scholarly journals Can Managed Realignment Buffer Extreme Surges? The Relationship Between Marsh Width, Vegetation Cover and Surge Attenuation

2021 ◽  
Author(s):  
Joshua Kiesel ◽  
Leigh R. MacPherson ◽  
Mark Schuerch ◽  
Athanasios T. Vafeidis
Keyword(s):  
Sea Level ◽  
Vegetation Cover ◽  
Coastal Wetlands ◽  
Water Levels ◽  
Coastal Protection ◽  
Return Periods ◽  
Managed Realignment ◽  
Extreme Water Levels ◽  
The Relationship

AbstractManaged realignment (MR) involves the landward relocation of sea defences to foster the (re)creation of coastal wetlands and achieve nature-based coastal protection. The wider application of MR is impeded by knowledge gaps related to lacking data on its effectiveness under extreme surges and the role of changes in vegetation cover, for example due to sea-level rise. We employ a calibrated and validated hydrodynamic model to explore relationships between surge attenuation, MR width(/area) and vegetation cover for the MR site of Freiston Shore, UK. We model a range of extreme water levels for four scenarios of variable MR width. We further assess the effects of reduced vegetation cover for the actual MR site and for the scenario of the site with the largest width. We show that surges are amplified for all but the largest two site scenarios, suggesting that increasing MR width results in higher attenuation rates. Substantial surge attenuation (up to 18 cm km−1) is only achieved for the largest site. The greatest contribution to the attenuation in the largest site scenario may come from water being reflected from the breached dike. While vegetation cover has no statistically significant effect on surge attenuations in the original MR site, higher coverage leads to higher attenuation rates in the largest site scenario. We conclude that at the open coast, only large MR sites (> 1148 m width) can attenuate surges with return periods > 10 years, while increased vegetation cover and larger MR widths enable the attenuation of even higher surges.

scholarly journals The role of the reef–dune system in coastal protection in Puerto Morelos (Mexico)

2018 ◽  
Vol 18 (4) ◽  
pp. 1247-1260 ◽  
Author(s):  
Gemma L. Franklin ◽  
Alec Torres-Freyermuth ◽  
Gabriela Medellin ◽  
María Eugenia Allende-Arandia ◽  
Christian M. Appendini
Keyword(s):  
Sand Dunes ◽  
Coastal Flooding ◽  
Water Levels ◽  
Coastal Protection ◽  
Dune System ◽  
Fore Reef ◽  
Extreme Water Levels ◽  
Reef Environments ◽  
Storm Impact

Abstract. Reefs and sand dunes are critical morphological features providing natural coastal protection. Reefs dissipate around 90 % of the incident wave energy through wave breaking, whereas sand dunes provide the final natural barrier against coastal flooding. The storm impact on coastal areas with these features depends on the relative elevation of the extreme water levels with respect to the sand dune morphology. However, despite the importance of barrier reefs and dunes in coastal protection, poor management practices have degraded these ecosystems, increasing their vulnerability to coastal flooding. The present study aims to theoretically investigate the role of the reef–dune system in coastal protection under current climatic conditions at Puerto Morelos, located in the Mexican Caribbean Sea, using a widely validated nonlinear non-hydrostatic numerical model (SWASH). Wave hindcast information, tidal level, and a measured beach profile of the reef–dune system in Puerto Morelos are employed to estimate extreme runup and the storm impact scale for current and theoretical scenarios. The numerical results show the importance of including the storm surge when predicting extreme water levels and also show that ecosystem degradation has important implications for coastal protection against storms with return periods of less than 10 years. The latter highlights the importance of conservation of the system as a mitigation measure to decrease coastal vulnerability and infrastructure losses in coastal areas in the short to medium term. Furthermore, the results are used to evaluate the applicability of runup parameterisations for beaches to reef environments. Numerical analysis of runup dynamics suggests that runup parameterisations for reef environments can be improved by including the fore reef slope. Therefore, future research to develop runup parameterisations incorporating reef geometry features (e.g. reef crest elevation, reef lagoon width, fore reef slope) is warranted.

scholarly journals The Role of Beach Morphology and Mid-Century Climate Change Effects on Wave Runup and Storm Impact on the Northern Yucatan Coast

