Faculty Publications
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Item Coastal erosion and mitigation methods - global state of art(2010) Hegde, A.V.Coastal erosion is assuming large proportions these days. Global climate change coupled with local attributes is eroding the coasts of the world in alarming proportions. Most of the conventional protection methods are hard, short lived, expensive and not eco-friendly. Trend in coastal erosion mitigation and protection has been shifting these days towards soft but novel, eco-friendly methods. Pro-active methods are being developed and used which are eco-friendly, construction-friendly, cheaper and which also reasonably address the root cause of the problem without much 'side effects'. Many non-traditional ways to armor, stabilize or restore beaches, including the use of patented precast concrete units, geotextile sand-filled bags, green belts, bio-engineering, sand fencing, beach-face dewatering systems, integrated costal protection methods are being used. Retreat from the coast is also thought about, in many circles. Present study consists the global coastal erosion scenario and also some of the state of the art soft and pro-active erosion mitigation methods.Item Seawalls: Performance and their failure analysis along Southern Karnataka, West Coast of India(2012) Rao, S.; Hegde, A.V.; Dwarakish, G.S.; Janardhan, J.; Venkat Reddy, D.Beach erosion is a major problem along the south west coast of India. The beach erosion particularly along the south Karnataka coast is due to, 1) direct attack of waves in an open coast, which might have been intensified in some areas due to wave refraction, 2) erosion at river mouths where one or two rivers together join the sea. The coastal protection works adopted along the South Karnataka coast are mainly the seawalls. However, some portions of these seawalls have been damaged either partially or fully. A critical study shows that these failures are due to the scouring at the toe structure. Scouring causes the failure of the seawall due to loss of support. A calculated risk may be taken to design the seawall without taking scour depth into account but provide for adequate maintenance in case scour occurs and partial failure of the seawall takes place. © 2012 Cafet-Innova Technical Society. All rights reserved.Item Shoreline management plan for a protected but eroding coast along the southwest coast of India(Elsevier B.V., 2017) Noujas, V.; Thomas, K.V.; Ajeesh, N.R.Coastal erosion is a serious problem of concern along the southwest (SW) coast of India. Various coastal protection measures have been applied for the recovery of the coast, but the devastating effect of erosion still continues. The present study focuses on a coastal stretch situated on the southern sector of the SW coast of India, where Sundar and Sannasiraj (2006) proposed a groyne field along with an existing seawall to control severe erosion. In order to confirm the net littoral drift of this region and for a preliminary assessment of the performance of the groynes prior to construction of the proposed groyne field, two groynes were initially constructed as a pilot program in 2008-09. Periodic monitoring of shoreline position with the two groynes in place was carried out during 2009-14. A shoreline evolution model for the study region was setup, calibrated, and validated using field observations during 2010-11. In addition to traditional shoreline evolution modelling procedures, a profile simulation model was applied for simulating the shoreline behaviour during extreme monsoon seasons. The validated LITPACK model has been used to evaluate the performance of the proposed groyne field in controlling erosion, and the study also considered testing a modified transitional groyne field proposed as an alternative solution to the existing problem, and the modified transitional groyne field was found to be more effective than the prior design. A beach is expected to develop about 30–50 m within the groyne cells during the fair season which enhances the possibility of retaining a minimum beach width of 10 m during monsoon periods. © 2017 International Research and Training Centre on Erosion and Sedimentation / the World Association for Sedimentation and Erosion ResearchItem Development of resilient breakwater against earthquake and Tsunami(American Society of Civil Engineers (ASCE) onlinejls@asce.org, 2019) Chaudhary, B.; Hazarika, H.; Murakami, A.; Fujisawa, K.The coastal areas in Japan suffered devastating damage due to the great East Japan earthquake and tsunami in 2011. Breakwaters collapsed mainly because of foundation failures during the earthquake and tsunami. Due to the breakwater failures, the tsunami entered the coastal zones and imposed deep devastation. This study focused on the development of reinforcing countermeasures for a breakwater foundation that can produce a resilient breakwater against earthquakes and tsunamis, such