Hydrological and planting design of an experimental raingarden at the Royal Botanic Garden Edinburgh

A new experimental raingarden has been created at the Royal Botanic Garden Edinburgh (RBGE) to help cope with the impacts of more frequent and intense rainfall events. Raingardens offer a sustainable, nature-based solution to flood mitigation by mimicking natural rainwater retention and infiltration characteristics within a constructed bioretention system. By incorporating specially selected plants that can withstand both very wet and very dry conditions, raingardens also provide enhanced biodiversity capacity. This paper reports on the hydrological design of the raingarden, which is aimed at reducing the occurrence of waterlogging and localised flooding within RBGE, before discussing the selection and cultivation of the planting. It is hoped that the mix of plants chosen will encourage a great diversity of wildlife, providing nectar sources for insects and bees in summer, and homes for invertebrates and food for seed-eating birds in winter. With the raingarden having been in place for over a year at the time of writing, reflections on its maintenance and upkeep during that time and performance assessment for significant storm events will also be discussed.