Two competing flood control and drainage management (FCDM) systems, namely, the ‘silt-dredging and regulative-drainage management (SRM)’ and the ‘tidal river-basin management (TRM)’ systems were implemented in the Southwest coastal zone of Bangladesh as a safeguard for agricultural production. The fundamental difference between these two FCDM systems is that the SRM is a conventional system based on hard engineering structure and heavily dependent on routine dredging; in contrast, the TRM is a natural system. This paper primarily evaluates these two contrasting and competing FCDM systems from the perspectives of productive efficiency, going beyond the traditional approach which often takes an engineering perspective. Evaluation of these two FCDM systems has been made on three distinctive measurements including ‘technical efficiency’, ‘yield-gap’ and ‘potential yield increment’. The results reveal that the conventional flood defence system (SRM) marginally outperforms the natural system (TRM) in terms of productivity with paddy. This is despite SRM being more expensive to deliver, as well as the fact that, due to a relative sea-level rise with the SRM system, it is likely to become increasingly expensive in the future. In contrast, TRM benefits from counteracting a relative sea-level rise in an environmentally friendly way, keeping maintenance costs low.