Figure 2 - uploaded by Mark Douglas Spalding
Content may be subject to copyright.
The movement of water within a wave. (a) Circular oscillatory motion when the wave is not depth-limited. (b) Elliptical oscillatory motion in a wave which is depth-limited. Adapted from Anderson et al. (2011).
Contexts in source publication
Context 1
... propagate energy, rather than water, across space. While the water itself moves orbitally (Fig. 2), the waves propagate horizontally, carrying wave energy with them. The energy of a monochromatic wave is related to the square of its ...
Context 2
... slowed down more than successive crests until at some point, the waves break onto the shore, dissipating the energy in the wave. Waves become depth-limited when the depth of the water is approximately half the wavelength of the wave. At this point, the oscillatory motion of the water changes from circular oscillations to elliptical oscillations (Fig. ...
Citations
... Hence, a revisit and/or reorientation of the current efforts in managing Manila Bay and its environs should be an urgent matter. We know that the presence of mangroves may attenuate 13 to 66 percent of swell waves over 100 m of this coastal forest (McIvor et al. 2012). This means that a focus on restoring even just a kilometer belt (i.e., ca. 5% of the 20 km stretch) of mangroves along the northern coastline of the bay should result in a significant bio-shielding effect, attenuating waves and filtering disastrous debris that may also go with storm surges. ...
Manila Bay is plagued by various environmental challenges. This chapter revisits the changes in mangrove occurrence and distribution relative to the spatio-temporal changes and history of the 200 km coastline of the entire Manila Bay. Using topographic maps, brackish water ponds, and toponyms, we found that about 75,000 to 90,000 hectares of mangroves apparently existed in the 1900s, comprising ca. 10 percent of the river basin. At present, only barely 1 percent (<1,000 ha) is left, reflecting massive deforestation largely due to conversion into brackish water fishponds, salt pans, and rice paddies as well as development into residential and industrial settlements. Knowing the bay’s history, it is imperative to protect the ecological integrity of Manila Bay and to restore former mangrove areas as the government moves forward in its rehabilitation programs, projects, and activities. The Manila Bay story seems to be a microcosm of national and global significance, exemplifying how we deal with development projects which transform our coastal ecosystems into other uses. We stress the need for more environmental scientists looking through broader spatio-temporal lenses in our work toward conserving the Philippine coastal ecosystems. This chapter discusses specific policy recommendations in setting a clear rehabilitation roadmap for Manila Bay Coastal Ecosystems considering present and projected climate scenarios.
... Mangrove forests are tropical and sub-tropical coastal ecosystems that reduce flood risk along coastlines worldwide [1][2][3][4] , among many other ecosystem services 5 . Wave and surge attenuation by mangroves is estimated to reduce flood protection costs by 65 billion USD per year 2 , and could decrease the adaptation costs of coastal infrastructure by 71-168 billion USD by 2080 4 . ...
... Comparison between wave heights obtained using the wave model given by Eqs.(1)(2)(3)(4), H model , and the validation wave heights H val from (a) model results obtained with an unvegetated profile by Vuik et al.22 , and (b) case studies with vegetation from Wesenbeeck et al.54 (dark green dots) and Vuik et al.22 (light green dots). ...
Mangrove forests reduce wave attack along tropical and sub-tropical coastlines, decreasing the wave loads acting on coastal protection structures. Mangrove belts seaward of embankments can therefore lower their required height and decrease their slope protection thickness. Wave reduction by mangroves depends on tree frontal surface area and stability against storms, but both aspects are often oversimplified or neglected in coastal protection designs. Here we present a framework to evaluate how mangrove belts influence embankment designs, including mangrove growth over time and failure by overturning and trunk breakage. This methodology is applied to Sonneratia apetala mangroves seaward of embankments in Bangladesh, considering forest widths between 10 and 1000 m (cross-shore). For water depths of 5 m, wave reduction by mangrove forests narrower than 1 km mostly affects the slope protection and the bank erodibility, whereas the required embankment height is less influenced by mangroves. Sonneratia apetala trees experience a relative maximum in wave attenuation capacity at 10 years age, due to their large submerged canopy area. Once trees are more than 20 years old, their canopy is emergent, and most wave attenuation is caused by trunk and roots. Canopy emergence exposes mangroves to wind loads, which are much larger than wave loads, and can cause tree failure during cyclones. These results stress the importance of including tree surface area and stability models when predicting coastal protection by mangroves.
