Lessons learnt from adaptation planning in four deltas and coastal cities

Abstract

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.

Generic adaptation pathways for coastal archetypes under uncertain sea-level rise

“…Continuing on the pathway of protection through dikes in combination with drainage and pumping is a common pathway in urbanized deltas (e.g., deltaic part of the Netherlands [14]; Jakarta, Indonesia [40]). Nevertheless, nature-based defences to reduce waves are increasingly considered [41] to reduce flood risk, and could thus shift the pathway.…”

Developing signals to trigger adaptation to sea-level rise

“…Methods for planning under conditions of uncertainty are being used increasingly, separately or together, for problems like SLR [13]. Adaptation pathways planning has emerged as a way to frame future adaptation decisions [14][15][16][17][18][19][20][21]. It is based on the principle that adaptation cannot be undertaken through a single action in the context of deep uncertainty, but is rather a process to be managed over time as conditions change [14].…”

“…Comparing observed events (like storm-tide frequency) with their pre-specified trigger-values, enables decisions to be made on whether adaptation actions need to be taken; monitoring for signals and triggers enables timely adaptive actions to be taken [18]. Identifying, evaluating and using indicators to develop adaptationthresholds, signals and triggers for climate adaptation has received little attention in the literature so far [18,21]. Signals function as 'early warning' that [33] showing median projection (line) and 95% confidence intervals (shaded), along with a schematic illustrating adaptation-threshold, trigger (decision-point) and early signal in relation to SLR and pathway performance.…”

Collaborative Modelling for Informed Decision Making and Inclusive Water Development

“…An adaptive planning approach was followed during modelling analyses to achieve flexibility in the allocation of water over time (Jeuken et al 2015;Speed et al 2013). Four scenario conditions (all in relation to spatial planning) were considered to analyse future system performance: population growth, economic development, climate change and institutional setting.…”