Numerical Model Study of Hydrodynamics and Siltation and...

Government of India Ministry of Water Resources, River Development and Ganga Rejuvenation

CENTRAL WATER AND POWER RESEARCH STATION Pune, Maharashtra, India

Numerical Model Study of Hydrodynamics and Siltation

and Wave Tranquility Study for the Navigation of the

Dharamtar Creek (Amba River)

GOVERNMENT OF INDIA

MINISTRY OF WATER RESOURCES

CENTRAL WATER AND POWER RESEARCH STATION

PUNE 411 024, INDIA

NUMERICAL MODEL STUDY REPORT

March 2015

Numerical Model Study of Hydrodynamics and Siltation

and Wave Tranquility Study for the Navigation of the

Dharamtar Creek (Amba River)

JSW Dharamtar Port Pvt. Limited March 2015

Numerical Model Study of Hydrodynamics and Siltation and Wave Tranquility Study for the Navigation of the Dharamtar Creek (Amba River)

Mathematical Modelling Report i JSW Dharamtar Port Pvt. Limited

Contents

1 Introduction ................................................................................................................................... 10

1.1 Background .................................................................................................................................. 10

1.2 The project ................................................................................................................................... 12

1.3 Summary of Terms of Reference ................................................................................................. 14

1.4 Intent of the report ........................................................................................................................ 14

1.5 Format of the report ..................................................................................................................... 14

2 Site Condition ............................................................................................................................... 15

2.1 Geographical Location ................................................................................................................. 15

2.2 Meteorological and Oceanographic Conditions ........................................................................... 16

2.2.1 Temperature ................................................................................................................................. 16

2.2.2 Rainfall ......................................................................................................................................... 16

2.2.3 Relative Humidity ......................................................................................................................... 16

2.2.4 Wind ............................................................................................................................................. 17

2.2.5 Wave Climate ............................................................................................................................... 18

2.2.6 Tides ............................................................................................................................................. 21

2.2.7 Currents ........................................................................................................................................ 21

3 Site Investigations ........................................................................................................................ 22

3.1 General ......................................................................................................................................... 22

3.2 Bathymetric Survey ...................................................................................................................... 22

3.3 Tidal Data ..................................................................................................................................... 22

3.4 Current ......................................................................................................................................... 22

3.5 Temperature ................................................................................................................................. 26

3.6 Salinity and Total Suspended Solid ............................................................................................. 27

3.7 Bed Samples ................................................................................................................................ 30

4 Numerical Simulations ................................................................................................................. 32

4.1 General ......................................................................................................................................... 32

4.2 MIKE 3 FM ................................................................................................................................... 33

4.3 MIKE 21 FM - Regional Model Setup .......................................................................................... 35

4.3.1 General ......................................................................................................................................... 35

4.3.2 Bathymetry ................................................................................................................................... 35

Mathematical Modelling Report ii JSW Dharamtar Port Pvt. Limited

4.3.3 Tidal data (Boundary) ................................................................................................................... 36

4.3.4 Model Set up ................................................................................................................................ 38

4.3.5 Regional Model Calibration .......................................................................................................... 38

4.3.6 Regional Model Results ............................................................................................................... 41

4.4 MIKE 21 FM – Local Model Set-up for Existing Conditions ......................................................... 44

4.4.1 Model Set Up................................................................................................................................ 44

4.4.2 Bathymetry ................................................................................................................................... 44

4.4.3 Flow Hydrodynamics .................................................................................................................... 46

4.4.4 Sedimentation Model – MIKE 21 MT ........................................................................................... 51

4.4.5 Model Set up – MIKE 21 MT ........................................................................................................ 52

5.4.5 Wave tranquillity ........................................................................................................................... 54

5.4.6 Shoreline Evolution due to Construction ...................................................................................... 54

4.5 Disposal of the Dredged sediments ............................................................................................. 54

5 Conclusions and Recommendations ........................................................................................... 55

5.1 Conclusions .................................................................................................................................. 55

5.2 Recommendations ....................................................................................................................... 55

Mathematical Modelling Report i JSW Dharamtar Port Pvt. Limited

Tables

Table 3-1: Grain size distribution of the collected samples (in % of dry weight) ...... 31

Table 4-1: Details of Model Set Up .......................................................................... 38

Table 4-2: Details of Model Set Up .......................................................................... 44

Table 4-3: Parameters applied in the model simulations ......................................... 53

Table 4-4: Concentration applied during non-monsoon and monsoon period ......... 53

Mathematical Modelling Report ii JSW Dharamtar Port Pvt. Limited

Figures

Figure 1-1: Location of the Dolvi facility on the Map of India (top) and on the map

of Maharashtra (bottom) ......................................................................... 11

Figure 1-2: The existing barge berthing facility at Dharamtar ................................... 12

Figure 2-1: Location of the proposed Facility in side Dharamtar Creek .................... 15

Figure 2-2: Location of the proposed Existing waterfront and Steel plant Facility in

side Dharamtar Creek ............................................................................. 16

Figure 2-3: Wind rose diagram (Source: IMD, 1976 – 2015). .................................. 17

Figure 2-4: Cumulative frequency graph for the wind speed (Source: IMD, 1976 –

2015). ...................................................................................................... 17

Figure 2-5: Wave height rose diagram Offshore (IMD, 1976 – 2015). ...................... 19

Figure 2-6: Cumulative frequency graph for wave height (Source: IMD, 1976 –

2015). ...................................................................................................... 20

Figure 2-7: Wave period rose diagram Offshore (IMD, 1976 – 2015). ...................... 20

Figure 3-1: Bathymetry chart of the area – MMB survey ........................................... 23

