Lessons learnt from adaptation planning in four deltas and coastal cities

Deltas and coastal cities around the world face the need to adapt to uncertain future changes. We compared adaptation planning on flood risk management in four cases based on three main elements of adaptive planning: to prepare for a wide range of plausible future scenarios; to respond to change with robust and flexible actions; and to monitor critical changes to be able to reassess the plan accordingly. Differences can be observed in the implementation of these elements. Good practices could be distinguished: cases consider a wide range of future scenarios; short-term decisions are coupled with long-term options while envisioning these options and possibilities for switching between them through adaptation pathways; opportunities originating from other agendas to achieve multiple objective investments are seized; and the system's resilience is improved by a wide variety of measures. At the same time some barriers for using adaptive planning approaches were identified: the use of a wide range of scenarios is only accepted in an exploratory phase of planning. Structural flood protection measures taken in the past do constrain future choices. The potential for monitoring and reassessment of options is hampered by the fact that trends in some variables cannot be detected.