ABSTRACT
River channel management operations frequently respond to a channel-related hazard such as bank erosion, which is often depicted as ‘instability’, although such instability also produces environmentally valuable river assets. Specific risks can be estimated from knowing where, when, how long-lived and how much adjustment will occur, all influencing the robustness and resilience of the habitats dependent on the channel environment (5.1). Approaches for determining the risk of hazard occurrence have the goal of understanding river channel sensitivity to change so that management can respond appropriately to the type of hazard and the risk of its occurrence (5.2). Sensitivity to change in drainage basins undisturbed by human activity is a response to drainage basin characteristics that provide both extrinsic and intrinsic controls on river channel processes that are variable in time and space (5.3). However, river channel sensitivity to change is also conditioned by the impact of human activities on runoff, sediment production and calibre, flow magnitude, duration and timing, flow hydraulics and sediment transport processes (5.4). Consequently, river channels are complex, sensitive phenomena where the risk of hazards and the risk to assets prompt six fundamental implications for river channel management (5.5).