Figure 3-2: Tidal Levels at the Dharamtar Jetty ........................................................ 24

Figure 3-3: Location of the Current Measurements .................................................. 24

Figure 3-4: Current plots of stations 1 to 5 in sequence ........................................... 25

Figure 3-5: Current plots of stations 1 to 5 in sequence ........................................... 26

Figure 3-6: Locations of monitoring stations for salinity and TSS ............................. 28

Figure 3-7: Salinity and TSS profile at Station 1 ....................................................... 28

Mathematical Modelling Report iii JSW Dharamtar Port Pvt. Limited



Figure 3-8: Locations of Bed Samples collected in the Dharamtar Creek ................ 30

Figure 4-1: Extents of the global model, showing tidal station of C-Map .................. 35

Figure 4-2: Flexible mesh showing the Model Domain of the Model ........................ 36

Figure 4-3: Tidal Levels on the Nothern Boundary ................................................... 37

Figure 4-4: Tidal Levels on the Southern Boundary .................................................. 37

Figure 4-5: Disacharge Boundary data for the up-stream Amba River boundary ..... 38

Figure 4-6: Calibration plot showing measured and predicted current speed (top)

and direction (bottom) at Station 1 .......................................................... 39







Figure 4-10: Flood Current Vectors ............................................................................. 42

Figure 4-11: Ebb Current Vectors ............................................................................... 43

Figure 4-12: Profile series extarcted from the global model for the Local model

boundary ................................................................................................. 44

Figure 4-13: Local Bathymetry (finite Mesh) for the Model Simulation ....................... 45

Figure 4-14: Local Bathymetry (finite Mesh) – close up for the Model Simulation ...... 46

Mathematical Modelling Report iv JSW Dharamtar Port Pvt. Limited

Figure 4-15: Local Bathymetry (finite Mesh) – close up for the Model Simulation –

With Reclamation .................................................................................... 46

Figure 4-16: Current speed in the Local Model under Flood tide ................................ 47

Figure 4-17: Current speed in the Local Model under Ebb tide .................................. 48

Figure 4-18: Current speed in the Local Model under Flood tide – With reclamation . 49

Figure 4-19: Current speed in the Local Model under Ebb tide – With reclamation.... 50

Figure 4-20: Extracted Current Speed at location t1 and t2 – Without reclamation -

Flood tide ................................................................................................ 51

Figure 4-20: Extracted Current Speed at location t1 and t2 – With reclamation -

Flood tide ................................................................................................ 51

Mathematical Modelling Report v JSW Dharamtar Port Pvt. Limited

SYMBOLS AND ABBREVIATIONS

Symbols and abbreviations used are generally in accordance with the following list.

1 Proper names and organisations - India

BIS .................... Bureau of Indian Standards

GAIL… ………..Gas Authority of India

IAPH.................The International Association of Ports and Harbours

MMB…………….Maharashtra Maritime Board

MCZMA ........... Maharashtra Coastal Zone Management Authority

MIDC ................ Maharashtra Industrial Development Corporation

MLDB ............... Main Lighting Distribution Board

MoEF ................ Ministry of Environment and Forests

MoS .................. Ministry of Shipping

MPCB ............... Maharashtra Pollution Control Board

MSEDCL .......... Maharashtra State Electricity Distribution Company Limited

NHO ................. National Hydro graphic Office, Dehra Dun

OCIMF..............The Oil Companies International Marine Forum

PINAC .............. Permanent International Association of Navigation Congress

SIGTTO.............Society of International Gas Tankers & Terminal Operators Ltd.

SoI………………Survey of India

2 Proper names and organisations – Other

BA ..................... British Admiralty

BR .................... Beckett Rankine

Mathematical Modelling Report vi JSW Dharamtar Port Pvt. Limited

BS ..................... British Standard

IMO ................... International Maritime Organization

ISPS ................. International Ship and Port facility Security code

UTM.................. Universal Transverse Mercator (map projection)

WGS ................. World Geodetic System (ellipsoid for map projection)

3 Other abbreviations

Approx. ............. approximately

cif ...................... cost, insurance, freight

dia ..................... diameter

feu .................... forty foot equivalent unit (container)

fob .................... free on board

max ................... maximum

min .................... minimum

No ..................... number (order) as in No 6

nr ...................... number (units) as in 6 nr

Panamax .......... ship of max permissible beam of 32.2m for transiting the Panama

Canal

ppt .................... parts per thousand

teu .................... twenty-foot equivalent unit (container)

BOOT ............... Build – Own - Operate – Transfer

CCTV................ Closed Circuit Television

CSR .................. Corporate Social Responsibility

CBRM………….Coal bearing raw material

Mathematical Modelling Report vii JSW Dharamtar Port Pvt. Limited

DPR .................. Detailed Project Report

EIA .................... Environmental Impact Assessment

HAT .................. Highest Astronomical Tide

MHWS .............. Mean High Water Spring tides

MHS……………Material Handling System

MSL .................. Mean Sea Level

MLWS............... Mean Low Water Spring tides

LAT ................... Lowest Astronomical Tide

CD .................... Chart Datum

ICD ................... Inland Container Depot

IT ...................... Information Technology

IBRM…………..Iron bearing raw material

LOA .................. Length overall (of a ship)

LCL ................... Less Than Container Load / Consolidation Containers

M ...................... “mega” or one million (106)

MVA……………Mega volt ampere

MoU .................. Memorandum of Understanding

SEZ .................. Special Economic Zone

ToR ................... Terms of Reference

VTMS ............... Vessel Traffic Management System

4 Units of measurement

Length, area and volume

mm ................... millimetre(s)

