Faculty Publications
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Item Erosion and Accretion in the Netravati River Stretch: Spatiotemporal Analysis Using Geospatial Approach(Springer Science and Business Media Deutschland GmbH, 2024) Makhdumi, W.; Shwetha, H.R.; Dwarakish, G.S.Understanding erosion and accretion, which are critical geomorphic processes, is essential for effective river management and conservation. Erosion by removing soil and rock changes the river's shape, depth, and course. Accretion, conversely, involves the deposition and accumulation of sediment, shaping features like riverbanks and floodplains. Focused on a 30 km stretch of the Netravati River, in the southwestern region of India, this study used Survey of India toposheets and Landsat images to track changes over time (1973, 1998, 2022). The Normalised Difference Water Index (NDWI) and image classification were employed for the analysis which revealed notable spatiotemporal variations in these processes. From 1973 to 2022, the analysis estimated a total erosion of 510.43 hectares and an accretion of 317.71 hectares. The years 1973–1998 witnessed more accretion (417.6 hectares) than erosion (229.08 hectares). And, from 1998 to 2022, erosion dominated at 438.37 hectares, with only 56.97 hectares of accretion. These variations can be attributed to both natural processes and human interventions. Notably, the construction of a vented dam in 1993 at Thumbe, followed by the subsequent dam in 2016, 50 m downstream of the old dam, influenced the sediment dynamics and flow patterns in the Netravati River, potentially impacting erosion and accretion processes. This research adds to our understanding of erosion and sediment changes in the Netravati River over time. The dams and hydraulic structure upstream along with geospatial techniques offer researchers and river managers a unique opportunity to examine river shape impacts and thus develop sustainable strategies for river preservation. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.Item Integrated coastal zone management plan for Udupi coast using remote sensing, geographical information system and global position system(SPIE spie@spie.org, 2008) Dwarakish, G.S.; Vinay, S.A.; Dinakar, S.M.; Pai, B.J.; Mahaganesha, K.; Natesan, U.Coastal areas are under great pressure due to increase in human population and industrialization/commercialization and hence these areas are vulnerable to environmental degradation, resource reduction and user conflicts. In the present study an Integrated Coastal Zone Management Plan (ICZMP) has been developed for Udupi Coast in Karnataka, along West Coast of India. The various data products used in the present study includes IRS-1C LISS-III + PAN and IRS-P6 LISS III remotely sensed data, Naval Hydrographic Charts and Survey of India (SOI) toposheets, in addition to ground truth data. Thematic maps such as land use/ land cover map, bathymetry map, shoreline configuration map, transportation and drainage network maps, GPS survey map, CRZ map, contour map, DEM, inundation map, critical erosion area map were prepared. A Coastal Vulnerability Index has also been calculated for the study area to know the resistance of study area to sea level rise and is demarcated into four categories; Very high, High, Moderate and Low vulnerability, and a vulnerability map has been prepared. The results of the present study are encouraging. Some of the specific conclusions of the study are; about 50% study area is prone to erosion, river mouths along study area show shifting tendency towards south, and the beaches along the Udupi Coast are maintaining dynamic equilibrium. Coastal Zone Information System (CZIS) has been developed through V.B.6.0 using results of various data analysis. © 2008 Society of Photo-Optical Instrumentation Engineers.Item Coastal vulnerability assessment of the future sea level rise in Udupi coastal zone of Karnataka state, west coast of India(2009) Dwarakish, G.S.; Vinay, S.A.; Natesan, U.; Asano, T.; Kakinuma, T.; Venkataramana, K.; Pai, B.J.; Babita, M.K.Udupi coast in Karnataka state, along the west coast of India, selected as a study area, is well known for sandy beaches, aquaculture ponds, lush greenery, temples and major and minor industries. It lies between 13°00?00?-13°45?00? north latitudes and 74°47?30?-74°30?00? east longitudes, the length of the coastline is 95 km, and is oriented along the NNW-SSE direction. It is vulnerable to accelerated sea level rise (SLR) due to its low topography and its high ecological and touristy value. The present study has been carried out with a view to calculate the coastal vulnerability index (CVI) to know the high and low vulnerable areas and area of inundation due to future SLR, and land loss due to coastal erosion. Both conventional and remotely sensed data were used and analysed through the modelling technique and by using ERDAS Imagine and geographical information system software. The rate of erosion was 0.6018 km2/yr during 2000-2006 and around 46 km of the total 95 km stretch is under critical erosion. Out of the 95 km stretch coastline, 59% is at very high risk, 7% high, 4% moderate and 30% in the low vulnerable category, due to SLR. Results of the inundation analysis indicate that 42.19 km2 and 372.08 km2 of the land area will be submerged by flooding at 1 m and 10 m inundation levels. The most severely affected sectors are expected to be the residential and recreational areas, agricultural land, and the natural ecosystem. As this coast is planned for future coastal developmental activities, measures such as building regulation, urban growth planning, development of an integrated coastal zone management, strict enforcement of the Coastal Regulation Zone (CRZ) Act 1991, monitoring of impacts and further research in this regard are recommended for the study area. © 2009 Elsevier Ltd. All rights reserved.Item Geomorphological behaviour of Sasihithlu, Mangalore coast, west coast of India(2011) Nagaraj, G.; Karjagi, A.; Kumar, M.; Dwarakish, G.S.Beach geomorphological studies have been carried out with help of conventional methods and remote sensing techniques. Conventional methods include beach profile surveys and beachwidth measurements whereas remote sensing techniques involved in utilization of satellite images, digitization and analyses. Beach profile surveys and beachwidth measurements are carried out at monthly intervals over a period of one year (September 2009 to September 2010) to understand dynamics of sediment along the coastal segment of 7km at Sasihithlu, north off Mangalore