A critical review of Natural Flood Management application and spatial prioritisation approaches in tropical island catchments.

Tropical island communities face substantial hydrometrological threats, including flood inundation. Flood risk is increasing, driven by climate change but also other factors including urbanisation, land-cover and land-use (LCLU) change, making flood management challenging to address in practice. Protecting, restoring, and emulating the natural functions of catchments to reduce flood risk, also known as Natural Flood Management (NFM), is a promising method for improving flood management. Global NFM research is in its infancy and NFM research in tropical island states has tended to focus on individual catchment projects. Therefore, overall trends, challenges, and opportunities for NFM in tropical island catchments are poorly understood and, until now, have not been reviewed across these geographies. A particular gap in NFM understanding in tropical island catchments is how NFM options can be best implemented within any particular catchment - specifically where NFM should be located, how modelling can support these decisions and the influence of different catchment characteristics on these decisions. This literature review aims to explore what, where and how NFM has been used in catchments in tropical island states, with a specific focus on catchment characteristics and spatial modelling. This paper draws on research and interconnections between multiple environmental science spheres, by reviewing both academic and grey literature to better understand how NFM has been applied in tropical island states, with a primary focus on Pacific Island Countries and Territories (PICTs). The research highlights that some islands have greater potential for exploiting NFM due to their physical catchment characteristics and data availability. NFM spatial modelling approaches need to be further developed and adapted to specific tropical island community requirements to improve inland flood resilience at the pace needed and to ensure resources are directed optimally.