geomorphological analysis of khor al udeid area in jariyan al batnah, qatar

8/13/2019 Geomorphological analysis of Khor al Udeid area in Jariyan al Batnah, Qatar

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Geomorphological analysis of Khor al Udeid area in Jariyan alBatnah, Qatar

Preston S. Cook

Brigham Young University, Department of Geological Science

ABSTRACT

Using visible spectrum remote sensing data from various satellites, I measured the aver-

age dune movement over eight years on three different barchan dunes in Khor al-Udeid in Qatar.

The objective of measuring dune migration velocity in Khor al-Udeid is to determine whether

or not dunes move slower over shallow tidal seas or on dry land. The rst dune was the wettest

and has an average velocity of 10 meters per year. The second dune is somewhat wet and has an

average velocity of 22 meters per year. This high velocity is probably more closely related to

dune size than wetness, as it is signicantly smaller than the other two dunes. The third dune is

the driest and it’s average velocity is 7.5 meters per year.

For the ood tide delta I conducted a channel density analysis and a qualitative middleground bar (MGB) shape analysis. The channel density of the delta is 142 square meters of delta

area per meter of channel. I hypothesize that channel density in tidal deltas is related to sediment

load, depth of the delta and ow rate. The MGB shape analysis shows that ood tide DMB con-

centrate north of the delta mouth, while ebb tide MGB are more common on the east and west

sides of the delta. The most reasonable explanation for this phenomenon is that the momentum of

the incoming ood tide concentrates the ow directly away from the delta mouth, while ebb tides

drain from all sides of the delta equally.

INTRODUCTION

Khor al-Udeid is a morphologically diverse located in Jariyan al Batnah, the south-east-

ern department of Qatar (Figures 1 & 2). The dominant feature of the area is a ood tide delta

that connects a shallow tidal inlet to a deep inland sea. The area south and east of the tidal inlet

is an erg dominated by barchanoid dunes. The area north and west of the inlet is an extensive

sabkha. The ood tide delta and erg were the focus of my research. To represent all phases of

my research, I will rst discuss background information and the methods involved in studying

the ood tide delta and erg; after which I will explain the results of the study and conclusions of

the research. Finally, I will describe the processes that acted on the environment to produce these

sedimentary features.

Background

Flood tide deltas

Flood tide deltas form in shallow tidal inlets that open to larger, deeper inlets or seas(Stauble et al., 1988). Two factors induce sedimentation in a ood tide delta: drag on hyperpyc-

nal ows and decrease in ow velocity due to opening of the distribution basin (Morris, 2013).

As more dense water ows in from the deeper inlet during ood tide, the conditions are right

for hyperpycnal ow. The sediment loaded hyperpycnal ow drags on the shallow bottom of the

inlet, lowering ow velocity and inducing sedimentation. As sediment charged tides move out

of the conned tidal inlet neck and into the broad distribution basin, ow velocity decreases and

sediment falls out of suspension.


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Source: Esri, DigitalGlobe, GeoEye, i-cubed, USDA, USGS, AEX,Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community

51°22'0"E

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Visible Spectrum Image of Khor al-Udeid, Qatar

Figure 1. Panchromatic 15m resolution image of Khor al-Udeid, Qatar from Landsat 7 satellite. The tidal

inlet is in the center of the image. The ood tide delta separates the tidal inlet from the inland sea. Barch-

an dunes migrate across the tidal inlet from the north to south. Barchanoid dune elds are visible in the

southwest and southeast corners. The dunes selected for migration velocity measurements are numbered

one through three.

1

2

3


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Legend

Sabkha

Tidal Inlet

Erg

Flood Tide Delta

Inland Sea1

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Geomorphological Map of Khor al-Udeid, Qatar

Figure 2. Geomorphological map of the different features of Khor al-Udeid, Qatar.


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Satellite specifcations

I used panchromatic data from three different satellites: GeoEye-1, Spot 5 and Landmark

7. Each satellite has a different spatial resolution.

GeoEye-1. GeoEye-1 provides half meter resolution panchromatic images and 1.65m

multi-spectrum images. For the MGB shape analysis and the channel density analysis, I used

GeoEye-1 panchromatic images. Spot 5. Spot 5 was launched in 2002 and has a panchromatic spatial resolution of 2.5 or 5

meters. Both the 2005 and 2013 images of the dunes were Spot 5 meter resolution images.