2021 ◽  
Vol 9 (5) ◽  
pp. 518
Author(s):  
Gabriela Medellín ◽  
Martí Mayor ◽  
Christian M. Appendini ◽  
Ruth Cerezo-Mota ◽  
José A. Jiménez
Keyword(s):  
Climate Change ◽  
Sea Level ◽  
Water Levels ◽  
Transformation Model ◽  
Wave Runup ◽  
Beach Morphology ◽  
Extreme Water Levels ◽  
Storm Impact ◽  
Wave Conditions

Wave runup is a relevant parameter to determine the storm impact on barrier islands. Here, the role of the beach morphology on wave runup and storm impact was investigated at four coastal communities located on the northern Yucatan coast. Current wave conditions based on regional wind simulations, topo-bathymetric transects measured at each location, and a nonlinear wave transformation model were employed to reconstruct multi-year runup time series. Dune morphology features and extreme water levels (excluding storm surge contributions) were further employed to determine the storm impact at each site for different return periods. Despite the similar offshore conditions along the coast, extreme water levels (i.e., runup and setup) showed intersite differences that were mainly ascribed to subaerial and submerged morphological features. Numerical results showed that the average surf zone beach slope, sandbars, berm, and dune elevation played an important role in controlling extreme water levels and storm impact at the study sites under the present climate. Moreover, in order to assess the potential effect of climate change on coastal flooding, we analyzed wave runup and storm impact in the best-preserved site by considering wave conditions and sea level rise (SLR) projections under the RCP 8.5 scenario. Modelling results suggest no significant increase in the storm impact regime between the present and future conditions in the study area unless SLR is considered. It was found that to accurately estimate SLR contribution, it should be incorporated into mean sea level prior to performing numerical wave runup simulations, rather than simply adding it to the resulting wave-induced water levels.

scholarly journals EXTREME LEVELS ARISING FROM METEOROLOGICAL SURGES

1974 ◽  
Vol 1 (14) ◽  
pp. 1 ◽  
Author(s):  
P. Ackers ◽  
T.D. Ruxton
Keyword(s):  
Sea Level ◽  
North Sea ◽  
High Tide ◽  
Water Levels ◽  
Return Periods ◽  
The North ◽  
Extreme Water Levels ◽  
Independent Events ◽  
The North Sea

The design of coastal works depends on estimating the probabilities of extreme water levels, as well as of waves Previous studies of surge-affected levels have extrapolated observed annual maxima or the n highest levels in n years to predict rarer events In addition to using these well-established methods, m this study of tide levels on the Essex coast of Britain a long term record of extreme levels was synthesised by adding surge residuals at the time of predicted HW to predicted HW levels, treating them as statistically independent events Many more large surge residuals have been measured than extreme water levels as many surges are associated with small tides Events with return periods up to 1000 years may be estimated without extrapolating beyond the range of observed surge residuals and predicted tides This method is assessed in relation to previous methods and information relevant to the design of coastal works in the south western part of the North Sea was obtained In addition to forecasting the probabilities of high tide levels, the study included wave forecasts and the encounter probabilities of combinations of sea level and wave height for various aspects of coastal developments.

scholarly journals Effect of Variations in Water Level and Wave Steepness on the Robustness of Wave Overtopping Estimation

2020 ◽  
Vol 8 (2) ◽  
pp. 63
Author(s):  
Nils B. Kerpen ◽  
Karl-Friedrich Daemrich ◽  
Oliver Lojek ◽  
Torsten Schlurmann
Keyword(s):  
Water Level ◽  
Wave Spectrum ◽  
Water Environment ◽  
Physical Modelling ◽  
Storm Surges ◽  
Water Levels ◽  
Coastal Protection ◽  
Wave Steepness ◽  
Wave Overtopping

The wave overtopping discharge at coastal defense structures is directly linked to the freeboard height. By means of physical modelling, experiments on wave overtopping volumes at sloped coastal structures are customarily determined for constant water levels and static wave steepness conditions (e.g., specific wave spectrum). These experiments are the basis for the formulation of empirically derived and widely acknowledged wave overtopping estimations for practical design purposes. By analysis and laboratory reproduction of typical features from exemplarily regarded real storm surge time series in German coastal waters, the role of non-stationary water level and wave steepness were analyzed and adjusted in experiments. The robustness of wave overtopping estimation formulae (i.e., the capabilities and limitations of such a static projection of dynamic boundary conditions) are outlined. Therefore, the classic static approach is contrasted with data stemming from tests in which both water level and wave steepness were dynamically altered in representative arrangements. The analysis reveals that mean overtopping discharges for simple sloping structures in an almost deep water environment could be robustly estimated for dynamic water level changes by means of the present design formulae. In contrast, the role of dynamic changes of the wave steepness led to a substantial discrepancy of overtopping volumes by a factor of two. This finding opens new discussion on methodology and criteria design of coastal protection infrastructure under dynamic exposure to storm surges and in lieu of alterations stemming from projected sea level rise.

