Maximising runoff retention by vegetated landscape elements positioned through spatial optimisation

Abstract

Ecosystem services provided by vegetated landscape elements (vLEs) are increasingly recognised. One of the services provided is the mitigation of downstream flood risk. Obviously, the type and spatial configuration of vLEs impact the magnitude and timing of the runoff retention. Hence policy programs focused on the conservation and restoration of vLEs would benefit from a capability to determine the optimal spatial configuration of vLEs leading to maximum impact for minimal cost.We integrated the Landlab rainfall-runoff model in an iterative spatial optimisation framework to deal with rasterised linear parcel boundaries whereby the cumulative capability to reduce discharge through the installation of vLEs is the ranking criterion. We applied the procedure to a 191 ha agricultural watershed situated in the Belgian Loess belt encompassing 34 km parcel boundaries.Our results demonstrated that discharge volume can be more effectively reduced when vLEs are implemented based on the priority ranking obtained through our approach compared to both a random positioning of vLEs of the same length and type and the existing vLE configuration. The priority parcel boundaries are mainly located along preferential flow paths, highlighting the importance of the upslope area associated with vLEs and the infiltration enhancement they provoke. The application potential of the optimisation approach is not limited to the topic of finding priority locations for vLEs to reduce discharge but can be applied in a variety of disciplines that require answering questions about the optimal spatial configuration of interventions.