A Systematic Review of Monitoring Approaches to Assess Hydrological Conditions in Small Catchments With Natural Flood Management

ABSTRACT Natural Flood Management (NFM) has gained prominence as a sustainable approach to flood risk reduction, particularly in small catchments where traditional grey infrastructure is less viable. However, understanding the effectiveness of NFM is closely tied to the quantity and quality of hydrological monitoring. In small catchments, this monitoring remains inconsistent, whereas high‐quality, high‐frequency networks maximise the likelihood of detecting NFM effects. This is the first systematic review to analyse current approaches to streamflow and rainfall monitoring used to assess NFM performance in small catchments (defined as < 25 km2), consolidating data from 33 studies (65 catchments) into a practitioner‐oriented decision matrix that links site conditions, cost and certainty to method selection. The reviewed dataset consolidates example NFM interventions and associated monitoring approaches, highlighting the benefits and limitations of each method in a single, accessible resource. The review also highlights gaps, including limited baseline data, short monitoring durations, and infrequent reporting of costs and methods. A decision matrix is presented to support practitioners in selecting streamflow monitoring methods based on site conditions and resources for small catchments. Recommendations to improve standardisation, reporting, and the adoption of low‐cost, scalable techniques, including community‐led and non‐contact approaches (remote sensing and drone imagery) are also given.