Dynamic disturbance regime approach in river restoration: concept development and application

In recent years, numerous restoration measures have been initiated to ecologically and morphologically improve rivers based on self-dynamic development. A wealth of monitoring studies has been implemented to evaluate these restoration measures. Such restored river systems, however, must develop for years to decades to achieve a (dynamic) equilibrium, with an equally lengthy period before serious evaluation is possible. Thus, modelling approaches that accurately quantify the underlying processes and their manifold interactions are useful tools for river management. This paper presents a new conceptual approach for analyzing the interrelationship among plant succession, morphology, and hydrological impacts. Based on the dynamic disturbance regime approach, the model concept addresses interdisciplinary processes in river morphodynamics. The development of the concept is outlined, and the approach is applied considering three different process types: (1) metastable, (2) oscillation, and (3) acyclic. All three describe the relationship between vegetation succession/retrogression and the impact of disturbances. We show that addressing these three different process types helps the prediction of intermediate and long-term river system development by going beyond steady-state monitoring results to consider future dynamic developments. Moreover, classifying these process types and comparing them with reference (natural) conditions helps evaluation of the river system and subsequently definition of management strategies.