Exploring the limits and gaps of flood adaptation

Abstract

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’. Here we present a risk-based framework to systematically examine the technical, social and behavioural constraints that contribute to adaptation gaps. We argue that, without overcoming these constraints, adaptation gaps will widen under climate change, exposing increasing populations to heightened flood risk. This may then require more radical actions including relocation, as risks become intolerable. 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. This study addresses the limitations and constraints of flood adaptation. These limits could result in a growing ‘adaptation gap’ (the difference between actual and desirable flood risk), leading to unbearable risks and pushing communities in flood zones into retreat.