Maximum Wave Height Research Articles

Freak wave in high-order weakly nonlinear wave evolution with bottom topography change

In deep-water, quasi-resonant four-wave interaction gives rise to the occurrence probability of extreme wave height, which leads to freak wave as a natural disaster. As water wave enters shallow water, four-wave interaction becomes weak and wave shoaling makes this effect become complicated. This study conducts a Monte Carlo simulation in modified Nonlinear Schrödinger equation considering bottom topography change, and gives spatial evolution of high-order nonlinearity in wave train from statistical moment. The result indicates, slope angle plays an important role in a shallow water depth, and steep slope brings about a significant enhancement of extreme event in distribution of maximum wave height and surface elevation.

\u201cGrey swan\u201d storm surges pose a greater coastal flood hazard than climate change

In this paper, we show that over the next few decades, the natural variability of mid-latitude storm systems is likely to be a more important driver of coastal extreme sea levels than either mean sea level rise or climatically induced changes to storminess. Due to their episodic nature, the variability of local sea level response, and our short observational record, understanding the natural variability of storm surges is at least as important as understanding projected long-term mean sea level changes due to global warming. Using the December 2013 North Atlantic Storm Xaver as a baseline, we used a meteorological forecast modification tool to create “grey swan” events, whilst maintaining key physical properties of the storm system. Here we define “grey swan” to mean an event which is expected on the grounds of natural variability but is not within the observational record. For each of these synthesised storm events, we simulated storm tides and waves in the North Sea using hydrodynamic models that are routinely used in operational forecasting systems. The grey swan storms produced storm surges that were consistently higher than those experienced during the December 2013 event at all analysed tide gauge locations along the UK east coast. The additional storm surge elevations obtained in our simulations are comparable to high-end projected mean sea level rises for the year 2100 for the European coastline. Our results indicate strongly that mid-latitude storms, capable of generating more extreme storm surges and waves than ever observed, are likely due to natural variability. We confirmed previous observations that more extreme storm surges in semi-enclosed basins can be caused by slowing down the speed of movement of the storm, and we provide a novel explanation in terms of slower storm propagation allowing the dynamical response to approach equilibrium. We did not find any significant changes to maximum wave heights at the coast, with changes largely confined to deeper water. Many other regions of the world experience storm surges driven by mid-latitude weather systems. Our approach could therefore be adopted more widely to identify physically plausible, low probability, potentially catastrophic coastal flood events and to assist with major incident planning.

A Comparison of Soft Computing Methods for the Prediction of Wave Height Parameters

In the previous studies on the prediction of wave height parameters, only the significant wave height has been considered as the unknown parameter to be predicted. However, the other wave height parameters, which may be required for the design of coastal structures depending on their importance level, have been neglected. Therefore, in this study, novel soft computing methods were used to predict all wave height parameters required for the design of coastal structures. To this end, wave data were derived from a buoy located in Southwest Black Sea Coast. Then, Multi-layer Perceptron Neural Network (MLPNN) and Adaptive-Neuro Fuzzy Inference System (ANFIS) models were developed to predict wave height parameters. Various input combinations were selected to create seven different sub-models. These sub-models were applied using developed MLPNN and ANFIS models. Accuracy of sub-models were evaluated for each wave height parameters in terms of performance evaluation criteria. The results showed that the wave height parameters predicted by the MLPNN and ANFIS methods are similar and both methods yield results acceptable for design purposes. However, for maximum wave height, Hmax, ANFIS sub-model yields slightly better results.

