Wave Runup for Nowshahr Breakwater at Tide and EBB Scenarios

This study investigates runup design at breakwaters and design criteria under tidal and ebb scenarios for both head and truck of Nowshahr breakwater. First part includes runup height calculations based on shore protection manuals. Based of wave height, frequency, and water depth at the toe runup height has been calculated and Second portion has been dedicated to design of head and truck of Nowshahr port based on Hudson stability formula. Collision of wave and the breakwater head, results in immediate reduction in wave energy. As wave energy propagated gradually decreases when it meets the trunk. The results showed that in both conditions weight of head would be higher than the trunk of breakwater. while, both head and trunk are designed based on high strength materials, but the head has higher degree of importance in terms of design criteria. Hudson formula is responsible for the stability of breakwater structure. Tidal case which considers a non-breaking wave as well as ebb scenario including a breaking wave has been studied to include two extreme conditions occurs to breakwaters. The results showed the higher weight of head is responsible for stability of breakwater at both conditions.

Simulating Destructive and Constructive Morphodynamic Processes in Steep Beaches

Short-term beach morphodynamics are typically modelled solely through storm-induced erosion, disregarding post-storm recovery. Yet, the full cycle of beach profile response is critical to simulating and understanding morphodynamics over longer temporal scales. The XBeach model is calibrated using topographic profiles from a reflective beach (Faro Beach, in S. Portugal) during and after the incidence of a fierce storm (Emma) that impacted the area in early 2018. Recovery in all three profiles showed rapid steepening of the beachface and significant recovery of eroded volumes (68–92%) within 45 days after the storm, while berm heights reached 4.5–5 m. Two calibration parameters were used (facua and bermslope), considering two sets of values, one for erosive (Hm0 ≥ 3 m) and one for accretive (Hm0 < 3 m) conditions. A correction of the runup height underestimation by the model in surfbeat mode was necessary to reproduce the measured berm elevation and morphology during recovery. Simulated profiles effectively capture storm erosion, but also berm growth and gradual recovery of the profiles, showing good skill in all three profiles and recovery phases. These experiments will be the basis to formulate event-scale simulations using schematized wave forcing that will allow to calibrate the model for longer-term changes.

Arctic tsunamis threaten coastal landscapes and communities – survey of Karrat Isfjord 2017 tsunami effects in Nuugaatsiaq, western Greenland

On the 17 June 2017, a massive landslide which mobilized 35–58 million m3 of material entered the Karrat Isfjord in western Greenland. It triggered a tsunami wave with a runup height exceeding 90 m close to the landslide, ca. 50 m on the opposite shore of the fjord. The tsunami travelled ca. 32 km along the fjord and reached the settlement of Nuugaatsiaq with ca. 1–1.5 m high waves which flooded the terrain up to 9 m a.s.l. (above sea level). Tsunami waves were powerful enough to destroy the community infrastructure, impact fragile coastal tundra landscape, and unfortunately injure several inhabitants and cause four deaths. Our field survey carried out 25 months after the event results in documentation of the previously unreported scale of damage in the settlement (ca. 48 % of infrastructure objects including houses and administration buildings were destroyed by the tsunami). We have observed a recognizable difference in the concentration of tsunami deposit accumulations between areas of the settlement overwashed by the wave and areas of runup and return flow. The key tsunami effects preserved in the coastal landscape were eroded coastal bluffs, gullied and dissected edges of cliffed coast in the harbour, and tundra vegetation compressed by boulders or icebergs rafted onshore during the event.

Runup of long waves on composite coastal slopes: numerical simulations and experiment