Landmark 7. The Landmark 7 satellite provides 15 meter resolution panchromatic

images. For my geomorphological map and wide view image I used the panchromatic images

from Landmark 7.

METHODS

Average dune migration velocity

I hypothesize that wet dunes will migrate slower than dry dunes. Water should increase

dune cohesion, making them resistant to low velocity winds. To test my hypothesis, I selectedthree different barchan dunes around Khor al-Udeid (Figure 1). The rst dune is completely sur -

rounded by water. The second dune is migrating along a spit surrounded on two sides by water.

I would assume that this dune is moderately wet. The third dune is on land. Since the dunes are

in close proximity, they should experience the same wind patterns, thus migration speed should

vary only due to wetness or size.

In order to measure average dune migration velocity, two different datasets were loaded

as separate layers in ArcGIS. The rst dataset was an 2005 panchromatic image of the Khor

al-Udeid area provided by the Spot 5 satellite. The second dataset was a 2013 image of the Khor

al-Udeid area also provided by the Spot 5 satellite. The opacity of the 2013 image was set to

70%, so that the 2005 image could be seen underneath. With both layers visible and positioned

on top of each other, it is possible to measure migration distance. Using the measure tool in

ArcGIS, I measured the distance between the peak of each dune in 2005 against the peak of

the same dune in 2013. By dividing the distance between the dune peaks through time by eight

years, the average dune migration velocity over the last ve years can be obtained.

Channel density analysis

While drainage density is used all over the world to study drainage basins, there has been

no research conducted on channel density in tidal deltas. I propose that channel density in tidal

deltas is related to three factors. The rst factor is sediment drop out rate. As sediment drops

out at higher rates, the channels are more likely to form distributary mouth bars and bifurcate,

increasing channel density. The second factor is clay content. Bank cohesion rises with claycontent; thus, systems with low clay content are more likely to breach levees and create new

channels. The third factor is topography of the delta’s depositional basin. For example, a delta

depositing into a at plane is more likely to spread out and form numerous channels. Conversely,

a delta depositing into a topographically varied zone will have channels that follow paths of low

topography.

By drawing a polyline and switching back and forth between lower resolution Landsat 7

images and higher resolution GeoEye-1 images, I traced all of the tidal channels in the ood tide


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delta. I then created a polygon and traced the boundaries of the delta. Using the attribute tables

for the channel polyline and delta polygon, the total channel length and the total area contained

in the ood tide delta were achieved. The channel density was obtained by dividing the area of

the delta by the total channel length. The total area of the delta and channels measured for the

study are shown in Figure 3.

Middle ground bar shape analysis

Using both Landsat 7 and GeoEye-1 images in ArcGIS, I used polygons to trace the di-

mensions of middle ground bars (MGB). I hypothesized that middle ground bars would be more

pointed in shape on one side or the other depending on whether ood or ebb tides dominated in

that region. After qualitatively assessing the shape of each MGB, I judged it to be dominated

either by ood tides, ebb tides or equally affected by both (Figure 4).


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Tidal Channels and Distribution Area for the Flood Tide Delta in Khor al-Udeid, Qatar

Figure 3. Panchromatic 1.65m resolution image from GeoEye-1 satellite. The area of the ood tide delta

is highlighted with a transparent yellow. The channels used for the channel density analysis are light blue.


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RESULTS

Average dune migration velocity

The rst and wettest dune moved south 80 meters over eight years, giving it an average

migration velocity of 10 meters per year. The moderately wet second dune moved south about

175 meters over eight years, with an average migration velocity of 22 meters per year. The

dry third dune migrated 60 meters south-southeast over eight years, with an average migration

velocity of 7.5 meters per year.

Channel density analysis

The total area of the ood tide delta is about 8,500,000 square meters. The total length of

the channels in the delta is about 60,000 meters. Thus the channel density rounds to 142 square

meters of delta per meter of channel length.


Of the major middle ground bars, 27 were ood tide dominated, 5 were ebb tide dominat-


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Tidal Channels and Distribution Area for the Flood Tide Delta in Khor al-Udeid, Qatar

F

F

F F

FF

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E

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F

Figure 4. Panchromatic 1.65m resolution image from the GeoEye-1 Satellite. Well formed bars are high-

lighted with transparent white. Bars shaped dominantly by ood tides are denoted with a letter F. Bars

shaped by ebb tides are denoted with an E and bars formed equally by both ood and ebb tides are de-

noted with an F/E label. The F bars are concentrated in the middle lobe of the delta, while E and F/E bars

are more common on the eastern and western lobes of the delta.