... Mangroves contribute significantly in reducing the risk of floods in low lying regions of the coastal zone (Hochard et al., 2019a(Hochard et al., , 2019bMenéndez et al., 2020;Gijsman et al., 2021). There is evidence that contend that mangroves have the capacity to lower wave height by 13 and 66% over a distance of 100 m of forest (McIvor et al., 2012a(McIvor et al., , 2012b. Mangroves have specific characteristics that influence how waves decrease through the forest including their dense above ground canopy and their particular robust root structure that lessen water flow and scatter wave energy (Marois and Mitsch, 2015;Gijsman et al., 2021). ...
... Quartel et al., 2007;Vo-Luong and Massel, 2008;Bao, 2011), by even 50-99% across a 500 m wide mangrove forest. As waves pass through mangroves, several factors affect wave height including water depth which is based on the topography and bathymetry of the location and tidal phase, wave height, mangrove tree species, age and size (McIvor et al., 2012a(McIvor et al., , 2012b. According to Bao's (2011) study on mangroves in Vietnam measured along 92 transects, mean wave height decreased by 21% over the first 40 m of the forest, 17% over the following 40 m and an overall reduction of 35% over the first 80 m forest (McIvor et al., 2012a). ...
... As waves pass through mangroves, several factors affect wave height including water depth which is based on the topography and bathymetry of the location and tidal phase, wave height, mangrove tree species, age and size (McIvor et al., 2012a(McIvor et al., , 2012b. According to Bao's (2011) study on mangroves in Vietnam measured along 92 transects, mean wave height decreased by 21% over the first 40 m of the forest, 17% over the following 40 m and an overall reduction of 35% over the first 80 m forest (McIvor et al., 2012a). ...
... Wave height reduction due to the interaction with coastal salt marshes 7 and mangroves [8][9][10][11][12][13] is well established in the literature and mostly acts at the local scale of the wetland. Less well understood are the factors that control storm surge reduction by vegetation 14 , with the majority of observational and modelling studies focusing on storm surge mitigation due to the resistance exerted by salt marshes [15][16][17][18][19][20][21][22][23][24] and few studies demonstrating the value of mangroves [25][26][27][28][29][30][31] . ...
Coastal vegetation can reduce extreme water levels during storm events, but the controlling factors and processes in complex estuary or delta systems are still unclear. This limits an effective implementation of nature-based coastal defences in delta mega-cities in low-lying coastal areas. Here we have numerically modelled how mangroves can offer coastal protection to the large coastal cities located in the Pearl River Delta (China), such as Guangzhou and Shenzhen, during strong typhoons, like Hato (2017). Water level attenuation by mangroves is effective during extreme water level conditions and differences in mangrove forests’ properties drive their coastal protection function. The local (within-wetland) attenuation of extreme water levels is more effective with wide vegetation patches and higher vegetation drag. Narrower vegetation patches can still provide non-local (upstream) water level attenuation if located in the upper estuary channels, but their design needs to avoid amplification of water levels in other delta areas. Mangroves can provide nature-based coastal defences in complex deltas, but effective design of mangrove-based defences requires location-specific predictions and a deep understanding of forest structural characteristics, according to numerical simulations of water levels attenuation for the Pearl River Delta, China.
... Coastal wetlands such as mangrove swamps and tidal marshes offer coastal protection by acting to reduce wave energy and currents, reducing the risks of flooding and storm surges. Even narrow bands of mangrove forests along a coastline can decrease wave height and energy, for example McIvor et al. (2012) found mangrove forests decreased wave energy by an average of 13%-66% over a distance of 100 m, preventing wave damage and erosion during high tides. Coastal wetlands are particularly important as a part of nature-based solution to the challenges posed by sea-level rise and storm surges, leading to beneficial ecosystem services. ...
... The wave dissipation energy has been modelled through three processes: bottom friction (Madsen et al., 1988), wave depth-induced breaking (Battjes and Janssen, 1978) and dissipation by vegetation (Suzuki et al., 2012). This last vegetation module, has been used in recent works for including the influence of vegetation on wave fields (McIvor et al., 2012;Vuik et al., 2016;Van Rooijen et al., 2016). The module consists of a parametrization of wave energy proportional to specific submerged vegetation features: stem density, stem average height, canopy width and the drag coefficient. ...
