Morphotectonic of Euphrates River between Al-Qaim and Haditha cities, western Iraq

The study area is located between Haditha and Al-Qaim cities, western Iraq. The research aims to demonstrate the effects of tectonic activity and structural features on the course of the Euphrates River by using field studies and remote sensing techniques to know the structures, hydrological indicators and morphometric properties which affected upon river course. Two main software, ArcGIS 10.8 and EARDAS Imagine, are used. The extension phases during Late Cretaceous develop Anah Graben and Abu Jir normal fault that delineate the course of the Euphrates River whereas the positive inversion of Anah Graben and the dextral movement along of the Abu Jir fault zone formed Anan Anticline and pressure ridges during the E-M Miocene respectively, determine the river course along both structures, many indications of hydrological and morphometric properties reflect the impact of the last activities that prevent it to creep or change the direction of its course.


Introduction
Morphotectonic analysis is an important method for analyzing an area's tectonic activity since it has a high link with structural discontinuities and geomorphological abnormalities [1].Many researchers used Remote Sensing (R.S.) and Geographic Information System (GIS) techniques for morphological and morphometric analyses in western Iraq or geological purpose [2][3] [4].The research area is located along river of Euphrates Basin (ERB) in northwest Iraq's western desert, following the course of the Euphrates River from Al-Qaim near the Iraq -Syria border to Haditha city.The study area's coordinates are between latitude (34 ⸰ 23′ 16″ N, 34 ⸰ 08′ 25″ N) and longitude (40 ⸰ 54′ 16″ E, 42 ⸰ 22′ 21″ E) figure 1.The total area of the basin is 6965.132km 2 Although the projected perimeter of the basin was 611.736 km.Tectonics of the research area is taken into consideration as the line between the inner and outer shelves of the Arabian platform [5].This area was described as active during the E-M Miocene due to the northward movement of the Arabian plate [6].Not only Anah anticline was developed but also the subsurface Akkas anticline south of the Anah structure [7].The importance and justification of this research lie in the absence of the previous morphometric studies which can detail the study of properties of the Euphrates River basin between Al-Qaim and Haditha cities and how subsurface structures effect on the course of the Euphrates River.The object of this research includes; The morphotectonic analysis of the basin between both cities, finding a relation between tectonic impacts, structures, landforms and the course of the river, and analyzing the tectonic activity within the study area.

Geological setting
Stratigraphy, most of the area is covered by Euphrates Formation (L.Miocene) which is contains of shallow marine fossiliferous carbonates and calcareous claystone.The Middle Miocene Fatha Formation which is composed of lagoonal gypsum, carbonate and calcareous claystone is well deposited in the north of the area [8].The exposure of the reefal limestone of the Upper Oligocene Anah Formation is restricted only in some deeply incised valleys [9] Figure 2.
The study area is located along the boundary between Iraqi territory's stable and unstable shelves.It contains two subsurface structures, the first is the Anah graben that is superposed by the Anah monocline or Anah Anticline, and the second is the north part of the Abu Jir fault zone [9] [10].The area was active during the E-M Miocene due to the Arabian Plate Northward Movement [7].Dextral movement occurred along the north part of the Abu Jir fault zone while positive inversion took place on the Anah graben, which develops the Anah Anticline, both formed during the Early-Middle Miocene [7] [10] [11].

