D.P.C. Laknath - Academia.edu (original) (raw)

Papers by D.P.C. Laknath

Research paper thumbnail of Understanding the Collision of Debris Carried by Tsunami-Like Flows on a Residential Structure

Volume 4: Ocean Space Utilization

Collision force exerted by single cuboid elements with different dimensions and sizes, subjected ... more Collision force exerted by single cuboid elements with different dimensions and sizes, subjected to dissimilar dam-break waves were investigated in this study to determine their ability to induce forces on a one storey residential structure with respect to the wave only forces. The observations indicated that a significant amount of additional force was exerted on the house model with several delivery modes and impacting patterns. The smaller size of cuboid subjected with lower wave conditions induced a considerably larger force, whereas for higher flow conditions, it was not as sensitive to the wave forces. In contrast, the larger size of the cuboid yielded a lower force for lower wave condition and displayed a considerable increment for larger waves. Several governing parameters were identified to be incorporated in the presently available formulations to estimate the debris impacts.

Research paper thumbnail of Application of Hydrological Study Methodologies Used in African Context for Water Security in Asian Countries

Water Security in Asia, 2021

Research paper thumbnail of Simulation of Nearshore Coastal Processes for Development of Fishery Harbour

Asian and Pacific Coasts 2017, 2017

Research paper thumbnail of Simulation of 2004 Tsunami Inundation in Galle City in Sri Lanka and Revisit the Present Evacuation Measures

Coastal Engineering Proceedings, 2020

Tsunami inundation was successfully reproduced for the Galle City, Sri Lanka using Delft3D-Flow m... more Tsunami inundation was successfully reproduced for the Galle City, Sri Lanka using Delft3D-Flow model and Delft Dashboard Tsunami Tool. Previously identified tsunami hazard maps agreed with the simulation results. Existing tsunami early warning system and preparedness for evacuation are in a favourable condition. Based on the outcome of numerical simulation and field investigations, suitable horizontal evacuation measures were proposed, and vertical evacuation points were suggested primarily considering the identified hazardous zones with lack of proposed buildings and evacuation routes in previous studies.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/g4V0c8GQepE

Research paper thumbnail of Wave Climate Study Around Kirinda Fishery Harbour In Sri Lanka Using SWAN Model

Seasonal sand accumulation problem in Kirinda fishery harbour is well known problem among the har... more Seasonal sand accumulation problem in Kirinda fishery harbour is well known problem among the harbours in Sri Lanka. To elucidate the possible sand transport patterns close to the harbour area, wave climate study was carried out using SWAN modeling system. After analyzing global reanalysis wind data, SWAN model was executed for the selected representative simulation periods of southwest and northeast monsoon by wind forcing. On the basis of estimated wave parameters, sea and swell waves and longshore sand transport directions were investigated. During the southwest monsoon, sea and swell wave propagation from southwest direction is identified. For northeast monsoon, two distinct wave directions corresponding to the sea and swell waves were recognized. Finally, longshore sand transport process occurs during the southwest monsoon season, from southwest direction is recognized as the main cause for the seasonal closure of the entrance.

Research paper thumbnail of Study on sediment accumulation processes in Kirinda Fishery Harbour, Sri Lanka

Kirinda fishery harbour is a well known harbour in Sri Lanka for its seasonal sand accumulation p... more Kirinda fishery harbour is a well known harbour in Sri Lanka for its seasonal sand accumulation problem. This phenomenon occurs throughout the year and it becomes severe during the south-west monsoon season. As a result, the harbour entrance is often blocked completely, diminishing the safe navigation access. Even after the harbour was modified, this problem was not solved completely. In order to elucidate the possible mechanisms of this process, we performed a field survey and investigated the seasonal variation of wave climate, bathymetry and shoreline changes. From our investigation, it was concluded that, sediment accumulation process inside the harbour basin and entrance are mainly due to sediment transport from the south direction during south-west monsoon season.