as foundations reinforced with sheet piles and gabions. Physical model tests were carried out for scaled-down breakwater models to examine the performance of the reinforcing countermeasures under an earthquake and tsunami. During the tests, the developed reinforced model was found to be effective in mitigating the damage of the breakwater created by the earthquake and tsunami. Numerical simulations were performed to further clarify the mechanism. © 2018 American Society of Civil Engineers.Item Physical model studies on damage and stability analysis of breakwaters armoured with geotextile sand containers(Elsevier Ltd, 2021) Elias, T.; Shirlal, K.G.; E.v, K.Harnessing the advantages of geotextile sand containers (GSCs), numerous submerged breakwaters and shoreline protection structures have been constructed worldwide. But an emerged breakwater structure with geotextile armour units, capable of replacing the conventional structures, is rarely discussed. A 1:30 scaled physical experimentation is chosen as a preliminary investigation to test the feasibility of using GSCs as breakwater armour units. Structural design is evolved based on a comprehensive literature survey. The paper focuses on the stability parameters and damage characteristics of the proposed structure. Four different configurations are subjected to waves, confining to Mangaluru's wave parameters. Effect of armour unit size and sand fill ratio on the stability of the structure is analysed and it is concluded that changing sand fill ratio from 80% to 100% shot up the structural stability to a maximum of 14%. Increasing bag size also resulted in the increased stability up to 8%. Experiments revealed that the best performing configuration could withstand wave heights up to 2.7 m. Stability curves for all tested configurations are discussed and can serve as an effective guideline for designing GSC breakwaters. © 2020 Elsevier LtdItem Performance characteristics of a conical pile head breakwater: An experimental study(Elsevier Ltd, 2021) Hunasanahally Sathyanarayana, A.H.; Suvarna, P.S.; Umesh, P.; Shirlal, K.G.Breakwaters are constructed for dissipating the wave energy and safeguarding the coastline from destructive wave forces. Conventional pile breakwater built using prismatic circular piles has been proven to provide partial protection efficiently. In the present study, the conventional pile breakwater is modified by widening the pile's cross-sectional area at the surface level in a conical shape. The concept of introducing the conical shape is to attenuate the concentrated wave energy, mainly focusing at the surface. The influence of the structural parameters such as diameter, height and clear spacing of the conical pile head is investigated experimentally for various monochromatic wave climatic conditions. The investigation is also focused on determining the influence of the second row on performance characteristics. The analysis shows that the least transmission coefficient (Kt) of 0.662 for the configuration of D/Hmax = 0.4, Y/Hmax = 1.5 and b/D = 0.1 for a single row of piles. Further, the second row of piles' inclusion resulted in improved attenuation characteristics of conical pile head breakwater (CPHB) with the least Kt of 0.582 at an optimal B/D of 0.4. The performance of the CPHB is compared with the theoretical solutions of conventional pile breakwater. The results indicate that the introduction of pile head on conventional pile breakwater is beneficial in improving wave attenuation. A set of empirical equations is developed based on the experimental values for quick prediction of Kt and Kr. The estimated values of Kt and Kr are in line with the experimental data with a coefficient of determination (R2) of 0.91 and 0.90, respectively. The overall performance of the CPHB is found to be promising as a potential coastal protection structure. © 2021 Elsevier LtdItem Hydraulic performance of perforated enlarged pile head breakwaters through laboratory investigation(Elsevier Ltd, 2021) Suvarna, P.S.; Hunasanahally Sathyanarayana, A.H.; Umesh, P.; Shirlal, K.G.An economical, ecofriendly and efficient breakwater system is vital for coastal protection and harbour tranquility. In this regard, various researchers are working to develop the appropriate solutions to encounter site-specific challenges. With this viewpoint, concept of enlarged pile head breakwater is developed. The study focuses on improving the hydraulic efficiency of pile breakwater by enlarging the structure near the free surface and providing it with perforations. Effect of percentage distribution of perforations, size of perforations and percentage of perforations on wave transmission, reflection and dissipation characteristics of the structure is investigated. The physical experiments are conducted in a two-dimensional wave flume under varying monochromatic wave climates. Results indicate that the pore size highly dominants the wave