The climate
Except for the mountainous region in the country's north and northeast, which has a Mediterranean climate, Iraq's climate is continental, subtropical, and semi-arid.[12].The Iraqi Western Desert has an arid climate.Because of the little precipitation, it is known as the desert, significant areas are covered with exceptionally fertile soil where various sorts of flowers and other forms of vegetation flourish during rainy seasons.The study of climate conditions is crucial here to give an overview of the climatic character of the investigated area.Climate data Evaporation (mm), Temperature in (°C), Rainfall (mm), Sunshine (h/day), Relative humidity (%), and Wind speed (m/s) were measured at the Haditha meteorological station from 1988 to 2020.Haditha station is located 50 meters above sea level at longitude 42° 36′ 81" easterly and latitude 34° 09' 34" northerly [13].The climate parameters were averaged monthly and annually in this study in Table 1 and Figure 3.  4. Methodology Three main topics are used, the hydrological indices to recongnize basins; A drainage system can be automatically drawn and measured using an elevation raster or digital elevation model (DEM) as input.The second topic is morphometric research is crucial to many areas of geoscience, including all study area sub-basins, a morphometric analysis of the terrain, areal, formal measurements and the drainage network of the basin has been conducted.The third topic is how the subsurface and surface structures affect to course of the Euphrates River.Two main software were used for image processing; ArcGIS 10.8 and EARDAS Imagine.Some field visits were conducted during which some of the structures that affected to course of the Euphrates River were studied, in addition to a comparison between the study conducted using satellite data with what is found in the field.

Results and discussions
The goal of such technical analyse is to achieve greater objectivity in description and interpretation the surface of the earth.It is more important now because a better technique is used in all general and natural scientific investigations.Two important techniques that use for this goal are hydrological indices and morphometric properties.
5.1 The hydrological indices 5.1.1Fill The Fill command specifies unexpected sinks in numeric elevation file data, which are cells with height values that are significantly lower than the height values of neighboring cells.Often these depressions are caused by defects in the digital elevation model, and these need to be removed and a new DEM file free of depressions must be created is mean the fill which has the same form as the original visual but differs in data by removing all impediments from highs and lows [14].In the research area the low value is 146 and the high value is 559.In general, the area increases in height from northeast to southwest Figure 4.

Flow Direction
Flow direction is a tool that is used to determine the path in which water flows from one cell to another, by matching the height (level) of the cell to the levels of the different cells.The flow direction tool works by assigning a value to each direction that water will flow [15] Figure 5.

Flow Accumulation
Flow accumulation generates a raster of accumulation flow to every cell by adding the weights of all cells that flow into each down a slope cell [14]

Stream Order
Stream networks are recovered by assigning integer value 1 for explain the stream network and no -data for explain the background to the flow accumulation layer.Following that, the stream is ordered according to [16].The highest-order stream segment is the stream through which all water and sediment discharge passes.After that, the stream order layer is assigned an integer number corresponding to the stream orders (Arc GIS Desktop 10.8 help).Finally, the layer is converted into a continuous vector feature (shapefile format) with the same stream ordering as before.Figure 7.There are two trends of the main valley of the basins, the first one is northeast and the second is southwest, both trends appear more pronounced throughout the Abu-Jir fault zone that is subjected to strike-slip fault, one of the trends along antithetic minor faults, the another along synthetic minor faults, therefore existing of both types of trends in the area between Al-Qaim and Anah cities reflects no pure inversion on Anah graben but it was accompanied by a simple striking movement.

Watershed
It using to determine river basins, to identify river basins, it is necessary to know where the beginning or end of the basin [17].The last step in the hydrological inducing is Basin, it represented by dividing the study area into sub-basins (SB).After that we can doing morphometry analysis on these sub-basins Figure 8.

Morphometric Properties
The morphometric studies refer to the mathematical examination of the surface of the Earth's shape and the discovery of mathematical relationships between topography and Geometry drainage networks [18].For all study area sub-basins, a morphometric analysis of the terrain, areal, formal measurements and the drainage network of the basin has been conducted.As an appropriate method to get the morphometric analysis, R.S. techniques, Geographical Information Systems (GIS), and obtaining satellite imagery were employed.for the evaluation of relationships between morphometric indicators, the investigation of those indicators' responses to tectonic activity, and understanding of those indicators' responses.To enable statistical analysis, we start by normalizing the findings of all the indices.

