Iraqi Geological Journal

Abstract


Introduction
Morphometric analysis is one of the most current developments in geomorphological studies focusing on river basins. The morphological characteristics of drainage are important for understanding the underlying structure, geomorphology, and hydrological characteristics of the river basins, to assess and manage the potential of groundwater and surface water (Mahala, 2020). Furthermore, morphometric analysis aids in the identification of physical changes in the drainage system through time because of natural or anthropogenic disturbances (Khan et al., 2021) as well as a detailed understanding of morphometric properties is important to control floods (Prabhakaran and Jawahar Raj, 2018;Abdeta et al., 2020). Watershed morphometry is affected by some factors: geology, lithology, hydrology, structure, and climate (Majeed and Nasraldin, 2021). Recently, applying this analysis using geospatial techniques began to take an essential place in geomorphological studies and research, replacing traditional measurement methods such as field observation and topographic maps (Mangan et al., 2019). Applying this technique allows for discovering the geomorphology characteristics of many basins that are either unmapped or inaccessible (Tukura et al., 2021), where remote sensing data is proven to be the most efficient technique which is used to analyze the morphometric drainage catchment for such cases . This performance improved by integrating with the Geographic Information System (GIS) by providing many useful tools for studying watershed delineation, hydro-morphometric analysis, and water resource suitability assessment (Aziz et al., 2020;Abdulrazzaq et al., 2019;Agbasi et al., 2019).
The Heshkaro river basin is an important basin to Dohuk city, although there are no details studies of the Heshkaro River watershed regarding the hydro-morphometric analysis. Therefore, this research aims to apply geospatial techniques to discover the hydromorphometric characteristics of the Heshkaro River basin in Duhok city, Northern Iraq. The results of this research can be used to ensure the integrated management successfully of the basin in aspects of urban planning, flooding protection, and hydraulic structures construction.

Description of the Study Area
The Heshkaro River is one of the two main rivers crossing Duhok City, located between 36° 47' 30" and 36° 57' 30" N latitude and 43° 0' 0" and 43° 07' 30" E longitude. The study area's elevation ranges between 529 to 1350 m (Fig 1). This river originates from a place close to the village of Bade in the north and heads south towards the city of Duhok, where it unites with the Duhok River in the far southwest of the city. Where the Heshkaro River crosses the urban area in the southern part of its. The total area of the watershed is (79.2) km2 as estimated by (Mohammed, 2021). Climatic factors (particularly temperature and precipitation) have a substantial impact on water resources. The Climatologic condition of the study area is similar to that of the Mediterranean region (Gokalp and Mohammed, 2019). The Mediterranean climate is distinguished by dry summers and a moderate amount of precipitation in winter (Mzuri et al., 2021). Moreover, often accompanied by snow due to the presence of mountain ranges. Forests, shrubs, and grasslands with some villages cover the upper portion of the basin, and the lower portion is an urban area with little vegetation land. Geologically, the current study occupies a wide area extending from Bade to the north and Duhok city to the south, including a major fold structure called Bekhair anticline, Duhok anticline, and Duhok syncline. Moreover, this studied area is located within the High Folded Zone. The rock unit exposed in the study area from the oldest deposits to recent are (Bakhma Formation, Shiranish Formation, Aaliji Formation, Kolosh Formation, Sinjar Formation, Gercus Formation, Avanah Formation,pilaspi Formation, lower Fars Formation, Upper Fars Formation) (Bamerni et al., 2021).

Results and Discussion
The morphometric parameters of the Heshkaro River have been determined using the suggested methodology steps of this study. The automated getting of these parameter values has been done by using the ArcGIS program.

Linear Aspect
This parameter is important to determine the shape, as well as the relative relief of the watersheds (Rajasekhar et al., 2020) . The Length of the basin is found about (14.6 km) for the study area, which indicates low runoff of the basin (Kar et al., 2015).
Is defined as the boundary length of the stream watered (Fatah et al., 2020). The perimeter of the study area is 50.7 km.
• Stream order (Su) The Stream order is a good indicator of discharge, drainage area, and stream size (Hamad, 2020). The Heshkaro river system basin is divided into five orders (Table 2) (Fig 3). The relationship between the stream order and the number of streams shows inverse behavior ( Fig 4A).

• Stream number (Nu)
This parameter has a significant effect on runoff through the dimensions and sizes of the branches (Noori et al., 2019). The stream number is influenced by many factors such as; geology, rock type, slope, climate, and topography (Majeed and Nasraldin, 2021). The total number of streams of the Heshkaro river basin has been calculated are (359), in the first-order (276), second-order (65), thirdorder (15), fourth-order (2), and fifth-order stream (1) ( Table 2).

