The Coastal Property Boundary in California: Recommendations to Improve Determination of the Mean High Tide Line in Light of Sea Level Rise

Population risk assessments of sea level rise are key to understanding the impacts of climate change on coastal communities and necessary for adaptation planning. Future sea level rise exposes coastal populations to a spectrum of risk, but assessments often define exposure narrowly, such as areas experiencing permanent inundation only. We reviewed the most common sea level rise exposure assessment methods and identified three widely used spatial definitions of physical exposure risk: mean higher high water, the 100-year floodplain, and the low-elevation coastal zone. Taken individually, each treat risk to sea level rise as binary (affected or not affected), resulting in narrow definitions, homogenizing risk and exposure across space and time. We present a framework that integrates and smooths these classifications under a single continuous metric. To do so, we advance a sophisticated spatiotemporal flood-modeling approach -- expected annual exposure -- based on a probabilistic spatial envelope that unifies spatial extents between the high-tide line and the 10,000-year floodplain. We show that the effects from sea level rise will impact far more people far sooner than previously thought. In particular, our results suggest that single, binary extent assessments either underestimate or overestimate the magnitude of the at-risk populations while also spatially homogenizing the impacts to sea level rise. Our advance on modeling annual exposure provides a more robust and holistic assessment of the populations most at-risk to flooding from sea level rise. This typology can be used to guide new research connecting risk of sea level rise to related adaptation policies and planning.

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Compounding effects of sea level rise and fluvial flooding

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1620325114 ◽

2017 ◽

Vol 114 (37) ◽

pp. 9785-9790 ◽

Cited By ~ 104

Author(s):

Hamed R. Moftakhari ◽

Gianfausto Salvadori ◽

Amir AghaKouchak ◽

Brett F. Sanders ◽

Richard A. Matthew

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Hazard Assessment ◽

Failure Probability ◽

River Flow ◽

Flood Hazard ◽

High Tide ◽

Probability Method ◽

Flood Hazards ◽

Flood Hazard Assessment

Sea level rise (SLR), a well-documented and urgent aspect of anthropogenic global warming, threatens population and assets located in low-lying coastal regions all around the world. Common flood hazard assessment practices typically account for one driver at a time (e.g., either fluvial flooding only or ocean flooding only), whereas coastal cities vulnerable to SLR are at risk for flooding from multiple drivers (e.g., extreme coastal high tide, storm surge, and river flow). Here, we propose a bivariate flood hazard assessment approach that accounts for compound flooding from river flow and coastal water level, and we show that a univariate approach may not appropriately characterize the flood hazard if there are compounding effects. Using copulas and bivariate dependence analysis, we also quantify the increases in failure probabilities for 2030 and 2050 caused by SLR under representative concentration pathways 4.5 and 8.5. Additionally, the increase in failure probability is shown to be strongly affected by compounding effects. The proposed failure probability method offers an innovative tool for assessing compounding flood hazards in a warming climate.

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A newly reconciled data set for identifying sea level rise and variability in Dublin Bay

10.5194/os-2021-92 ◽

2021 ◽

Author(s):

Amin Shoari Nejad ◽

Andrew C. Parnell ◽

Alice Greene ◽

Peter Thorne ◽

Brian P. Kelleher ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Tide Gauge ◽

High Water ◽

Data Set ◽

Quality Checks ◽

Bayesian Linear Regression ◽

The Mean ◽

Water Values ◽

Water Level Measurements

Abstract. We provide an updated sea level dataset for Dublin for the period 1938 to 2016 at yearly resolution. Using a newly collated sea level record for Dublin Port, as well as two nearby tide gauges at Arklow and Howth Harbour, we perform data quality checks and calibration of the Dublin Port record by adjusting the biased high water level measurements that affect the overall calculation of mean sea level (MSL). To correct these MSL values, we use a novel Bayesian linear regression that includes the Mean Low Water values as a predictor in the model. We validate the re-created MSL dataset and show its consistency with other nearby tide gauge datasets. Using our new corrected dataset, we estimate a rate of 1.08 mm/yr sea level rise at Dublin Port between 1953–2016 (95 % CI from 0.62 to 1.55 mm/yr), and a rate of 6.48 mm/yr between 1997–2016 (95 % CI 4.22 to 8.80 mm/yr). Overall sea level rise is in line with expected trends but large multidecadal varaibility has led to higher rates of rise in recent years.

