Spatial Optimisation for River Restoration Planning in Nova Scotia, Canada

Abstract

River restoration is believed to have the greatest chance of success when action is considered in the broader context of the riverscape. However, methods are lacking to fully integrate systemic connectivity into decision-making. Optimisation, a method of prioritisation, is capable of accounting for longitudinal connectivity, spatial interdependence, and cumulative effects of anthropogenic barriers such as dams and culverts. In addition, optimisation can help ensure that limited restoration funds are efficiently allocated. Despite these advantages, it remains under-employed. I present optimisation models for maximising connectivity within a river network (i.e., undirected connectivity) and connectivity between the network and its outflow (i.e., directed connectivity) and demonstrate their application on three river networks in Nova Scotia, Canada. Non-additive cumulative effects of barriers and key budget thresholds that yielded better returns on investment were observed. The methods and models address current challenges in implementation of the optimisation approach to systematic river restoration planning.