&lt;p&gt;The goal of this study is to investigate the effect of the bottom shape on wave runup. The obtained results have been confronted with available analytical predictions and a dedicated numerical simulation campaign has been carried out by the team. We study long wave runup on composite coastal profiles. Two types of beach profiles are considered. The Coastal Slope 1 consists of two merged plane beaches with lengths 1.2 m and 5 m and beach slopes tan &amp;#945; = 1:10 and tan &amp;#946; = 1:15 respectively. The Coastal Slope 2 also consists of two sections: plane beach with length 1.2 m and a beach slope &amp;#945;, which is merged with a convex (non-reflecting) beach. The latter is constructed in the way, that its total height and length remain the same as for the Coastal Slope 1.&lt;/p&gt;&lt;p&gt;The study is conducted with numerical (in silico) and experimental approaches.&lt;/p&gt;&lt;p&gt;Experiments have been conducted in the hydrodynamic flume of the Nizhny Novgorod State Technical University n.a. R.E. Alekseev. Both composite beach profiles were constructed in 2019. The Coastal Slope 1 consists of three parts made of aluminum. The plain beach part of the Coastal Slope 2 is also made of aluminum, and the convex profile consists of two parts made of curved PLEXIGLAS organic glass. The water surface oscillations are measured using capacitive and resistive wave gauges with recording frequencies of up to 80 Hz and 100 Hz respectively. Wave runup is measured by a capacitive string sensor installed along the slope.&lt;/p&gt;&lt;p&gt;A series of experiments on the generation and runup of regular wave trains with a period of 1s, 2s, 3s and 4s were carried out. The water level was kept constant for all experiments and was equal to 0.3 meters. Up to now, 21 experiments have been carried out (10 and 11 experiments for each Coastal Slope respectively).&lt;/p&gt;&lt;p&gt;A comparative numerical study is carried out in the framework of the nonlinear shallow water theory and the dispersive theory in the Boussinesq approximation.&lt;/p&gt;&lt;p&gt;As a result, we compare the long wave dynamics on these two bottom profiles and discuss the influence of nonlinearity and dispersion on the characteristics of wave runup. It is shown numerically that, in the framework of the nonlinear shallow water theory, the runup height on the Coastal Slope 2 tends to exceed the corresponding runup height on the Coastal Slope 1, that also agrees with our previous results (Didenkulova et al. 2009; Didenkulova et al. 2018). Taking dispersion into account leads to an increase in the spread in values of the wave runup height. As a consequence, individual cases when the runup height on the Coastal Slope 1 is higher than on the Coastal Slope 2 have been observed. In experimental data, such cases occur more often, so that the advantage of one slope over another is no longer obvious. Note also that the most nonlinear breaking waves with a period of 1s have a greater runup height on Coastal Slope 2 for both models and most experimental data.&lt;/p&gt;

Tsunamis unleashed by rapidly warming Arctic degrade coastal landscapes and communities – case study of Nuugaatsiaq, western Greenland

On the 17th of June 2017, a massive landslide which mobilized ca. 35–58 million m3 of material entered the Karrat Fjord in western Greenland. It triggered a tsunami wave with a runup height exceeding 90 m close to the landslide, ca. 50 m on the opposite shore of the fjord. The tsunami travelled ca. 32 km across the fjord and reached the settlement of Nuugaatsiaq with ca. 1–1.5 m high waves, which were powerful enough to destroy the community infrastructure, impact fragile coastal tundra landscape, and unfortunately, injure several inhabitants and cause 4 deaths. Here we report the results of the field survey of the surroundings of the settlement focused on the perseverance of infrastructure and landscape damages caused by the tsunami, carried out 25 months after the event.

Froude characterization for unsteady single-surge dry granular flows: impact pressure and runup height

The impact and pileup mechanisms of unsteady granular flows impacting a rigid barrier are governed by the Froude conditions (Fr). Velocity and depth vary along the length of the flow. There is currently no widely accepted approach for characterizing Fr for impact and runup problems. In this study, a discrete element method (DEM) model was calibrated against a physical flume test. Eighty-six simulations were performed using the DEM model to investigate the equivalent Fr governing pileup height and impact pressure for unsteady single-surge dry granular flows against a rigid barrier. Fr and the grain diameter were varied. Results reveal that Fr within the frontmost 5% of a flow governs both pileup height and impact pressure. Thus, taking frontal velocity and maximum flow depth within the frontmost region is crucial for properly characterizing the runup height and impact load. Consistent characterization of Fr is possible near the longitudinal centre of a flow; the frontmost Fr can then be extrapolated from calibration curves. Results imply that existing studies that predict impact pressure based on nonfrontal Fr values may underestimate impact pressure by a factor of up to 2.

Runup, Inundation, and Sediment Characteristics of 22 December 2018 Indonesia Sunda Strait Tsunami

A tsunami caused by a flank collapse of the southwest part of the Anak Krakatau volcano occurred on 22 December 2018. The affected area of the tsunami included a coastal area located at the edge of Sunda Strait, Indonesia. To gain an understanding of the tsunami event, field surveys were conducted a month after the incident. The surveys included measurements of runup height, inundation distance, tsunami direction, and sediment characteristics at 20 selected sites. The survey results revealed that the runup height and inundation distance reached 7.8 m and 292.2 m, both was found at Site Cagar Alam, part of Ujung Kulon National Park. Tsunami propagated radially from its source and arrived in coastal zone with direction was between 25° and 350° from North. Sediment samples were collected at 27 points in tsunami deposits with a sediment thickness of 1.5–12 cm. The distance of the sediment deposit area from the coast was 40 %–90 % of the distance of the inundation caused by the tsunami. The highest elevation of deposits was 60 %–90 % of the highest runup. Sand sheets were sporadic, highly variable, and highly influenced by topography. Grain sizes in the deposit area were finer than those at their sources. The sizes ranged from fine sand to boulders, with medium sand and coarse sand being dominant. All sediment samples had a well sorted distribution. An assessment of the boulder movements indicates that the tsunami runup had minimum velocities of 4.0–4.5 m/s.