Fluvial Flood Research Articles

Applying the Urban Systems Abstraction Hierarchy as a Tool for Flood Resilience

AbstractClimate change will mean cities are exposed to more frequent short‐term shocks such as floods. City‐scale resilience is achieved by understanding how these shocks interact with longer‐term stressors (e.g., social inequality). The Urban Systems Abstraction Hierarchy (USAH) has been developed for this purpose. In this paper, Glasgow (UK) is used as a case study application, to demonstrate how resilience theory can be operationalized through the application of the USAH. Results demonstrate how the USAH can quantify interdependencies between tangible physical entities in the city and intangible outcomes that monitor city stressors, and specifically how these outcomes change in response to a 1:200‐year fluvial flood return period in Glasgow. Resilience concepts such as multifunctionality, redundancy and diversity are applied to interpret the results and their implications for longer‐term resilience in Glasgow. The findings from the application of the USAH show that the outcome Social equality and equity is influential for longer‐term resilience in Glasgow, whilst Reliable communications and mobility is an important outcome for flood resilience.

Mapping Pluvial Flood-Induced Damages with Multi-Sensor Optical Remote Sensing: A Transferable Approach

Pluvial floods caused by extreme overland flow inland account for half of all flood damage claims each year along with fluvial floods. In order to increase confidence in pluvial flood susceptibility mapping, overland flow models need to be intensively evaluated using observations from past events. However, most remote-sensing-based flood detection techniques only focus on the identification of degradations and/or water pixels in the close vicinity of overflowing streams after heavy rainfall. Many occurrences of pluvial-flood-induced damages such as soil erosion, gullies, landslides and mudflows located further away from the stream are thus often unrevealed. To fill this gap, a transferable remote sensing fusion method called FuSVIPR, for Fusion of Sentinel-2 & Very high resolution Imagery for Pluvial Runoff, is developed to produce damage-detection maps. Based on very high spatial resolution optical imagery (from Pléiades satellites or airborne sensors) combined with 10 m change images from Sentinel-2 satellites, the Random Forest and U-net machine/deep learning techniques are separately trained and compared to locate pluvial flood footprints on the ground at 0.5 m spatial resolution following heavy weather events. In this work, three flash flood events in the Aude and Alpes-Maritimes departments in the South of France are investigated, covering over more than 160 km2 of rural and periurban areas between 2018 and 2020. Pluvial-flood-detection accuracies hover around 75% (with a minimum area detection ratio for annotated ground truths of 25%), and false-positive rates mostly below 2% are achieved on all three distinct events using a cross-site validation framework. FuSVIPR is then further evaluated on the latest devastating flash floods of April 2022 in the Durban area (South Africa), without additional training. Very good agreement with the impact maps produced in the context of the International Charter “Space and Major Disasters” are reached with similar performance figures. These results emphasize the high generalization capability of this method to locate pluvial floods at any time of the year and over diverse regions worldwide using a very high spatial resolution visible product and two Sentinel-2 images. The resulting impact maps have high potential for helping thorough evaluation and improvement of surface water inundation models and boosting extreme precipitation downscaling at a very high spatial resolution.

Multi-timescale dynamics of extreme river flood and storm surge interactions in relation with large-scale atmospheric circulation: Case of the Seine estuary

The present work investigates the multi-timescale dynamics of extreme fluvial-surge interactions (EFS) in a river-tide environment, in the case of the Seine estuary. This environment is considered an excellent natural laboratory to analyze river-surge interaction because of its time-varying flow and the available water-level records provided by tide gauges along the estuary. A spectral approach has been used to investigate the multi-timescale changes in EFS, governed by fluvial and marine contributions, in relation to the historical events of flood-storm concomitance and the large-scale atmospheric circulation. The spectral components of EFS, calculated at five stations along the estuary, highlighted a series of variability modes varying from the inter-month (∼3–6 months) to the inter-annual (∼2-, ∼3-5- and ∼6-8-years) scales and exhibiting, respectively, 55% and 20% of the total variability. The contribution of marine and fluvial effects in the EFS varies along the estuary and according to the timescale from seasons, when the interaction is governed by tidal deformation, to years. The connection of the historical flood-storm events with the EFS signal changes in their spectral signature according to their severity as well as the energetic physical drivers acting in each event: events with high return period are manifested at larger scales while events with low return period are limited to small scales.Finally, the examination of the physical relationships between the EFS and the global climate mechanisms has demonstrated the key role of the Sea Level Pressure (SLP) and the North Atlantic Oscillation (NAO) acting, respectively, in anti-phase at ∼1-2-yr and in phase at scales larger than 3-yr. The signature of the climate drivers operates differently according to the timescale; they are identified within the ∼80% of the inter-annual EFS. This signature is more significative since the 2000s when the increase in the NAO generates a rise in EFS variability. ∼20% of EFS would be related to the non-linear effects of the timescale interactions and other local mechanisms operating at such scales.This finding highlights the non-stationarity of the multi-timescale dynamics of marine storms and fluvial floods, and the relevance of the climate connection use for assessing the compound multi-hazard events at large-scales.

