A geomorphic approach to the identification of river recovery potential

While many studies have documented pathways of river degradation, few studi es have assessed the character, capacity, and stages of river recovery. In this paper, a generic procedure to measure river recovery is developed and applied in Bega catchment, on the south coast of New South Wales (NSW), Aus tralia. The approach is based on analysis of geomorphic units and ergodic r easoning. Historical data and field analyses are used to identify stages of river evolution throughout Bega catchment. From this, stages of river cond ition and pathways of adjustment are assessed for three river styles at dif ferent positions within the catchment. Five categories of river condition a re identified. Intact reaches operate in a self-adjusting manner, whereby p rocesses maintain the pre-disturbance geomorphic character of the reach. Th e processes occurring in restoration reaches maintain and enhance the geomo rphic structure of the reach. These reaches are moderately resilient to cha nge. The river has experienced degradation, but has recovered to a conditio n approximating its pre-disturbance character and behavior. Degraded reache s are still adjusting to disturbance and the processes of recovery have not yet begun. The river is experiencing progressive deterioration away from t he structure and function of the predisturbance condition. Turning-point re aches are at the transitional stage where they can either recover or revert to a degraded state. Finally, a creation reach has a self-adjusting charac ter and behavior but operates under altered catchment boundary conditions. The character and behavior of the river do not equate to pre-disturbance co nditions; rather, the river is well adjusted to the prevailing catchment bo undary conditions of water and sediment transfer, and vegetation cover and composition (among many factors). Once these conditions have been identifie d for each river style, all reaches in a catchment are placed on pathways o f degradation and recovery, and predictions made about their direction of c hange. The three river styles analyzed in Bega catchment demonstrate differ ing recovery pathways. Some reaches are adjusting toward a restored conditi on, while others are adjusting toward a new (or creation) condition. The ge omorphic recovery potential of each reach is determined by assessing the co nnectivity of reaches throughout the catchment and interpreting limiting fa ctors to recovery (e.g., water and sediment transfer, vegetation and coarse woody debris [CWD] character and distribution).