Site-specific deterministic and probabilistic tsunami hazard assessment for Diba-Oman and Diba-Al-Emirates

Destructive tsunamis were reported in the Oman Sea after large earthquakes. The Northern Sultanate of Oman and United Arab Emirates (UAE) were subjected to two confirmed tsunamis on 27 November 1945, caused by an Mw 8.1 earthquake in Makran subduction zone, and on 24 September 2013 following the Mw 7.7 Baluchistan earthquake. In this study, deterministic and probabilistic tsunami hazard assessments are performed for the coasts of Diba-Oman and Diba-UAE, which are located on the western coast of the Oman Sea. The tsunami risk of these coasts increases due to the construction of many infrastructures and urban concentration in these localities. The study focuses on earthquake-induced tsunamis, thus requiring the estimation of the maximum credible earthquake. The generation area is the Makran subduction zone, which is divided herein into EMSZ (East Makran subduction zone) and WMSZ (West Makran subduction zone). The maximum credible earthquakes of Mw 8.8 for the EMSZ and Mw 7.2 for the WMSZ are utilized as specific scenarios for the deterministic approach. The Mw 8.8 EMSZ scenario results in a maximum tsunami inundation distance of more than 300 m. Maximum inundation distance larger than 300 m occurs due to the Mw 7.2 western MSZ scenario. For these scenarios, numerical simulations show a maximum flow depth exceeding 1.75 m. The probabilistic hazard assessment utilizes the logic tree approach to estimate the probability of exceedance of 0.25, 0.5, 0.75, and 1.0 m wave height in 100 and 500 years exposure times. This analysis indicates that the likelihood that a maximum wave height exceeds 0.5 m ranges from 10 to 40% in 100 years and from 30 to 80% in 500 years.

Seasonal to decadal scale shoreline changes along the Cameroonian coastline, Bay of Bonny (1986 to 2020)

The Bay of Bonny, located along the Cameroon coastline, is home to diverse ecosystems. It is under significant pressure from large human activity, but remains very little studied, like much of the Gulf of Guinea. In order to understand its long-term shoreline variations and the role the wave regime plays in the evolution of the coastline, a study was conducted on the basis of optical image archives from Landsat 5∕7∕8 and Sentinel-2A/2B satellite missions acquired between October 1986 and May 2020, coupled with daily ERA-Interim wave re-analysis data covering the period from January 1986 to August 2019. Overall, the results show that the evolution of the coast is highly variable in space and time, as indicated by different levels of erosion (30.55 %), and accretion (27.7 %) on the decadal-scale, with the most significant variations occurring in estuarine areas. Nevertheless, 41.75% of the Cameroon shoreline remains stable during the study period. Three main periods (1986–1994; 1995–2005; 2006–2020) during which the coast underwent significant changes a different location were identified, reaching a retreat rate of up to −10 m/year in the northern section during the first period 1986–1994. The annual trend of significant wave heights anomaly along the coast (−5.6 to −4.1 mm/year) with wave height maxima estimated at 1.46 ± 0.65 m, where observed during the summer months (July–August). Monthly shoreline changes are inversely correlated with wave climate in some segments. Eigenvalue orthogonal decomposition analyses (Mode 1, Empirical Orthogonal Function) show that 76.3% of the observed variability would be due to the relatively strong local influence of erosion and accretion. This local influence can be related to wave regime at shorter timescale (monthly to seasonal) and the sediment variability from the source inland to the coast at longer timescale (seasonal to decadal). These observations explain a complex pattern of shoreline changes with an almost continuous retreat shoreline during the period 1986–2013 and a reversal in trend towards accretion during the period 2013–2020. EOF mode 2 explains 23.7% of variability, which can be potentially associated with the synergetic relationship between tidal currents and wave-induced longshore current, tidal currents and possibly pockets of human activity. This is attributed to an overall decrease in the supply of sediment via the coastal transport system that prevails in the Gulf of Guinea.

