Effect of vegetation on run-up and wall pressures due to cnoidal waves
TL;DR: In this article, the effect of vegetation on attenuating run-up over a plane slope of 1 : 30 due to the propagation of cnoidal waves was investigated. But the authors focused on the vertical wall fronted by two vegetation types, namely tandem and staggered vegetation.
Abstract: A comprehensive experimental investigation was carried out to understand the effect of vegetation in attenuating run-up over a plane slope of 1 : 30 due to the propagation of cnoidal waves. Two different types of vegetation configurations, namely tandem and staggered, are considered. Dynamic pressures exerted along a vertical wall fronted by these two vegetation types were measured, and the typical variation of dimensionless peak pressures for different relative depths of submergence of the pressure ports is reported as a function of dimensionless parameters involving the vegetation and wave characteristics. Further, typical results on the variation of the dimensionless peak run-up versus the surf similarity parameter only for the staggered configuration are also herein reported. Finally, the percentage reduction in wave run-up and pressures on the wall due to the presence of wall fronted by vegetation are reported.
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01 Jan 2018
TL;DR: In this article, the effect of vegetation on wave attenuation through an experimental approach was analyzed. But, the authors focused on the effects of vegetation in terms of its behavior with wave and vegetation motion and not completely understood.
Abstract: Coastal populations around the world are at a greater risk of damage from coastal hazards due to the unprecedented rise of global climate change characterized by sea-level rise, longer and frequent droughts and floods, heightened cyclonic and storm surge activities. The narrow fringe of vegetated coastal habitats along the shores of continents mainly acts as a buffer for the impacts of rising sea levels and wave action. The losses from natural disasters like the 2004 Indian Ocean tsunami, Hurricane Katrina, and others have reached an all-time high, and the decision-makers now realize that coastal habitats have an important role to play in risk reduction. Though coastal vegetation, as a shore protection method, is sustainable, environment friendly, and cost-effective, its behavior with wave is very complex, especially because of the coupling between the waves and vegetation motion and is therefore, not completely understood. Numerical modelling approach, having based on more assumptions and field study, being uneconomical fomented the need for the study in the form of physical modelling. This paper focuses on figuring out the effect of vegetation on wave attenuation through an experimental approach. The wave flume of length 50 m, height 1 m, and width 0.71 m is used to study the characteristic behavior of submerged heterogeneous vegetation of varying width for wave heights ranging from 0.08 to 0.16 m with an increment of 0.02 m and wave periods 1.8 and 2 s in water depths of 0.40 and 0.45 m. Measurements of wave heights at locations along the vegetation were observed to quantify wave attenuation and its trend.
2 citations
01 Jan 2018
TL;DR: In this article, the effect of artificial emergent vegetation of meadow widths 1 and 2 m on wave run up through an experimental study was brought out by using a 50 m long wave flume.
Abstract: Coastal vegetation can protect people and property from erosion and flooding, potentially providing a solution for conservation and development. Recently, there has been a substantial interest in the ability of natural vegetation to protect people and infrastructure from storm, wind, and wave damage. These ecosystem services provide new and powerful reasons for conservation of coastal habitats and may represent solutions that balance conservation and development. Since the costs of installing hard structures for coastal protection are very high; strong negative public reaction to rock emplacements along the coast often aggravate the problem; research in the field of soft measures of coastal protection is important which highlights the need and importance of a sustainable, environment friendly, and cost efficient solution such as coastal or beach vegetation. This paper tries to bring out the effect of artificial emergent vegetation of meadow widths 1 and 2 m on wave run up through an experimental study. The tests were carried out with emergent vegetation placed on the bed of a 50 m long wave flume. For wave heights ranging from 0.08 to 0.16 m at an interval of 0.02 m and wave periods ranging from 1.4 to 2 s in water depths of 0.40 and 0.45 m, measurements of wave run up over the beach slope were observed.
1 citations
TL;DR: In this paper, two machine learning techniques, KNN and Ensemble of Decision Trees (EDT), were employed to identify the most critical pre-storm morphological factors in determining the road vulnerability, expressed as a binary variable to impact storms.