Research paper thumbnail of Wave Hindcasting and Extreme Value Analysis for North-Western Coast of Sri Lanka

Research paper thumbnail of Elucidation of Seasonal Sediment Transport Processes In Kirinda Fishery Harbour In Sri Lanka Using XBeach Model

Seasonal sand accumulation processes in Kirinda Fishery Harbour was studied using field data and ... more Seasonal sand accumulation processes in Kirinda Fishery Harbour was studied using field data and numerically reproduced results. In order to explain the bottom topography variation occurred during February 2005 February 2006 period in the vicinity of the harbour, a 2DH numerical model, XBeach was successfully used. XBeach model was executed for the selected dominant wave conditions of southwest and northeast monsoons. On the basis of reproduced longshore current patterns, sand transport directions and resultant accretion and erosion areas for both southwest and northeast monsoons were explained. Considering the topography variations and current directions, main sand movement direction from south to north directions during the southwest monsoon was explained. Sand deposition inside the basins and entrance resulted from the sand inflow through the entrance by flow currents during the sand transport process from south to north direction. Further, during the northeast monsoon, accretion...

Research paper thumbnail of Study on Damages of Laver Aquaculture Facilities in Tokyo Bay from 2011 Tohoku Earthquake Tsunami

1Technology Center, Taisei Corporation, laknath@pub.taisei.co.jp 2Technology Center, Taisei Corpo... more 1Technology Center, Taisei Corporation, laknath@pub.taisei.co.jp 2Technology Center, Taisei Corporation, hndtkh01@pub.taisei.co.jp 3Technology Center, Taisei Corporation, kazunori.ito@sakura.taisei.co.jp 4Faculty of Urban Innovation, Yokohama National University, jsasaki@estuarine.jp 5Technology Center, Taisei Corporation, yuriko.takayama@sakura.taisei.co.jp 6Technology Center, Taisei Corporation, od-ykn00@pub.taisei.co.jp

Research paper thumbnail of Storm Surge Simulation in Nagasaki During the Passage of 2012 Typhoon Sanba

Coastal Engineering Proceedings, 2014

As a result of global warming effect, storm surges generated by extreme weather events such as tr... more As a result of global warming effect, storm surges generated by extreme weather events such as tropical cyclones, typhoons and hurricanes, significantly impact to the life and property in storm-surge prone coastal low-lying areas. Therefore, numerical modeling systems, comprising meteorological, hydrodynamic and wave simulation capabilities are essential for the storm surge hindcasting and forecasting phases in disaster mitigation and management processes. Accordingly, we assessed the applicability of two meteorological simulation methods; (1) Mesoscale Meteorological Model MM5 and (2) Delft Dashboard (DDB) Tropical Cyclone Tool, together with Delft3D FLOW-WAVE coupled modeling system to simulate the storm surges in Nagasaki coast during the passage of 2012 typhoon SANBA. Storm surge generated by MM5-Delft3D and DDB-Delft3D systems in Nagasaki area were reasonably agreed with the observations. Thus, applicability of both meteorological simulation techniques together with Delft3D FLOW-WAVE coupled modeling system to simulate the storm surge was validated with a reasonable level of accuracy. Further, compared to the MM5-Delft3D system, fast and easy simulation capability of DDB-Delft3D system was identified. However, in terms of accuracy, MM5-Delft3D system demonstrated much better performance in outer regions of the typhoon than the DDB-Delft3D system.

Research paper thumbnail of Analysis of Cyclone Events in Bay of Bengal and Simulation of Storm Surge in Eastern Coast of Sri Lanka

APAC 2019, 2019

Characteristics and behavior of cyclones occurred in Bay of Bengal during last 4 decades in the l... more Characteristics and behavior of cyclones occurred in Bay of Bengal during last 4 decades in the light of global warming effect and applicability of Delft3D modeling system with Delft Dashboard Tropical Cyclone to simulate storm surge levels in eastern coast of Sri Lanka during the passage of 2000 Cyclone (BOB 06) were investigated in this research. Through the statistical analysis of cyclone characteristics, increasing trend of sustained wind speed with the increase of sea surface temperature (SST) over the Bay of Bengal was identified for the considered period though there is no trend for annual cyclone variation. In this study, spatially varying wind and pressure fields of 2000 Cyclone were reproduced by using Delft Dashboard Tropical Cyclone Tool. FLOW model of Delft3D system was used to simulate the hydrodynamic effects caused by wind, atmospheric pressure changes and tidal forces. Thus, Delft Dashboard Tropical Cyclone Tool, together with Delft3D FLOW-WAVE coupled modeling system could simulate storm surge level in eastern coast of Sri Lanka for 2000 Cyclone event with a satisfactory level of accuracy.

