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ABSTRACT Despite increased understanding and adoption of nature‐based solutions (NBSs) within urban and coastal areas, large‐scale NBS for fluvial flood mitigation remain challenging to study and implement. A stronger evidence base is needed to identify critical research gaps and to best inform the design and deployment of NBS on the watershed scale. We synthesize evidence of the performance and co‐benefits of NBS for fluvial flood mitigation based on a systematic review of 131 peer‐reviewed papers worldwide, developing an Ecosystem Focus Type (EFT) to compare flood mitigation across large‐scale NBS. While we find that NBS can mitigate fluvial floods across all EFTs, our study also highlights that inconsistencies in measurement methods, a dearth of empirical case studies, and large variability in reported values limit generalization and comparison across NBS. Co‐benefits for fluvial flood NBS are numerous, but few are quantified, and study methods vary with regard to specific NBS. Social benefits of NBS, including benefits to communities most in need of support, are infrequently part of these studies. There is a clear need to develop common design and performance standards for large‐scale NBS and for guidance on which measures are key to consider and monitor for flood mitigation and co‐benefits. The success of large‐scale NBS for fluvial flood mitigation will depend on research and practice guided by transdisciplinary systems thinking approaches that can deliver evidence‐based, community‐driven outcomes. 

Abstract Understanding local patterns of rainfall variability is of great concern in East Africa, where agricultural productivity is dominantly rainfall dependent. However, East African rainfall climatology is influenced by numerous drivers operating at multiple scales, and local patterns of variability are not adequately understood. Here, we show evidence of substantial variability of local rainfall patterns between 1981 and 2021 at the national and county level in Kenya, East Africa. Results show anomalous patterns of both wetting and drying in both the long and short rainy seasons, with evidence of increased frequency of extreme wet and dry events through time. Observations also indicate that seasonal and intraseasonal variability increased significantly after 2013, coincident with diminished coherence between ENSO (El Nino Southern Oscillation) and rainfall. Increasing frequency and magnitude of rainfall variability suggests increasing need for local-level climate change adaptation strategies.