To the Editor —

The study by Auerbach et al.1 advances understanding of the drivers of flood risk in natural and embanked regions of the coastal and tidal regions of Bangladesh. The quantification of sedimentation rates and how effectively periodic opening and closing of polders may result in elevation recovery is valuable in the context of reducing the vulnerability of coastal Bangladesh to flooding in the twenty-first century.

However, we are surprised at the authors' apparent lack of awareness of the long-practiced protocol called tidal river management (TRM) and its successful implementation for over a decade in coastal Bangladesh2,3. TRM involves the periodic cutting and closing of polders to accelerate land accretion (or reclamation). TRM as a concept has been around since the 1990s and has been practised or analysed by many local stakeholder entities such as the Institute of Water Modelling of Bangladesh for elevation recovery in several (embanked) regions in coastal Bangladesh. Thus, the management strategy advocated by Auerbach et al.1 is not so innovative.

In summary, we commend the authors' quantitative work on understanding flood risk on embanked polder regions. However, the Letter could be more cognizant of previous studies and could have benefited by learning from local wisdom to potentially make their research more useful to the local stakeholders4.