Flood adaptation measures such as levees, flood-proofing structures, nature-based solutions and flood insurance are essential to cope with the growing flood risk caused by climate change and urban development into flood-prone areas.

However, many communities in flood zones are ill-protected because the implementation of adaptation measures is hindered by a variety of constraints to adaptation, including the cost, limitations on institutional capacity and societal inertia. When adaptation efforts fall short relative to a desired level due to a combination of constraints, it results in an “adaptation gap”.

In our paper, we present a risk-based framework to systematically examine the technical, social and behavioural constraints that contribute to adaptation gaps. We argue that quantitative flood risk assessments must consider constraints and adaptation gaps systematically, especially where they may lead to flood adaptation limits.

Without assessing these dynamic relationships, flood managers may overestimate the efficacy of flood adaptation measures and underestimate the unequal distribution of flood risks. (by Jeroen Aerts, Institute for Environmental Studies)