The time variability of evapotranspiration and soil water storage in long series of rainfall-runoff process

Biologia ◽  
2009 ◽  
Vol 64 (3) ◽  
Author(s):  
Josef Buchtele ◽  
Miroslav Tesař
Keyword(s):  
Vegetation Cover ◽  
Dominant Role ◽  
Water Storage ◽  
Water Levels ◽  
Soil Water Storage ◽  
Time Variability ◽  
Rainfall Runoff ◽  
Groundwater Storage ◽  
Surface Water Storage

AbstractNatural variability, i. e. climatic oscillation, influences the development of vegetation in the annual cycle. At the same time it creates the conditions for the changes of the vegetation cover even in the scale of centuries. This is the phenomenon, which causes the variation or tendencies in evapotranspiration demands and consequently of water storage regime, and its long scale change is sometimes disregarded. The simulation of rainfall-runoff process has been used for the re-evaluation of the assumed evapotranspiration demand due to the developing vegetation cover and of groundwater storage in the catchments. The simulations provide the results, which illustrate the dominant role of transpiration in comparison with other components of evapotranspiration. The simulations also illustrate the interaction between evapotranspiration and groundwater storage. Additionally, the modelling confirms that it could be useful to compare the parameters for the recession process of simulated sub-surface water storage with the decreases of observed outflow of springs and/or with the course of water levels in the bore holes.

scholarly journals How Sediment Transport Sways Wetland Stability

Eos ◽  
2016 ◽  
Vol 97 ◽  
Author(s):  
Lily Strelich
Keyword(s):  
Sediment Transport ◽  
Sea Level Rise ◽  
Suspended Sediment ◽  
Sea Level ◽  
Coastal Wetlands ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration

Scientists examine the role of variables like tides and suspended sediment concentration to improve methods of evaluating coastal wetlands and how they may respond to future sea level rise.

scholarly journals Assessing the extreme risk of coastal inundation due to climate change: A case study of Rongcheng, China

2017 ◽  
Author(s):  
Aiqing Feng ◽  
Jiangbo Gao ◽  
Shaohong Wu ◽  
Yanzhong Li ◽  
Xiliu Yue
Keyword(s):  
Climate Change ◽  
Sea Level Rise ◽  
Sea Level ◽  
Water Levels ◽  
Assessment Model ◽  
Rcp Scenarios ◽  
Extreme Water Levels ◽  
Extreme Risk ◽  
Extreme Flood

Abstract. Extreme water levels, caused by the joint occurrence of storm surges and high tides, always lead to super floods along coastlines. Given the ongoing climate change, this study explored the risk of future sea-level rise on the extreme inundation by combining P-III model and losses assessment model. Taking Rongcheng as a case study, the integrated risk of extreme water levels was assessed for 2050 and 2100 under three Representative Concentration Pathways (RCP) scenarios of 2.6, 4.5, and 8.5. Results indicated that the increase in total direct losses would reach an average of 60 % in 2100 as a 0.82 m sea-level rise under RCP 8.5. In addition, affected population would be increased by 4.95 % to 13.87 % and GDP (Gross Domestic Product) would be increased by 3.66 % to 10.95 % in 2050 while the augment of affected population and GDP in 2100 would be as twice as in 2050. Residential land and farmland would be under greater flooding risk in terms of the higher exposure and losses than other land-use types. Moreover, this study indicated that sea-level rise shortened the recurrence period of extreme water levels significantly and extreme events would become common. Consequently, the increase in frequency and possible losses of extreme flood events suggested that sea-level rise was very likely to exacerbate the extreme risk of coastal zone in future.

scholarly journals TIME-VARYING EMULATOR FOR SHORT- AND LONG-TERM ANALYSIS OF COASTAL FLOODING (TESLA-FLOOD)

2018 ◽  
pp. 4
Author(s):  
Dylan Anderson ◽  
Peter Ruggiero ◽  
Fernando J. Mendez ◽  
Ana Rueda ◽  
Jose A. Antolinez ◽  
...  
Keyword(s):  
Sea Level ◽  
Storm Surges ◽  
Coastal Flooding ◽  
Water Levels ◽  
Sea Level Anomalies ◽  
Extreme Water Levels ◽  
Flooding Risk ◽  
The Individual ◽  
Flooding Events

