Preparing for Sea-Level Rise through Adaptive Managed Retreat of a New Zealand Stormwater and Wastewater Network

Transience of Coastal Water Table Rise in Response to Sea-Level Rise

Coastal shallow groundwater is susceptible to adverse sea-level rise (SLR) impacts. Existing research primarily focuses on SLR-induced salinization of coastal aquifers. There is limited understanding of the magnitudes and rates of water table rise in response to SLR, which could lead to groundwater flooding and associated infrastructure challenges. This study used a variable-density groundwater flow model to quantify the transient movement of the water table in response to various SLR scenarios and rates, considering a range of aquifer parameters for both fixed-head and fixed-flux inland boundary conditions. The SLR scenario based on realistic and progressive SLR projections resulted in a smaller water table rise than the instantaneous or gradual SLR scenarios at 100 years, despite a final identical SLR. Rates of water table rise were always less than SLR, decreased with distance from the coastline, and were proportional to SLR. The magnitude and rate of water table rise in response to SLR were largest for fixed-flux conditions. It also took longer for the rate of water table rise to equilibrate after the commencement of SLR for fixed-flux conditions than for fixed-head conditions. As such, fixed-flux conditions represent a greater hazard for water table rise, and the maximum impact may not be experienced for decades. This delayed response poses challenges to planners and managers of coastal groundwater systems. Introducing a drain reduced water table rise more on the inland side of the drain than on the coastal side. Subsurface infrastructure may limit SLR impacts, but further effects need to be carefully considered.

Adaptive Planning Approaches for Coastal Climate Adaptation: Process and Key-elements

The paradigm of Adaptive Planning and Management provides several methodological approaches for designing robust adaptive plans to cope with uncertain future changes, namely the Adaptation Pathways' method (APs). These approaches, particularly those containing APs, have captured increasing interest in the field of coastal climate adaptation as useful for guiding its planning and management. While these approaches have been tested in several research cases, there are still few real cases of application into coastal spatial planning instruments. Furthermore, the lack of implementation of coastal adaptation actions in urbanized coasts worldwide, so-called adaptation gaps, points to the need of investigating to what extent these Adaptive Planning approaches containing APs are being applied in coastal plans. A deeper analysis of cases of application of these approaches in coastal plans is required to understand how adaptive plans are being crafted. This article focusses on the two major cases of application of APs-based Adaptive Planning and Management approaches into planning and management instruments - the Thames Estuary 2100 Plan and the Delta Programme - to identify what elements were essential to design an adaptive plan and operationalize an Adaptive Planning and Management approach, including ingredients that the plan had to meet to be robust and adaptive. Our results suggest that at least five elements are required to craft and deliver a robust adaptive plan and accomplish a real Adaptive Planning and Management.

Climate change impacts on wastewater infrastructure: A systematic review and typological adaptation strategy

Wastewater infrastructures play an indispensable role in society's functioning, human production activities, and sanitation safety. However, climate change has posed a serious threat to wastewater infrastructures. To date, a comprehensive summary with rigorous evidence evaluation for the impact of climate change on wastewater infrastructure is lacking. We conducted a systematic review for scientific literature, grey literature, and news. In total, 61,649 documents were retrieved, and 96 of them were deemed relevant and subjected to detailed analysis. We developed a typological adaptation strategy for city-level decision-making for cities in all-income contexts to cope with climate change for wastewater structures. 84% and 60% of present studies focused on the higher-income countries and sewer systems, respectively. Overflow, breakage, and corrosion were the primary challenge for sewer systems, while inundation and fluctuation of treatment performance were the major issues for wastewater treatment plants. In order to adapt to the climate change impact, typological adaptation strategy was developed to provide a simple guideline to rapidly select the adaptation measures for vulnerable wastewater facilities for cities with various income levels. Future studies are encouraged to focus more on the model-related improvement/prediction, the impact of climate change on other wastewater facilities besides sewers, and countries with low or lower-middle incomes. This review provided insight to comprehensively understand the climate change impact on wastewater facilities and facilitate the policymaking in coping with climate change.

Managed retreat and planned retreat: a systematic literature review

Vulnerable locations, such as coastlines, are at a high risk of loss and damage. Such places will suffer deleterious impacts as climate change impacts are increasingly realized. As societies try to adapt to these impacts, managed or planned retreat-aimed at moving people and assets away from vulnerable locations-is gaining increased attention. Despite this increased attention, systematic literature reviews of the retreat literature remain scarce. This paper undertakes such review and uncovers a marked increase in retreat scholarly research papers in the past 5 years. An analysis of 135 managed and planned retreat journal articles is completed. Findings include a strong emphasis on regional or local case studies exploring governance, policy or institutional settings and levers across a range of geographies. Property rights and market interventions, such as compensation schemes, evidence the prevalence of neoliberal predilections. This emphasizes the importance of renewed engagement with political economy scholarship vis-à-vis climate change adaptation, also supported by the sharp increase in the evidenced social and environmental justice impacts. This article is part of the theme issue 'Nurturing resilient marine ecosystems'.