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Author: search.filters.author.John, B.M.Has files: No

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    Laboratory investigations on the effect of fragmentation and heterogeneity of coastal vegetation in wave height attenuation
    (Springer, 2019) Shirlal, K.G.; John, B.M.; Rao, S.
    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. © Springer Nature Singapore Pte Ltd. 2019.
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    Effect of artificial vegetation on wave attenuation - An experimental investigation
    (Elsevier Ltd, 2015) John, B.M.; Shirlal, K.G.; Rao, S.
    In the wake of threats posed by rising sea levels and increasing severity of storms, the use of soft measures in coastal protection is acquiring an ever increasing importance. Coastal vegetation acts as a complex interface ecosystem between human communities and the sea and provides important ecosystem services by protecting these communities from coastal hazards, providing critical habitat for fishes and marine invertebrates and primary food source for animals like sea turtles. This paper tries to bring out the effect of simulated vegetation on wave attenuation through an experimental study. The tests were carried out with submerged artificial seagrass and artificial rigid vegetation in a 50 m long wave flume. For wave heights ranging from 0.08 m to 0.16 m at an interval of 0.02 m and wave periods 1.8 s and 2 s in water depths of 0.40 m and 0.45 m, measurements of wave heights at locations along the vegetation were observed. © 2015 The Authors. Published by Elsevier Ltd.
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    Laboratory investigations of wave attenuation by simulated vegetation of varying densities
    (Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2019) John, B.M.; Shirlal, K.G.; Rao, S.
    Coastal communities across the world are facing the need to adapt to rising sea levels, an increase in the frequency of natural hazards like storm surges, cyclones, tsunamis, and an increase in beach erosion. This present-day scenario calls for a sustainable, environment-friendly, and cost efficient solution for coastal protection. Under these circumstances, the role of vegetation in providing ecosystem services to coastal populations is becoming increasingly prominent. This work presents the results of an experimental study carried out with simulated rigid submerged and emergent vegetation meadows of varying plant densities in a wave flume 50 m long, 0.71 m wide and 1.1 m deep. The material used for modeling the vegetation is nylon. The tests are carried out with regular waves for water depths of 0.40 and 0.45 m, and wave periods 1.4–2 s at an interval of 0.2 s. Five different wave heights ranging from 0.08 to 0.16 m at an interval of 0.02 m are generated. Measurements of wave heights at different locations indicate an exponential decay in wave height along the vegetation meadow which leads to wave attenuation and confirms that vegetation can be a viable option for coastal protection. © 2017, © 2017 Indian Society for Hydraulics.
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    Wave attenuation characteristics of simulated heterogeneous vegetation
    (Indian Academy of Sciences, 2020) John, B.M.; Shirlal, K.G.; Rao, S.
    Vegetated coastal ecosystems often coexist as diverse seascapes, well connected to each other by various biological, chemical and physical processes. It is of interest to study the effect of heterogeneity in vegetation using models of different combinations of submerged, emergent and compound vegetation on wave attenuation and coastal flooding. This article showcases the results of a physical model study conducted with different types of heterogeneous vegetation models in a two-dimensional wave flume, with wave height attenuation expressed in terms of percentage reduction in wave height and the subsequent extent of inundation expressed in terms of wave run-up on the beach. The test runs were carried out with monochromatic waves of height ranging from 0.08 to 0.16 m in water depths of 0.40 and 0.45 m and wave periods of 1.4–2 sec. The experimental results revealed the significant capability of vegetation in attenuating waves to the tune of 72% to 87%, and controlled flooding in terms of run-up of 0.31 to 0.76 times the wave height. However, the compound heterogeneous model proved to be the most efficient in controlling wave height and coastal flooding. © 2020