UM QASR Sedemintation Challanges
Abstract:
The report illustrate the hydraulic invistigations ,the sediments models established to simulate the comlplex sedimentation processes in Um Qasr new port & the ideas & suggestion to remedy.
It describes the surveys & collected necessary data for better understanding of sedementation & verification of numerical modelling.
CONTRASTING STYLES OF SEDIMENTATION
Withen 200 km-long coastal zone of Kuwait,two contrasting styles of sedimentation
noticed well.the northern part of the gulf under the influence of :
1.The Euphurates-Tigris-Karun multipile delta system into the northern basin
2.The pattern of counter-clockwise of tidal water
A clastic, tidal-flat sabkha , unique regime characterises mesotidal (the range of tide 4-2 m)
coastline of northern golf & maximum flooding is depending on the coincidence of high
spring &/or storm tides with southeasterly wind, therefore the area can be descibed
as a Wind -Tidal flat (Reda, 1986)
the sedments are rich in detrital, silt-sized carbonate. the origion of fine grain mud
and silt fraction is controversial (pelky &Noble ,1966), good part of this fraction is carbonate( mostly
low Mg-Calcite & some dolomite ) believed to have formed through fluvial influx from Shatt AL-Arab with minor orthochemical precipitation (Purser,1973; Stoffer & Ross ,1979 )
recently , shown that the suspended material in these waters are dominatly derital carbonates, & there is no evidence for direct precipitation.
the counter-clockwise currents transport these sediments ( which came from the 3 rivers )
to Kuwait bay , which been delivered to coast line by daily tides.
.SEDIMENTATION PROBLEMS
The upper parts of the Gulf water have high concentration of sediments, partly due to the
sediments carried with the rivers that have outlets in the area and partly due to the wind borne
particles from the prevalent north-westerly Shamal. The sediment rich water of the Gulf is carried into
the port approaches with the tidal movements and deposited in areas with calm waters like river
Experience shows that the deposition of sediments in the Iraqi ports and approaches is substantial
and amounting to approximately 10 million m3 per year. & constitutes a specific problem with regard to sedimentation as this short approach - roughly 1 nautical mile - will require a yearly
maintenance dredging in the order of 2 million m3.
As a consequence of the need for dredging of the sediment deposited in the Um Qasr New Port,
there is a need for extra dumping areas and breakwaters to contain the dredged material. Therefore,
the money to be spent on dredging works and the logistics involved herein are substantial; annually in
the order of USD 10 mio and will require a lot of resources to control the operations in different areas
of the channels.
Finding new economical and practical ways to reduce the sedementation problems
The methods required to analyse and simulate the sedimentation processes and the remedial actions
proposed to make low sedimentation in the Um Qasr New Port, are described in the following:
FIELD MEASUREMENTS
PURPOSE
The main purpose of the present field survey programme is to establish basis for and verification of
the hydrographic and sedimentation modelling carried out as a key element of the study. Iraqi experts
within GCPI and in the scientific community at the Basrah University have been responsible for collecting data
& played good role in the data analysis. Another important purpose of the study
has been capacity building of the concerned authorities and institutions e.g. by supply and training
PROGRAMM
for the field measurements have involved:
• Preparatory activities
o Procurement and supply of survey vessel "Al Salam" and miscellaneous marine
survey equipment (single beam echo sounder, RTK, ADCP, tidal gauges, water and
sediment sampling equipment)
o Training of Iraqi staff in the use and maintenance of the equipment by Danish experts
(in Denmark and Kuwait).
• Survey activities in Iraq
• Analysis and reporting
SCOPE
The survey works have comprised:
Bathymetry
• Bathymetric survey
Ship borne single beam echo sounder, advanced GPS positioning
• Water level recordings
Pressure cells, digital display
• Flow measurements
Ship borne Acoustic Doppler Current Meter (ADCP)
• Suspended matter
Several water samplers
• Sedimentation
Core bottom sampler, haps sampler, Van Veen sampler
.MODELLING
A conceptual understanding of the hydraulic conditions was developed by the hydraulic experts of
COWI in co-operation with the experts H.J. Vested (DHI), L. Dall (EIVA) and J. Fredsøe (The
Technical University, Denmark). The results were discussed with experts from GCPI and Basrah
University in order to keep all involved parties on the same level of understanding of the status and the
direction of the project.
The initial hydraulic assessment of the flow situation identified an exchange eddy at the entrance of
Um Qasr New Port that contributes significantly to the sedimentation in the Um Qasr New Port,
see Figure 3. By narrowing the entrance to the port by breakwaters the siltation contribution due to
the exchange eddy can potentially be reduced. However, these breakwaters must be designed in such
a way that they do not jeopardize the navigation to the port.
Alternative layouts and alignments of the breakwaters were modelled by means of state-of-the-art
numerical modelling of the complex hydraulic flows and sedimentation conditions at the port entrance.
The modelling was carried out by DHI based on the field data that were collected by GCPI (Um
Qasr) and MSC (Basrah University).
Since a significant reduction of sedimentation can be achieved by narrowing of the port entrance, the
effect of the breakwaters on the navigational conditions had to be investigated in detail. Alternative
breakwater layouts and different wind and current conditions were simulated for representative ships
using real-time navigation simulators at FORCE Technology in Copenhagen. Port pilots from Um
Qasr took active part in the simulations.
