The online-first version of an article I co-authored with Chris Van Dyke is now available from Earth Surface Processes and Landforms: “Principles of geomorphic disturbance and recovery in response to storms.”
The most important geomorphic responses to storms are qualitative changes in system state. Minor storms produce no state change or very rapid recovery to pre-storm state, and extinction events wipe out the system. In other cases disturbance results in a state change, which may be transitional (change to a previously existing state), state space expansion (change to a new state), and clock-resetting events that return the system to its initial state. Recovery pathways are much more varied than the monotonic progressions represented in classic vegetation succession and linear channel evolution models. Those linear sequential pathways are only one of several archetypal recovery pathways, which also include binary, convergent, divergent, and more complex networks. Filter dominated systems are more likely to follow linear sequential or convergent patterns, whereas amplifier-dominance is characteristic of divergent and more complex mesh or fully-connected patterns. Amplifier domination is also more likely to lead to evolutionary or state space expansion responses. Amplification and filtering in geomorphic response and recovery can be assessed using the ’Four R’s’ framework of response, resistance, relaxation, and recursion. High resistance and resilience, rapid relaxation times, and stable recursive feedback networks reduce or offset effects of disturbances, thus filtering their impacts. Conversely, low resistance and resilience, slow relaxation, and dynamically unstable feedbacks can exaggerate disturbances, creating disproportionately large and long-lived impacts, thereby amplifying disturbances. Unless new filter mechanisms evolve (either autogenically or anthropically), or the number of extinction or clock-resetting events increases, intensified storminess will result in more geomorphic variability. These ideas are applied to a case study of a flood on the Clark Fork River, Montana, USA.
KEYWORDS: storms; disturbance; recovery; resilience; amplifiers; filters