coastline. Six locations are selected based on their significant site characteristics along the coastal segment. It is observed erosion with steeper slopes during the monsoon and simultaneously deposition with flat and wider exposed slopes during the fair weather season. But the more drastic and dramatic changes are observed in the vicinity of Mulki-Pavanje rivermouth, since the rivers Mulky and Pavanje bring any kind of sediments irrespective of seasons. Because of this the profiles alter dramatically in the vicinity of rivermouth. It is estimated that the Sasihithlu beach has experienced a net loss of about 2515m 3/m, a net gain of about 3525m 3/m and hence a gain of about 1010m 3/m sediments in an annual cycle. Addition to conventional methods, remote sensing analysis is also carried out to detect the influence of rivers and their flow on rivermouth system in recent decades (1988-2009) with the help of satellite images and GIS tools. It is observed that the shifting tendency of rivermouth either south or north irrespective of seasons. However a detailed investigation on shoreline pattern showed a clear indication of shifting shoreline towards south. Therefore present study suggests to construct coastal protection structures on either side of the rivermouth, through that the damage to the property could be minimized. © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.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 Effect of disturbed river sediment supply on shoreline configuration: A case study(Taylor and Francis Ltd., 2022) Yadav, A.; Dodamani, B.M.; Dwarakish, G.S.The magnitude of river sediment supply and its distribution play a significant role in coastal sediment dynamics, especially in erosion and deposition. Due to the construction of the dam, obstruction in the natural flow of water occurs, and part of the sediment is trapped. In the present study, the Kali river catchment and its river-mouth at Karwar, Devbagh, and Ravindranath Tagore beaches are considered as the study area, to assess the impact of dams on coastal processes. Landsat data for 42 years, from 1975 to 2017, were collected and analyzed using DSAS, an ArcGIS extension. The sediment yield estimated at the Kali river basin outlet, without the dam is 4.19 t/ha/yr and with the dam, it is estimated to be 1.42 t/ha/yr. Similarly, for the Aghanashini river basin outlet, the sediment yield was found to be 4.58 t/hr/yr. From the results of shoreline analysis, it is found that after the construction of the dam, Devbagh beach is under erosion at the rate of ?0.93 m/yr End Point Rate (EPR) and ?0.47 m/yr Linear Regression Rate (LRR). Ravindranath Tagore beach also has undergone erosion, which is ?0.75 m/yr (EPR) and ?0.97 m/yr (LRR). Further, both the beaches have been changed to the erosion zone. © 2021 Indian Society for Hydraulics.Item Time-series analysis of erosion issues on a human-intervened coast– A case study of the south-west coast of India(Elsevier Ltd, 2023) Parvathy, M.M.; Balu, R.; Dwarakish, G.S.Coastal erosion has long been identified as a cause of concern for the state of Kerala, situated in the Indian subcontinent, affecting the life and livelihood of millions residing in the coastal belt. The increased human interference supplemented by changes in the climatic pattern in recent years has modified the coastal scenario of the state altogether. The present study attempts to evaluate the effect of anthropogenic influences in modifying the coastal scenario to review the efficiency of the coastal management policy adopted by the state over the years. For this purpose, the shorelines extracted from the available multi-temporal satellite images are analysed using DSAS software to calculate the shoreline change rate prior to 2000 (1973-98) and post-2000 (2002-21) using the linear rate of regression method. The study seeks to key out critically eroding areas, subsequently exploring the possible conducive reasons for the changed coastal scenario. The results indicate a reduction of 34.5% in the share of eroding length, with a visible shift in a substantial portion of coastal stretch from the mild erosion category to the stable category. Despite the state's continuous efforts to curb the issue, the long-term shoreline change over the past 49 years (1973–2021) reveals erosion to be dominant in nearly 39.12% of the coastal length, with the share of eroding length in the southern, central and northern regions as 33.8%, 38.67% and 44.04%, respectively. The results point towards the dominance of human interventions accompanied by climate change impacts as the primary reason for transforming the coast, necessitating the need to modify the state's current coastal management policy. The research emphasises the need for a comprehensive coastal management plan for the state to take heed of the changing climatic scenario. © 2023 Elsevier LtdItem Development of a regional-scale erosion vulnerability assessment approach along a human-intervened coast–a case study from the southern part of Kerala, India(Taylor and Francis Ltd., 2025) Parvathy, M.M.; Balu, R.; Dwarakish, G.S.The coastal district of Thiruvananthapuram, situated in the southern part of the state of Kerala, is endowed with sandy beaches, majestic cliffs, scenic backwaters and rocky promontories, aside from hosting a sizeable coastal population, well-known tourist attractions, unique biodiversity, and numerous developmental activities. However, erosion is one hazard that gravely impacts these zones, disturbing the coastal environment and affecting the lives of thousands residing in these regions. The present study attempts to identify the critical vulnerable areas to erosion, considering the combined influence of hazard parameters, i.e. drivers of erosion and risk parameters, i.e. the assets at stake. A multi-criteria decision-making approach, integrated with expert ranking, is adopted in the present study to identify and classify the vulnerable stretches, demanding urgent intervention to prevent further erosion and safeguard vital resources. The results indicate that approximately 10% of the coast falls under low vulnerability, 77% under medium vulnerability, 12 % under high vulnerability, and 1% under very high vulnerability. The coastal reaches of Shangumugham and Anchuthengu are identified as highly vulnerable and in urgent need of intervention. The spatial distribution of vulnerability necessitates a focused and site-specific management plan to tackle the present and possible erosion issues and protect critical resources. © 2025 Indian Society for Hydraulics.