Research paper thumbnail of Simulation of Tsunami Inundation in East Coast of Sri Lanka

APAC 2019, 2019

Present tectonic activities around the Andaman–Sumatran subduction zone gives an alarming signal ... more Present tectonic activities around the Andaman–Sumatran subduction zone gives an alarming signal of a possibility of occurring tsunamis in the Indian Ocean again and could bring devastation for rim countries in the Indian Ocean. Hence, proper understanding about possible tsunami inundation levels is a prerequisite for disaster prevention and management processes in tsunami prone areas such as low elevation coastal areas in the eastern coast of Sri Lanka. Therefore, as an initial step, present study was carried out to simulate tsunami propagation and inundation for Kallady city in the eastern coast of Sri Lanka to understand about vulnerable areas for future tsunamis. Kallady is a low lying, populated coastal city in eastern province of Sri Lanka. In this study, tsunami wave propagation and inundation in Kallady area under different scenarios namely, 2004 tsunami event and two hypothetical tsunamis with magnitudes of 9.5 and 10.5 respectively, where the epicenter of the earthquake of hypothetical two tsunamis was assumed to be similar to the 2004 tsunami event. Tsunami wave propagation and successive land area inundation were simulated using ELIMO and Nays2DFlood solvers of iRIC interface accordingly. Bathymetric and topography data were obtained from GEBCO, SRTM and recent field investigations in 2017. Initial sea surface elevations were simulated using Okada’s formula. ELIMO resolves well the wave propagation. However, Nays2D Flood determines inundation level significantly lower since it only employs water level record to model the inundation.

Research paper thumbnail of Understanding the Collision of Debris Carried by Tsunami-Like Flows on a Residential Structure

Volume 4: Ocean Space Utilization

Collision force exerted by single cuboid elements with different dimensions and sizes, subjected ... more Collision force exerted by single cuboid elements with different dimensions and sizes, subjected to dissimilar dam-break waves were investigated in this study to determine their ability to induce forces on a one storey residential structure with respect to the wave only forces. The observations indicated that a significant amount of additional force was exerted on the house model with several delivery modes and impacting patterns. The smaller size of cuboid subjected with lower wave conditions induced a considerably larger force, whereas for higher flow conditions, it was not as sensitive to the wave forces. In contrast, the larger size of the cuboid yielded a lower force for lower wave condition and displayed a considerable increment for larger waves. Several governing parameters were identified to be incorporated in the presently available formulations to estimate the debris impacts.

Research paper thumbnail of Application of Hydrological Study Methodologies Used in African Context for Water Security in Asian Countries

Water Security in Asia, 2021

Research paper thumbnail of Simulation of Nearshore Coastal Processes for Development of Fishery Harbour

Asian and Pacific Coasts 2017, 2017

Research paper thumbnail of Simulation of 2004 Tsunami Inundation in Galle City in Sri Lanka and Revisit the Present Evacuation Measures

Coastal Engineering Proceedings, 2020

Tsunami inundation was successfully reproduced for the Galle City, Sri Lanka using Delft3D-Flow m... more Tsunami inundation was successfully reproduced for the Galle City, Sri Lanka using Delft3D-Flow model and Delft Dashboard Tsunami Tool. Previously identified tsunami hazard maps agreed with the simulation results. Existing tsunami early warning system and preparedness for evacuation are in a favourable condition. Based on the outcome of numerical simulation and field investigations, suitable horizontal evacuation measures were proposed, and vertical evacuation points were suggested primarily considering the identified hazardous zones with lack of proposed buildings and evacuation routes in previous studies.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/g4V0c8GQepE