Abstract: This work considers a database of pre-storm morphological factors and documented impacts along a coastal roadway. Impacts from seven storms, including sand overwash and pavement damage, were documented via aerial photography. Pre-storm topography was examined to parameterize the pre-storm morphological factors likely to control whether stormwater levels and waves impact the road. Two machine learning techniques, K-nearest neighbors (KNN) and ensemble of decision trees (EDT), were employed to identify the most critical pre-storm morphological factors in determining the road vulnerability, expressed as a binary variable to impact storms. Pre-processing analysis was conducted with a correlation analysis of the predictors’ data set and feature selection subroutine for the KNN classifier. The EDTs were built directly from the data set, and feature importance estimates were reported for all storm events. Both classifiers report the distances from roadway edge-of-pavement to the dune toe and ocean as the most important predictors of most storms. For storms approaching from the bayside, the width of the barrier island was the second most important factor. Other factors of importance included elevation of the dune toe, distance from the edge of pavement to the ocean shoreline, shoreline orientation (relative to predominant wave angle), and beach slope. Compared to previously reported optimization techniques, both machine learning methods improved using pre-storm morphological data to classify highway vulnerability based on storm impacts.
01 Jan 2019
TL;DR: In this paper, the authors present the results of a physical model investigation carried out with a fragmented heterogeneous vegetation model in a wave flume 50 m long, 0.71 m wide and 1.1 m deep.
Abstract: It has long been known that “bio-shields” do function as a sustainable solution for preserving our coasts. The presence of gaps in the “bio-shield”, that is, the forest cover, referred to as patchiness, is a common phenomenon in natural habitats. Various anthropogenic and natural causes can result in such gaps in coastal forests. This paper presents the results of a physical model investigation carried out with a fragmented heterogeneous vegetation model in a wave flume 50 m long, 0.71 m wide and 1.1 m deep. The heterogeneous meadow is modelled as a combined body of artificial submerged seagrass, rigid vegetation and emergent vegetation. To study the effect of fragmentation in vegetation, transverse gaps of varying widths are introduced in the heterogeneous model. The material used for modelling is polyethylene and nylon. The test runs were carried out with monochromatic waves of heights ranging from 0.08 to 0.16 m in water depths of 0.40 and 0.45 m, and wave periods 1.8 and 2 s. The wave height measurements at different locations within the vegetated meadow exhibit an exponential decay of wave heights. The presence of gaps in vegetation does not have a significant effect on wave height reduction. However, the experimental study revealed that heterogeneous vegetation showed a great promise leading to considerable wave attenuation, thus offering a good level of protection to life and property on the leeside.
References
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TL;DR: In this article, an approximate theory is presented for non-breaking waves and an asymptotic result is derived for the maximum runup of solitary waves on plane beaches, and a series of laboratory experiments is described to support the theory.
Abstract: This is a study of the runup of solitary waves on plane beaches. An approximate theory is presented for non-breaking waves and an asymptotic result is derived for the maximum runup of solitary waves. A series of laboratory experiments is described to support the theory. It is shown that the linear theory predicts the maximum runup satisfactorily, and that the nonlinear theory describes the climb of solitary waves equally well. Different runup regimes are found to exist for the runup of breaking and non-breaking waves. A breaking criterion is derived for determining whether a solitary wave will break as it climbs up a sloping beach, and a different criterion is shown to apply for determining whether a wave will break during rundown. These results are used to explain some of the existing empirical runup relationships.
866 citations
TL;DR: In this paper, the authors investigated the behavior of a wave as it climbs a sloping beach and obtained explicit solutions of the equations of the non-linear inviscid shallow-water theory for several physically interesting wave-forms.
Abstract: In this paper, we investigate the behaviour of a wave as it climbs a sloping beach. Explicit solutions of the equations of the non-linear inviscid shallow-water theory are obtained for several physically interesting wave-forms. In particular it is shown that waves can climb a sloping beach without breaking. Formulae for the motions of the instantaneous shoreline as well as the time histories of specific wave-forms are presented.
