Faculty Publications
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Item Reef-an ecofriendly and cost effective hard option for coastal conservation(Springer Netherlands, 2008) Shirlal, K.G.; Rao, S.; Radheshyam, B.; Ganesh, V.Rubble mound breakwaters are the structures which are meant to reflect and dissipate energy of the wind generated waves and thereby to prevent their incidence on water area intended to protect. Submerged breakwater with its crest at or below still water level (SWL) can cause substantial wave attenuation and can be effectively used in places where tidal variations are small and only partial protection from waves is required, like harbour entrance, beach protection, small craft harbours etc. © 2008 Springer Netherlands.Item 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.Item Wave run-up, run-down studies on berm breakwater with concrete cubes as armour units([publishername] World Scientific, 2011) Rao, S.; Shirlal, K.G.; Balakrishna Rao, K.; Janardhan, P.The basic principle involved in the design of berm breakwater is provision of a wide berm at or around the water level with smaller size stones in the armour, which are allowed to move till an equilibrium slope is achieved. This paper presents the results of experimental studies conducted on the wave run-up, run-down characteristics of berm breakwater using concrete cube as artificial armour unit. The experiments were conducted under following conditions, berm width = 0.45m, water depths 0.37, 0.40 & 0.43m, breakwater slope 1:1.5. The weight of concrete cube is 79.5 gm. The wave heights used in the experiments are 0.10, 0.12, 0.14, and 0.16 m and wave periods are 1.6 and 2.0 sec. From the experimental study it is found that the run-up is more for longer period waves in comparison with the shorter period waves. With the increase in deep water wave steepness the run-up and run-down was found to decrease for all the water depths considered. The run-up values (Ru/Ho) vary from 0.52 to 1.08. The range of run-down values (Rd/Ho) varies from 0.45 to 0.88. In berm breakwater the run-up and run-down values were reduced by 35.91% and 23.81% when compared with conventional rubble mound breakwater. © 2019, World Scientific. All rights reserved.Item Physical model studies on stability of geotextile sand containers(Elsevier Ltd, 2015) Shirlal, K.G.; Mallidi, R.R.Coast parallel submerged breakwaters made of Geotextile Sand Containers (GSCs) are increasingly being incorporated into coastal management solutions because of their cost effective and environmentally friendly characteristics. These reduce the wave action on the lee side by forcing wave breaking and their stability is a function of the relative crest width, crest height, and the damage. The present work involves a physical model study on 1V:2H sloped trapezoidal submerged reefs constructed with 485 gm GSCs with different alignments like Perpendicular, Parallel, and Flemish. They have a height (h) of 0.25 m and varying crest widths (B) and are tested for stability for wave heights (H) of 0.1 m and 0.12 m and wave periods (T) of 1.5 s to 2.5 s in a water depth (d) of 0.3 m. © 2015 The Authors. Published by Elsevier Ltd.Item 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.Item Coastal Protection Using Geosynthetic Containment Systems—An Indian Timeline(Springer Science and Business Media Deutschland GmbH, 2021) Elias, T.; Shirlal, K.G.Maritime countries like India face serious coastal erosion issues. Over 1200 km of Indian coastline is identified as eroding. Unavailability and high cost of natural rocks remain as a major hindrance for construction of conventional hard options like breakwaters, seawalls and groynes. This has forced coastal engineers to find nature friendly and economical alternatives. Experiences from Australia, Germany and United States prove the efficacy of geotextile containment systems in coastal protection. This chapter aims at reviewing Indian examples of protection works using geosynthetic and geotextile containment systems from early 1980s. Geosynthetic protection structures include groynes, submerged reefs, seawalls and breakwaters. Benefits and difficulties in implementation of protection works are identified by reviewing prominent works conducted in the east and west coast of India. Experiences at Hamla, Dahanu and Pentha helped in replacing conventional structures with geotubes. Equilibrium beach profile is attained using near-shore geotube reef system at Hamla and Dahanu, Maharashtra, whereas reef constructed using geotextiles at Candolim, Goa suffered serious damage due to vandalism and toe scour. Geosynthetic systems along with gabions and rock armours improve the stability, wave dissipation and reflection characteristics as seen in Pentha, Odisha and Uppada, Andhra Pradesh. Lack of proper design criteria and deliberate destruction by vandals remains as the major threat. Countering these challenges, geosynthetic containment systems offer a cost-effective alternative to conventional coastal protection methods in India. © 2021, Springer Nature Singapore Pte Ltd.Item Experimental Study of Pipe Artificial Reef on Wave Attenuation(Springer Science and Business Media Deutschland GmbH, 2025) Xaviour, S.; Shirlal, K.G.Submerged artificial reefs are the coastal structures that protect the coast-line in an effective way with minimum damage to the coastal environment and enhance the marine ecology in the region. The artificial reefs (AR) commonly used come in various shapes and sizes, which offer different levels of coastal protection and serve various recreational purposes. This paper discusses a physical model study that provides insight into comparing the performance of circular pipe-shaped submerged artificial reef structures made of two different diameter pipes, tested under different wave conditions in a wave flume. The inference of the study shows that the larger diameter AR shows comparatively less wave transmission compared to the smaller diameter AR. However, the wave transmission reduction is considerably less with the maximum change noted to be under 26%. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.Item Item A laboratory investigation on perforated hollow piles in two rows was conducted in a two dimensional regular wave flume to study the wave transmission and reflection characteristics. The influence of incident wave steepness, relative clear spacing between the piles and rows of piles on transmission co-efficient and reflection co-efficient have been investigated. The effect of staggering of piles in the rows on both transmission and reflection co-efficients was also studied. The present study has revealed that for perforated pile groups incident wave steepness, relative clear spacing between the piles, relative clear spacing between the rows of piles influence both transmission and reflection co-efficients. Staggering of piles reduces reflection from the perforated piles. Perforated piles have smaller transmission and reflection co-efficient values compared to that of non-perforated piles at lower wave steepness.(Wave transmission and reflection for two rows of perforated hollow piles) Rao, S.; Shirlal, K.G.; Rao, N.B.S.2002