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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. 

Hurricane Harvey, a category 4 hurricane on the Saffir-Simpson hurricane wind scale that approached from the Gulf of Mexico, caused severe flooding in Texas and Louisiana. Recorded water levels along the Brazos River exceeded historic high-water levels, and erosion and slope failures of riverbanks were observed in many locations along the river. A near-surface site investigation was conducted in the Brazos River along a short section in Sugarland, Texas, post-Hurricane Harvey. In situ tests were conducted using a portable free fall penetrometer and a chirp sonar. Results showed that sediment properties varied between different locations. Weaker sediments underlying a loose top layer were observed at both riverbanks reaching a penetration depth of ~20 cm, whereas stiffer sediments were found at the center of the river with an estimate of maximum quasi-static bearing capacity ranging from 25 to 300 kPa at sediment depths less than 7 cm. Particle size distributions varied as well depending on the location. Results suggest a correlation between sediment strength and backscatter intensity of the chirp sonar. In summary, in situ geotechnical properties across and along short sections of the Brazos River exhibited a significant variability, likely governed by the local sediment remobilization processes that was reflected in portable free fall penetrometer and chirp sonar measurements of the riverbed surface. 

Phipps Peninsula is a sandy peninsula located near the town of Yakutat, Alaska. In the summer of 2018, a field study was conducted in three areas of the peninsula. All three locations feature complex sediment remobilization processes shaping the local geomorphology. Here, variations in geotechnical properties at the three test sites are investigated. For this purpose, a portable free fall penetrometer (PFFP) was deployed along several transects at the three sites, totaling approximately 750 deployments throughout the course of the study. Since field studies using PFFP on sub-aerial and intertidal beach areas are limited, and results are highly variable, novel methods were implemented for the analysis of the PFFP data. This study represents a first step towards the use of PFFP data to characterize geotechnical properties on sub-aerial and intertidal beaches. Temporal differences in strength are discussed in the context of local physical processes, and spatial variability was related to differences in morphology and hydrodynamics.