attenuation than considering the increasing percentage of perforations with the small size of the pore. Perforations effectively reduce the Kt of about 10%–18% to that of non-perforated pile head breakwater. Hydraulic efficiency of enlarged pile head breakwater is optimum when D/Hmax = 0.6, Y/Hmax = 1.0, b/D = 0.2, S = 0.25D, pa = 75% and P = 22.5 at 0.3 m water depth. A hybrid theoretical solution is developed based on the current set of experimental data for the quick estimate of hydraulic coefficients. The proposed hybrid equation for the perforated pile breakwater predicts more desirable values of Kt, Kr and Kd. The proposed concept of breakwater gives a reasonably enhanced hydraulic efficiency than the compared type of breakwaters. © 2021 Elsevier LtdItem Experimental Investigation of the Hydraulic Performance of Breakwater Structures with Geotextile Armor Units(American Society of Civil Engineers (ASCE), 2022) Elias, T.; Shirlal, K.G.Geotextile sand containers (GSCs) gained popularity recently as a modern age coastal protection measure. Its usability as an ecofriendly alternative for traditional breakwaters overcomes issues such as scarcity and quarrying prohibition of natural rocks. The current work involves a 1:30 scaled physical experimentation on the hydraulic performance of an emerged, nonovertopping breakwater model with GSCs. Four configurations of GSC structures are analyzed for their runup, rundown, and reflection characteristics confining to wave parameters of Mangaluru. The study revealed that the reflection coefficient (Kr) for GSC structures could range from 0.26 to 0.69. In addition, reducing GSC fill percentage from 100 to 80 is found to be more effective (up to 64%) in reducing reflection, runup, and rundown rates, than altering GSC size. These results can serve as a practical guideline for designing GSC breakwaters. © 2022 American Society of Civil Engineers.Item Effect of armour unit layers and placement mode in the determination of stability of geotextile sand container (GSC) breakwaters(Elsevier Ltd, 2022) Elias, T.; Geetha, T.; Shirlal, K.G.Geosynthetic Sand Containers (GSCs) are increasingly harnessed for their coastal protection capabilities. Recent studies point to its efficacy to be used even as armour units of breakwaters. The current investigation aims at understanding the effect of armour unit layers and placement modes in altering the stability of GSC breakwaters. Single-layered and double-layered GSC structures with slope parallel and perpendicular placement are tested for stability against wave conditions of the Mangaluru coast. A 1:30 scaled monochromatic wave flume model study is adopted to detail the damage levels and stability of various GSC breakwaters. It is observed that the stability of structure increased by up to 17% when supplemented with double layers. Structure tends to be stable with increasing armour units size and fill percentage. Larger bags stacked to double layers is found to be the most stable configuration. 80% filled, slope parallel placement exhibited the least stability. The paper dealt with all factors affecting structure stability and deduced stability nomograms helpful for coastal engineers to design GSC breakwaters. © 2022Item Investigations on the development of hybrid mound breakwaters for tsunami defense(Elsevier Ltd, 2025) Sajan, M.K.; Chaudhary, B.; P K, A.; Sah, B.Tsunamis significantly damage coastal infrastructure and lives, resulting in extensive economic implications. Despite the global adoption of breakwaters as a primary coastal defence measure, it was observed that the structural integrity of several of these breakwaters was compromised during past tsunamis. The present study addresses these vulnerabilities of breakwaters by particularly focusing on the most commonly adopted rubble mound type breakwater. Further, this study introduces a novel technique in order to enhance the reliability of these structures by mitigating the tsunami induced failure mechanisms. In the novel technique, wrap-faced geogrids are implemented to reinforce the rubble mound without compromising the breakwater functionality in dissipating the incident wave energy through transmission. A comprehensive evaluation was carried out, including tsunami overflow tests, analytical assessments, and numerical simulations, to ascertain the effectiveness of the novel hybrid mound breakwater. The findings indicate that the developed hybrid mound breakwater withstood level 1 tsunamis with a 96.7 % reduction in settlement. One of the critical failure mechanism of breakwaters observed during past tsunamis was due to the seepage induced scouring of the foundation. The hybrid mound breakwater showcased a 42.37 % reduction in the foundation pore water pressure during tsunami by incorporating cut off walls. The numerical simulations also reconfirmed the enhanced performance of hybrid mound breakwater to protect the coasts from future tsunamis. © 2025