Areal Characteristics
Among these attributes is the study of the areal basin(A), length basin (Lb), and perimeter basin(P) are considered very important in morphometric analysis.The basin area is a region of land where all precipitation drains into a single stream or ravines that feed a mainstream.It displays the amount of water that downpour can produce.The primary hydrological elements of a watershed are always thought to be the area of the drainage system.This region can represent the overall amount of surface water, which essentially comes from precipitation [19].Numerous factors affect the basin area, the most important of which are time, climate, geological formations, and tectonic activity.As a result, the area changes based on the various criteria described above from one basin to another.The total area of the Euphrates River basin between Al-Qaim and Haditha cities is about 6965.06Km2, which calculated by ArcGIS software by using the Digital Elevation Model (DEM) layer.The study area is divided into six sub-basins (figure 8), and the area ratio of these basins to the total area of the basin varies.The greatest percentage was recorded in the sub-basin (SB5), which got 49.42% with a total area of 3442.19Km2, while the smallest percentage was recorded in the sub-basin (SB4), which got 4.86% with a total area of 239.89 Km2.table 2. Figure 6 shows all the low-order valleys in each sub-basin that meet a mainstream along a single line for all the sub-basins (red dots).This line is parallel to the Euphrates River and represents the beginning of the Anah anticlinal structure, which is only interrupted by the main streams and then supplies into the Euphrates River.Also, Figure 8 shows the areas of sub-basins are small, all of these factors reflect the influence of tectonic activity on drainage basins.
One of the most important morphometric characteristics is basin length, which has been calculated on the digitization map generated from DSM with assistance from the ArcGIS software [20].From the mouth of the Euphrates River on the right bank to the farthest point on its perimeter, the length of the (ERB) within the study area was measured, the longest one is 104.13 km for SB2 and the shortest one is 29.82 km for SB4 Table 2. Short-length drainage basins are located in high relief areas with slopes that enable them to form.The drainage basin's perimeter is the outer boundary enclosing its area.[21].The perimeter basin of the Euphrates River in the study area was measured by ArcGIS software.The longest perimeter which represent by sub-basin (SB5) is about 354.72Km, while the shortest perimeter basin which represents by the sub-basin (SB4), is about 92.22 km Table 2.The perimeter of the drainage basin represents the water dividing line between the basin and other adjacent basins.A small length of the basin perimeter reflects less geomorphological development due to the recentness of these basins, because they were affected by tectonic activity that occurred along the course of the River Euphrates from the Miocene upward.

Formal characteristics
Studying the formal characteristics of the basins facilitates an understanding of the nature of the dominant digital geomorphological procedures that take place in the basin.One of the most significant indicators for measuring the shape of the geometry basin is the elongation ratio (Re), circularity ratio (Rc), lemniscate ratio (Ri) and form factor (Rf), The Elongated ratio for the Euphrates River the basin in the study area was found to be between (0.24 -0.73This indicates that the basin has an elongated shape.It implies that the basin spreads longitudinally, which may be related to the rocky formations characterized by carbonate rocks that are widely distributed in the studied area, in addition, the basin's numerous fractures and faults contributed to its inclination toward an elongated shape.All of the past data, Because of the large distance traversed by the water waves during their movement from the feeding areas to the valley mouth, the area and form characteristics confirm that the basin's shape is far from circular, which represents the basin's characteristics of regular surface flow and relatively modest drainages.The elongated ratio value reflects the region's high relief and steep ground slope.Applying the equation of circularity ratio to the basin of the Euphrates River in the study area, the circularity ratio different from 0.2 to 0.35.This low value indicates that the basin is far from the circular shape.This value reflects high relief and structurally controlled drainage systems [22].Form factor to the Euphrates River basin, the value of the basin form factor range between (0.14-0.42), this value shows that it is not a round basin form, which is due to the nature of the rocks and the environment in those areas.

