PIANC Working Group 236: Sustainable Management of the Navigability of Natural Rivers

The PIANC InCom/Envicom Working Group 236 was established in early 2021 to develop PIANC guidelines for improving navigability conditions on natural or quasi-natural rivers, while maintaining morphological processes, river form, and function. A natural river system exhibits two important characteristics – 1) unregulated hydrology and 2) unconstrained morphology. The key objectives of the WG236 – Sustainable Management of the Navigability of Natural Rivers – include: 1) development of guidelines to improve and maintain the navigability in natural rivers; 2) assess the sustainability of river training works designed to improve the navigability; 3) assess the sustainability of dynamic river management (monitoring and shifting of navigation aids to adapt the navigation channel to the river dynamics); 4) highlight the technical, operational, economic and environmental considerations for navigation in free-flowing rivers compared to that in regulated rivers and canals; and 5) improve the understanding of the physical processes in natural rivers, developed with or without river training works. The developed guidance includes a planning framework for developing a navigability improvement masterplan for a natural river system, and the integrated and adaptive management strategies that can be applied at a system scale. Specific interventions and measures have been identified that are analysed to meet the dual goals of maintaining morphological river function and improving navigability conditions. These measures include dynamic charting; morphological dredging and disposal management; Temporary, Adaptable, and Flexible Training Structures (TAFTS); riverbed armouring and sediment nourishment; rock excavation; meander cutoffs and oxbow development; localized traditional river training structures; and channel closure structures. The impacts and strategies for mitigating impacts associated with some of the measures are analysed and discussed. Finally, the continual monitoring, management, and operational tools available for improving navigability in a morphologically active river system are presented.