Principles of geomorphic disturbance and recovery in response to storms

Abstract

ABSTRACT: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. Filterdominated 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.

Linking geomorphic change due to floods to spatial hydraulic habitat dynamics

“…Although the short time period in other ecosystem types, which are often cited as creating or maintaining heterogeneity (Foster, Knight, & Franklin, 1998;Romme & Knight, 1982). In the case of Elbow River, the disturbance appears to be a clock-resetting event that returns the system to an initial state with complete geomorphic and habitat turnover (Phillips & Van Dyke, 2016). In the case of Elbow River, the disturbance appears to be a clock-resetting event that returns the system to an initial state with complete geomorphic and habitat turnover (Phillips & Van Dyke, 2016).…”

“…Due to their inherent rarity and unpredictability, the effects of large infrequent disturbances such as floods are difficult to study reliably and remain poorly understood (Church, 1980;Turner & Dale, 1998). In particular, information on geomorphic process rates and recovery trajectories is needed to inform flood risk management and maintain ecosystem services in an age of climate extremes (Gaston and Blackburn 1999;Naylor et al, 2017;Phillips & Van Dyke, 2016). In particular, information on geomorphic process rates and recovery trajectories is needed to inform flood risk management and maintain ecosystem services in an age of climate extremes (Gaston and Blackburn 1999;Naylor et al, 2017;Phillips & Van Dyke, 2016).…”

Geomorphic effectiveness: a linear concept in a non‐linear world

“…The nature and configuration of sensitivity and connectivity controls within a geomorphic system will determine the ability of that system to respond to the range of possible disturbance events (Figure ). The severity and distribution of geomorphic responses can reshape the ability for system response so that subsequent events impact the system at a different state, with a different ability to respond to, and recover from, disturbance events (Schumm, ; Downs and Gregory, ; Phillips and Van Dyke, ). Over time, the reactive relationship between geomorphic response and response ability creates a history or memory of antecedent conditions that influence the ability of a system to respond to any given event (Pickup and Rieger, ; Dollar, ; Brierley, ; Fryirs, ) (Figure ).…”

“…Costa, ; Gupta and Fox, ; Anderson and Calver, ; Wolman and Gerson, ; Sloan et al , ; Milan, ; cf. Phillips and Van Dyke, ).…”

“…Russell, ; Thorn, ; Renwick, ). Recent reviews of key geomorphological concepts such as ‘connectivity’ (Bracken et al , ; Fryirs, ; Bracken et al , ), ‘sensitivity’ (Fryirs, ), and ‘recovery’ (Phillips and Van Dyke, ) highlight that continuing use of these concepts without consistency in definition, terminology, and quantification will cause confusion and misinterpretation. The future of many of these concepts now lies in our ability to review and critically evaluate their contribution in an era of expanding technology and data resolution.…”