as patterns between discrete process regimes in headwater channels (e.g. perennial flow, mass wasting, etc.) and their ecological significance.

Diversity and variability inevitably result in uncertainty, which confounds development of accurate predictive tools. However, we can learn much from approaches taken within the context of ecology, where variability is treasured. Ecosystems are most robust when a full component of diverse conditions exist. Land-use management of any type will inevitably diminish the range of naturally occurring processes, add new processes, or alter the rates & magnitudes of important processes. Simplistic protection strategies favored by many regulatory systems exacerbate ecosystem sustainability by minimizing variability & diversity. Ecosystem-based approaches that focus on managing process regimes may offer an attractive alternative to simplistic prescription-based regulatory systems. Such systems should include strategies for manipulating disturbance zones, maintenance zones and refuge zones in a mosaic of landscape patterns that may shift over time in response to overall ecosystem sensitivity and/or stability.