Mathematical Modelling Report viii JSW Dharamtar Port Pvt. Limited

m ...................... metre(s)

km ..................... kilometre(s)

n. mile ............... nautical mile(s)

mm2 .................. square millimetre(s)

m2 ..................... square metre(s)

km2 ................... square kilometre(s)

ha ..................... hectare(s)

m3 ..................... cubic metre(s)

Time and time derived units

s ........................ second(s)

min .................... minute(s)

h ....................... hour(s)

d ....................... day(s)

wk ..................... week(s)

mth ................... month(s)

yr ...................... year(s)

mm/s................. millimetres per second

km/h.................. kilometres per hour

m/s .................... metres per second

knot................... nautical mile per hour

Mass, force and derived units

kg ...................... kilogram(s)

g ....................... gram = kg x 10-3

Mathematical Modelling Report ix JSW Dharamtar Port Pvt. Limited

t ........................ tonne = kg x 103

displacement .... the total mass of the vessel and its contents. (This is equal to the

volume of water displaced by the vessel multiplied by the density of the

water.)

DWT ................. dead weight tonne, the total mass of cargo, stores, fuels, crew and

reserves with which a vessel is laden when submerged to the summer

loading line. (Although this represents the load carrying capacity of the

vessel it is not an exact measure of the cargo load).

Mt ..................... million tonnes = t x 106

TPD...................Tonnes per day

TPH/tph.............Tonnes per hour

Other units

°C ..................... degrees Celsius (temperature)

Mtpa ................. million tons per annum

Mathematical Modelling Report 10 JSW Dharamtar Port Pvt. Limited

1 Introduction

1.1 Background

JSW Group is one of the fastest growing business conglomerates with a strong presence

in the core economic sector. This Mr. Sajjan Jindal led enterprise has grown from a steel

rolling mill in 1982 to a multi business conglomerate worth US $ 11 billion within a short

span of time. As part of the US $ 16.5 billion O. P. Jindal Group, JSW Group has

diversified interests in Steel, Energy, Minerals and Mining, Aluminium, Infrastructure,

Cement and Information Technology.

JSW Group has grown significantly over the years and taking steps for rapid expansion to

ramp up the capacity of Vijaynagar Steel Plant in Karnataka from the present 10 MTPA to

12 MTPA by the year 2014. In addition, JSW Energy Limited, a JSW Group company, is

the first independent Power producer to set up 2 units of 130 MW each and 4 units of 300

MW each and producing power using Corex gas and coal.

The JSW group owns and operates JSW Steel Limited, Dolvi Works, a 3.2 Million tons per

annum (Mtpa) Steel plant based at Dolvi, Maharashtra working on BF-DR-CONARC-CSP

process. The plant also has facilities for cold rolling, galvanizing, colour coating,

galvalume, and supplements the pipe and tube plant at Kalmeshwar, Nagpur in the state

of Maharashtra.

The JSW Infrastructure Ltd (JSWIL) is a JSW Group company which is presently into

design, finance, development, operation and maintenance of ports, rail/road and inland

water connectivity, development of port based SEZ and other related infrastructure

developments works along with terminal handling operations and port management. The

JSWIL has constructed a mega port in Jaigarh, near Ratnagiri, in Maharashtra, with a

present capacity of 15 Mtpa through a Special Purpose Vehicle (SPV) presently under

expansion to 50 Mtpa. Another Subsidiary of JSWIL, the South West Port Limited (SWPL),

has developed berth number 5A and 6A in the Mormugao Port Trust on BOOT basis and

has successfully handled more than 50 million cargos in about 9 years.

JSW Dharamtar Port Limited (JSWDPL) is a SPV under the aegis of JSWIL, to handle the

proposed EXIM cargo of the JSW Steel Limited, Dolvi works. The Plant was taken over

from the erstwhile M/s Ispat Industries Limited, in the Year 2011. The Steel plant has

unique distinction of having road, rail and water connectivity. It is located on the right bank

of the Amba River, which falls in to the Dharamtar Creek, before merging in to the Arabian

Sea. There is a barge handling facility which mostly handles raw materials for the Steel

Plant. The location of the JSW Steel Limited, Dolvi works is shown in Figure 1.1 below.


Figure 1-1: Location of the Dolvi facility on the Map of India (top) and on

the map of Maharashtra (bottom)

The cargo in the fair season, is handled at the Mumbai outer anchorage (mostly in the

Bravo anchorage), and then transported through barges to the Jetty at Dharamtar,

near Dolvi. The berthing facility consists of 430 m barge berth with two approaches as

shown in Figure 1.2. The berth is equipped with two barge unloaders and two LHM

250 Leibherr Cranes.


Figure 1-2: The existing barge berthing facility at Dharamtar

1.2 The project

Modern day industry requires a larger market and economical transportation systems to

get its input or base materials at lowest costs and the finished products are disposed at

many destinations at a comparative cost. To achieve this, appropriate transportation

facilities are very essential. Thus, such propositions are possible only if such industries are

set up as near as possible to a seaport.

The existing berthing facility at Dharamtar is for handling of barges. Originally designed for

barge sizes of 2500 DWT, presently barges up to 3700 DWT are handled at the berth.

There are 4 berths (Berth no 1 to 4) totaling to about 331.5 m in one alignment. Berth no. 5

of about 100 m long, is at an angle of 30. The berth structure is designed on pile

foundations and has a concrete RCC decking. The berth is provided with two approaches,

which apart from providing access to the berths carry the conveyor systems as well.

