Flooding of Sandy Beaches in a Changing Climate. The Case of the Balearic Islands (NW Mediterranean)

The fate of the beaches around the world has paramount importance as they are one of the main assets for touristic activities and act as a natural barrier for coastal protection in front of marine storms. Climate change could put them at risk as sea levels rise and changes in the wave characteristics may dramatically modify their shape. In this work, a new methodology has been developed to determine the flooding of sandy beaches due to changes in sea level and waves. The methodology allows a cost-effective and yet accurate estimation of the wave runup for a wide range of beach equilibrium profiles and for different seagrass coverage. This, combined with regional projections of sea level and wave evolution, has allowed a quantification of the future total water level and coastline retreat for 869 beaches across the Balearic Islands for the next decades as a function of greenhouse gases emission scenario. The most pessimistic scenario (RCP8.5) at the end of the century yields an averaged percentage of flooded area of 66% under mean conditions which increases up to 86% under extreme conditions. Moreover, 72 of the 869 beaches of the region would permanently disappear while 314 would be completely flooded during storm episodes. Under a moderate scenario of emissions (RCP4.5), 37 beaches would permanently disappear while 254 would disappear only during storm episodes. In both cases, the average permanent loss of beach surface at the end of the century would be larger than 50%, rising over 80% during storm conditions. The results obtained for the Balearic Islands can be extrapolated to the rest of the Mediterranean as the beaches in all the regions have similar characteristics and will be affected by similar changes in sea level and wave climate. These projections indicate that adaptation plans for beach areas should be put in place as soon as possible.

Power Enhancement of WEC Array via Wave Runup in Channel

When waves pass through a channel, wave elevation is observed to increase, a phenomenon known as wave runup. Attempts are made to utilize the wave runup along a channel supported on a floating platform to enhance the energy generation from the array of point absorber WECs. Such floating platforms could be integrated into the floating breakwater, floating pier or other floating platforms utilized as floating cities for efficient ocean space utilization. The channel is created by modelling two vertical walls supported on a floating platform with WECs deployed in the channel. The performance of the wave farm in terms of energy generation and interaction factor are assessed. The paper investigates the effect of channel widths and depths on the power absorption of the arrays. A three-stepped floating platform with varying depths along the channel is then studied to obtain optimal depths along the channel where the highest energy is harvested. Thereafter, three arrays of WECs deployed in a larger three-stepped channel floating platform are considered and the effectiveness of such configuration in harvesting energy is assessed. The wave elevation surrounding the wave farm is presented to show the effect the wave runup has on energy generation. The results show that the energy generation of wave energy converters when the arrays are placed in a three-stepped channel floating platform could be increased significantly. A q-factor above 1.0 could be achieved for wave periods greater than 6s and the array can generate greater energy for omnidirectional waves.

Highwater Mark Collection after Post Tropical Storm Dorian and Implications for Prince Edward Island, Canada

Prince Edward Island (PEI), Canada has been experiencing the consequences of a rising sea level and intense storms on its coasts in recent years. The most recent severe event, Post Tropical Storm Dorian (Dorian), began impacting Prince Edward Island on 7 September 2019 and lasted for over 20 h until the morning of 8 September 2019. The measurement of highwater marks (HWM) from the storm was conducted between 25 September and 25 October 2019 using a high precision, survey grade methodology. The HWM measured included vegetation lines, wrack lines, beach, cliff, and dune morphological features, and tide gauge data at 53 locations in the Province along coastal areas that are exposed to high tides, storm surge, high winds, and wave runup. Photos were taken to provide evidence on the nature of the HWM data locations. The data reveal that Dorian caused extensive coastal floods in many areas along the North and South Coast of Prince, Queens and Western Kings Counties of Prince Edward Island. The floods reached elevations in excess of 3.4 m at some locations, posing threats to local infrastructure and causing damage to natural features such as sand dunes in these areas. The HWM data can provide useful information for community and emergency response organizations as plans are developed to cope with the rising sea level and increased frequency of highwater events as predicted by researchers. As Dorian has caused significant damage in several coastal areas in PEI, better planning using an enhanced storm forecasting and coastal flood warning system, in conjunction with flood stage values, could possibly have reduced the impacts of the storm in the impacted areas. This could help enhance public understanding of the potential impacts in local areas and how they can prepare and adapt for these events in the future.