Bathymetry
The bathymetric survey was carried out in early 2007 using the fully equipped survey vessel "Al
Salam". The
resulting mapping of the data for Umm Qasr is shown in Figure 4 below. The data are
plotted onto a satellite picture in order to give the correct understanding and overview. The survey
results indicate that considerable sedimentation takes place at the entrance to the port. This is in line
with experience as GCPI has a dredger placed here more or less permanently for maintenance
dredging.
This new bathymetry is important key information necessary to determine the net changes of the water depths since the earlier survey carried out by UNDP in 2005.
. SEDIMENT CHARACTERISTICS
Sediment characteristics were investigated at different sampling campaigns in 2007. The density and
the grain size distribution of the sediments in suspension were determined as well as the surface
sediments at different locations. It is found that the sediment is well sorted and very fine silt with a
typical d50 grain size of about 10µm.
The content of suspended sediment in different heights in the water column and at different phases in
the tidal cycle was measured. The sampling location is in the Um
Qasr New Port, fairly close to the port entrance. It is seen that the concentration of suspended matter
is closely correlated to the tidal cycle. Further, there is no clear indication that the bottom water is
significantly more turbid than the surface water.
NUMERICAL MODELLING
The Danish Hydraulic Institute (DHI) numerical model MIKE21 was applied. The model solves the
governing equations for conservation of momentum and mass integrated over the vertical. The applied
MIKE21 set-up consists of the Hydrodynamic (HD) module that describes water levels and velocities
and the Mud Transport (MT) module for simulation of cohesive sediments. The bathymetry was represented in the model by a flexible mesh in order to describe the local flow field in the entrance and around breakwaters and breakwaters with a high resolution. In order to provide realistic boundary conditions for the MIKE21 model, the entire Arabian Gulf was modelled with a hydraulic model. This was done for a one-month period with forecasted forcing at the Strait of Hormuz. This model fed a river model (MIKE11) for the entire Khor Az Zubair and this model provided the boundary conditions, in form of river discharge and water levels, for the detailed high resolution MIKE21 model of Umm Qasr New Port. The detailed model was simulated for a 5 days tidal period. Figure 3 shows a comparison between simulated currents and ADCP measurements at ebb tide. As it is seen from Figure 3 the measurements verify the simulations. Measurements and simulations are compared for the same tidal phase (approximate), but the dates are different (for practical reasons). However, it is obvious that the simulated current speeds correspond very well with the measurementsFigure 4 compares the simulated sediment transport with satellite image (Google Earth). The tidal situation is low water and the flow is rising. Sediment rich water (grey) from the Khor Az Zubair is entering the New port at the south and
and the sediment poor water (blue) is leaving the port at the north. The comparison shows that the simulation captures the observed phenomenon of the sediment inflow at start of rising tide.
The model was applied to assess a number of different breakwater layouts at the port entrance. The
total sedimentation in the berth areas and navigation channel was calculated and the reduction determined relative to the existing situation. The layouts were evaluated from a navigation point of view until an optimal layout was determined taking both sedimentation and navigational aspects into consideration.
Disscussion
Extensive sedimentation represents one of the major obstacles for efficient operation of the Iraqi ports and in particular for the Um Qasr New Port. Several breakwater layouts that reduce the entrance width to the port were studied with respect to their potential for reducing the sedimentation rate in the port and their impact on navigation. The analysis of the complex hydraulics and sedimentation processes in Umm Qasr New port revealed that a substantial reduction of the annual sedimentation can be achieved by narrowing the port entrance. The sedimentation pattern is relatively complex over the tidal cycle. The resulting net effect is sensitive to the physical properties of the settling velocities of the sediment, occurrence of fluid mud and also to the local flow pattern in the opening of the New Port. The measurements assisted in reducing this uncertainty. The sedimentation modelling indicates a possible reduction of the maintenance dredging in Umm Qasr New Port of about 20% out of an annual dredging amount of about 2 million m.A process of interactions between the findings from the sediment modelling and the navigation simulations was necessary to develop an optimised layout. shows an opening relatively far to the north and two breakwaters that have a slight angle inward into the New port. Economic estimates for construction of the breakwaters and the savings in dredging indicate a pay back time of about 5 years8, which is considered to be favourable.
It is therefore concluded that feasible options exist that can remedy the sedimentation problems in the
Umm Qasr New Port by substantially reducing the yearly maintenance dredging requirements.
By providing state-of-the-art marine survey equipment and subsequent training of the Iraqi experts in
the use of this equipment and related software, the Iraqi port authority now has the capability to
monitor the hydraulic regime and sedimentation in the ports and approaches.
GCPI and MSC participation in the data analysis and modelling activities has enhanced the
understanding of the complex hydraulic and sedimentation processes in the Iraqi ports and
approaches, which will enable GCPI to assess and venture into future developments of the Iraqi ports.
References:
1: https://www.researchgate.net
2: Al-Imarah, F.J.M., Hantoush, A.A. and Nasir, A.M. Petroleum hydrocarbons in water and sediments of the Northwest Arabian Gulf 1980 – 2005. Aquatic Ecosy
3:Kuwait & Northern Arabian Gulf : A Stud In Quaternary Sedimentation By An