The present logistical chain for the Dharamtar facility is fairly simple. The mother vessels

are handled at the anchorage and load the barges using ship’s gear. The barges then

move in to the creek and travel to the berth and gets unloaded. The empty barges are

serviced and start their journey back to the anchorage for re-loading. Typically this is the

fair weather operation, which spans 8 months in year. At this outer anchorage there are no

depth restrictions and therefore, vessels up to cape size ships could call in. The ships do


move shoreward during the midstream handling as they lighten themselves. This

effectively reduces the distance of travel of the barges travel, resulting in savings in fuel

and time of travel.

In the monsoon season, due to the wave disturbance in the outer anchorage, the action of

cargo transfer shifts to the inner anchorage. In such a scenario, due to the depth

limitations in the inner anchorage, mother vessels up to 40,000 DWT only could be

serviced. The vessels generally come partially loaded to be handled inside the inner

anchorage. The inner anchorage provides the necessary tranquility for cargo handling.

However, it must be understood that the number of inner anchorages are limited. About 5

anchorages are being developed by the Mumbai Port Trust. Though additional anchorages

could be developed, but the efficiency would be low.

Therefore, with the increase in the cargo volumes, the dependencies on the inner

anchorages should be reduced proportionately. There are two inherent inadequacies

ingrained in the inner anchorage operations.

1. Handling of vessel sizes limited to 40000 DWT. Hence the freight charges

increases.

2. Since the numbers of anchorages are limited, as the number of ships to be handled

increase, the waiting time also increase.

Accordingly, in order to reduce redundancies and uncertainties in the system it was

decided to do away with the inner anchorage for the planning of the cargo movement in

the Phase II and Phase III. Instead the cargo could be shifted and handled from Jaigarh

Port, where the turnaround of the ship would be much higher.

In the report (as in the Logistic studies), the fair weather cargo is considered to be handled

from the outer anchorage and the monsoon cargo from the Jaigarh Port. In another

scenario the entire cargo is being handled from the Jaigarh Port. The logistic study is dealt

in a separate report; the present report would only deal with the Mathematical model

studies as part of compliance for the construction and expansion of the water front

structures for handling the increased cargo volumes.


1.3 Summary of Terms of Reference

The broad scope of work for the mathematical model study report would include the

following:

Review of the existing reports, available data and documents

Data collection and collation

Mathematical model studies

Discussion of the Results

1.4 Intent of the report

The purpose of this report is to determine the impact of the waterfront development in

order to handle the enhanced cargo volumes.

The report would discuss the siltation and the morphological changes in the creek as well.

1.5 Format of the report

The report is arranged as below:

Chapter 1: Introduction

Chapter 2: Site Condition

Chapter 3: Field Investigations

Chapter 4: Model Set up

Chapter 5: Conclusions and Recommendations


2 Site Condition

2.1 Geographical Location

The location of Dharamtar Creek and Karanja Creek along the west coast of India, and

proposed Thermal Power Plant (TPP) are shown in Figure 2.1. The location of the

proposed TPP lies between latitudes 180 43’ to 180 45’ North and 720 58’ to 720 59’ East

as shown in Figure 2.2. The general topography of the area is flat terrain surrounded by

creeks on three sides.

Figure 2-1: Location of the proposed Facility in side Dharamtar Creek


Figure 2-2: Location of the proposed Existing waterfront and Steel plant

Facility in side Dharamtar Creek

2.2 Meteorological and Oceanographic Conditions

2.2.1 Temperature

The mean of the highest air temperature recorded at Mumbai is 350 C in the months of

April and May while the mean lowest is 160 C recorded in the month of January. Mean

daily maximum and minimum temperatures are 340 C and 220 C respectively.

2.2.2 Rainfall

The average yearly rainfall is about 2098 mm, of which 1965 mm (93.66%) occur during

June to September. Usually maximum average monthly rainfall of 709 mm occurs in July.

There is practically no rainfall from December to April.

2.2.3 Relative Humidity

Mean yearly relative humidity at 0830 hours is 77% while the same at 1730 hours is 71%.

The monthly average is lowest in February (62%) and highest in July to September (85%).


2.2.4 Wind

Ship observed offshore wind data for a period of 35 years from 1976 to 2015 were

obtained from the India Meteorological Department (IMD) and analysed for the grid

covering Lat. 18o - 20o N and Long 71o - 73o E, which centers the area of interest. The

distribution of wind speed and direction is presented in Figure 2.3. The observations

represent measurements taken at sea level for 3 minutes. It may be seen that west is the

predominant direction and that the wind speed is less than 10 m/s for 88% of the time as

shown in figure 2.4.

It was observed that the predominant wind is NE-N-NW in January. It gradually shifts

towards west and by May it becomes NW to SW. During the months of June, July and

August, the wind blows from W to SW. From September the wind direction starts changing

and by December, again the predominant sector becomes NE-N-NW.

Figure 2-3: Wind rose diagram (Source: IMD, 1976 – 2015).

Figure 2-4: Cumulative frequency graph for the wind speed (Source: IMD,

1976 – 2015).


0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40

Percentage

Wind Speed (m/s)

Cumulative Frequency - Wind Speed

It may be observed that during the fair weather season viz. October to May, the wind

speed is less than 6 m/s for about 91% of the time. However, during the monsoon season

(June to September), the wind speed is less than 8 m/s knots for only 62% of the time. It

may also be seen that during the peak monsoon period (July and August), wind speed of 6

to 13 m/s occurs for about 29% of the time. Wind speed of 13 m/s knots is seldom

exceeded.