Wave runup and overtopping on smooth-slope NEXC block

Constant wave runup and overtopping during monsoon coupled with storm-surge events have poses threat to the coastal’s community in flooding and land loss. The study was to further the research on the wave interaction issue using the modified NAHRIM Coastal Protection and Expansion (NEXC) block. The aim was to determine the significant relationship prediction model from the experiment variables due to water level changes. The study was conducted in 30 m long, 2 m height, and 1.5 m width of wave flume using gamma 3.30 of wave height JONSWAP spectrum under 1:15 and 1:8 mobile bed scenarios. Parameters were downscaled to 1:10 and based on Peninsular Malaysia’s east coast hydrodynamics conditions. 36 different test scenarios were simulated every 20 minutes with three repetitions, enables 108 samples to be retrieved. Using statistical tools, correlation tests between the variables in the experiment results indicates wave runup, significant wave height and overtopping discharges are strongly correlated to the bed gradient and smooth-slope NEXC block. Changes in water level from shallow to deep, mild to steep mobile bed gradient with 30° to 60° block affect the relationship Hs-q decrease while Ru2%-q positively increase. Overtopping was not directly affected by water level but positively affected on wave runup and negatively to significant wave height. The fitted relationship design model using a General Full Factorial method was verified with 0.338069 of standard error and 98.12 % of R-square. Finally, the significant relationship predictive model was obtained to have 26 interaction terms in the model successful.

Enhanced surf zone and wave runup observations with hovering drone-mounted LiDAR

We demonstrate that a hovering, drone-mounted laser scanner (LiDAR) paired with a survey-grade satellite and inertial positioning system measures the wave transformation across the surf zone and the resulting runup with accuracy almost equal to a stationary truck-mounted terrestrial LiDAR. The drone, a multi-rotor small uncrewed aircraft system (sUAS), provides unobstructed measurements by hovering above the surf zone at 20 m elevation while scanning surfaces along a 150 m-wide cross-shore transect. The drone enables rapid data collection in remote locations where terrestrial scanning may not be possible. Allowing for battery changes, about 17 minutes of scanning data can be acquired every 25 minutes for several hours. Observations were collected with a wide (Hs = 2.2 m) and narrow (Hs = 0.8 m) surf zone, and are validated with traditional land-based survey techniques and an array of buried pressure sensors. Thorough post-processing yields a stable ( = 1.7 cm) back beach topography estimate comparable to the terrestrial LiDAR ( = 0.8 cm). Statistical wave properties and runup values are calculated, as well as bathymetry inversions using a relatively simple nonlinear correction to wave crest phase speed in the surf zone, illustrating the utility of drone-based LiDAR observations for nearshore processes.

Exposure of Loggerhead Sea Turtle Nests to Waves in the Florida Panhandle

Wave wash-over poses a significant threat to sea turtle nests, with sustained exposure to waves potentially resulting in embryonic mortality and altered hatchling locomotor function, size, and sex ratios. Identifying where and under what conditions wave exposure becomes a problem, and deciding what action(s) to take (if any), is a common issue for sea turtle managers. To determine the exposure of sea turtle nests to waves and identify potential impacts to hatchling productivity, we integrated a geographic information system with remote sensing and wave runup modeling across 40 nesting beaches used by the Northern Gulf of Mexico Loggerhead Recovery Unit. Our models indicate that, on average, approximately 50% of the available beach area and 34% of nesting locations per nesting beach face a significant risk of wave exposure, particularly during tropical storms. Field data from beaches in the Florida Panhandle show that 42.3% of all nest locations reported wave exposure, which resulted in a 45% and 46% decline in hatching and emergence success, respectively, relative to their undisturbed counterparts. Historical nesting frequency at each beach and modeled exposure to waves were considered to identify priority locations with high nesting density which either experience low risk of wave exposure, as these are good candidates for protection as refugia for sustained hatchling production, or which have high wave exposure where efforts to reduce impacts are most warranted. Nine beaches in the eastern Florida Panhandle were identified as priority sites for future efforts such as habitat protection or research and development of management strategies. This modeling exercise offers a flexible approach for a threat assessment integration into research and management questions relevant to sea turtle conservation, as well as for other beach species and human uses of the coastal environment.

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.

A global analysis of extreme coastal water levels with implications for potential coastal overtopping

Climate change and anthropogenic pressures are widely expected to exacerbate coastal hazards such as episodic coastal flooding. This study presents global-scale potential coastal overtopping estimates, which account for not only the effects of sea level rise and storm surge, but also for wave runup at exposed open coasts. Here we find that the globally aggregated annual overtopping hours have increased by almost 50% over the last two decades. A first-pass future assessment indicates that globally aggregated annual overtopping hours will accelerate faster than the global mean sea-level rise itself, with a clearly discernible increase occurring around mid-century regardless of climate scenario. Under RCP 8.5, the globally aggregated annual overtopping hours by the end of the 21st-century is projected to be up to 50 times larger compared to present-day. As sea level continues to rise, more regions around the world are projected to become exposed to coastal overtopping.