Research paper thumbnail of Wave Climate Study Around Kirinda Fishery Harbour In Sri Lanka Using SWAN Model

Seasonal sand accumulation problem in Kirinda fishery harbour is well known problem among the har... more Seasonal sand accumulation problem in Kirinda fishery harbour is well known problem among the harbours in Sri Lanka. To elucidate the possible sand transport patterns close to the harbour area, wave climate study was carried out using SWAN modeling system. After analyzing global reanalysis wind data, SWAN model was executed for the selected representative simulation periods of southwest and northeast monsoon by wind forcing. On the basis of estimated wave parameters, sea and swell waves and longshore sand transport directions were investigated. During the southwest monsoon, sea and swell wave propagation from southwest direction is identified. For northeast monsoon, two distinct wave directions corresponding to the sea and swell waves were recognized. Finally, longshore sand transport process occurs during the southwest monsoon season, from southwest direction is recognized as the main cause for the seasonal closure of the entrance.

Research paper thumbnail of Study on sediment accumulation processes in Kirinda Fishery Harbour, Sri Lanka

Kirinda fishery harbour is a well known harbour in Sri Lanka for its seasonal sand accumulation p... more Kirinda fishery harbour is a well known harbour in Sri Lanka for its seasonal sand accumulation problem. This phenomenon occurs throughout the year and it becomes severe during the south-west monsoon season. As a result, the harbour entrance is often blocked completely, diminishing the safe navigation access. Even after the harbour was modified, this problem was not solved completely. In order to elucidate the possible mechanisms of this process, we performed a field survey and investigated the seasonal variation of wave climate, bathymetry and shoreline changes. From our investigation, it was concluded that, sediment accumulation process inside the harbour basin and entrance are mainly due to sediment transport from the south direction during south-west monsoon season.

Research paper thumbnail of Wave Hindcasting and Extreme Value Analysis for North-Western Coast of Sri Lanka

Research paper thumbnail of Elucidation of Seasonal Sediment Transport Processes In Kirinda Fishery Harbour In Sri Lanka Using XBeach Model

Seasonal sand accumulation processes in Kirinda Fishery Harbour was studied using field data and ... more Seasonal sand accumulation processes in Kirinda Fishery Harbour was studied using field data and numerically reproduced results. In order to explain the bottom topography variation occurred during February 2005 February 2006 period in the vicinity of the harbour, a 2DH numerical model, XBeach was successfully used. XBeach model was executed for the selected dominant wave conditions of southwest and northeast monsoons. On the basis of reproduced longshore current patterns, sand transport directions and resultant accretion and erosion areas for both southwest and northeast monsoons were explained. Considering the topography variations and current directions, main sand movement direction from south to north directions during the southwest monsoon was explained. Sand deposition inside the basins and entrance resulted from the sand inflow through the entrance by flow currents during the sand transport process from south to north direction. Further, during the northeast monsoon, accretion...

Research paper thumbnail of Study on Damages of Laver Aquaculture Facilities in Tokyo Bay from 2011 Tohoku Earthquake Tsunami

1Technology Center, Taisei Corporation, laknath@pub.taisei.co.jp 2Technology Center, Taisei Corpo... more 1Technology Center, Taisei Corporation, laknath@pub.taisei.co.jp 2Technology Center, Taisei Corporation, hndtkh01@pub.taisei.co.jp 3Technology Center, Taisei Corporation, kazunori.ito@sakura.taisei.co.jp 4Faculty of Urban Innovation, Yokohama National University, jsasaki@estuarine.jp 5Technology Center, Taisei Corporation, yuriko.takayama@sakura.taisei.co.jp 6Technology Center, Taisei Corporation, od-ykn00@pub.taisei.co.jp

Research paper thumbnail of Storm Surge Simulation in Nagasaki During the Passage of 2012 Typhoon Sanba