• Stream length (Lu)
Stream length (Lu) is the principle of geometric similarity in basins is generally increasing in order (Horton, 1945). Generally, higher stream orders have shorter streams, while lower stream orders have longer streams. This relationship between stream length and stream order is inverse (Majeed and Nasraldin, 2021). The results of the stream length of the study area were (214.13km) for the total stream length, 1st order is (114.13 km), 2nd (60.7 km), 3rd (22.40 km), 4th (4.5 km), and 5th (12.4 km) ( Table 2).

• Mean stream length (Lsm)
This parameter is a reflection that exposes the typical size of drainage network components and the basin surfaces that contribute to it (Singh et al., 2020). In the current study, the mean stream length (Lsm) in 1st order is (0.41 km), 2nd (0.93 km), 3rd (1.49 km), 4th (2.25 km), and for 5th order (12.4 km) ( Table 2), indicates that the mean stream length value increases as stream order increases ( Fig 4B).
• Stream length ratio (RL) The stream length ratio has a significant influence on the surface flow, discharge, and erosional features (Arulbalaji and Padmalal, 2020). The Stream length ratio values of the Heshkaro river basin are (0.53 for 1st to 2nd), (0.37 for 2nd to 3rd), (0.20 for 3rd to 4th), and (2.76 for 4th to 5th) order of streams, respectively as shown in (Table 2). noted that the fifth-order streams have a higher stream length ratio, while the fourth-order streams have a lower ratio. • Bifurcation ratio (Rb) The most fundamental parameter for defining the stream patterns in the basin, which are intricately linked to the watershed structure and climatic conditions, is the bifurcation ratio. It illustrates both the watershed's discharge pattern and the basin's geometry. Additionally, it is useful for measuring flooding in the area (Bogale, 2021). In the present study, the Bifurcation ratio (Rb) values of the Heshkaro river basin are given in (Table 2). The mean bifurcation ratio of the study area is (4.52) which indicates a moderate value, which means the geological structure of the Heshkaro River has little effect on the drainage basin pattern and is within a low runoff range.

Areal Aspect
• Basin area (A) The total drainage area of the Heskkaro river basin is (81.1 km 2 ), it is classified as a moderate area according to (Majeed and Nasraldin, 2021) classification.

• Stream frequency (FS)
This parameter is defined as the number of branches per square meter of the area (Horton, 1932).
The FS value of the study area is found about (4.43) streams/km 2 (Table 4) which is a low value according to (Table 3). A high value of stream frequency indicates more surface runoff and basin relief, while a low value indicates more percolation and less basin relief (MR et al., 2019). Furthermore, represents the texture of the drainage network, permeability, runoff, infiltration capacity as well as relief of the basin. (Mahala, 2020).

• Drainage density (Dd)
Horton has specified that Dd by the length of whole branches to the total drainage area expressed in km/km 2 (Horton, 1932). The Dd of the study area was a low value is (2.62) km/km 2 (Table 4) (Fig 5). Several studies have shown a significant relationship between drainage density and climate. Where a low value represents a low precipitation intensity, and high permeability of the basin (Majeed and Nasraldin, 2021). Furthermore, a Low drainage density produces a coarse drainage texture while a high drainage density produced a fine drainage texture. • Drainage texture (T) Drainage texture is described as the entire number of the catchment streams to the perimeter of the catchment (Horton, 1945). The drainage texture of the Heshkaro river was (7.08) per km (Table 4), which indicates the basin is a fine texture according to smith's (1950) classification (Smith, 1950). Many factors, including precipitation, slope, infiltration capacity, and vegetation, influenced drainage texture. Moreover, erosion and dissection increase when drainage texture increases (Bogale, 2021).

• Elongation ratio (Re)
This aspect is defined as the proportion between the diameter circular watershed to the maximum watershed length (Schumm, 1956). Re value of the study area is about (0.39) which refers that the watershed is elongated according to the Schumm classification (Schumm, 1956). This value is indicating that the Heshkaro River has a more elongated shape, which is described as a low steep slope, low runoff discharge, high infiltration capacity, and evaporation. • Circularity ratio (R c ) The circular ratio is defined as the area of a circle with the like diameter of the watershed's perimeter to the area of the watershed (Miller, 1953).The Rc of the watershed is (0.40) ( Table 4), indicating that the basin has less circularity in shape, low discharge runoff, and high permeability of the soil. Where many factors have been taken into consideration that affects the circularity ratio: stream length, stream frequency, land use/land cover, geological structure, climate, slope, and relief of the basin (Hamad, 2020).