The presence of seagrass along the Romanian coast is currently seen as an important component of the marine ecosystem. Moreover, seagrass meadows play an additional wave energy dissipation role that has also to be considered among other ecosystem services. Assessing the impact of a seagrass meadow on the local hydrodynamics is needed to present an integrated protection and adaption plan for discussion with local stakeholders and coastal managers. The impact on wave heights of a possible seagrass meadow, located in front of the barrier beach at the Mangalia marsh on the southern Romanian coast, has been analysed using numerical modelling. Several seagrass configurations have been studied, for low and average wave conditions from various directions. The same waves were used after adding a vegetation mask to the analysed domain, to simulate the presence of a seagrass meadow. The results of the numerical simulations were extracted in several output points, located along three transects crossing the vegetation mask. They show the most significant reduction in the calculated wave energy density during a year of 16.6%, occurring within the seagrass meadow. Our results suggest that, for the southern Romanian coast, seagrass could be introduced in coastal protection plans as an additional measure for wave attenuation.
... In addition, they provide critical habitats for various terrestrial, estuarine, and marine species, as well as a source of and sink for nutrients and sediments, benefitting other inshore marine habitats like seagrass beds and coral reefs (Kathiresan and Bingham, 2001;Duke et al., 2007). Mangrove ecosystems protect coastlines through the protection of coastal and nearshore habitats during extreme weather events (e.g., storm surges and severe winds) (McIvor et al., 2012), they also ensure the safety of coastal assets such as agricultural areas by suppressing wave activity, as well as the stabilization of coastlines and dunes by reducing erosion through wave reduction and sediment accretion (Das, 2020). Furthermore, mangrove forests provide a range of services to coastal communities, such as food, timber, non-timber forest products, and traditional medicines, as well as shelter for indigenous people from physical disturbances like coastal erosion (Osti et al., 2009). ...
Etongo et al.: Growth rate and survivorship of R. mucronata, A. marina, and C. tagal seedlings with freshwater and seawater treatment-5409-APPLIED ECOLOGY AND ENVIRONMENTAL RESEARCH 20(6):5409-5431. Abstract. Mangroves play an important role in coastal ecosystems worldwide, performing vital functions like protecting coastlines, seagrass, and coral reefs, purification of water, trapping sediments, and providing nursery grounds for many terrestrial and aquatic organisms. Despite their importance, mangroves are threatened worldwide due to increasing human development in coastal areas, and therefore, efforts to restore degraded mangrove ecosystems have gained traction. Mangrove restoration requires specialized knowledge and skills, ranging from selecting seeds, to the planting of seedlings in nurseries and along degraded coastlines. The following study explores the survivorship and growth rate of seedlings of three mangrove species-namely Avicennia marina, Rhizophora mucronata, and Ceriops tagal-in freshwater and seawater treatments. The experiment was conducted in a nursery-based environment to inform mangrove rehabilitation programs. Root count and length, leaf count and length, and the length of the entire seedling were measured for each sample species every week for 12 weeks. The data were analyzed using two-way ANOVA to identify significant differences in the measured variables between each species in the freshwater and seawater treatments. Seedlings grown in freshwater revealed a more rapid growth rate and lower mortality relative to those in seawater. Mangrove seedlings can be raised in nursery-based environments. They can be irrigated using freshwater with species like A. marina, less constrained by freshwater and hence display higher growth rates. Therefore, A. marina should be considered a priority species for mangrove restoration, given its relatively higher growth rate than the other species in the experiment.
... Mangrove forests are vital for global environment protection but mismanaged human interventions in coastal areas may lead to their decline. Their importance is not limited to reducing the impact of natural disasters (McIvor et al., 2012), but also contributing in nutrient cycling (Kim et al., 2016), bioremediation as well as phytoremediation of heavy metal pollutants (Usman et al., 2013), source of potential plant extracts (Sohaib et al., 2022a), host for diversity of microorganisms (Sohaib et al., 2022b), which are a source of novel commercial products and take part in host plant survival (Alarfaj et al., 2015;Ameen et al., 2016;Bibi et al., 2017), and acts as carbon sink (Donato et al., 2011). Mangroves and their associates have the potential to sequester about 22.8 million metric tons of carbon per year (Giri et al., 2011;Jennerjahn and Ittekkot, 2002). ...