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Missing evidence for stepwise postglacial sea level rise and an approach to more precise determination of former sea levels on East China Sea Shelf

Marine Geology ◽

10.1016/j.margeo.2013.12.004 ◽

2014 ◽

Vol 348 ◽

pp. 52-62 ◽

Cited By ~ 22

Author(s):

Chunting Xue

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

East China Sea ◽

Precise Determination ◽

East China ◽

Sea Levels ◽

China Sea ◽

East China Sea Shelf

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Recent Sea Level Change in the Black Sea from Satellite Altimetry and Tide Gauge Observations

ISPRS International Journal of Geo-Information ◽

10.3390/ijgi9030185 ◽

2020 ◽

Vol 9 (3) ◽

pp. 185 ◽

Cited By ~ 1

Author(s):

Nevin Avşar ◽

Şenol Kutoğlu

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Black Sea ◽

Satellite Altimetry ◽

Tide Gauge ◽

The Black Sea ◽

Sea Level Changes ◽

Early 19Th Century ◽

Mean Sea Level ◽

The Mean

Global mean sea level has been rising at an increasing rate, especially since the early 19th century in response to ocean thermal expansion and ice sheet melting. The possible consequences of sea level rise pose a significant threat to coastal cities, inhabitants, infrastructure, wetlands, ecosystems, and beaches. Sea level changes are not geographically uniform. This study focuses on present-day sea level changes in the Black Sea using satellite altimetry and tide gauge data. The multi-mission gridded satellite altimetry data from January 1993 to May 2017 indicated a mean rate of sea level rise of 2.5 ± 0.5 mm/year over the entire Black Sea. However, when considering the dominant cycles of the Black Sea level time series, an apparent (significant) variation was seen until 2014, and the rise in the mean sea level has been estimated at about 3.2 ± 0.6 mm/year. Coastal sea level, which was assessed using the available data from 12 tide gauge stations, has generally risen (except for the Bourgas Station). For instance, from the western coast to the southern coast of the Black Sea, in Constantza, Sevastopol, Tuapse, Batumi, Trabzon, Amasra, Sile, and Igneada, the relative rise was 3.02, 1.56, 2.92, 3.52, 2.33, 3.43, 5.03, and 6.94 mm/year, respectively, for varying periods over 1922–2014. The highest and lowest rises in the mean level of the Black Sea were in Poti (7.01 mm/year) and in Varna (1.53 mm/year), respectively. Measurements from six Global Navigation Satellite System (GNSS) stations, which are very close to the tide gauges, also suggest that there were significant vertical land movements at some tide gauge locations. This study confirmed that according to the obtained average annual phase value of sea level observations, seasonal sea level variations in the Black Sea reach their maximum annual amplitude in May–June.

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New elevation data triple estimates of global vulnerability to sea-level rise and coastal flooding

Nature Communications ◽

10.1038/s41467-019-12808-z ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 70

Author(s):

Scott A. Kulp ◽

Benjamin H. Strauss

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

High Tide ◽

Water Levels ◽

Low Carbon ◽

Digital Elevation ◽

Elevation Data ◽

Global Mean Sea Level ◽

Elevation Model ◽

Global Mean

Abstract Most estimates of global mean sea-level rise this century fall below 2 m. This quantity is comparable to the positive vertical bias of the principle digital elevation model (DEM) used to assess global and national population exposures to extreme coastal water levels, NASA’s SRTM. CoastalDEM is a new DEM utilizing neural networks to reduce SRTM error. Here we show – employing CoastalDEM—that 190 M people (150–250 M, 90% CI) currently occupy global land below projected high tide lines for 2100 under low carbon emissions, up from 110 M today, for a median increase of 80 M. These figures triple SRTM-based values. Under high emissions, CoastalDEM indicates up to 630 M people live on land below projected annual flood levels for 2100, and up to 340 M for mid-century, versus roughly 250 M at present. We estimate one billion people now occupy land less than 10 m above current high tide lines, including 230 M below 1 m.