2.2.5 Wave Climate

The ship observed wave data were collected from the India Meteorological Department

(IMD) for the quadrant bounded by Latitudes 18o to 20o N and Longitudes 71o to 73o E,

between 1976 and 2005. The annual distribution of wave heights is given in the form of

wave rose diagrams in Figures 2.5. It may be seen that the predominant directions of

waves in the deep sea are from SW to NW. It can also be seen that waves are less than 1

m, 2 m and 3 m in height for 77, 94 and 98% of the time respectively as may be observed

from the cumulative frequency curve given as Figure 2.6. Figure 2.7 shows the wave rose

for wave period.


During the pre-monsoon period (January to May) over 92.93% of waves are less than 3 m

in height. During the monsoon period (June to September) wave heights are less than 2 m

for 85 % and less than 3 m for 97% of the time. During the post monsoon period (October

to December) wave heights are more than 3 m for 0.9% of the time. The predominant

wave directions are in the NW quadrant for pre-monsoon period, from W to SW during the

southwest monsoon and from NE to NW in the post-monsoon period. These wave heights

applicable for the offshore conditions and wave are completely attenuated as they enter

the well-protected creek.

Figure 2-5: Wave height rose diagram Offshore (IMD, 1976 – 2015).


Figure 2-6: Cumulative frequency graph for wave height (Source: IMD,

1976 – 2015).

0

10

20

30

40

50

60

70

80

90

100

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6

Percentage

Wave Height (m)

Cumulative Frequency - Wave Height

Figure 2-7: Wave period rose diagram Offshore (IMD, 1976 – 2015).


2.2.6 Tides

The tides in the Mumbai region are of the semi-diurnal type, i.e., characterized by

occurrence of two high and two low waters every day. There is a marked inequality in the

levels of the two low waters in a day. The important tidal datum planes with respect to

Chart Datum at Apollo Bandar (Latitude 180 55’ N, Longitude 720 50’ E) are as under.

MHWS + 4.4 m

MHWN + 3.3 m

MSL + 2.5 m

MLWN + 1.9 m

MLWS + 0.8 m

It may be mentioned that the tidal levels mentioned above get modified, albeit to a minor

extent, by coastal geometry and configuration at the proposed port site.

2.2.7 Currents

The currents in the Mumbai region in the near shore zone are tide induced with reversal at

high and low waters. The current speeds are of the order of 0.75 m/s to 1.5 m/s (1.5 to 3

Knots).


3 Site Investigations

3.1 General

The site investigations were carried out for collecting field data with regard to, bathymetry

of the area, tidal levels, current, temperature, salinity and total suspended solids (TSS)

specific to the area under consideration. The collected data is used both as input to the

mathematical model as well as for calibration.

3.2 Bathymetric Survey

Bathymetric survey was conducted by Mumbai Maritime Board (MMB) of the area as

shown in figure 3.1and the levels were reduced to chart datum. This was used as the

basic bathymetry for the model and calculation of the dredging quantities.

3.3 Tidal Data

Tidal data was collected at the Dharamtar Jetty. The zero of the tide pole was connected

to the Bench Mark by levelling. The observations after tide is reduced to chart datum are

given as Figure 3.2.

It can be seen that the maximum tide is 5.45 m and tidal range is 5 m. This tide will be

used at the lower boundary defining the flow of the creek near Dharamtar Jetty.

3.4 Current

Current data was collected at 5 locations as shown in Figure 3.3. The time series of

current speed are plotted and given in Figure 3.4.


Figure 3-1: Bathymetry chart of the area – MMB survey


Figure 3-2: Tidal Levels at the Dharamtar Jetty

Figure 3-3: Location of the Current Measurements


Figure 3-4: Current plots of stations 1 to 5 in sequence


3.5 Temperature

The temperature monitoring was carried out at the four locations where current was also

measured (Figure 3.3) at specified depth from the water surface as provided in Figure 3.5.

Figure 3-5: Current plots of stations 1 to 5 in sequence

Station 1

23

23.5

24

24.5

25

25.5

26

4.12.06

12:05

4.12.06

15:25

4.12.06

18:45

4.12.06

22:05

5.12.06

01:25

5.12.06

04:45

5.12.06

08:05

5.12.06

11:25

Time

Tem

pe

ratu

re (

0C

)


3.6 Salinity and Total Suspended Solid

The water samples were analysed by MMB using CTD meter for the TSS and the salinity

of the creek at three locations as depicted in Figure 3.6. The salinity and TSS profiles of

the above said locations are given in Figure 3.7 to 3.9.


Figure 3-6: Locations of monitoring stations for salinity and TSS

Figure 3-7: Salinity and TSS profile at Station 1

Salinity Profile at Station 1

26

27

28

29

30

31

32

33

34

4.12.06

12:05

4.12.06

13:55

4.12.06

18:25

4.12.06

20:25

5.12.06

1:20

5.12.06

3:20

5.12.06

7:20

5.12.06

9:20

Time

Sali

nit

y (

%)

0.2 m from the Top 0.4 m from the Top 0.6 m from the Top

TSS Profile at Station 1

0

100

200

300

400

500

600

700

800

900

4.12.06

12:05

4.12.06

13:55

4.12.06

18:25

4.12.06

20:25

5.12.06

1:20

5.12.06

3:20

5.12.06

7:20

5.12.06

9:20

Time

TS

S (

mg

/l)





242526272829303132

3.12.06

11:10

3.12.06

13:10

3.12.06

17:35

3.12.06

19:35

3.12.06

00:25

4.12.06

2:25

4.12.06

6:25

4.12.06

8:25

Time

Sa

lin

ity (

%)



