radiotracer study to investigate the spatial dispersion pattern of ...€¦ · radiotracer study to...
Post on 14-May-2020
6 Views
Preview:
TRANSCRIPT
Radiotracer Study to Investigate the Spatial Dispersion Pattern
of Dredged Materials in Hooghly Estuary, West Bengal, India K. K. Bhar, H. J. Pant, B. Chaudhury, K. Chakraborty, V. K. Sharma
Presented by
Dr. Kalyan Kumar Bhar
Department of Civil Engineering
Indian Institute of Engineering Science and Technology, Shibpur
A Collaborative Research between
• Indian Institute of Engineering Science and Technology, Shibpur, India
• Kolkata Port Trust, India
• Isotope Productions & Applications Division Bhabha Atomic Research Centre (BARC), India
Introduction
Port Navigation
• Maintenance of the navigation channel leading to the dock is the
prime concern of any port authority.
• Usually dredging is done to improve the draft in the shipping
channel, which is very expensive.
Study Area
Study Area
Hooghly Estuary
Study Area
• Confluence of river Hooghly
with Bay of Bengal.
• Approx. area: 4000 sq. km.
• Location: 21°31′N–23°20′N and
87°45′E–88°45′E.
• Part of the world's largest
delta: the Ganges-Brahmaputra
delta, which lies partly in
Bangladesh and partly in India.
• Navigable waterway for two
major ports Kolkata and
Haldia.
Location
Study Area
• Funnel shaped estuary with the breadth and cross-sectional area at
the mouth is 25km and 156250m2 and decreases to 6 km and
36,799m2 at the head end.
• Well mixed estuary and mixing zones of the estuary extends up to
Diamond harbour, about 80 km upstream.
• It receives 4 small rivers. River Damodar and Rupnarayan at its
head, and River Haldi and Rasulpur at the middle.
• The estuary is very shallow, depth is only 6m on the average and
nowhere deeper than 20m.
Characteristics
Study Area
• It has an annual run-off of approximately 493 km3
• Carries about 616x106 t of suspended solids to the estuarine mouth
• It has a large number of tidal bars and tidal islands of which Sagar
Island, Lower Long Sand, and Nayachar are important.
• Sagar Island, the largest of the Sundarban biosphere positioned at
the mouth of the estuary and bifurcates it into two channels, the
western channel is retained as Hooghly and eastern is named as
Mooriganga.
Characteristics
Study Area Navigation Channels
Problem Kolkata/ Haldia Port
• Requires maintenance dredging throughout the year
• Five to six Trailing Hopper Suction dredgers are deployed
• These dredgers use the tidal window to dredge
• Dredged materials are disposed to dumping ground
• Movement from dredging site to dumping site takes more time
than actual dredging
• Cost becomes prohibitive
Problem
• Dumping into a nearby site may reduce the cost, but there is always
a possibility of return of the disposed materials to the dredged site
during return of tides.
• There is an urgent need to identify the optimum location of the
disposal site.
Haldia Port
Objective
To identify the movement and dispersion pattern of the dredged
materials that will help in determining the optimal disposal
distance from the dredging site.
Approach
This project used both these two approaches.
• Dynamics of sediment dispersion in an estuary is a complex flow
phenomenon.
• Radioactive particle tracing and numerical hydrodynamic
modeling are complementary methods of studying complex flow
phenomena in natural system.
Radiotracer Experiment
Radiotracer Experiment Steps
• Selection of site for radiotracer injection
• Preparation of radiotracer
• Injecting the radiotracer mixed with sediments on the seabed
• Tracking of radiotracer in successive months
• Plotting and analysis of tracking data
Radiotracer Experiment Site Selection : Survey
Radiotracer Experiment Site Selection : Survey
Radiotracer Experiment Selected Site for Injection
Selected site for radiotracer experiment near the dumping site for dredged materials
Radiotracer Experiment Preparation of Tracer
• The radiotracer should have identical physico-chemical properties
and hydrodynamic behaviour as that of the natural sediment.
