Safe development paradox: evidence and methodological insights from a systematic review

Hydrological hazards pose significant threats worldwide, resulting in extensive societal and environmental impacts. To mitigate these impacts, structural protection measures like levees are commonly implemented. However, these measures can overlook complex human-water interactions and cause unintended consequences, such as the safe development paradox (SDP) and its sub-phenomena, the levee effect (LE), where risk reduction efforts paradoxically increase risk in the long run due to a false sense of safety. Despite the growing body of research on the SDP and LE, existing evidence remains fragmented due to the diverse methodologies and variables considered. To address this gap, we systematically reviewed 94 studies spanning 2001–2023 to synthesize the methodological approaches, variables, and evidence in this field. Most of the reviewed studies (75%) provided conclusive evidence to support the occurrence of the SDP and LE via three key mechanisms: (a) increased development in protected areas, (b) reduced preparedness and false sense of safety, and (c) increased damage from rare disaster events. About 40% of the reviewed case studies focused solely on exposure, overlooking other critical dimensions of the SDP and LE, such as vulnerability and behavioral aspects linked to a false sense of safety. Furthermore, the effect of non-structural and individual adaptation measures on the SDP and LE remains underinvestigated. A more holistic assessment of these socio-hydrological phenomena should thus include aspects such as preparedness, vulnerability, and risk perception. This holistic approach would enable a better understanding of the diversity of scenarios where the SDP and LE can manifest, providing policymakers with essential information to prevent unintended consequences of adaptation.