An official website of the United States government
Two sessions were organized during the 2018 Fall AGU Meeting entitled, (1) Coastal Response to Extreme Events: Fidelity of Model Predictions of Surge, Inundation, and Morphodynamics and (2) Improved Observational and Modeling Skills to Understand the Hurricane and Winter Storm Induced Surge and Meteotsunami. The focus of these sessions was on examining the impact of natural disasters on estuarine and coastal regions worldwide, including the islands and mainland in the northwestern Atlantic and the northwestern Pacific. The key research interests are the investigations on the regional dynamics of storm surges, coastal inundations, waves, tides, currents, sea surface temperatures, storm inundations and coastal morphology using both numerical models and observations during tropical and extratropical cyclones. This Special Issue (SI) ‘Estuarine and coastal natural hazards’ in Estuarine Coastal and Shelf Science is an outcome of the talks presented at these two sessions. Five themes are considered (effects of storms of wave dynamics; tide and storm surge simulations; wave-current interaction during typhoons; wave effects on storm surges and hydrodynamics; hydrodynamic and morphodynamic responses to typhoons), arguably reflecting areas of greatest interest to researchers and policy makers. This synopsis of the articles published in the SI allows us to obtain a better understanding of the dynamics of natural hazards (e.g., storm surges, extreme waves, and storm induced inundation) from various physical aspects. The discussion in the SI explores future dimensions to comprehend numerical models with fully coupled windwave- current-morphology interactions at high spatial resolutions in the nearshore and surf zone during extreme wind events. In addition, it would be worthwhile to design numerical models incorporating climate change projections (sea level rise and global warming temperatures) for storm surges and coastal inundations to allow more precisely informed coastal zone management plans.
more »
« less
Coastal topography and hydrogeology control critical groundwater gradients and potential beach surface instability during storm surges
Abstract. Ocean surges pose a global threat for coastal stability.These hazardous events alter flow conditions and pore pressures in floodedbeach areas during both inundation and subsequent retreat stages, which canmobilize beach material, potentially enhancing erosion significantly. Inthis study, the evolution of surge-induced pore-pressure gradients is studied through numerical hydrologic simulations of storm surges. The spatiotemporal variability of critically high gradients is analyzed in three dimensions. The analysis is based on a threshold value obtained for quicksand formationof beach materials under groundwater seepage. Simulations of surge eventsshow that, during the run-up stage, head gradients can rise to the calculated critical level landward of the advancing inundation line. During thereceding stage, critical gradients were simulated seaward of the retreatinginundation line. These gradients reach maximum magnitudes just as sea levelreturns to pre-surge levels and are most accentuated beneath the still-water shoreline, where the model surface changes slope. The gradients vary alongthe shore owing to variable beach morphology, with the largest gradientsseaward of intermediate-scale (1–3 m elevation) topographic elements (dunes)in the flood zone. These findings suggest that the common practices inmonitoring and mitigating surge-induced failures and erosion, which typically focus on the flattest areas of beaches, might need to be revised to include other topographic features.
