Implications of disclosure and non-disclosure of flood hazard maps – a synthesis for the Canadian context

Abstract

Flood is an increasingly costly and impactful hazard in Canada. Risk management approaches need to be applied to stem rising costs and impacts of floods. The foundational tool that supports many risk management strategies is the development of flood mapping products. In Canada, however, there is only a patchwork of flood mapping available, and there is further variability in the accessibility of this information to private and public sectors. This article draws on published studies to synthesize the potential benefits and disbenefits of making flood maps more available and accessible in the Canadian context, with a focus on real-estate transactions, but also with consideration of implications to land use planning, flood insurance uptake, and social equity impacts. The review highlights that accessibility and regulated disclosure of flood maps reduce property values marginally, but not to the full discount that should be applied if flood risks were fully accounted for or realized. There are also substantial benefits of making flood mapping products more accessible, including greater social equity, by removing the challenge of data asymmetry (where some buyers and sellers have better information than others), better emergency preparedness, and increased insurance uptake to manage residual risks.