Abstract
Al-Adhaim dam basin is extended across the boundaries of Salahuddin, Kirkuk, and Sulaymaniyah provinces in the northern part of Iraq, covering an area of 11831 km2. The area is covered mainly in most upperparts by sedimentary rocks of the lower Eocene to Pliocene ages. The lower parts are occupied by sheet runoff deposits from the Quaternary age. The objectives of the current study are to carry out detailed measurements of hypsometric parameters to evaluate the degree of erosion conditions and to show the essential factors controlling the development of geomorphic stages in different parts of the basin. The analysis was carried out based on ASTER GDEM data using ArcGIS v10.6 hydrology toolbox and the morphometric toolbox and dividing the basin into fifteen sub-basins. The results show that the Al-Adhaim basin passes in the monadnock phase with a hypsometric integral of 19.02% and a highly concaved hypsometric curve. The sub-basins are classified into two groups of geomorphic stages, i.e., mature stage and Monadnock stage with hypsometric integral values between 18.4% and 34.6%. The results reveal the basin was controlled mainly by slopes, lineaments, Tertiary outcrops, Quaternary deposits, and hydrological soil groups B and D.
Highlights
The hypsometric analysis is a quantitative study of the drainage basin, and it reflects the geomorphic cycle and the manner of mass distribution in the basin
Hypsometric analysis of drainage basin is based on the hypsometric curve (HC) as a graphical representation of relative area situated above various altitudes on the abscissa, and relative altitude on the ordinate and hypsometric Integral (HI) calculated from the ratio of the area below HC to that of the rectangle delimited by the maximum values on the abscissa and ordinate (Strahler, 1952b; Strahler, 1957 and Zavoianu, 1985)
According to the HI values and HCs, the geomorphic cycle of erosion and the watershed are divided into three stages; Monadnock stage (HI ≤ 35%) refers to a phase represents isolated and erosion-resistant hills and mountains that rise above the general erosion level, which is called a peneplain (Vanderwaal and Ssegane, 2013), equilibrium, Mature stage (35% ≤ HI ≤ 60%) and non-equilibrium, Youth stage (HI ≥ 60%) mean the watershed is highly susceptible to more erosion (Strahler, 1952b)
Summary
The hypsometric analysis is a quantitative study of the drainage basin, and it reflects the geomorphic cycle and the manner of mass distribution in the basin. The hypsometric properties are used to study small-scale basins of low order to evaluate the geomorphic cycle and determine the mass distribution within the basin from base to top (Miller, 1953; Schumm, 1956 and Strahler, 1952b). The HI has been widely used in the interpretation of the stages of watersheds according to equilibrium and non-equilibrium phases of landscape because of uplift and denudation processes, and providing a measure of landmass volume distribution remaining beneath or above a basal reference plane (Ohmori, 1993; Singh et al, 2008; Strahler, 1952a; Vivoni et al, 2008 and Willgoose and Hancock, 1998). According to the HI values and HCs, the geomorphic cycle of erosion and the watershed are divided into three stages; Monadnock stage (HI ≤ 35%) refers to a phase represents isolated and erosion-resistant hills and mountains that rise above the general erosion level, which is called a peneplain (Vanderwaal and Ssegane, 2013), equilibrium, Mature stage (35% ≤ HI ≤ 60%) and non-equilibrium, Youth stage (HI ≥ 60%) mean the watershed is highly susceptible to more erosion (Strahler, 1952b)
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