Distribution characteristics of waves in Sanmen Bay based on field observation

The wave characteristics in the nearshore waters of Sanmen Bay are presented based on the AWAC-measured data from October 2016 to September 2017 at the wave observation station with 7.5m water depth. The wave parameters and the wave spectral variations are statistically analyzed, and the wave height distribution, the wave period distribution, and the joint distribution of wave height and period are discussed. The results indicate that the measured distribution of wave height agrees well with the Weibull distribution. When the spectral width is small, the various theoretical distribution models of wave period have their own reference values for the study of the distribution of measured wave period. The measured distribution of wave period has the best agreement with the Weibull distribution when the spectral width is large. The Longuet-Higgins model (1983) and the Sunfu model can be fitted to the joint distribution of wave height and period in this sea area, but the fitting effect is poor. The dominant wave direction and the strong wave direction are both E, with a frequency value of 40.27%. The maximum wave height (Hmax) of 2.71m was observed during the observation period due to the influence of typhoon Talim.

Response of ocean surface waves to the co‐occurrence of Boreal Summer Intra-Seasonal Oscillation and El Niño Southern Oscillation

Studies related to the combined effect of different atmospheric oscillations on the ocean surface waves are limited. The present study focuses on the change in wave climatology due to the combined effect of Boreal Summer Intra-Seasonal Oscillation (BSISO) and El Nino Southern Oscillation (ENSO) using 40 years of reanalysis data on the Asian Summer Monsoon Region (ASMR). Composite analysis of surface wind, significant wave height, wind-sea, swell and mean wave period are analysed corresponding to different ENSO–BSISO phase combinations. The study showed noteworthy differences in wave parameters when ENSO–BSISO phases are analysed together. In El Nino–BSISO combined phase, enhancement of north-easterly wind causes the advancement in the reversal of wind direction (north-easterly to monsoon enhanced south-westerly) and disrupted propagation of positive wind and wave anomalies. Conversely, during La Nina–BSISO co-occurrence, south-westerlies are enhanced and as a result, the negative north-easterly anomalies are disrupted. In all the ENSO–BSISO combined phases, maximum wave height variability occurs at the South China Sea owing to the combined action of the north Indian Ocean (NIO) and Western North Pacific (WNP) surface wind forcing. High fluctuations in Tm over the NIO and WNP are observed during different ENSO–BSISO phase combinations. The phase relationship of Hs with Tm and the significant height of wind-sea (Hsw) and swell (Hss) are assessed to understand the propagation of swells. Due to the effect of multiple atmospheric perturbations, significant changes in Hs occur over the coastal regions of the NIO.

Coastal Wetlands Exposure to Storm Surge and Waves in the Albemarle-Pamlico Estuarine System during Extreme Events

Coastal wetlands provide a series of ecosystem services, including flood risk reduction. However, the flood risk reduction from such a complex ecosystem is dependent on incoming extreme hurricane-driven hydrodynamic and wave conditions. This study develops a numerical modeling-based approach for investigating coastal wetlands exposure to storm surge and waves during hurricanes by combining maximum water depth (MWD) and significant wave height (MHs) model outputs with the National Wetland Inventory for the Albemarle-Pamlico Estuarine System. Results show that various hurricanes lead to similar bimodal and bidirectional spatiotemporal flood patterns as a function of the lagoon’s geometry and storm track, with most overland hydrodynamic extremes impacting western Pamlico Sound and the bayside-Outer Banks. Clear positive dependency between MWD and MHS were observed over most wetland classes, with significantly higher magnitudes over estuarine emergent vegetation. In contrast to MWD, sharp MHS attenuation was found as the water propagates inland, leading to high MWD but lower MHS eventually reaching palustrine woody vegetation hundreds of meters away from the coastline. Improved understanding of how storm surge dynamics move across the bays and through the different wetland types, demonstrates the importance of considering the bay-side flood impacts over the coastal vegetation. The spatially distributed MWD and MHS estimates, along with the temporal patterns identified through the use of the TMax, allow coastal managers and engineers to better understand where, when, and by how much, the estuarine APES wetlands are more likely to be exposed to high water depths and waves.

