Table 6 Geomorphic principles that underpin interpretations of evolutionary trajectory to determine what is realistically achievable (Truth 4)

Catchment-specific drivers and controls upon forms and rates of river adjustment determine the evolutionary trajectory of a river. Such analyses relate river character and behaviour at the reach-scale to the pattern of river types and their (dis)connectivity relationships at the catchment scale

Some evolutionary adjustments are reversible (i.e., the reach operates within its range of variability). In other instances, irreversible change to a different type of river may occur

Reach scale sensitivity and (dis)connectivity relationships (the distribution of buffers, barriers, blankets and boosters) determine how legacies, path dependencies and lagged, off-site responses to disturbance events are conveyed through a catchment (the response gradient)

Changes to sediment sources and the flow/sediment regime impact upon the balance of impelling and resisting forces, the aggradational–degradational balance of the river, and associated trajectories and rates of river adjustment, in the past and future. Some reaches (types of river) are subject to progressive adjustment, others are characterised by threshold-induced change

Hotspots, threatening processes and reaches that are primed to change are important considerations in strategic approaches to proactive and precautionary planning

Legacy effects, the imprint of the past upon contemporary river character, behaviour and condition, vary markedly from system to system, now and into the future

Recovery takes different forms and works in different ways, shaped by different processes, for different types of river

The river recovery diagram provides a conceptual tool to appraise the condition of each reach today relative to the past, helping to assess how trajectories shape prospective futures

Recovery potential is shaped by system-specific pressures and limiting factors (e.g., reach sensitivity, legacy effects, changing (dis)connectivity relations, etc.), informing interpretations of whether flow/sediment budgets (and other considerations) will facilitate recovery and over what timeframe

Foresighting exercises scope prospective futures to derive a realistically achievable vision, using modelling exercises to predict the likelihood of differing scenarios