0

100

200

300

400

500

600

700

3.12.06

11:10

3.12.06

13:10

3.12.06

17:35

3.12.06

19:35

3.12.06

00:25

4.12.06

2:25

4.12.06

6:25

4.12.06

8:25

Time

TS

S (

mg

/l)




23

2425

26

27

2829

30

2.12.06

10:25

2.12.06

12:25

2.12.06

16:55

2.12.06

18:55

2.12.06

23:50

3.12.06

1:50

3.12.06

5:30

Time

Sali

nit

y (

%)




0

100

200

300

400

500

600

2.12.06

10:25

2.12.06

12:25

2.12.06

16:55

2.12.06

18:55

2.12.06

23:50

3.12.06

1:50

3.12.06

5:30

Time

TS

S (

mg

/l)


3.7 Bed Samples

The grain size distribution analysis was carried out at three locations as shown in figure

3.9 3.1, presents the description of the analysis. The texture of bed material at location 1,

which is closest and most relevant to the site, is clayey with very little sand. But as one

moves towards the Dharamtar creeks mouth the percentage of sand content increases

because of its vicinity from the sea.

Figure 3-10: Locations of Bed Samples collected in the Dharamtar Creek


Table 3-1: Grain size distribution of the collected samples (in % of dry

weight)

Locations Sand Silt Clay Texture

1 14.90 2.10 83.00 Clayey

2 35.50 3.70 60.80 Clayey

3 35.00 58.00 7.00 Silty


4 Numerical Simulations

4.1 General

Cooling system is a part of the proposed power plant. This system includes an intake,

which supplies cold water to the power plant, used for cooling the condensers. The

resulting warm water is then collected and discharged through a suitably designed outfall.

Understanding of hot water dispersion in the system is essential for two reasons. Firstly, it

should be ascertained that rise in ambient water temperature should not be more than the

standards given by MoEF to safeguard marine life and environment. Secondly because

the flow dynamics of the area results in the mixing of the warm water with the water near

the intake and if this water is permitted, the efficiency of the power plant is bound to affect

as mentioned in section 4. It is therefore necessary to separate the intake and the outfall

hydraulically, so that, mixing of warm water is limited if not prevented altogether. The

process known as ‘recirculation’ is required to be determined accurately, if the power plant

has to run with full efficiency.

Numerical hydrodynamic modeling is a very handy tool to track this thermal plume arising

from the hot water discharges of the power plant. The mathematical model, especially the

3D models help in ascertaining the movement of the warm water either fully mixed or

stratified, in the water body. The 3D model is also capable of giving the change of the

temperature and salinity across the depth and the temperature gradient if any.

The major characteristics of the cooling water systems assumed for the present study are:

Discharge flow approximately 100 m3/s

Outflow velocity 1 m/s

Ambient water temperature 26ºC

Temperature increase 5°C

No change in salinity takes place

Intake depth -3m

Outfall at surface


In order to determine the dispersion of the warm water in the water body with accuracy, it

is necessary to set up a correct hydrodynamic model. This is carried out as discussed

below.

To begin with a global mesh model was set up to study the flow pattern in Dharamtar

Creek. It was necessary to setup a global model as no boundary information near the

mouth of Dharamtar Creek was available. Accordingly, in the first step, a global model was

set up with the tidal boundaries extracted from CMAP chart systems. In the second step,

boundary information from the calibrated global model was extracted and a local model

was set up. This ensured that the hydrodynamics in the local model was satisfactorily

achieved

Accordingly, the scheme of the model studies is,

2D regional model with C-Map tidal data for existing conditions

2D local model with boundary information extracted from global model

3D local model with extracted boundary information from global model with 5 m

dredging.

4.2 MIKE 3 FM

All modelling for the re-circulation study was carried out using DHI’s model suite for three-

dimensional (3D) hydrodynamic modelling, MIKE 3 Flexible Mesh (FM). MIKE 3 is

applicable for the study of a wide range of phenomena, including:

Tidal exchange and currents, including stratified flows

Heat and salt re-circulation

Mass budgets of different categories of solutes and other components such as

brine

MIKE 3 FM solves the time-dependent conservation equations of mass and momentum in

three dimensions, the so-called Reynolds-averaged Navier-Stokes equations. The flow

field and pressure variation are computed in response to a variety of forcing functions,

when provided with the bathymetry, bed resistance, wind field, hydrographic boundary

conditions, etc. The conservation equations for heat and salt are also included. MIKE 3

uses the UNESCO equation for the state of seawater (1980) as the relation between


salinity, temperature and density. The hydrodynamic phenomenon included in the

equation is:

Tidal flows and currents

Effects of buoyancy and stratification

Turbulent (shear) diffusion, entrainment and dispersion

Coriolis forces

Barometric pressure gradients

Wind stress

Variable bathymetry and bed resistance

Flooding and drying of inter-tidal areas

Hydrodynamic effects of creek and outfalls

Interlinking of sources and sinks (both mass and momentum)

Heat exchange with the atmosphere including evaporation and precipitation

MIKE 3 FM has an advection dispersion equation solver that simulates the spread of heat

and of dissolved and suspended substances subject to the transport processes described

by the hydrodynamics. A full heat balance is included in MIKE 3 for the calculation of water

temperature.

MIKE 3 FM is based on an unstructured flexible mesh and uses a finite volume solution

technique. The meshes are based on linear triangular elements. This approach allows for

a variation of the horizontal resolution of the model grid mesh within the model area to

allow for a finer resolution of selected sub-areas; in this case in the areas around the

cooling water intakes and outfalls of the Q-Chem I and II plants.