Terrain characteristic
The river basin terrain is very important in both geomorphological and hydrological investigations.it is good to understand the topography of the area.understanding the mechanisms that contributed to the formation of land surface features within the basin's limits, it is also possible to identify the river basin's erosive stage from its erosive cycle [23].Furthermore, terrain characteristics exhibit strong relationships with several spatial and longitudinal variables, as well as river drainage network parameters.These characteristics include the following: -Relief ratio (Rr), the relief ratio value of the study area is ranges from 2.82 for SB2 to 7.17 for SB4; Ruggedness number (Rn), in the study area the ruggedness number is varies from 2.84 in SB2 to 8.53 in SB6.This value indicates a high basin relief, these numbers show the roughness of the surface and the difficulty of the topography in these basins, which is attributable to the activity of water erosion processes; and drainage texture (Dt), the Euphrates River basin's drainage texture in the research area The water drainage network includes the total form of the basin's river tributaries.Analyzing the drainage network's features helps to comprehend the features of the water basin area by establishing the connections between the drainage networks and the basin's dimensions and natural features (geology, climate, slope, soil, etc.) on the one hand, and the stream orders and their drainage areas on the other.The drainage density of the ERB. is ranges from 0.8 to 1.8 km -1 .According to [24], The study area's drainage density is classified as extremely low to low.Table 3, this low result suggests that soil through which the streams run has a high infiltration capacity, with minimal variation in topographic heights and sparse vegetation.
The analysis of the drainage network in the Euphrates river basin that it has reached the 5 th order represented by SB1, SB2, SB3, SB4, SB6 and 6 th order in SB5, and this reflects the extensiveness and breadth of the drainage network throughout the basin.According to the equation, bifurcation ratio of the Euphrates River basin varies between 2 and 8.The drainage frequency value ranges from (0.31) for SB5 to (0.82) for SB6.There is a significant difference in drainage frequency results, the Fd in the study area is categorized from low to high according to [24].This value tends to increase from east to west except of SB5.[10].The second subsurface structure is the Abu Jir fault zone, which divides into two parts, north and south, the north part of which extends NW-SE from Hit city to Anah City, where it meets Anah Graben, passing through Haditha City.The Abu Jir fault zone behaves as normal fault develops with Anah Graben [11].These two subsurface structures had a major impact on delineating the course of the Euphrates River which is running now days.The western part of Anah graben was subject to the positive inversion that develops of Anah monocline or anticline along the southern bank of the Euphrates, whereas the northern part of the Abu Jir fault zone underwent strike-slip movement, that formed pressure ridges due to the developed of positive flower structures along the southwestern bank of the river.Both positive inversion and flower structures were due to the north movement of the Arabian Plate during the Early-Middle Miocene [6].Anah Anticline and pressure ridges of the Abu Jir fault Zone have marked the southern and southwestern banks of the river respectively, that it runs parallel to them and cannot creep toward south or southeast Figure 9.

Figure 1 .
Figure 1.Location map of the research area done by ArcGIS V. 10.8.

Figure 2 A
Figure 2 A. Euphrates Fm. in Fahimi Valley, B. Reefal limestone of Anah Fm. in Hajlan Valley.

Figure 4 .
Figure 4.In general, the study area increases in height from northeast to southwest.

Figure 5 .
Figure 5. Flow direction of the research area done by ArcGIS V.10.8.

Figure 6 .
Figure 6.Flow accumulation of the study area

Figure 7 .Figure 8 .
Figure 7. Stream orders.Red dots are begging of main stream

Figure 9 .
Figure 9.Some structural features that reflect the impact of tectonic activities on the course of the Euphrates River; A. Cliff due to Abu Jir fault zone, B. The north limb of Anah Anticline, C. Local anticline near Rawah City, D. Inclined beds near Anah City, and E. Jebbab Valley cut Anah Anticline.

Table 2 .
Areal characteristics of study area

Table 3 .
Morphometric properties of the sub-basinsTwo subsurface structures are present under the course of the Euphrates River, the first one is Anah graben, that forms during the Late Cretaceous.It extends E-W about 250km from the Iraqi-Syrian border eastward, that divides into two parts by the Abu Jir fault zone, western and eastern parts