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A Flow-Calibrated Method to Project Groundwater Infiltration into Coastal Sewers Affected by Sea Level Rise

Water ◽

10.3390/w12071934 ◽

2020 ◽

Vol 12 (7) ◽

pp. 1934

Author(s):

Adrienne Fung ◽

Roger Babcock

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Monitoring Data ◽

Groundwater Levels ◽

Flow Monitoring ◽

System A ◽

Coastal Cities ◽

The Mean ◽

Groundwater Infiltration

Collection systems in coastal cities are often below the groundwater table, leading to groundwater infiltration (GWI) through defects such as cracks and poor lateral connections. Climate-change-induced sea level rise (SLR) will raise groundwater levels, increasing the head and thus the inflow. A method has been developed to predict GWI when groundwater levels change using calibration with sewershed flow monitoring data. The calibration results in a parameter that characterizes the porosity of the collection system. A case study is presented for a coastal city with reliable flow monitoring data for eight days that resulted in a large range of effective defect sizes (minimum 0.0044 to maximum 0.338 radians), however, the range of predicted future GWI in currently submerged pipes varied by only 12% from the mean. The mean effective defect predicts 70 to 200% increases in GWI due to SLR of 0.3 to 0.9 m (1 to 3 ft), respectively, for currently submerged pipes. Predicted additional GWI for pipes that will become submerged due to SLR will increase GWI to values that approach or exceed the current average dry weather flow. This methodology can be used for planning of infrastructure improvements to enhance resiliency in coastal communities.

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The effects of tidal changes on the frequency of nuisance flooding events in the United States

10.5194/egusphere-egu2020-12115 ◽

2020 ◽

Author(s):

Sida Li ◽

Thomas Wahl ◽

David Jay ◽

Stefan Talke ◽

Lintao Liu

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

High Tide ◽

The United States ◽

Tide Gauges ◽

Relative Sea Level ◽

Relative Sea Level Rise ◽

Tidal Changes ◽

Cape Fear ◽

The U.S

<p>Nuisance flooding (NF) or high tide flooding describes minor nondestructive flooding which can nonetheless cause substantial negative socio-economic impacts to coastal communities. The frequency of NF events has increased and accelerated over the past decades along the U.S. coast, leading to changes ranging from 300% to 900%. This is mainly a result of sea level rise reducing the gap between high tidal datum and flood thresholds. While long-term relative sea level rise is the main driver for the increased number of NF events, other factors such as variability in the Gulf stream, the storm climate, and infragravity waves can also contribute. Another important driver that is often overlooked is related to changes in coastal and estuary tides, through secular trends in the amplitudes of major tidal constituents. In this presentation we assess the role of tidal changes in modulating the frequency of NF events along the U.S. coastline. We analyze hourly records from 49 U.S. tide gauges for which the National Weather Service has defined NF thresholds. We find that (1) overall across all tide gauges the number of NF days has increased since 1950 due to changes in coastal tides, adding up to 100 NF days in recent years (on top of the increase due to relative sea level rise), (2) more tide gauges experience an increase in NF events than a decrease due to changes in tides, (3) tide gauges in major estuaries which have undergone major anthropogenic alterations experience the strongest changes; in Wilmington (Cape Fear estuary), for example, 10-40% of NF events in recent years can be attributed to tidal changes.&#160;</p>

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