Urban expansion along the coastal sites is one of the major causes of the deterioration of mangrove habitats. This study aimed to report the current status of different mangrove environments in Saudi Arabia. Mangrove soil and sediment-water samples were collected from the coasts of the Arabian Gulf and the Red Sea for their physical, chemical, and heavy metal analysis. The mean values (n = 42) of heavy metals in the soil showed that Fe (2200 ppm) > Mn (91.9 ppm) > Zn (66.11 ppm) > Cr (62.40 ppm) > Ni (33.64 ppm) > Cu (31.06 ppm) > Pb (30.69 ppm) > Co (27.06 ppm). While the mean values (n = 15) of heavy metals in the sediment-water were as follows; Cr (0.1978 ppm) > Fe (0.1016 ppm) > Pb (0.0792 ppm) > Co (0.0706 ppm) > Mn (0.0356 ppm) > Cu (0.0317 ppm) > Ni (0.0215 ppm). The average values of Zn, Ni, Cu, Pb, and Co were greater than those reported previously in the Red Sea and Arabian Gulf coastal sediments. At the same time, Mo and Cd were not detected in any studied soil sample. The correlation analysis revealed that the EC of mangrove soil was positively correlated with SOM, Ca, Mg, Na, and K, while the EC of sediment-water was positively correlated with Na, K, and Cu. Landfilling, sewage pollution, mismanagement of solid waste, and contamination due to other anthropogenic activities may lead to heavy metal hazards and the loss of large areas of mangrove plants in this region. Therefore, the findings of this study should be considered to understand and design the management strategy of mangrove forests in the area of study.
... However, rapid sea level rise and intensified human activities have induced mangrove mortality ranging from 30 to 50% over the past 50 years (Lovelock et al., 2015;FAO, 2020;Bryan-Brown et al., 2020). Globally, wave energy damping by narrow fringes of mangroves during storms largely reduced due to large-scale loss of mangrove forests resulting from human destruction (Yanagisawa et al., 2010;McIvor et al., 2012). Improving our understanding on mangrove forest capability of attenuating wave during storms is therefore an urgent need to gain awareness of the crucial role in coastal protection provided by these ecosystems thus pushing authorities toward effective protection and restoration policies. ...
... Mangroves also acted as a bioshield when Typhoon Sarah impacted Guangxi Province in China in 1986 (Chen et al., 2013). Evidence has been found by McIvor et al. (2012) and Lovelock et al. (2015) that both wind and swell wave heights could been reduced significantly over relatively short distances. Wave attenuation provided by mangroves have also been investigated via field observations, laboratory experiments, and numerical modeling (Alongi, 2009;Bao, 2011;Willemsen et al., 2016;Montgomery et al., 2019). ...
Frequently, large-scale typhoon-induced casualties and financial losses in global mega-delta cities can be buffered to a large extent by the presence of mangrove wetlands occurring in tropical coastal zones. However, there is little information about how mangrove wetland dynamics induce wave energy damping. Here, a series of biomorphodynamic field data was acquired during a storm period induced by Typhoon Sinlaku over a mangrove wetland in the Nanliu Delta, the largest delta of the northern Beibu Gulf in China; these data revealed the wave attenuation process of native Aegiceras corniculatum (AC). The results indicated that the wave damping coefficient of AC was higher during the storm period than during normal weather conditions. Sapling and adult AC were densely distributed in the field and had a greater effect on reducing wave height than seedlings, which were sparsely distributed, even though seedlings might have a stronger damping ability. Moreover, wave height was linearly attenuated with landward wave propagation distance along a transect of AC plots of different ages. Our work further indicated that the slopes and intercepts of the linear fits between wave height and landward wave propagation distance under storm and normal conditions were closely related to incident wave height, the water level and submerged vegetation volume. These results highlight the role of AC trees of different ages and densities under distinct weather conditions in the wave attenuation process.
... Storm surges can be slowed down by wide mangrove tracts, reducing surge height by 4-48 cm per km mangrove belt width that the storm surge goes through. Furthermore, they reduce water level and slow surface waves (McIvor et al., 2012). Wave heights can be reduced by between 13 and 66% over 100 m of mangroves . ...