PEMBANGKIT LISTRIK TENAGA GELOMBANG LAUT DENGAN MENGGUNAKAN TEKNOLOGI OSCILATING WATER COLUMN (OWC) DI PERAIRAN MARANA

The alternatives to overcome electricity shortage in Indonesia is wave generating. One of the methods conducted in this research is OWC (Oscilating Water Column) based on study area criteria (Marana Village). OWC method can convert ocean wave energy atwave columnoscillationto generate electricity. To be able to produce electricity, this OWC device will train the wave energy through the OWC door hole. This research determine the amount of waves that can be utilized in Marana waters to be converted into units of electricity (watts). The amount of wave height that can be used, depends on the amount of wind that is in the waters of Marana. In addition to wave height, tidal is also needed to know the placement of Oscilating Water Column (OWC) is so that when the tidal water occurs, OWC is still in the condition of the wave. In addition, the bathymetry of the sea is also needed to know at the depth of how placed this OWC. Based on the results obtained from wave forecasting using the 2002-2006 wind data obtained maximum wave height for 5 years is 0.204 m in Year 2003. Which can generate electricity of 0.688 watts. Where from concluded in Marana waters do not have the potential to build Sea Wave Power Plant.

Characteristics of Sea Waves Condition at The Northern and Eastern of Bintan Island within Period of 2015-2019

The objective of this research was to collect the comprehensive information about the characteristics of sea waves in the northern and eastern of Bintan Island Sea based on differentiation in oceanographic conditions between the north and east coast of Bintan Island. The north coast of Bintan Island faces the open seas directly with a potential high wave and cause several characters of coastal damage, including coastal abrasion. The characteristics of sea waves are obtained by forecasting, namely converting wind speed values using the SPM (Shore Protection Manual) method. The results of this study collected comprehensive information of sea waves on the north coast during the 2015-2019 period showed a dominant pattern with the direction of sea wave propagation from north and south, while for the eastern region the wave propagation trends prevailing from north and southeast. The maximum sea wave height in the northern of Bintan Island Sea reaches 3.32 m with a period of 8.70 s while in the eastern of Bintan Island Sea the maximum of wave height condition reaches 2.90 m with a period of 8.32 s. The maximum sea wave conditions on the north and east coasts of Bintan Island occur during the north wind season (December-February) and is directly proportional to the requirements of higher wind speeds. The minimum sea wave conditions occur during the east monsoon (March-May) where during that period the wind speeds that blow are very low condition. The results of this study indicate that wind speeds in northern Bintan Island are related to wave conditions. Our research proves that higher wind speeds form higher wave conditions.

Thirty-Nine-Year Wave Hindcast, Storm Activity, and Probability Analysis of Storm Waves in the Kara Sea, Russia

The recurrence of extreme wind waves in the Kara Sea strongly influences the Arctic climate change. The period 2000–2010 is characterized by significant climate warming, a reduction of the sea ice in the Arctic. The main motivation of this research to assess the impact of climate change on storm activity over the past 39 years in the Kara Sea. The paper presents the analysis of wave climate and storm activity in the Kara Sea based on the results of numerical modeling. A wave model WAVEWATCH III is used to reconstruct wind wave fields for the period from 1979 to 2017. The maximum significant wave height (SWH) for the whole period amounts to 9.9 m. The average long-term SWH for the ice-free period does not exceed 1.3 m. A significant linear trend shows an increase in the storm wave frequency for the period from 1979 to 2017. It is shown that trends in the storm activity of the Kara Sea are primarily regulated by the ice. Analysis of the extreme storm events showed that the Pareto distribution is in the best agreement with the data. However, the extreme events with an SWH more than 6‒7 m deviate from the Pareto distribution.

