Wandering wetlands: spatial patterns of historical channel and floodplain change in the Ramsar-listed Macquarie Marshes, Australia

Abstract

In the context of static conservation reserves, dynamic fluvial processes and patterns of river channel and floodplain change are problematic for environmental management. Floodplain wetlands that evolve by erosion and sedimentation experience changes in the location and extent of channels and wetlands regardless of conservation reserve boundaries. We describe historical channel and floodplain change in an Australian wetland of international ecological significance, the southern Macquarie Marshes, and synthesise the role of avulsion in wetlands that move laterally on the broader floodplain. Avulsion has shifted the foci of flooding and areas of aquatic habitat in the system over the last century. By ~1925, active wetlands surrounding the Old Macquarie River and the original conservation area contracted around Monkeygar Creek within the present nature reserve, and the boundary of this reserve has changed little since the 1940s. Ecological changes associated with continued wetland desiccation in the reserve triggered a recent Ramsar Article 3.2 notification for the Macquarie Marshes, prompting management responses from government agencies. Fluvial morphodynamics and their impacts on wetland ecology should be specifically recognised and integrated with adaptive management plans to combine new findings with lessons learned from previous intervention strategies for the long-term ecological sustainability of floodplain wetlands.