National-Scale Built-Environment Exposure to 100-Year Extreme Sea Levels and Sea-Level Rise

Paulik, Ryan; Stephens, Scott; Bell, Robert G.; Wadhwa, Sanjay; Popovich, Ben

doi:10.3390/su12041513

Cited by 33 publications

(39 citation statements)

References 38 publications

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“…Research has shown that non-linear interactions between tide, wind and morphology influence surge generation inside enclosed estuaries (e.g. Plüß et al, 2001;Rego and Li, 2010;Orton et al, 2012), a subject for further research in NZ since there are few long-term sea-level records to help quantify extreme storm-tide frequency and magnitude in NZ upperestuarine locations.…”

Section: Tidal Influencementioning

confidence: 99%

Spatial and temporal analysis of extreme storm-tide and skew-surge events around the coastline of New Zealand

Stephens

Bell

Haigh

2020

Nat. Hazards Earth Syst. Sci.

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Abstract. Coastal flooding is a major global hazard, yet few studies have examined the spatial and temporal characteristics of extreme sea level and associated coastal flooding. Here we analyse sea-level records around the coast of New Zealand (NZ) to quantify extreme storm-tide and skew-surge frequency and magnitude. We identify the relative magnitude of sea-level components contributing to 85 extreme sea level and 135 extreme skew-surge events recorded in NZ since 1900. We then examine the spatial and temporal clustering of these extreme storm-tide and skew-surge events and identify typical storm tracks and weather types associated with the spatial clusters of extreme events. We find that most extreme storm tides were driven by moderate skew surges combined with high perigean spring tides. The spring–neap tidal cycle, coupled with a moderate surge climatology, prevents successive extreme storm-tide events from happening within 4–10 d of each other, and generally there are at least 10 d between extreme storm-tide events. This is similar to findings from the UK (Haigh et al., 2016), despite NZ having smaller tides. Extreme events more commonly impacted the east coast of the North Island of NZ during blocking weather types, and the South Island and west coast of the North Island during trough weather types. The seasonal distribution of both extreme storm-tide and skew-surge events closely follows the seasonal pattern of mean sea-level anomaly (MSLA) – MSLA was positive in 92 % of all extreme storm-tide events and in 88 % of all extreme skew-surge events. The strong influence of low-amplitude (−0.06 to 0.28 m) MSLA on the timing of extreme events shows that mean sea-level rise (SLR) of similarly small height will drive rapid increases in the frequency of presently rare extreme sea levels. These findings have important implications for flood management, emergency response and the insurance sector, because impacts and losses may be correlated in space and time.

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Section: Tidal Influencementioning

confidence: 99%

Spatial and temporal analysis of extreme storm-tide and skew-surge events around the coastline of New Zealand

Stephens

Bell

Haigh

2020

Nat. Hazards Earth Syst. Sci.

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“…Hutt city is protected from fluvial flooding by one of New Zealand's most comprehensive flood protection schemes on the Hutt River [34]. Paulik [10,35] have shown that the wider Wellington region (including Hutt City) has some of the highest pipeline exposure to rising coastal hazards and accordingly some of the highest associated replacement costs of water infrastructure in New Zealand. In New Zealand, SLR is the primary driver of coastal flooding.…”

Section: Study Areamentioning

confidence: 99%

“…To assess the spatial risk exposure of assets in the study area, hazard data layers for the present-day 1% annual exceedance probabilities (AEP) of coastal flood water levels combined with 0.1 m increments of SLR (relative to present mean sea level) [10] were used. In this dataset, the coastal-flood level was comprised of storm-tide and wave setup water level in Wellington Harbor (Figure 1) [10]. These derived hazard layers were overlain with selected infrastructure asset data layers, comprised of polyline and point data that determined the spatial exposure to coastal flood hazards.…”

Section: Stormwater and Wastewater System Thresholdsmentioning

confidence: 99%

“…These derived hazard layers were overlain with selected infrastructure asset data layers, comprised of polyline and point data that determined the spatial exposure to coastal flood hazards. SLR increment overlays were mapped onto asset layers for exposure up to +1.2 m SLR using RiskScape [10]. RiskScape is a decision-support and visualization tool that combines the three layers from a Hazard Module, a Vulnerability Module, and an Asset Module [44] to generate a spatial realization of exposed assets at risk from infrequent coastal-flood events for SLR (hazard) increments in the study area.…”