Extreme Wind and Waves in U.S. East Coast Offshore Wind Energy Lease Areas

The Outer Continental Shelf along the U.S. east coast exhibits abundant wind resources and is now a geographic focus for offshore wind deployments. This analysis derives and presents expected extreme wind and wave conditions for the sixteen lease areas that are currently being developed. Using the homogeneous ERA5 reanalysis dataset it is shown that the fifty-year return period wind speed (U50) at 100 m a.s.l. in the lease areas ranges from 29.2 to 39.7 ms−1. After applying corrections to account for spectral smoothing and averaging period, the associated pseudo-point U50 estimates are 34 to 46 ms−1. The derived uncertainty in U50 estimates due to different distributional fitting is smaller than the uncertainty associated with under-sampling of the interannual variability in annual maximum wind speeds. It is shown that, in the northern lease areas, annual maximum wind speeds are generally associated with intense extratropical cyclones rather than cyclones of tropical origin. Extreme wave statistics are also presented and indicate that the 50-year return period maximum wave height may substantially exceed 15 m. From this analysis, there is evidence that annual maximum wind speeds and waves frequently derive from the same cyclone source and often occur within a 6 h time interval.

Extreme waves induced by cyclone Nargis at Myanmar coast: numerical modeling versus satellite observations

The deltaic coast of Myanmar was severely hit by tropical cyclone Nargis in May 2008. In the present study, a top-down numerical simulation approach using the Weather Research and Forecasting (WRF) and Simulating WAves Nearshore (SWAN) models was conducted to study the meteorological and offshore wave characteristics of cyclone Nargis near the coast of Myanmar. The WRF simulation results agree well with the observed data from the India Meteorological Department. SWAN simulation results were compared with the WaveWatch 3 model by National Oceanic and Atmospheric Administration and validated against available measurement data from satellites. The model results show relatively good agreement, and hindcast with satellites data (significant wave height only) shows a correlation coefficient value of 0.89. The SWAN and satellite comparisons also show better fit for high wave conditions. The resulted maximum significant wave height of 7.3 m by SWAN is considerably higher in energy than the seasonal waves normally prevalent at Myanmar’s deltaic coast. The possibility of high energy waves due to cyclones should be considered during the design and operation of coastal and offshore projects in the area, particularly given the risks that climate change can intensify cyclones in the future. Since Myanmar lacks a dense network of in-situ observational stations, the methodology used in the current study presents the potential application of various numerical techniques and satellite data to estimate extreme wave conditions near the Myanmar coast.

Time-Dependent Tsunami Source Following the 2018 Anak Krakatau Volcano Eruption Inferred from Nearby Tsunami Recordings

The eruption of the Anak Krakatau volcano, Indonesia, on 22 December 2018 induced a destructive tsunami (the Sunda Strait tsunami), which was recorded by four nearby tidal gauges. In this study we invert the tsunami records and recover the tsunami generation process. Two tsunami sources are obtained, a static one of instant initial water elevation and a time-dependent one accounting for the continuous evolution of water height. The time-dependent results are found to reproduce the tsunami recordings more satisfactorily. The complete tsunami generation process lasts approximately 9 min and features a two-stage evolution with similar intensity. Each stage lasts about 3.5 min and elevates a water volume of about 0.13 km3. The time, duration and volume of the volcano eruption in general agree with seismic records and geomorphological interpretations. We also test different sizes of the potential source region, which lead to different maximum wave height in the source area, but all the results of time-dependent tsunami sources show the robust feature of two stages of wave generation. Our results imply a time-dependent and complex process of tsunami generation during the volcano eruption.

Otsenki amplitudnykh kharakteristik nakata voln tsunami na razlichnykh uchastkakh Chernomorskogo poberezh'ya