Coastal Engineering Proceedings, 2014

As a result of global warming effect, storm surges generated by extreme weather events such as tr... more As a result of global warming effect, storm surges generated by extreme weather events such as tropical cyclones, typhoons and hurricanes, significantly impact to the life and property in storm-surge prone coastal low-lying areas. Therefore, numerical modeling systems, comprising meteorological, hydrodynamic and wave simulation capabilities are essential for the storm surge hindcasting and forecasting phases in disaster mitigation and management processes. Accordingly, we assessed the applicability of two meteorological simulation methods; (1) Mesoscale Meteorological Model MM5 and (2) Delft Dashboard (DDB) Tropical Cyclone Tool, together with Delft3D FLOW-WAVE coupled modeling system to simulate the storm surges in Nagasaki coast during the passage of 2012 typhoon SANBA. Storm surge generated by MM5-Delft3D and DDB-Delft3D systems in Nagasaki area were reasonably agreed with the observations. Thus, applicability of both meteorological simulation techniques together with Delft3D FLOW-WAVE coupled modeling system to simulate the storm surge was validated with a reasonable level of accuracy. Further, compared to the MM5-Delft3D system, fast and easy simulation capability of DDB-Delft3D system was identified. However, in terms of accuracy, MM5-Delft3D system demonstrated much better performance in outer regions of the typhoon than the DDB-Delft3D system.

Research paper thumbnail of Analysis of Cyclone Events in Bay of Bengal and Simulation of Storm Surge in Eastern Coast of Sri Lanka

APAC 2019, 2019

Characteristics and behavior of cyclones occurred in Bay of Bengal during last 4 decades in the l... more Characteristics and behavior of cyclones occurred in Bay of Bengal during last 4 decades in the light of global warming effect and applicability of Delft3D modeling system with Delft Dashboard Tropical Cyclone to simulate storm surge levels in eastern coast of Sri Lanka during the passage of 2000 Cyclone (BOB 06) were investigated in this research. Through the statistical analysis of cyclone characteristics, increasing trend of sustained wind speed with the increase of sea surface temperature (SST) over the Bay of Bengal was identified for the considered period though there is no trend for annual cyclone variation. In this study, spatially varying wind and pressure fields of 2000 Cyclone were reproduced by using Delft Dashboard Tropical Cyclone Tool. FLOW model of Delft3D system was used to simulate the hydrodynamic effects caused by wind, atmospheric pressure changes and tidal forces. Thus, Delft Dashboard Tropical Cyclone Tool, together with Delft3D FLOW-WAVE coupled modeling system could simulate storm surge level in eastern coast of Sri Lanka for 2000 Cyclone event with a satisfactory level of accuracy.

Research paper thumbnail of Simulation of Tsunami Inundation in East Coast of Sri Lanka

APAC 2019, 2019

Present tectonic activities around the Andaman–Sumatran subduction zone gives an alarming signal ... more Present tectonic activities around the Andaman–Sumatran subduction zone gives an alarming signal of a possibility of occurring tsunamis in the Indian Ocean again and could bring devastation for rim countries in the Indian Ocean. Hence, proper understanding about possible tsunami inundation levels is a prerequisite for disaster prevention and management processes in tsunami prone areas such as low elevation coastal areas in the eastern coast of Sri Lanka. Therefore, as an initial step, present study was carried out to simulate tsunami propagation and inundation for Kallady city in the eastern coast of Sri Lanka to understand about vulnerable areas for future tsunamis. Kallady is a low lying, populated coastal city in eastern province of Sri Lanka. In this study, tsunami wave propagation and inundation in Kallady area under different scenarios namely, 2004 tsunami event and two hypothetical tsunamis with magnitudes of 9.5 and 10.5 respectively, where the epicenter of the earthquake of hypothetical two tsunamis was assumed to be similar to the 2004 tsunami event. Tsunami wave propagation and successive land area inundation were simulated using ELIMO and Nays2DFlood solvers of iRIC interface accordingly. Bathymetric and topography data were obtained from GEBCO, SRTM and recent field investigations in 2017. Initial sea surface elevations were simulated using Okada’s formula. ELIMO resolves well the wave propagation. However, Nays2D Flood determines inundation level significantly lower since it only employs water level record to model the inundation.