Section: Stormwater and Wastewater System Thresholdsmentioning

confidence: 99%

“…Consequences and compounding hazards induced by SLR include more frequent flooding and increasing erosion, groundwater levels, saltwater intrusion, liquefaction risk, and drainage problems. In New Zealand, rising sea levels especially threaten coastal infrastructure, communities, and low-lying ecosystems [8][9][10][11][12]. National-scale assessments indicate that wastewater and stormwater infrastructure are more exposed to SLR than other coastal infrastructure [10,13,14].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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Sea-level rise increasingly affects low-lying and exposed coastal communities due to climate change. These communities rely upon the delivery of stormwater and wastewater services which are often co-located underground in coastal areas. Due to sea-level rise and associated compounding climate-related hazards, managing these networks will progressively challenge local governments as climate change advances. Thus, responsible agencies must reconcile maintaining Levels of Service as the impacts of climate change worsen over the coming decades and beyond. A critical question is whether such networks can continue to be adapted/protected over time to retain Levels of Service, or whether eventual retreat may be the only viable adaptation option? If so, at what performance threshold? In this paper, we explore these questions for stormwater and wastewater, using a dynamic adaptive pathway planning (DAPP) approach designed to address thresholds and increasing risk over time. Involving key local stakeholders, we here use DAPP to identify thresholds for stormwater and wastewater services and retreat options, and for developing a comprehensive and area-specific retreat strategy comprising pathway portfolios, retreat phases, potential land use changes, and for exploring pathway conflicts and synergies. The result is a prototype for an area near Wellington, New Zealand, where a managed retreat of water infrastructure is being considered at some future juncture. Dynamic adaptive strategies for managed retreats can help to reduce future disruption from coastal flooding, signal land use changes early, inform maintenance, and allow for gradual budget adjustments by the agencies that can manage expenditure over time. We present this stepwise process in a pathway form that can be communicated spatially and visually, thereby making a retreat a more manageable, sequenced, adaptation option for water agencies, and the communities they serve.

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Integrating new sea‐level scenarios into coastal risk and adaptation assessments: An ongoing process

Nicholls

Hanson

Lowe

et al. 2021

WIREs Climate Change

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The release of new and updated sea‐level rise (SLR) information, such as from the Intergovernmental Panel on Climate Change (IPCC) Assessment Reports, needs to be better anticipated in coastal risk and adaptation assessments. This requires risk and adaptation assessments to be regularly reviewed and updated as needed, reflecting the new information but retaining useful information from earlier assessments. In this paper, updated guidance on the types of SLR information available is presented, including for sea‐level extremes. An intercomparison of the evolution of the headline projected ranges across all the IPCC reports show an increase from the fourth and fifth assessments to the most recent “Special Report on the Ocean and Cryosphere in a Changing Climate” assessment. IPCC reports have begun to highlight the importance of potential high‐end sea‐level response, mainly reflecting uncertainties in the Greenland/Antarctic ice sheet components, and how this might be considered in scenarios. The methods that are developed here are practical and consider coastal risk assessment, adaptation planning, and long‐term decision‐making to be an ongoing process and ensure that despite the large uncertainties, pragmatic adaptation decisions can be made. It is concluded that new sea‐level information should not be seen as an automatic reason for abandoning existing assessments, but as an opportunity to review (i) the assessment's robustness in the light of new science and (ii) the utility of proactive adaptation and planning strategies, especially over the more uncertain longer term. This article is categorized under: Assessing Impacts of Climate Change > Scenario Development and Application

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National-Scale Built-Environment Exposure to 100-Year Extreme Sea Levels and Sea-Level Rise

Cited by 33 publications

References 38 publications

Spatial and temporal analysis of extreme storm-tide and skew-surge events around the coastline of New Zealand

Spatial and temporal analysis of extreme storm-tide and skew-surge events around the coastline of New Zealand

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

Integrating new sea‐level scenarios into coastal risk and adaptation assessments: An ongoing process

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