PORT & HARBOUR PLANNING & MODELLING
“Dynamics in the field of coastal
hydraulics, estuarine hydraulics,
river hydraulics and coastal
morphology can be forecast using
modeling techniques. Such
modeling tools help in smart
decision making in large
infrastructure projects. The cost
effectiveness that such forecasts
bring can be significant.”
Dr Balakrishna Sharma
1
Port & Harbour Planning & Modelling – Working with nature’s complexities
Man's endeavor in understanding the behavior of nature is commendable. He has achieved
considerable success in predicting complex physical phenomena occurring in nature.
Today, the dynamics in the field of coastal hydraulics, estuarine hydraulics, river hydraulics
and coastal morphology can be forecast using modeling techniques. For every engineering
project to be successful understanding the existing natural physical phenomena becomes
essential. The safety and sustainability of an engineering design depends on the accurate
assessment of the impact of any manual intervention on the prevailing environment.
Today’s advanced modeling tools and technologies help in the feasibility and safety of large
scale, long tenured infrastructure projects.
Key influencers in port & harbour layout planning
Coastal hydrodynamics and its impact on the shoreline
Understanding coastal hydrodynamics plays a major role in planning port and harbor
layouts. Coastal hydrodynamics relates to study of flow fields due to tide and waves. The
tidal hydrodynamics are based on the tidal level variations which are well predicted along
the coastline. The wave hydrodynamics are due to propagation and deformation of waves
as they travel from deep sea to near shore. The detailed information about the
hydrodynamics in the coastal region is essential to study the feasibility of development of
ports and harbors and to predict resulting morphological changes in the adjoining coast.
The resulting morphological changes subsequent to the proposed developments in the
coastal areas are due to change in the sedimentation pattern, which needs to be predicted
using mathematical models.
Coastal Hydrodynamics management through model simulations
Mathematical models are useful tools for simulating the coastal hydrodynamics and
morphological changes. The application of these models to obtain realistic information
requires expertise in modeling and interpreting the findings. In order to get best out of the
model simulations, one should have clear understanding about the purpose for which the
model has been developed and its limitations.
Tata Consulting Engineers has effectively put in technological expertise and modelling
tools to simulate coastal hydrodynamics essential for development of coastal structures
like, breakwaters, jetty, seawater intake structures, offshore outfalls and diffusers, design of
port layout, location of berths and orientation of navigational channels.
Ensuring safe navigation & berthing
HYDRODYNAMIC SIMULATIONS
Tidal hydrodynamics and wave simulations provide information on flow and tranquility
conditions which is vital for designing the layouts of ports and harbors and is essential for
economical design and construction of coastal structures. Most of the physical phenomena
to be considered while designing the harbor layout can be faithfully simulated using
mathematical models. In order to design the layout for the ports and harbors many aspects
are required to be studied, such as minimum interference with the natural flow conditions,
desired tranquility at berths, optimum length and orientation of breakwaters, etc.
Business case for model simulations
A series of tide and wave hydrodynamic simulations for different alternatives would guide
the engineer in arriving at the economical and technically feasible layout of offshore
structures. Major advantages of mathematical models studies are mainly, high speed and
low cost for carrying out the simulations for various alternatives.
Tidal hydrodynamic models provide velocity field in the computational domain during
different tidal conditions and Wave propagation models provide wave conditions which are
the basic input to simulate other aspects like sediment movement, thermal dispersion and
salinity dispersion.
SEDIMENT MOVEMENT UNDER TIDE & WAVE ACTIONS
Sedimentation is a major concern for ports and harbors. Sediment movement is highly
dynamic and site specific. Governing factors include coastline profile, type of sediment,
tide and wave conditions at site. To maintain the desired depths in the approach channels,
major ports carryout dredging at regular intervals. Thus, more care is required to be taken
while designing layouts to minimize the recurring cost on maintenance dredging. While
designing the layout, it is necessary to see that the sedimentation is minimum and natural
flushing is achieved.
Design of harbor layout without proper study may result in excessive sedimentation, at
times leading to abandoning of the site. Thus, it is essential to study different alternative
layouts considering prevailing hydrodynamics and sediment movement at the harbor site.
Navigational channels are worst hit by sedimentation if not designed and oriented properly.
The general trend is to dredge a straight channel along the shortest path from harbor to
deep waters to minimize the capital cost. However, this may result in excessive siltation
and in turn leads to exorbitant recurring cost for maintenance dredging.
Even while
orienting the breakwaters, if not studied from the point of sediment movement, harbor
would result in excessive sedimentation and may become a threat to safe navigation.
Sediment transport model studies provide fair idea about the siltation pattern for the given
breakwater layout and approach navigational channel considering tide and wave conditions
at the site. The limitations posed by existing natural tidal conditions can be overcome by
appropriate breakwater layout and channel orientation.
Technical knowledge in coastal processes and with support of model studies alternative
layouts and technical solutions can be provided by expert consultants. End-to-end design
solutions and modeling for feasible solutions to tackle sedimentation in navigational
channels are some areas that experts in the field such as Tata Consulting Engineers can
provide.