more »
« less
- PAR ID:
- 10383528
- Date Published:
- Journal Name:
- Hydrology and Earth System Sciences
- Volume:
- 26
- Issue:
- 23
- ISSN:
- 1607-7938
- Page Range / eLocation ID:
- 5987 to 6002
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Erosive beach scarps influence beach vulnerability, yet their formation remains challenging to predict. In this study, a 1:2.5 scale laboratory experiment was used to study the subsurface hydrodynamics of a beach dune during an erosive event. Pressure and moisture sensors buried within the dune were used both to monitor the water table and to examine vertical pressure gradients in the upper 0.3 m of sand as the slope of the upper beach developed into a scarp. Concurrently, a line‐scan lidar tracked swash bores and monitored erosion and accretion patterns along a single cross‐shore transect throughout the experiment. As wave conditions intensified, a discontinuity in the slope of the dune formed; the discontinuity grew steeper and progressed landward at the same rate as theR2%runup extent until it was a fully formed scarp with a vertical face. Within the upper 0.15 m of the partially saturated sand, upward pore pressure gradients were detected during backwash, influencing the effective weight of sand and potentially contributing to beachface erosion. The magnitude and frequency of the upward pressure gradients increased with deeper swash depths and with frequency of wave interaction, and decreased with depth into the sand. A simple conceptual model for scarp formation is proposed that incorporates observations of upward‐directed pressure gradients from this study while providing a reference for future studies seeking to integrate additional swash zone sediment transport processes that may impact scarp development.more » « less
-
While there is high certainty that chronic coastal hazards like floodingand erosion, are increasing due to climate change induced sea-levelrise, there is high uncertainty surrounding the timing, intensity, andlocation of future hazard impacts. Assessments that quantify theseaspects of future hazards are critical for adaptation planning under achanging climate and can reveal new insights into the drivers of coastalhazards. In particular, probabilistic simulations of future hazardimpacts can improve these assessments by explicitly quantifyinguncertainty and by better simulating dependence structures between thecomplex multivariate drivers of hazards. In this study, a regional-scaleprobabilistic assessment of climate change induced coastal hazards isconducted for the Cascadia region, USA during the 21st century. Threeco-produced hazard proxies for beach safety, erosion, and flooding arequantified to identify areas of high hazard impacts and determine hazarduncertainty under three sea-level rise scenarios. A novel chroniccoastal hazard hotspot indicator is introduced that identifies areasthat may experience significant increases in hazard impacts compared topresent day conditions. We find that Southern Cascadia and NorthernWashington have larger hazard impacts and hazard uncertainty due totheir morphologic setting. Erosional hazards, relative to beach safetyand coastal flooding, will increase the most in Cascadia during the 21stcentury under all sea-level rise scenarios. Finally, we find that hazarduncertainty associated with wave and water level variability exceeds theuncertainty associated with sea-level-rise until the end of the century.more » « less
-
Hurricane Irma, in 2017, made an unusual landfall in South Florida and the unpredictability of the hurricane’s path challenged the evacuation process seriously and left many evacuees clueless. It was likely to hit Southeast Florida but suddenly shifted its path to the west coast of the peninsula, where the evacuation process had to change immediately without any time for individual decision-making. As such, this study aimed to develop a methodology to integrate evacuation and storm surge modeling with a case study analysis of Irma hitting Southeast Florida. For this purpose, a coupled storm surge and wave finite element model (ADCIRC+SWAN) was used to determine the inundation zones and roadways with higher inundation risk in Broward, Miami-Dade, and Palm Beach counties in Southeast Florida. This was fed into the evacuation modeling to estimate the regional clearance times and shelter availability in the selected counties. Findings show that it takes approximately three days to safely evacuate the populations in the study area. Modeling such integrated simulations before the hurricane hit the state could provide the information people in hurricane-prone areas need to decide to evacuate or not before the mandatory evacuation order is given.more » « less
-
null (Ed.)Flood occurrence is increasing due to the expansion of urbanization and extreme weather like hurricanes; hence, research on methods of inundation monitoring and mapping has increased to reduce the severe impacts of flood disasters. This research studies and compares two methods for inundation depth estimation using UAV images and topographic data. The methods consist of three main stages: (1) extracting flooded areas and create 2D inundation polygons using deep learning; (2) reconstructing 3D water surface using the polygons and topographic data; and (3) deriving a water depth map using the 3D reconstructed water surface and a pre-flood DEM. The two methods are different at reconstructing the 3D water surface (stage 2). The first method uses structure from motion (SfM) for creating a point cloud of the area from overlapping UAV images, and the water polygons resulted from stage 1 is applied for water point cloud classification. While the second method reconstructs the water surface by intersecting the water polygons and a pre-flood DEM created using the pre-flood LiDAR data. We evaluate the proposed methods for inundation depth mapping over the Town of Princeville during a flooding event during Hurricane Matthew. The methods are compared and validated using the USGS gauge water level data acquired during the flood event. The RMSEs for water depth using the SfM method and integrated method based on deep learning and DEM were 0.34m and 0.26m, respectively.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/hess-26-5987-2022
