Leaky barriers are a widespread natural flood management measure in the United Kingdom. However, there is a lack of agreement in the representation of leaky barriers within hydrodynamic models. This study addresses this research gap. Firstly, a reach scale 1-dimensional model was developed utilising two approaches: (i) a roughness adjustment, ii) a hydraulic structure. Both modelling techniques were calibrated and validated individually using extensive on-site records over three years, and then their simulation performance was compared. At the local scale, the hydraulic structure method was substantially more accurate and realistic, and thus it was accepted as a robust modelling technique. Alongside this method, a recommended range of discharge coefficient values was developed. A 1-dimensional model of the upper Pipp Brook catchment was then created, comprising installed LBs with evidence of impoundment, and modelled for a range of return periods. A high level of blockage to the baseflow gap of the LB was required for a realistic simulation. This was supported by extensive hydrometric and photographic monitoring. The effectiveness of ten installed LBs was compared to the pre-NFM case, revealing significant flood risk benefits for more frequent flood events. Finally, a GIS method was implemented to determine the optimal locations of LBs based on their storage maximisation. The modelled optimised LB configuration initially led to flood risk benefits, but these were reduced when a realistic level of blockage was applied. This research has provided a robust modelling framework, including a range of suitable parameters for modelling LBs, supported by extensive hydrometric monitoring, which has been limited in this field to date. This has given confidence in assessing the effectiveness of a network of LBs and in implementing tools to optimise their performance. The scientific rigour provided by the extensive hydrometric monitoring data has enhanced the reliability of the resulting findings.