Destructive impact of erosion
Unlike sedimentation, erosion is more destructive and has severe impact on human
dwelling along the coastline. Estuarine rivers, tidal inlets and lee side of shore connected
breakwaters depending on the littoral current face severe erosion problems.
Thus, it becomes evident to study the site conditions and examine the behavior of the
shoreline before planning the development. It is a general trend to arrest erosion by
providing protection to the shore by placing boulders and stones without studying the
problem.
However, suitable shore protection measures can be evolved through detailed study of the
site conditions, behavior of coastline under the action of tide, tidal currents and wave
actions.
By simulating the hydrodynamics and sediment movement at site it may be
possible to arrive at reliable solution to promote deposition in the eroding zone.
OUTFALLS & ENVIRONMENT
The industrial effluents are generally disposed off in to rivers and coastal waters. Reject
waters from power plants are slightly warm and saline than the ambient waters and may
cause temperature rise in receiving water body that may affect the aquatic environment and
accelerate the growth of weeds, algae and plankton. In order to prevent adverse effects on
the environment, different standards are set by the environmental protection agencies in
different countries for discharging thermal effluents in natural bodies.
In view of this it is a general practice of environmentalists to propose outfall locations deep
in to the sea which may result in prohibitively high capital cost.
However, economically
viable and environmentally friendly solutions can be found by examining the coast line
profile, tidal conditions and aquatic environment prevailing at the site under consideration.
Method of disposal of reject water could be either, through open channel or
through
submarine outfalls to achieve desired mixing and without causing any adverse impact on
the prevailing environment.
Thermal dispersion models are used as design tools for identifying the appropriate outfall
location and evolving at diffuser system to study the zone of influence. The studies involve
simulation of hydrodynamic processes for tidal conditions, the advection, dispersion and
diffusion of thermal discharges
Typical Findings from Model Studies on Zone of Influence at Outfall Point
Effluent
Disposal
Points
Outfall at 5m
Zone of Influence
Temperature < 0.5 Deg. C
100m radius
depth
Remarks
Length of submarine pipe 600m
Minimum encroachment in to sea
100% dilution in 400m
Outfall at 10m
75m radius
depth
Length of submarine pipe 750m
Encroachment limited to 1000m
100% dilution in 200m
Outfall at 16m
depth
50m radius
Length of submarine pipe 1850m
Maximum encroachment in to sea
100% dilution in 75m
In case of submarine outfalls a suitable diffuser system can be designed by studying
development of thermal plumes under the action of tidal currents and analyzing the mixing
zone. Table above gives the typical findings from model studies of submarine outfalls.
Benefits of diffuser system modeling for outfall management
Design of diffuser system based on model studies provides cost effective solutions. It is
well known that offshore works are cost intensive, thus even marginal reduction in length of
submarine pipe would result in significant saving in the project cost.
In depth studies can be conducted on thermal dispersion and mixing zone analyses for
identifying most appropriate outfall location that meets environmental and regulatory
stipulations.
Apart from the environmental point of view the model studies also help in identifying the
locations of the Intake and Outfall points to avoid recirculation of warm water which would
adversely affect the efficiency of the CW system of Power plant.
Conclusion
Mathematical model simulations are useful tools for design of port and
harbour layout, intake and outfall structures
Model studies provide ample information about the post development
scenario, which is very important for any developmental projects.
Major advantages of mathematical models studies are mainly, high speed
and low cost for carrying out the simulations for various alternatives before
arriving at final solution
Design of diffuser system based on model studies provides cost effective
solutions.
Technical knowledge in coastal processes and with support of model
studies, technically viable solutions can be provided by expert consultants
for design of harbor layouts and outfall structures.
For more information on port modeling, port & harbor planning and layout studies, please
email the author at [email protected]
About the author
Dr. Balakrishna Sharma is an expert in modelling coastal processes. He has a
Masters in Civil Engineering and entered in to modelling in the field of coastal
engineering at Central Water & Power Research Station. He pursued his higher
studies in the development of 2-D and 3-D models in open channel hydraulics
and received his Doctorate from Indian Institute of Technology, Bombay. He has
received UN Research fellowship to carryout research in open channel flow
modeling with emphasis on diffusion and dispersion processes in 3 dimensions
at St Anthony Falls Hydraulic Lab & Minnesota Super Computer Institute,
University of Minnesota, USA.
He has more than 25 years of experience in providing consultancy services in
coastal engineering like, design of port layouts, sedimentation in harbours and
navigational channels, coastline erosion/accretion due to developments along the
coast, seawater intake and outfall system and thermal dispersion, through model
studies.
Dr Sharma has published 45 technical papers in National and International
journals and conferences. He has prepared more than 80 technical reports on
model studies for various development projects along the Indian coast.
He is a recipient of “Jalavigyan Puraskar” from Indian Society for Hydraulics and
also received C-DAC Mission-I Award-PARAM - Special Award in the category of
best parallel application Software for the work “Parallel hydrodynamic model for a
class of coastal engineering problems”.