692 citations
"Effect of vegetation on run-up and ..." refers background in this paper
...Carrier and Greenspan (1958) solved the shallow water equations analytically by obtaining solutions for the prediction of the long wave run-up over smooth plane beaches....
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TL;DR: A study conducted after the 26th of December 2004 tsunami in 18 coastal hamlets along the south-east coast of India reiterates the importance of coastal mangrove vegetations and location characteristics of human inhabitation to protect lives and wealth from the fury of tsunami.
Abstract: A study conducted after the 26th of December 2004 tsunami in 18 coastal hamlets along the south-east coast of India reiterates the importance of coastal mangrove vegetations and location characteristics of human inhabitation to protect lives and wealth from the fury of tsunami. The tsunami caused human death and loss of wealth and these decreased with the area of coastal vegetation, distance and elevation of human inhabitation from the sea. Human inhabitation should be encouraged more than 1 km from the shoreline in elevated places, behind dense mangroves and or other coastal vegetation. Some plant species, suitable to grow in between human inhabitation and the sea for coastal protection, are suggested.
656 citations
"Effect of vegetation on run-up and ..." refers background in this paper
...The dominant role of vegetation to reduce the inundation distance and run-up during the ingress of great Indian Ocean tsunami of 2004 is reported by Kathiresan and Rajendran (2005)....
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...distance and run-up during the ingress of great Indian Ocean tsunami of 2004 is reported by Kathiresan and Rajendran (2005). The studies of Mascarenhas and Jayakumar (2008) indicate that large stretches of the coast of Tamil Nadu (South East...
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Book•
01 Mar 1987
TL;DR: In this article, the authors describe wave mechanics and how to choose wave theories and design waves, and how this wave is used to obtain forces on a fixed offshore structure, if the structure is allowed to move, various methods of obtaining the motions of the structure are given.
Abstract: The subject of hydrodynamics applied to offshore structures is vast. The topics covered in this book aim to help the reader understand basic principles while at the same time giving the designer enough information for particular designs. Thus, results are given with derivations, and applications are discussed with the aid of examples, with an overview of the advantages and limitations of the method involved. This makes the book suitable as a text for undergraduate and graduate students specializing in offshore and ocean engineering. In addition, the final results, including tables and illustrations may be referenced directly without going through detailed derivations. They can therefore be used by design and applications engineers involved in offshore structure design. This title also introduces various types of offshore structures with reference to actual installations in various parts of the world. It describes wave mechanics and how to choose wave theories and design waves. After a choice of design wave is made, the author describes how this wave is used to obtain forces on a fixed offshore structure. If the structure is allowed to move, various methods of obtaining the motions of the structure are given. The short- and long-term responses are derived and different methods are described. The use of model tests to verify these methods at each step is shown.
632 citations
"Effect of vegetation on run-up and ..." refers methods in this paper
...Considering the drag/inertia force regime (Chakrabarti 1983), the corresponding diameters for the exposed vegetal stems were determined....
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TL;DR: A field study of the tidal currents, cohesive sediment dynamics and transport of organic carbon in a highly vegetated mangrove swamp was carried out at Middle Creek, Cairns, Australia as discussed by the authors.
Abstract: A field study of the tidal currents, cohesive sediment dynamics and transport of organic carbon in a highly vegetated mangrove swamp was carried out at Middle Creek, Cairns, Australia. The interaction of tidal currents and the vegetation generated jets, eddies and zones of stagnant waters which were numerically modelled. A high value of the Manning friction coefficient (n=0·1) was derived by the dense vegetation. About 80% of the suspended sediment brought in from coastal waters at spring flood tide was trapped in the mangroves, corresponding to about 10–12 kg of sediment m−1creek length/spring tide, resulting in a rise of the substrate by about 0·1 cm year−1. The selective trapping of clay was caused by flocculation of the finer particles in the mangroves. There was an indication of a slight inwelling of organic carbon. Creek water was readily differentiated from mangrove water by large differences in the molecular weight distribution of the dissolved organic carbon.
482 citations
"Effect of vegetation on run-up and ..." refers background in this paper
...Through experimental studies, Furukawa et al. (1997) demonstrated that the wave dissipation depends on the forest density and the diameter of the tree trunks....
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