The computational triangular grid of the model ranges from approximately 25m resolution

in the near field area around the intakes and outfalls to 500m in the far field. There is a

trade-off between the wish of a fine model resolution and the computational time as the

computational time increases with the number of elements. Furthermore, the stability of

the numerical scheme roughly speaking depends on the ratio between the triangle side

length and the bathymetric depth. The consequence of this is that small elements on deep

water require a small time step; therefore the very fine resolution should be limited to as

shallow water as possible.


4.3 MIKE 21 FM - Regional Model Setup

4.3.1 General

The extents of the regional model are shown in Figure 4.1. The available predicted tides at

Revadnada in the south and Worli Point in the north were derived from CMAP digitized

chart compilation.

Figure 4-1: Extents of the global model, showing tidal station of C-Map

4.3.2 Bathymetry

The bathymetry consisting of the coast and Dharamtar Creek was compiled on the basis

of the following.

Naval Hydrographic Chart no. 2016

MMB surveys as discussed in section 3.2

CMAP chart systems


Flexible mesh bathymetry was prepared for the global bathymetry model, is shown in

Figure 4.2.

Figure 4-2: Flexible mesh showing the Model Domain of the Model

4.3.3 Tidal data (Boundary)

There were four boundaries defined for the global model, namely, north, west, south and

downstream Dharamtar creek. The other boundaries of the creeks joining the Dharamtar

creek were considered closed. The distance of these boundaries was large enough to

have any effect on the results. The tidal levels at Worli Point and Revadanda were used to

define north and south boundaries and are shown in Figure 4.3 and 4.4 respectively. West

boundary was assumed to have flux as Zero, whereas upstream boundary was defined

with the tidal data collected near Dharamtar Jetty, as discussed in section 3.3 (Figure 4.5).

All the boundaries were corrected to the Mean Sea Level (MSL). These boundaries were


used to set up the initial model and to carry out calibration with respected to the collected

current observations.

Figure 4-3: Tidal Levels on the Nothern Boundary

Figure 4-4: Tidal Levels on the Southern Boundary


Figure 4-5: Disacharge Boundary data for the up-stream Amba River

boundary

4.3.4 Model Set up

The model set up for the present study is given in Table 4.1.

Table 4-1: Details of Model Set Up

Time step 30 seconds

Nodes 3099

Manning Number 40

Eddy Viscosity coefficient 0.28

Boundary Condition open sea Tidal elevations: Worli Point (N), Revadanda (S)

Simulation Period 1st

to 15th December (15 days)

4.3.5 Regional Model Calibration

The global flow model was calibrated comparing the current data collected at four sites.

The locations of these points are shown in Figure 3.3. Figure 4.6 to 4.9 presents the

calibration plots with respect to current speed and direction at different locations.


Figure 4-6: Calibration plot showing measured and predicted current

speed (top) and direction (bottom) at Station 1






Comparison between model predicted and measured values for current speed and current

direction showed a good fit. Thus, model is well calibrated and represents the conditions of

the study region within acceptable limits.

4.3.6 Regional Model Results

The model calibration was with in the acceptable limits and therefore the model could be

considered validated. Accordingly, the simulation results for the existing conditions and for

the predicted tides are discussed in the section.

The flow vectors for the existing conditions are presented in Figure 4.10 to 4.11 for the

flood as well the ebb conditions.


As mentioned in the beginning, global model was executed to derive the boundary

conditions for local model. Thus a vertical profile series was extracted presenting water

level across the Dharamtar creek. Water levels across Dharamtar creek on 7th December

2006 at 2:30 A.M. are shown in figure 4.12 as an example.

Figure 4-10: Flood Current Vectors


Figure 4-11: Ebb Current Vectors


Figure 4-12: Profile series extarcted from the global model for the Local

model boundary

4.4 MIKE 21 FM – Local Model Set-up for Existing Conditions

As explained above, in the second step the local 2D model was set up with existing

conditions but with profile boundary at Dharamtar creek extracted from the global model

as shown in figure 5.12 and introducing the intake and outfall.

4.4.1 Model Set Up

The model set up for the local model is given in Table 4.2.

Table 4-2: Details of Model Set Up

Time step 30 seconds

Nodes 2352

Manning Number 40

Eddy Viscosity coefficient 0.28

4.4.2 Bathymetry

The computational triangular grid of the model ranges from approximately 25 m resolution

in the near field area around the intake and outfall to 500m in the far field. The bathymetry

of the region was prepared on the basis MMB surveys and CMAP chart data same as

detailed in global model. Bathymetry used for the model is shown in Figure 4.13.


The model study was carried out to understand the tidal hydrodynamic behavior of flow,

probable siltation pattern in the harbour, and estimation shoreline changes in the proposed

layout. The proposed reclamation along the bank is shown as Figure 4.15.

Figure 4-13: Local Bathymetry (finite Mesh) for the Model Simulation


Figure 4-14: Local Bathymetry (finite Mesh) – close up for the Model

Simulation

Figure 4-15: Local Bathymetry (finite Mesh) – close up for the Model Simulation –

With Reclamation

4.4.3 Flow Hydrodynamics

A number of model simulations were performed to describe the hydrodynamic conditions

at the study area under a range of tidal and wind conditions. The flow regime under the

flood and ebb tides are shown in Figure 7.5 through 7.8. The velocity profile with

reclamation is shown in Figure 7.9 and 7.10. The velocity time series for the entire tidal


cycle is presented as figures 7.11 and 7.12 for the flood as well as the ebb tide near the

proposed development. The maximum and minimum values of the currents under the

flood and the ebb conditions are 0.57 m/s.