This paper is devoted to computational modelling of tsunami wave propagation and runup to the shore for some points on the Russian, Turkish, Bulgarian and Ukrainian coasts of the Black Sea. The nonlinear long wave model was used to solve the problem of wave propagation from hydrodynamic tsunami sources, which can constitute the greatest potential danger for the studied coast areas. The hydrodynamic sources were set in the form of an elliptical elevation, the parameters of which were chosen according to the sea level response to an underwater earthquake of magnitude 7. All the sources were located in seismically active areas, where tsunamigenic earthquakes had already occurred, along the 1500 m isobath. Near each of the studied points in the area above 300 m depths, we calculated marigrams, i.e. time-series of sea level fluctuations caused by the passage of waves. Then, a one-dimensional problem of tsunami propagation and run-up on the coast was solved for each of the points under study, where the obtained marigrams were used as boundary conditions. Peculiarities of tsunami wave propagation have been shown depending on the bottom and land relief in the studied areas of the Black Sea. Estimates have been obtained of the sea level maximum rise and fall during surge and subsequent coastal drainage for the characteristic scales of relief irregularity at different points. For possible tsunamigenic earthquakes, the largest splashes may occur in the region of Yalta (2.15 m), Cide (1.9 m), Sevastopol (1.4 m), and Anapa (1.4 m). Tsunami propagation in the Feodosiya and Varna coastal areas is qualitatively similar, with maximum wave heights of 0.64 m and 0.46 m, respectively. The coastlines of Evpatoriya (0.33 m) and Odessa (0.26 m) are least affected by tsunami waves due to the extended shelf.

FPGA Based Tsunami Wave Propagation Calculator

The authors continue to use hardware acceleration to calculate tsunami wave propagation in a few seconds at modern PC. The goal of this work is to develop original implementation the FPGA-based algorithm for nested-grids computations of tsunami wave propagation. The FPGA-based Calculator, for regular grid has been proposed and numerically tested earlier. Use of the nested grid approach makes it possible to calculate wave propagation almost until the shore line. Numerical tests are based on the real digital bathymetry at southern part of Japan. Mesh step variation of the gird is from 180 m to just 7 m. Realistic shape of the initial sea surface displacement at tsunami source was used. The detailed distribution of wave height maxima around and inside the Onahama port have been issued as a result of tsunami generated by a model source located along the Japan deep-water trench. The superfast FPGA calculator provides an opportunity to obtain the calculated wave parameters inside ports and harbours even before arrival of tsunami wave.

Observation of infragravity wave processes near the coastal cliffs of Chabahar (Gulf of Oman)

This study analyzed the characteristics of infragravity waves (hereafter IGWs) based on field observations collected near the plunging cliffs of Chabahar bay, Iran. Observations were made near Chabahar city during the summer monsoon season of 2018. The wave climate included two different durations of sea and swell predominance, with a maximum wave height reaching 2.5 m. Concurrent with the duration of the sea predominance, the ratio of IGW to swell wave height had an insensitive fluctuation against tidal variations, while this ratio had a strong negative correlation with tidal level during the high swell condition. The investigation of directional wave energy distribution revealed two correlated trends of shoreward and seaward IGWs with the wave regime.Larger values of the IGW reflection coefficients were observed during high sea wave conditions compared with high swell conditions. The IGW reflection coefficients decreased against swell energy growth with a logarithmic trend. The bound IGW energy fraction was studied using bispectral analysis. It is demonstrated that the maximum values of this parameter corresponded to high swell waves observed within low ebbs of the spring tide. The insignificant values of bound IGW energy fraction and the non-extended surf-zone revealed that most of the released IGWs originated from offshore and intermediate water depths. In addition, it was revealed that the inverse tidal trend of normalized IGW by swell height was due to bound IGW enhancement during ebb periods as a result of the nonlinear coupling of swell waves.