Assessing compound pluvial-fluvial flooding: Research status and ways forward

Compound weather and climate events have obtained increasing attention in recent years in the context of anthropogenic climate change. Compound pluvial-fluvial flooding (CPFF), usually referring to the superposition of heavy local rainfall in urban areas and riverbank overflow, is however rarely investigated. We perform a systematic literature review on this emerging topic and identify knowledge gaps. Major knowledge gaps concern the dependence between pluvial and fluvial flooding, and thus the co-occurrence probability, and its past and (possible) future changes. Although it is expected that CPFF increases in a warming world, we could not identify a single attempt to understand temporal changes. More systematic and comprehensive data collection and process documentation, particularly for pluvial and flash floods, are required to better understand and assess CPFF. Another major gap is the limitation of CPFF studies to hazard assessments. Implementing damage models would allow, with modest effort, to transfer hazard statements into risk statements. This would allow, in turn, to understand the scale of the problem in terms of societal relevance.

Compounding effects of urbanization, climate change and sea-level rise on monetary projections of flood damage

Climate change and urbanization play critical roles in compounding future flood risk due to their adverse impacts on the rainfall regime and sea level rise. Although past studies have predicted the spatiotemporal variations in flood risk, these have appreciable limitations, viz. (i) flood risk is predicted mainly by accounting for one driver at a time (either ocean flooding or fluvial flooding); and (ii) monetization of flood damage due to future flooding had not been investigated. However, multiple drivers could lead to flooding in coastal areas. This study presents an innovative approach for investigating the cumulative effects of urbanization, changes to the rainfall regime, and sea level rise on consequential flood damage in a coastal urban area. A comprehensive flood damage and hazard prediction model was developed by integrating 1D-2D aspects of MIKE FLOOD and GIS technology to assess the flood scenarios for 2040, 2070, and 2100 by investigating three predictor variables: urbanization, rainfall regime, and sea level rise. The factorial design approach was used to construct a total of 27 future flood scenarios. Time horizons of 30 years provided for effectively capturing climate change and its influence on the hydrologic regime. The Generalized Linear Model (GLM) was applied to create a statistical model based on future scenarios for each time horizon. Results confirmed that changes to the rainfall regime significantly influence the average annual damage (AAD) caused by flooding for all time horizons. At the same time, the significance of the effects of urbanization and sea level rise was found to vary. The model predicts that by 2040, urbanization would exacerbate AAD, with a significant contribution from sea level rise. In contrast, sea level rise would provide a marginally greater and more significant contribution to AAD compared to urbanization in 2040 and 2070. Compared to the base year 2017, AAD was 78%, 197%, and 351% higher in 2040, 2070, and 2100, respectively. The proposed flood damage prediction model developed can guide modelers and decision-makers in assessing the compounding flood damage for future flood management in any geographic location.

Losses from Fluvial Floods in Poland over the 21st Century – Estimation Using the Productivity Costs Method

Losses from Fluvial Floods in Poland over the 21st Century – Estimation Using the Productivity Costs Method

Changes in Nutrient Concentration Resulting From Floods and Their Impact on the Estuary–Sea Continuum