Figure 4-16: Current speed in the Local Model under Flood tide


Figure 4-17: Current speed in the Local Model under Ebb tide


Figure 4-18: Current speed in the Local Model under Flood tide – With reclamation


Figure 4-19: Current speed in the Local Model under Ebb tide – With reclamation


Figure 4-20: Extracted Current Speed at location t1 and t2 – Without reclamation -

Flood tide

Figure 4-21: Extracted Current Speed at location t1 and t2 – With reclamation -

Flood tide

The computational model was modified by incorporating the proposed developments as

shown in Figure 7.3 with reclamation behind the berth and was tested in the model.

The magnitude and direction of flow and flow pattern were observed. It was noticed that

the velocity magnitude remain unchanged even after the developments (reclamation).

Therefore the reclamation could be carried out without altering the flow regime in the area

indicating no impact of the development on the flow conditions.

4.4.4 Sedimentation Model – MIKE 21 MT

The MIKE 21 Mud Transport Module (MT) describes erosion, transport and deposition of

mud or sand/mud mixtures under the action of currents and waves.

Mud transport parameters

MIKE 21 MT is applicable for mud fractions alone as well as for sand/mud mixtures. The

following processes can be included in the simulation.


Forcing by waves

Sliding

Salt-flocculation

Detailed description of the settling process

Layered description of the bed, and

Morphological update of the bed

In the MT-module, the settling velocity varies, according to the salinity ( if included) and

the concentration taking into account flocculation in the water column. Furthermore,

hindered settling and consolidation in the fluid mud and under consolidated bed are

included in the model. Bed erosion can be either non-uniform, i.e. the erosion of soft and

partly consolidated bed, or uniform, i.e. the erosion of a dense and consolidated bed. The

bed is described as layered and characterized by the density and shear strength.

The Mud Transport Module can be applied to the study of engineering problems such as:

Sediment transport studies for fine cohesive materials or sand/mud mixtures in

estuaries and coastal areas in which environmental aspects are involved and

degradation of water quality may occur.

Siltation in harbour, navigational fairways, canals, rivers and reservoirs.

Dredging studies.

4.4.5 Model Set up – MIKE 21 MT

Bathymetry and the boundary conditions used in this setup are same applied in the local

model described in the chapter 4, section 5.5. Inlet and outfall points are introduced in the

bathymetry dredged up to 5 m. Local area extracted from modified bathymetry is shown in

Figure 4.13.

Model was executed for the period of 1day during non- monsoon as well as monsoon

conditions. Details on the set-up of MIKE 21 MT modules are provided in Table 4.3. Initial

and boundary concentration taken during non-monsoon and monsoon are provided in

table 4.4.

The model was then enforced for predicting the siltation pattern with the proposed using a

dredged depth of 3.5 m. The TSS concentration as indicated in chapter 3 was used. The

total annual siltation was found to be around 0.75 million cum per annum. It is observed


that the average depth of sediment deposition in the approach channel varies from 5 to 7

cm over a period of six months covering monsoon season. The estimated sedimentation in

the entire harbour region including approach channel and turning circle works out to be of

the order of 1-1.25 M Cu m which is based on the model study and literature survey of the

earlier studies.

Table 4-3: Parameters applied in the model simulations

S. No Parameters Value

1 No. of grain size fractions 1

2 No. of bed layer 1

3 Settling velocity 0. 05 m/s

4 Critical shear stress for deposition 0.05 N /m2

5 Power of erosion 1

6 Erosion coefficient 0.00001 kg/m2/s

7 Critical shear stress for erosion 0.05 N/m2

8 Density of bed layer 180 kg/m3

9 Bed roughness 0.001 m

Table 4-4: Concentration applied during non-monsoon and monsoon

period

S. No Parameters Value

1 Initial sediment concentration (non- monsoon) 0.004 kg /m3

3 Sediment concentration at downstream

boundary (non- monsoon) 0.0191 kg /m

3

4 Sediment concentration at upstream boundary

(non- monsoon) 0.0443 kg /m

3

5 Initial sediment concentration (monsoon) 0.02 kg /m3

6 Sediment concentration at downstream

boundary (monsoon) 0.02 kg /m

3

7 Sediment concentration at upstream boundary

(monsoon) 0.03 kg /m

3


5.4.5 Wave tranquillity

There is no wave effect near the proposed development as it is about 26 km from the sea

mouth. Waves cannot enter the creek due to restriction of width and depth.

5.4.6 Shoreline Evolution due to Construction

The model studies indicates no changes in the bank line of the river, as the eroding forces

due to the increase in the flow velocity due to the development is low.

This was also ascertained by studying the bank line evolution over the years.

4.5 Disposal of the Dredged sediments

The dredged sediments from the capital and the maintenance dredging would be disposed

at the established Mumbai Port Dumping ground on the high sea. This is an established

dumping ground and no additional study would be required for the same.


5 Conclusions and Recommendations

5.1 Conclusions

The study suggests that the proposed developments have negligible impact on the coastal

morphology of the creek. The following broad conclusions can be drawn

Dredging up to 5m of depth is proposed for the approach channel and the jetty

location. This would increase the flow channelization and flow efficiency of the river

(creek).

About 1 to 1.25 million m3 of maintenance dredging is required for a 5 m depth

channel.

There is no wave impact inside the port.

The coastal geo-morphology is not affected by the reclamation of 50 m width, as the

width is small in comparison to the river width.

The disposal of the dredged sediments can be done at the existing Mumbai Port

grounds.

5.2 Recommendations

The proposed development would have no or negligible impact on the river morphology

and the flow hydrodynamics, hence the development is recommended.

Numerical Model Study of Hydrodynamics and Siltation and...

Documents

Transcript of Numerical Model Study of Hydrodynamics and Siltation and...