North Sea Infragravity Wave Observations

Coastal safety assessments with wave-resolving storm impact models require a proper offshore description for the incoming infragravity (IG) waves. This boundary condition is generally obtained by assuming a local equilibrium between the directionally-spread incident sea-swell wave forcing and the bound IG waves. The contribution of the free incident IG waves is thus ignored. Here, in-situ observations of IG waves with wave periods between 100 s and 200 s at three measurement stations in the North Sea in water depths of O(30) m are analyzed to explore the potential contribution of the free and bound IG waves to the total IG wave height for the period from 2010 to 2018. The bound IG wave height is computed with the equilibrium theory of Hasselmann using the measured frequency-directional sea-swell spectra as input. The largest IG waves are observed in the open sea with a maximum significant IG wave height of O(0.3) m at 32 m water depth during storm Xaver (December 2013) with a concurrent significant sea-swell wave height in excess of 9 m. Along the northern part of the Dutch coast, this maximum has reduced to O(0.2) m at a water depth of 28 m with a significant sea-swell wave height of 7 m and to O(0.1) m at the most southern location at a water depth of 34 m with a significant sea-swell wave height of 5 m. These appreciable IG wave heights in O(30) m water depth represent a lower bound for the expected maximum IG wave heights given the fact that in the present analysis only a fraction of the full IG frequency range is considered. Comparisons with the predicted bound IG waves show that these can contribute substantially to the observed total IG wave height during storm conditions. The ratio between the predicted bound- and observed total IG variance ranges from 10% to 100% depending on the location of the observations and the timing during the storm. The ratio is typically high at the peak of the storm and is lower at both the onset and waning of the storm. There is significant spatial variability in this ratio between the stations. It is shown that differences in the directional spreading can play a significant role in this. Furthermore, the observed variability along the Dutch coast, with a substantially decreased contribution of the bound IG waves in the south compared to the northern part of the Dutch coast, are shown to be partly related to changes in the mean sea-swell wave period. For the southern part of the Dutch coast this corresponds to an increased difference with the typically assumed equilibrium boundary condition although it is not clear how much of the free IG-energy is onshore directed barring more sophisticated observations and/or modeling.

Investigation on abnormal wave dynamics in regular and irregular sea states

Peregrine breather solution of the nonlinear Schrödinger (NLS) equation can be treated as one of the excellent backbone models for abnormal wave in the ocean. Fully nonlinear numerical simulations performed with the higher-order spectral method reveal that its maximum amplification factor can be larger than the theoretical prediction in the regular background wave and that such breather dynamics has a high probability to persist even in a chaotic environment. Evidently, in both cases the maximum wave height attainable and the corresponding spatial evolutionary distance required are significantly affected by the initial background waves. In fact, whether the abnormal wave induced by breather dynamics can be generated, is mainly a localized behaviour, strongly dependent on the initial wave group energy as well as the detailed structure of this group.

Correction to: Seed Burial Alleviates Wave Energy Constraints on Zostera marina (Eelgrass) Seedling Establishment at Restoration-Relevant Scales

Bottlenecks for successful seedling establishment can be both biotic and abiotic, and understanding the contribution of these processes is important in restoration efforts in order to optimize use of limited seed supplies. Here we describe the results of 2 years of experiments assessing mechanisms for burial of Zostera marina (eelgrass) seeds in restoration-scale plots, and evaluating the resulting initial seedling success (establishment of seedlings 5 months after planting) relative to the achieved burial depths. The experiments were conducted at 6 sites in the lower Chesapeake Bay with a range of potential wave exposures, and the wave climate was assessed using WEMo, a hydrodynamic wave model. For linear experimental plots (7–50 m long) planted in 2009 and 2010 and evaluated in April 2010 and 2011, seed planting significantly increased initial seedling success relative to broadcast seeds. Sediment disturbance experiments conducted in both years showed disruption of surface sediments typically extended to a depth of 3 cm, with substantial variation among sites, suggesting seeds buried shallower than 3 cm could experience high losses from being washed out. Relative Wave Exposure values calculated by a wave forecasting software (WEMo) using wind data for the two experimental periods were not consistently correlated with seedling performance for either broadcast or planted seeds, likely as a result of difficulty in down-scaling the model with spatially coarse data. However, in many cases, high seedling success was seen at sites with low maximum wave heights. Overall, the results illustrate the important role that burial depth may play in eelgrass seedling establishment and show promise for increasing the initial success of seed-based restoration efforts.