Browsing by Author "Sharma, Garima."

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Assessment of coringa mangrove shoreline migration using geospatial techniques
(Journal of Operational Oceanography, 2020-11-06) Sharma, Garima.; Patnaik, K. V. K. R. K.
Coringa Mangroves in the Kakinada Bay have evolved as the second-largest mangroves in the East Coast of India over the last century. The Coringa Mangrove shoreline has accreted considerably in the past decades as observed from the satellite imageries, adding value to the natural biodiversity of flora and fauna. This study is focused on quantifying the long term changes of Coringa mangrove shoreline using the Landsat imageries for years 1977, 1988, 2000, and 2013 using the Digital Shoreline Analysis System. For a mangrove shoreline length of 20.5 km, 41 transects were cast at an interval of 500 m for calculating the change and their migration distance using three statistical methods, namely End Point Rate (EPR), Net Shoreline Movement (NSM) and Linear Regression Rate (LRR). Results showed that there was considerable growth of mangroves in the bay leading to the seaward migration of the mangrove shoreline from the year 1977– 2013. The study observed the difference in the mangrove shoreline migration dynamics in the South-eastern (near the bottom of the spit) and the western part of the Kakinada Bay. The calculated average degradation rate due to erosion is −5.19 m.yr−1 and the average accretion rate leading to their growth is 14.83 m.yr−1 for all transects of the 20.5 km mangrove shoreline stretch during this period. The results hold importance as they help in identifying the regions prone to mangrove degradation and enable management planning for the protection of the eroding stretch of the mangrove shoreline.
Long term morphodynamic evolution of Kakinada bay using upscaling methods
(Marine Engineers Review (India), 2020) Sharma, Garima.; Sivakholundu, K. M.; Patnaik, K. V. K. R. K.
Kakinada Bay has evolved over the last century dynamically by the action of wind, waves, tides and currents. Formation of Hope Island and development of Coringa Mangroves are attributed to the hydrodynamic 'forcings' and sediment dynamics. This study aims to predict the future morphological development of Kakinada Bay for next 100 years. The morphological model was built up in the DELFT 3D package. Model setting parameters were fixed after analysing their effect on the simulation results. For reducing the computational time and effort for simulating long term morphological development, upscaling methods such as morphological acceleration factor (MORFAC) and morphological tide were incorporated in the morphological model. Morphological tide was formed using tidal constituents - M2, O1 and K1. The MORFAC value for this study was chosen as 30 after undergoing the sensitivity test analysis using Brier Score Skill (BSS) Score. The model was run for 19 years for hindcasting and 100 years for forecasting. In order to establish confidence in the model, it was calibrated and validated using hindcast modelling. The hindcast simulation results were used to match the simulated shoreline with satellite observed shoreline from year 1988 to 2000, and 2006 to 2013 and the results were in good agreement. It was observed that the south-western part of the bay has accreted more rapidly while south-eastern part of the bay has undergone slight erosion. Thereafter long term morphological model was run for 100 years to predict the future evolution of bay. Results of these simulations show the capability of the long term morphological model to predict the spatial and temporal geo-morphological changes.
Study on the wave diffraction patterns in the Kakinada bay
(Indian Maritime University, Visakhapatnam, 2019) Sharma, Garima.; Patnaik, K. V. K. R. K.
Kakinada is one of the major upcoming ports of India and holds great importance for shipping activities. This region is said to be low-lying area and highly susceptible to erosion. To protect the port from action of waves, tides and strong currents, breakwater was constructed at the entrance of the channel. Current study makes an attempt to understand how wave energy gets reduced and wave diffraction occurs due to presence of the breakwater. Numerical solution of the mild slope equation and diffraction pattern are studied using MIKE 21 PMS model. Intense wave activity is higher during south west monsoon season than north east monsoon season. Significant wave heights have reduced considerably to 0-0.15m because of the breakwater during both the seasons and no waves are entering inside the bay. Waves have bent at the breakwater due to diffraction along with the formation of concentric ripples with the decreased wave heights.
Study on the wave diffraction patterns in the Kakinada bay
(Journal of offshore structure and technology, 2020) Sharma, Garima.; Patnaik, K. V. K. R. K.