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ed and 22 showed both strong ebb and strong ood features. It seems that bars in different parts

of the delta were inuenced more heavily by different tides.

CONCLUSIONS

Average dune migration velocityThere are not enough wet and somewhat wet dunes in the Khor al-Udeid area to conduct

a conclusive study, but the results are still intriguing. The somewhat wet dune is signicantly

smaller than the other two dunes. Due to its small size, it should migrate much faster than the

other two. I expect that its high migration velocity is a result of its size, rather than its wetness;

therefore, the data collected from this dune is useless in determining the effect of wetness on

dune migration velocity. The other two dunes were close to the same size, but the results contra-

dicted my hypothesis. The wet dune migrated at a higher velocity than the dry dune. Perhaps this

is a result of constant loss of dune volume in a wet environment. As the dune migrates, any sand

deposited below the water table ceases to migrate with the dune, effectively reducing the dune

size and presumably increasing migration velocity.

In the future, migration velocities from other wet ergs could be conducted to understandhow wetness affects dune migration.

Channel density

Since no other research has been conducted regarding channel density in tidal deltas,

there are no other channel density measurements to compare it to. Compared qualitatively to

other tidal deltas, the delta appears to have a high channel density. I suspect that this is a result of

low clay content due to the sandy environment and the at depositional basin.

Field work should be conducted at the ood tide delta in Khor al-Udeid in order to

understand ow rates, sediment load and sediment composition. More channel density analyses

ought to be conducted in different environments in order to understand how variations in ow

rates and sedimentation affect tidal delta morphology.


In the northern lobe of the ood tide delta the MGBs appear to be affected more heavily

by ood tides, while the eastern and western lobes show more ebb tide characteristics. I suspect

that the momentum of the incoming ood tide concentrates ood tide ow in a south to north

direction, which explains the abundance of ood tide shaped bars in the south-north channel

systems. During ebb tide, water drains more equally from all lobes of the delta, which allows the

bars to develop morphologies associated with ebb tides.

DEPOSITIONAL HISTORYThere are three major environments in Khor al-Udeid. The most obvious is the tidal inlet

and ood tide delta. The second environment is the erg that extends south and east of the tidal

inlet. The third environment is the sabkha that extends from the tidal inlet to the north and west.

Each environment has it’s own depositional history, though they are all directly related to the

processes associated with the Persian Gulf.

The orientation of the dunes in the deserts of Qatar suggest that the dominant wind

direction is north-northwest to south-southeast. Since Qatar is a peninsula that only shares its


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southern border with land, the majority of the sand is sourced from Qatar itself. If you follow the

dune elds into Qatar, they lead to sandy beaches. So, as the wind blows south off of the Persian

Gulf, it picks up sand from Qatar’s beaches and blows them towards Khor al-Udeid and Saudi

Arabia. The sand supply from the beaches is sparse, so Qatar is dominated by isolated barchan

dunes or barchanoid dune elds with wide inter-dunes.

The depositional history of the sabkha and the tidal inlet are strongly tied. The tidalinlet is connected to the sea via a deeper inland sea. During ood tides the colder, denser water

from the deep inland sea moves into the shallow tidal inlet as a hyperpycnal ow. As it does so,

it drags on the bottom, lowering the ow velocity and inducing sedimentation. During normal

tides, the ood and ebb tides cancel each other out and little to no deposition occurs. I propose

that the majority of deposition occurs during storm surges or spring tides when enough water

ows into the tidal inlet to ood the sabkha. If the Sabkha oods, it could greatly reduce the

effect of the following ebb tide. With accommodation space in the sabkha, the following ebb tide

would be unable to drain the sabkha. This would also explain the absence of a ebb tide delta on

the other side of the ood tide delta’s mouth.

REFERENCES

Morris, T.H., 2013, Interview. Nov 25, 2013.

Stauble, D.K., Da Costa, S. L., Monroe, K.L., and Bhogal, V.K., 1988, Inlet Flood Tidal Delta

Development through Sediment Transport Processes: Lecture Notes on Coastal and

Estuarine Studies, v. 29, p. 319-347.

geomorphological analysis of khor al udeid area in jariyan al batnah, qatar

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