• The tracer is prepared by incorporating 1% of inactive Scandium
in the glass composition, grinding the glass and mixing different
grain size fractions to have the same grain size distribution as that
of bed material.
• Scandium glass powder is then irradiated in the reactor to produce
Scandium-46.
Radiotracer Experiment Tracer Injection
Vessel with Tracer Apparatus
Radiotracer Experiment Tracer Injection
Preparing the Container
Radiotracer Experiment Tracer Injection
Pouring the Tracer into the Container
Radiotracer Experiment Tracer Injection
Container with tracer-sediment mixture
Radiotracer Experiment Tracer Injection
Immersing the Container for Dumping Tracer on Seabed
21-49-13.05N, 87-59-40.63E 27 November 2014
Radiotracer Experiment Tracking
Tracking Vessel
Radiotracer Experiment
Sledge with detector
Survey Vessel
Seabed
(a) Tracking System (b) Sledge with Detector
(c)Ratemeter connected to the Detector
(d) Track of Survey (DGPS)
(d) Recording Track Data
Tracking Procedure
Tracking
Radiotracer Experiment Tracking Schedule
• 16-18 December, 2014
• 6-8 January, 2015
• 3-5 February, 2015
• 10-12 March, 2015
Radiotracer Experiment Isocount Contours
16-18 December, 2014
Radiotracer Experiment
6-8 January, 2015
Isocount Contours
Radiotracer Experiment
3-5 February, 2015
Isocount Contours
Radiotracer Experiment
10-12 March, 2015
Isocount Contours
Hydrodynamic Modeling
Hydrodynamic Modeling AQUAVEO SMS
In this project Surface Water Modeling System (SMS) developed by
AQUAVEO is used as the computing platform for development and
running of the hydrodynamic models.
This software provides a robust computing interface with wide range
of numerical models for applications in
• Sediment transport
• Particle tracking
• Estuarine and Riverine analysis
• Coastal circulation, etc.
Hydrodynamic Modeling Model Development
• Selection of Coverage from Satellite Image
• Delineation of Flow Boundaries
• Bathymetry Data and Computational Grid
• Formation of Cartesian Grid
• Defining Boundary Conditions
• Defining Model Control Parameters
• Defining Observation Cells
• Model Run: Validation, Analysis
Hydrodynamic Modeling Bathymetry
Haldi River
Hydrodynamic Modeling Model Run: Validation
Plot of Observed and Simulated Water Surface Elevation near Nayachar
0
1
2
3
4
5
6
7
0 50 100 150 200 250 300 350
Wa
ter
Su
rfa
ce E
lev
ati
on
(m
)
Time (h)
Simulated
Observed
Hydrodynamic Modeling Model Run
Velocity Vector at Haldia-Jellingham Channel (Spring Flood)
Hydrodynamic Modeling Model Run
Velocity Vector at Haldia-Jellingham Channel (Spring Ebb)
Hydrodynamic Modeling Model Run
Variation of Depth and sediment transport vector at Haldia - Jellingham Channel
Hydrodynamic Modeling Model Run
Morphology change after 14 days of Simulation
Hydrodynamic Modeling Model Run
Morphology change after 28 days of Simulation
Hydrodynamic Modeling Model Run
L-Section of Channel
Hydrodynamic Modeling Model Run
Change in Section before and After Simulation
0
2
4
6
8
10
12
14
16
0 5000 10000 15000 20000 25000 30000
Dep
th (
m)
Distance from starting point (m)
27.11.14
22.01.15
Conclusion
Radiotracer study complemented with hydrodynamic simulation is
an effective approach to identify the movement and dispersion
pattern of the dredged materials in Hooghly estuary. It also helped
in determining the optimal disposal distance from the dredging site.
Thank You for Your Attention
top related