Kakinada is one of the major upcoming ports of India and holds great importance for shipping activities. This region is said to be low-lying area and highly susceptible to erosion. To protect the port from action of waves, tides and strong currents, breakwater was constructed at the entrance of the channel. Current study makes an attempt to understand how wave energy gets reduced and wave diffraction occurs due to presence of the breakwater. Numerical solution of the mild slope equation and diffraction pattern are studied using MIKE 21 PMS model. Intense wave activity is higher during south west monsoon season than north east monsoon season. Significant wave heights have reduced considerably to 0–0.15 m because of the breakwater during both the seasons and no waves are entering inside the bay. Waves have bent at the breakwater due to diffraction along with the formation of concentric ripples with the decreased wave heights.
The long - term morphological development of kakinada bay
(Indian Maritime University, Chennai, 2022) Sharma, Garima.; Sivakholundu, K. M.
The evolution of Kakinada Bay with Coringa Mangroves at its southern shore and Kakinada Spit and Hope Island at its eastern side has occurred over the past century. This morphological development of the bay is attributed to the biophysical interactions, hydrodynamic forcing like waves, winds, tides, currents and sediment dynamics occurring inside the bay. The processes governing the short-term (decadal) and long-term (century) morphology of the bay need to be studied to develop sustainable coastal management plan for the intermediate time-scale. This study is an effort to extend the use of process based models to longer time scales to provide better understanding of the morphological development by the action of various physical processes governing alone and in combination. This study answers the question if these long-term morphological modeling can produce the reliable results by creating nexus of two techniques „Remote Sensing and Numerical Modeling‟. The numerical modeling hindcast results are validated using remote sensing images. This study quantifies the rate of change of the shoreline of the bay using remote sensing images in the Digital Shoreline Analysis System (DSAS). The trend of erosion and accretion occurring inside the bay was obtained using indices End Point Rate (EPR), Net Shoreline Movement (NSM) and Linear Regression Rate (LRR). The rate and trend of sedimentation and erosion obtained with the satellite imageries are further used to statistically compare the transect–wise hindcast and forecast results. Thus this study demonstrates the model‟s ability to reproduce the long-term morphodynamic development of the bay. This study attempts to investigate the action of physical processes on the morphological changes of the bay over a period of 100 years. For long term morphological modeling various approaches are followed like Input Reduction, Model Reduction and Acceleration techniques. Input reduction simulates the long term morphological modeling using schematized input data like morphological tide, schematized wave which are representative sets of the entire data. Model Reduction follows the approach of giving only the most important processes in the model input. Acceleration technique approach uses the morphological acceleration factor which accelerates the morphological development by the assigned factor. Available variants of the morphological predictions have been considered for the study. The study attempts to answer the hypothesis made to choose the appropriate approach between the two statements issued by Lesser (2009) and Roelvink (1999). The approach for adopting model reduction following the correct use of acceleration techniques as stated by Lesser (2009): “In order to use a morphological acceleration technique in a coastal situation it is essential to identify which coastal processes play a significant role in (residual) sediment transport patterns over the space and time scales of interest”. The second approach following the statement given by Roelvink (1999) and quoted by Dastgheib A. (2012) as: “If you put enough of the essential physics into the model, the most important features of the morphological behavior will come out, even at the longer time scales”. The exercise was varied with different environmental forcing with three scenarios: a) Tide only following Model Reduction, b) Tide and Wave Combined, c) Tide and Wave combined action with decadal MSL changes. The planimetric and decadal volumetric changes, shoreline changes have been compared for all the three scenarios. The outcome of the morphodynamic modeling from the different sets of physical processes will help to isolate the role of each physical process that are making difference in the overall morphological changes of the bay. It aims to isolate the effect of waves by comparing two simulations one with only tide and other with both wave and tidal forcing. The study with obtained forecast results will identify the areas under erosion and accretion and quantify the rate of shoreline changes. These results can help further in taking steps for coastal management. Thus this study gives an exemplary integration of the available techniques that can be helpful for coastal development modeling.