The ability to predict coastal flooding events and associated impacts has emerged as a primary societal need within the context of projected sea level rise (SLR) and climate change. The duration and extent of flooding is the result of nonlinear interactions between multiple environmental forcings (oceanographic, meteorological, hydrological) acting at varying spatial (local to global) and temporal scales (hours to centuries). Individual components contributing to total water levels (TWLs) include astronomical tides, monthly sea level anomalies, storm surges, and wave setup. Common practices often use the observational record of extreme water levels to estimate return levels of future extremes. However, such projections often do not account for the individual contribution of processes resulting in compound TWL events, nor do they account for time-dependent probabilities due to seasonal, interannual, and long-term oscillations within the climate system. More robust estimates of coastal flooding risk require the computation of joint probabilities and the simulation of hypothetical TWLs to better constrain the projection of extremes (Serafin [2014]).

Salinity effects on mass loss and nutrient release in the litter decomposition of peatland macrophytes

2021 ◽  
Author(s):  
Cheryl Batistel ◽  
Gerald Jurasinski ◽  
Hendrik Schubert
Keyword(s):  
Mass Loss ◽  
Sea Level ◽  
Decomposition Rate ◽  
Coastal Wetlands ◽  
Nutrient Release ◽  
Decay Rates ◽  
Water Levels ◽  
The Other ◽  
Ecosystem Functions ◽  
Prime Concern

<p>Global mean sea level had been rising and accelerating in the last decades affecting coastal wetlands that are important carbon stores since they are susceptible to fluctuating water levels. Climate-change-driven sea-level rise, which is predicted to reach about one to two meters by 2100, may lead to dramatic shifts in the vegetation composition of coastal wetlands consequently influencing ecosystem functions including photosynthetic activity, biomass production, litter decomposability, and ultimately the pattern and rates of nutrient cycling, carbon storage, and greenhouse gas exchange. In this regard, aside from water level, changes in salinity that may especially influence the decomposition of dead plant material are also of prime concern.</p><p>Here, we provide a comparative evaluation of the decomposition rates of the dominant macrophytes in different nearby freshwater and brackish peatlands. We assumed that the degradability of leaf litter differs among species due to the difference in chemical composition. Two peatland sites, Schutower Moor (freshwater) and Diedrichshagen Moor (brackish) were selected to compare the decomposition rate and nutrient release of <em>Phragmites australis</em>, <em>Carex</em> sp. and <em>Schoenoplectus tabernaemontanii </em>as influenced by salinity. We used the litterbag method using senescent leaves or stem parts (for <em>S. tabernaemontanii</em>) of the macrophytes that were collected in late autumn. We deposited 30 litterbags per species per site and retrieved 5 of these per site after 1, 2, 4, 6, 8 and 12 months, respectively.</p><p>Regardless of site and species, the highest mass loss occurred in the first 35 days of decomposition with a strong decrease thereafter with almost flat slopes. The initial decay rates of the same species did not differ significantly between sites. However, the initial mass loss of the <em>S. tabernaemontanii</em> litter was significantly higher than the other species. This species has the highest decay coefficient of 0.008 d<sup>-1</sup> and 0.006 d<sup>-1</sup> in freshwater and brackish sites, respectively. These decay rates are up to four times faster compared to the other species resulting in empty litterbags a year after deployment indicating the complete decomposition of <em>S. tabernaemontanii </em>while other species had between 40% to 60% dry mass remaining. Initially, the carbon and nitrogen contents of <em>S. tabernaemontanii </em>were significantly lower than those of the other species while its initial sulfur content was significantly higher than of the other species. <em>S. tabernaemontanii </em>retained a relatively high amount of nitrogen, phosphorus, sulfur and magnesium throughout decomposition compared to the other species. This keeps the C:N, C:P, C:S, C:Mg and N:P ratios nearly constant from the start to the end of the study suggesting continuous microbial activities due to the availability of such nutrients in the detritus of <em>S. tabernaemontanii</em>. This confirms that <em>P. australis</em> and <em>Carex</em> sp. contribute to the formation of peat while <em>S. tabernaemontanii </em>does not.  </p><p>Litter quality showed to be a more important factor affecting decomposition than the little difference in salinity between sites (e.g. annual average of 3psu) that did not significantly affect the decomposition rate of macrophyte litter. Therefore, future similar studies should consider comparing sites with higher salinity levels.</p>

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