• Form factor (Ff)
Is defined as the ratio of the watershed's area to its length squared (Horton, 1932). The Ff value of the study area is (0.38) (Table 4), which shows the elongated shape, and low peak flow with a longer time. The value of the form factor remains less than (0.76) donates a circular basin and the low value of the form factor suggests an elongated basin (Aldharab et al., 2019).
The Constant channel maintenance value of the Heshkaro river basin is (0.38) km 2 /km (Table 4), which indicates that 0.39 km 2 of the watershed is required to sustain 1 km of the channel. The CCM value is affected by relief, climate, the permeability of rocks, and the vegetation type of the basin (Sarkar et al., 2020). This parameter relates inversely to the drainage density (Singh et al., 2020). • Length of overland flow (Lg) • The length of overland flow is considered the most influential variable influencing drainage basin hydrologic and physiographic development (Khan et al., 2021). The computed value of the Length of overland flow is (0.19) (Table 4), indicating high permeability and low to moderate slopes with low surface runoff. The Lg value is affected by the amount of precipitation, infiltration rate, and vegetation type. Table 3. Stream frequency classification for a number of streams (Sarkar et al., 2020)

Relief Aspect
• Basin relief (R) Relief is the most significant parameter for understanding the landform characteristic, weathering, and erosion processes of the basin, efficiency of floods, water flow, drainage development, and slope steepness (Sarkar et al., 2020 ;Tukura et al., 2021). The maximum height of the Heshkaro river basin is (1350 m), and the minimum height is (529m). Therefore, the relief of the basin is determined as (821 m), indicating low slope, low flood effectiveness, and low sediment transport (Table 5). • Relief ratio (Rr) The relief ratio of the study area is (0.06) moderate value (Table 5), which suggests that the watershed has a low to moderate slope and low runoff intensity. The Rr typically increases when the drainage area and size of the basin decrease (Lama and Maiti, 2019). Moreover, a high relief ratio value suggests that water is moving quickly toward the stream mouth, indicating considerable flood risk as well as a large transport of sediment (Majeed and Nasraldin, 2021).
Relative relief is one of the most accurate parameters for estimating the rate of erosion of a drainage basin (Majeed and Nasraldin, 2021). The Rhp value of the study area was (16.19) (Table 5), which shows that the erosion rate of the Heshkaro river basin is low.
The ruggedness number is high when the drainage density and relief are high and the slope is steep and long (Singh et al., 2020). Moreover. This morphometric parameter was used to calculate the undulation of the topography (Sarkar et al., 2020). The Ruggedness number value of the basin is (2.15) ( Table 5). The low value of the roughness number indicates that soil erosion has not yet manifested itself or that a gradual and modest flash flood has occurred.

• Slope
The slope is a significant parameter in hydro-morphometric analysis that represents the ratio of inclination of the basin in relation to the horizontal surface (Aldharab et al., 2019). The slope is affected by some factors such as geological structure, lithology, runoff, climate, and metrological parameters. Furthermore, the slope determines the inverse relation between infiltration and surface runoff (Rajasekhar et al, 2020). In the current study, the slope was ermined using (ALOS PALSAR DEM) and ArcGIS. The slope of this data ranged from 0 to 73.5, as shown in degrees (Fig 6). Most of the area is covered by a slope that does not exceed 14.4 degrees covered of the study area (Table 6). Where the side parts of the basin and the Duhok city border have a step and a very steep slope.

Conclusions
The current study found that, in terms of time and money savings, remote sensing and GIS approaches have largely replaced the conventional methods of morphometric analysis better to comprehend the geometric and hydrological characteristics of the watershed.The results indicated that the shape of the watershed is elongated according to the elongation ratio, circulatory ratio, and form factor. Additionally, the study was classified into a 5th-order stream with a total length of (214.13 km).The result of the mean bifurcation ratio is marked, which means the geological structure has a normal effect on the drainage pattern. Moreover, the stream order values increase with a decrease in the stream frequency and vice-versa. The study results showed that the watershed has moderate to low slope, low relief, low runoff, and high infiltration, with low erosion and sediment loading exposure.The results of this research demonstrate that the remote sensing data, which are integrated with GIS, provide a fundamental view of the hydrological behavior of a watershed through the flooding time.