AbstractEvaluating the contribution of rivers to coastal seas in the Earth system and accurately predicting marine environmental responses to climate change are crucial for mitigating and addressing future natural disasters, especially those related to extreme hydrological events, such as fluvial floods. The Changjiang (Yangtze) River Estuary (CRE) and the East China Sea continuum, known for high environmental stress, complex marine dynamic processes, and frequent flood events, were selected to determine the compound impacts of a severe flood that persisted for the whole of July 2017. We conducted three cruise surveys before and after this flood event. Our surveys revealed that the phosphate concentration in the channel of the CRE declined from 2 to <1 μM during the flood, while the nitrate concentration remained stable. We applied a coupled physical‐biogeochemical model to determine the spatio‐temporal influence of floodwater (freshwater from upstream during flood events). During the initial rising discharge stage, surface phytoplankton blooms triggered by enhanced stratification consumed phosphate and significantly increased the N:P ratio in the sea. The ratio was restored as the blooms diminished, but remained elevated due to lower phosphate floodwater in the northeastward area within the low‐salinity river plume. Model experiments also showed that phytoplankton biomass and N:P ratio in the flood plume region were sensitive to the riverine phosphate concentration inputs during the flood event.

Flood risk in Kuala Lumpur, Malaysia: A consideration of flood defences in a broadscale hydraulic model

AbstractA novel approach to consider local‐scale defence infrastructure in an urban environment, coupled with a broadscale hydraulic model framework, is applied to the capital city of Kuala Lumpur, Malaysia. Broadscale hydraulic modelling frameworks are often able to employ more complex models, but are typically limited to homogenous decision‐making to ensure standardised outputs across large regions. Conversely, small‐scale hydraulic modelling frameworks tend to better integrate local‐scale features but can be computationally expensive to scale up beyond a regional view. Improvements to the broadscale hydraulic model framework through the incorporation of defence systems yield a more accurate representation of fluvial flood risk. This study incorporates defences in Kuala Lumpur, yielding a reduction in our estimates of fluvial flood extent by around 40%. The results of this study are validated against a set of high‐quality observations, demonstrating the capability of the model framework in capturing flood risk in more than 95% of known flood risk zones in the city. Incorporating defence infrastructure using data‐driven decision making and existing functionality in the hydraulic model could be automated in future model builds. This new approach bridges the gap between local‐scale model frameworks and the broadscale, homogenous 2D hydraulic modelling studies.

Advancing operational flood forecasting, early warning and risk management with new emerging science: Gaps, opportunities and barriers in Kenya

AbstractKenya and the wider East African region suffer from significant flood risk, as illustrated by major losses of lives, livelihoods and assets in the most recent years. This is likely to increase in future as exposure rises and rainfall intensifies under climate change. Accordingly, flood risk management is a priority action area in Kenya's national climate change adaptation planning. Here, we outline the opportunities and challenges to improve end‐to‐end flood early warning systems, considering the scientific, technical and institutional/governance dimensions. We demonstrate improvements in rainfall forecasts, river flow, inundation and baseline flood risk information. Notably, East Africa is a ‘sweetspot’ for rainfall predictability at sub‐seasonal to seasonal timescales for extending forecast lead times beyond a few days and for ensemble flood forecasting. Further, we demonstrate coupled ensemble flow forecasting, new flood inundation simulation, vulnerability and exposure data to support Impact based Forecasting (IbF). We illustrate these advances in the case of fluvial and urban flooding and reflect on the potential for improved flood preparedness action. However, we note that, unlike for drought, there remains no national flood risk management framework in Kenya and there is need to enhance institutional capacities and arrangements to take full advantage of these scientific advances.

Indicator-based approach for fluvial flood risk assessment at municipal level in Slovakia

The article focuses on the mapping and assessment of fluvial flood risk at municipal level of Slovakia. The fluvial floods risk index (FFRI), composed of a hazard component and a vulnerability component, was computed for 2927 municipalities using spatial multicriteria analysis and geographic information systems (GIS). The fluvial flood hazard index (FFHI) was computed based on eight physical-geographical indicators and land cover representing the riverine flood potential and also the frequency of flood events in individual municipalities. The fluvial flood vulnerability index (FFVI) was calculated using seven indicators representing the economic and social vulnerability of municipalities. All of the indicators were normalized and weighted using the rank sum method. By aggregating the weighted indicators, we obtained the FFHI and FFVI in each municipality. The final FFRI is a result of a synthesis of the FFHI and FFVI. The results of this study can be used mainly in the framework of flood risk management at national spatial scale, but also for local governments and periodic update of the Preliminary Flood Risk Assessment document, which is carried out at the national level under the EU Floods Directive.

