Hydro-Morphological Analysis of Karaj River in the Urban Area from Beylqan to the Railway Bridge

Urban development and land use change have seriously damaged the quality and conditions of geomorphological equilibrium, drainage capacity and river ecosystem services. On the other hand, these changes and human interventions have affected the environmental sustainability of the area. To manage and prevent the loss of natural and geomorphological functions of rivers, it is necessary to assess the morphological quality of the river. In the Karaj River, due to the expansion of urbanization, encroachment on the riverbed, channeling, sand extraction, etc., serious damage has been inflicted on the river ecosystem. In the present study, the hydro-geomorphological quality of the Karaj River in the urban area of Karaj of Iran (from Beylqan Bridge to the railway bridge) was evaluated. Using IHG hydro-geomorphological index along the main river, the basin was divided into seven sections and the value of this index was determined for each section. The IHG index evaluates 9 parameters in three groups (Functional Quality, Channel Quality, Riparian Quality). The value of each parameter calculated between 1 and 10 depending on the physical state and performance of the river basin. Based on the results of this study, sections of 1, 2, 3, 4, 6 and 7 have poor hydro-morphological quality; and section 5 due to human activity (including changes in morphological pattern, construction of engineering structures, disconnection of the main waterway and floodplain) have very poor quality. Also, the hydro-geomorphological quality of the urban area of Karaj River has the most negative effects due to the expansion of city and residential space, urban facilities and uncontrolled extraction of sand. The results show that the IHG index is a good indicator and sensor for assessing the hydro-geomorphological quality of rivers.