Construction of a national natural hazard interaction framework: The case of Sweden

Recent multiple natural hazards and compound climate events studies have identified a range of interaction types and examined natural hazard interactions in various locations. Yet, there are calls for examining relevant multiple natural hazards in still unstudied national contexts as Sweden. Moreover, multi-hazard concepts rarely consider climate change effects, despite the call of the Intergovernmental Panel on Climate Change (IPCC) to adopt multi-hazard approaches and the growing recognition that compound events should be considered "normal". Using a systematic literature study, the paper presents a national natural hazard interaction framework for Sweden identifying 39 cascading, 56 disposition alteration, 3 additional hazard potential, and 17 coincident triggering interactions between 20 natural hazards. Reviewed gray literature, an expert workshop, and reviewed climate research suggest increases of multiple natural hazards with heat wave and heavy rain as triggering or driving events and with hydrological hazards, for instance, fluvial floods, landslides, and debris flows, as the main consequences.

Urban Flooding in Vancouver, Canada

Flooding can have devastating, long-lasting, and costly consequences, including the loss of life and displacement of communities. This review report summarizes the background, causes, and management practices of various urban flooding forms and mitigation efforts in Vancouver, British Columbia (BC) which is located on the Western part on the Pacific coast of Canada. The report makes use of existing literature to understand the flooding phenomena in Vancouver. The city is unique from a flood planning or management perspective because the city is vulnerable to every type of major flooding event, including pluvial, fluvial, and coastal flooding. Nevertheless, Vancouver is considered a globally sustainable city. As such, this report reviews various articles and research to determine the background and causes of various forms of floods experienced in Vancouver and the management practices put in place to mitigate flooding in the city. The study identifies measures in place to address every type of flooding event.

Quantification of Groundwater Hazards Related to Fluvial Floods via Groundwater Flow Modelling: A Review

Flood-related issues include the impact of groundwater on flood protection measures and other subsurface structures in a protected area. At the same time, subsurface elements of flood protection structures may significantly influence the natural groundwater regime and affect existing structures during non-flood periods. The paper provides an overview of hazardous factors linked to groundwater and specifies variables for the quantification of related hazards. Appropriate hydraulic groundwater flow models are presented and discussed, and their suitability for the modelling of individual typical problems and for hazard quantification is specified. The use of models and the application of CAD and GIS tools for data pre- and post-processing is mentioned in brief and demonstrated on examples of typical practical situations.

Anthropogenic amplification of geomorphic processes on fluvial channel morphology, case study in Gilgel Abay river mouth; lake Tana Sub Basin, Ethiopia

As a result of ongoing human induced or natural factors acting on river channels, banks, and within a catchment, alluvial river systems change their course and morphology over time. The base level changes and the backwater effects affect rivers entering a static water body. For coastal rivers, the planform changes are highly pronounced at the fluvial deltas and flood plains. Aggradation, degradation, progradation, meandering, and formation of islands and distributary channels are common processes on coastal rivers. This study investigates planform changes and landscape responses of Gilgel Abay river about 36 km stretch starting from the bridge, near Chimba, to its entrance to Lake Tana by using historical images for the last 60 years (1957–2020) and field observation. The study reach was divided in to three parts based on feature characteristics. For data preparation and analysis, image analysis software's; ENVI, ERDAS IMAGINE, and ArcGIS were used. From land use land cover classification, the land use pattern near the river flood plain and delta area changed significantly. The overall planform results (sinuosity, width, and island) show that, Gilgel Abay River within the study reach has shown little change in its planform for the last 60 years. However, the landscape of alluvial delta formed at the mouth of the river has shown huge change. Accretion-erosion result map shows, a maximum of 18.73 ± 1.97 m/y accretion and −12.48 ± 1.44 m/y erosion at the right side (eastward) and a maximum of 50.06 ± 1.44 m/y accretion and lost only 3.95 ± 1.97 m/y westward. The delta area analysis shows in the last five decades, 17.13 ha/yr of land has formed disproportionally out of which over 56% is added at the right shore of the river. In general, for the planform changes that occurred in Gilgel Abay river channel and fluvial delta, human-induced factors have a great contribution. Increasing interest for new settlements inside delta flood plain, productive agricultural land and artificial lake level rise changes the river planform and the delta appearance. Quantitative and qualitative mapping of river and delta coupling with feeding basins and floodplains is important to enhance and understand the socioeconomic influences on river morphology and needs an integrated management framework.

A climate-conditioned catastrophe risk model for UK flooding

Abstract. We present a transparent and validated climate-conditioned catastrophe flood model for the UK, that simulates pluvial, fluvial and coastal flood risks at 1 arcsec spatial resolution (∼ 20–25 m). Hazard layers for 10 different return periods are produced over the whole UK for historic, 2020, 2030, 2050 and 2070 conditions using the UK Climate Projections 2018 (UKCP18) climate simulations. From these, monetary losses are computed for five specific global warming levels above pre-industrial values (0.6, 1.1, 1.8, 2.5 and 3.3 ∘C). The analysis contains a greater level of detail and nuance compared to previous work, and represents our current best understanding of the UK's changing flood risk landscape. Validation against historical national return period flood maps yielded critical success index values of 0.65 and 0.76 for England and Wales, respectively, and maximum water levels for the Carlisle 2005 flood were replicated to a root mean square error (RMSE) of 0.41 m without calibration. This level of skill is similar to local modelling with site-specific data. Expected annual damage in 2020 was GBP 730 million, which compares favourably to the observed value of GBP 714 million reported by the Association of British Insurers. Previous UK flood loss estimates based on government data are ∼ 3× higher, and lie well outside our modelled loss distribution, which is plausibly centred on the observations. We estimate that UK 1 % annual probability flood losses were ∼ 6 % greater for the average climate conditions of 2020 (∼ 1.1 ∘C of warming) compared to those of 1990 (∼ 0.6 ∘C of warming), and this increase can be kept to around ∼ 8 % if all countries' COP26 2030 carbon emission reduction pledges and “net zero” commitments are implemented in full. Implementing only the COP26 pledges increases UK 1 % annual probability flood losses by 23 % above average 1990 values, and potentially 37 % in a “worst case” scenario where carbon reduction targets are missed and climate sensitivity is high.

A globally applicable framework for compound flood hazard modeling

Abstract. Coastal river deltas are susceptible to flooding from pluvial, fluvial, and coastal flood drivers. Compound floods, which result from the co-occurrence of two or more of these drivers, typically exacerbate impacts compared to floods from a single driver. While several global flood models have been developed, these do not account for compound flooding. Local-scale compound flood models provide state-of-the-art analyses but are hard to scale to other regions as these typically are based on local datasets. Hence, there is a need for globally applicable compound flood hazard modeling. We develop, validate, and apply a framework for compound flood hazard modeling that accounts for interactions between all drivers. It consists of the high-resolution 2D hydrodynamic Super-Fast INundation of CoastS (SFINCS) model, which is automatically set up from global datasets and coupled with a global hydrodynamic river routing model and a global surge and tide model. To test the framework, we simulate two historical compound flood events, Tropical Cyclone Idai and Tropical Cyclone Eloise in the Sofala province of Mozambique, and compare the simulated flood extents to satellite-derived extents on multiple days for both events. Compared to the global CaMa-Flood model, the globally applicable model generally performs better in terms of the critical success index (−0.01–0.09) and hit rate (0.11–0.22) but worse in terms of the false-alarm ratio (0.04–0.14). Furthermore, the simulated flood depth maps are more realistic due to better floodplain connectivity and provide a more comprehensive picture as direct coastal flooding and pluvial flooding are simulated. Using the new framework, we determine the dominant flood drivers and transition zones between flood drivers. These vary significantly between both events because of differences in the magnitude of and time lag between the flood drivers. We argue that a wide range of plausible events should be investigated to obtain a robust understanding of compound flood interactions, which is important to understand for flood adaptation, preparedness, and response. As the model setup and coupling is automated, reproducible, and globally applicable, the presented framework is a promising step forward towards large-scale compound flood hazard modeling.

Mitigating compound coastal water hazards in Eastern North Carolina

Eastern North Carolina (ENC), a predominantly rural region, experiences the intersection of fluvial, pluvial, and tidal flooding, which leads to complex and impactful outcomes. Managing these, often compounding, hazards is challenging, especially as climate change drivers, such as sea-level rise and more intense storms will likely lead to a greater incidence of compound coastal water events (CCWE). Using data from focus group interviews conducted with 41 planners and emergency managers, we examine the mitigation approaches pursued by rural counties in ENC located along the coast and those adjacent to it that share estuarine environments or linked riverine systems. Findings show that communities seek funding to clear streams and channels, to implement buyouts and elevation projects and for infrastructure maintenance. Communities also undertake floodplain management to minimize flood exposure while facing several barriers to adequate mitigation.

Detrital zircon geochronology and provenance of the Mesoproterozoic Husky Creek Formation: a fluvial sandstone recording the waning stages of one of Earth's largest magmatic episodes

The Mesoproterozoic Husky Creek Formation is an interlayered redbed and basalt package that overlies a ca. 2.5 km thick, regionally extensive basaltic plateau linked to the 1.27 Ga Mackenzie Large Igneous Province. This succession provides an opportunity to study the interaction between contemporaneous fluvial sedimentation and flood basalt volcanism. The Husky Creek Formation is approximately 1900 m thick, consisting predominantly of fluvial channel and subordinate floodplain and eolian strata dominated by lithic detritus intercalated with basalt flows. U–Pb dating of detrital zircon grains collected from four stratigraphic levels in the Husky Creek Formation reveals two main age groupings: (1) a 1270 Ma peak attributed to the Mackenzie Large Igneous Province; and (2) Pre-1.6 Ga detrital zircon ages, which reflect sources from a broad region of northwestern Laurentia and are interpreted to be recycled from underlying sedimentary rocks of the Hornby Bay Basin. An upsection decrease in the proportion of ca. 1270 Ma zircon grains, coupled with increasing sandstone compositional maturity, reflects the expansion of the drainage basin during burial of a volcanic pile, with recycling becoming more dominant as the Husky Creek Formation accumulated. The Husky Creek Formation was deposited in the waning stages of the Mackenzie Igneous Event by west-flowing rivers into a geographically restricted basin above an extensive mafic volcanic plateau. This paper provides insight into fluvial basin development during the aftermath of one of Earth's largest igneous events.

DIAGNOSING THE TERRESTRIAL WATER STORAGE VARIATION OVER THE NIGERIAN SPACE: THE GRACE PERSPECTIVE

Abstract. Besides its paramount role to life and human survival on the earth, water also plays a crucial role in understanding certain earth processes. Water can be quite hazardous, whether in a surplus state or in a deficit state. The former presents as flood, while the latter presents as drought. Nigeria, unfortunately, over the years has been shown not to be immune to both extreme states of water. It is, therefore, crucial to continually monitor the state of water in order to mitigate whatever danger both states may present to the nation. One key index for measuring the quantity of water on land is the Terrestrial Water Storage (TWS), which incidentally is obtainable from gravity data of the Gravity Recovery and Climate Experiment (GRACE) satellite mission. This study leverages on the availability of GRACE mascon data to give insight into the dynamics of TWS within Nigeria. The study observed an increasing trend of TWS in all hydrological areas and basins within Nigeria. Trends of up 10mm/year were observed in the Sokoto-Rima basin. The flash and fluvial flooding events of 2012 and 2015, were captured by GRACE satellites. In terms of its seasonal fluctuations, TWS values are relatively minimal in the first 6 months of the year and maximal in the remaining 6 months. Its peak value is usually observed around October of each year. A clear inter-annual pattern is also observed in peak values of TWS within the period of study (2002–2017).

Simulating the Impacts of an Applied Dynamic Adaptive Pathways Plan Using an Agent-Based Model: A Tauranga City, New Zealand, Case Study

Climate change and relative sea-level rise (RSLR) will increasingly expose coastal cities to coastal flooding, erosion, pluvial and fluvial flooding, episodic storm-tide flooding and eventually, permanent inundation. Tools are needed to support adaptive management approaches that allow society to adapt incrementally by making decisions now without creating path dependency and compromising decision-making options in the future. We developed an agent-based model that integrates climate-related physical hazard drivers and socio-economic drivers. We used it to explore how adaptive actions might be sequentially triggered within a low-elevation coastal city in New Zealand, in response to various climate change and socio-economic scenarios. We found that different adaptive actions are triggered at about the same RSLR level regardless of shared socio-economic pathway/representative concentration pathway scenario. The timing of actions within each pathway is dictated mainly by the rate of RSLR and the timing and severity of storm events. For the representative study site, the model suggests that the limits for soft and hard protection will occur around 30 cm RSLR, fully-pumped water systems are viable to around 35 cm RSLR and infrastructure upgrades and policy mechanisms are feasible until between 40 cm and 75 cm RSLR. After 75 cm RSLR, active retreat is the only remaining adaptation pathway.