Assessment of Hydromorphological Quality of the Sulachay River in Ardabil Province, Iran, using the Morphological Quality Index (MQI)

Background and Objectives
he natural flow regime of a river varies across daily, seasonal, annual, and long-term time scales. To describe the regular pattern of flow magnitude, timing, and variability, multiple observational data from water-level gauge curves are required (Poff et al., 1997). River flow regimes exhibit regional patterns that are primarily determined by basin size and geographical characteristics, including climate, geology, topography, and vegetation cover Rivers, under various environmental conditions, possess considerable complexity and diversity, and both natural and human factors influence them and alter their hydromorphological conditions. In fact, hydromorphological degradation caused by human interventions and river-channel modification is considered one of the most fundamental causes of river alteration. Several methods have been developed to assess the hydromorphological condition of rivers. One such method is the Morphological Quality Index (MQI), which was introduced for the first time in 2013 by Rinaldi et al., and presented as a modern tool for evaluating the morphological quality of river flows. Rinaldi et al. (2013).

Methodology
The Morphological Quality Index (MQI) is one of the most advanced methods for classifying the morphological condition of rivers, first introduced by Rinaldi et al. (2013). This index quantitatively assesses the morphological quality of a river by examining natural riverine forms and processes (functional aspects), human interventions and artificial structures, as well as adjustment mechanisms. In the MQI method, the index value ranges from 0 (very poor and fully artificial conditions) to 1 (completely natural and dynamic conditions). Therefore, the closer the MQI value is to 1, the more natural and stable the river’s morphological condition is (Rinaldi et al., 2013; 2016). The index consists of three main groups:
• 13 functional indicators (F1–F13) related to natural channel and floodplain processes and forms
• 12 artificial indicators (A1–A12) related to human interventions and structures
• Adjustment indicators used to modify scores based on specific local conditions
Functional Indicators (F1–F13)
These indicators assess the consistency of channel and floodplain forms and processes with the expected natural condition.
Artificial Indicators (A1–A12)
These indicators evaluate human interventions and artificial elements across three aspects:
• Continuity (dams and alterations in flow and sediment regime),
• Channel morphology (cross-sectional structures, artificial bank protections, levees, and channel realignment),
• Riparian vegetation (removal of woody debris and degradation of natural vegetation by human activities).
Findings
The results of Table 2 indicate that Reach 2, with a total raw score of 88 and an adjusted index (C) value of 68, has obtained the highest overall score, while Reach 5 has the lowest total score and Reach 4 has the lowest C index score (43). This reflects the negative influence of controlling factors—particularly the upstream dam—on the morphological dynamics of Reach 4.
Analysis of the functional indicators (F1–F13) reveals that Reach 2 has achieved high scores in most form and process indicators; however, it has received very low scores in the key channel dynamism indicators (F8, F10, F12, and F13). This weakness has resulted in a final MQI value of only 0.29 (very poor) for this reach, despite its high raw score.
The artificial indicators (A1–A12) show favorable conditions across all reaches. Indicators A1 to A3 (transversal and longitudinal structures) scored 6 in all reaches, indicating the absence of direct interventions such as dams, bridges, or artificial bank protections. Indicator A12 (bank stability) received a score of 5 in all reaches, demonstrating overall stability throughout the studied sections. These results confirm that, aside from the dam located in Reach 2, no major or direct anthropogenic interventions were observed in the channel bed or banks.
Overall, the significant discrepancy between the high raw scores and the low final MQI value in Reach 2 demonstrates the strong weighting of natural dynamism indicators in the MQI methodology (Table 2).
Conclusion
The assessment of the morphological quality of the Soolachay River using the MQI index showed that its values range from 0.29 to 0.81, displaying a clear decreasing trend from upstream to downstream. Reaches 1 and 4, with values of 0.81, fall within the “Good” class, while Reach 2, with a value of 0.29, is classified as “Very Poor.” Reaches 3, 5, and 6, with values ranging from 0.61 to 0.65, belong to the “Moderate” class. These variations are mainly influenced by the intensity of human interventions, land-use changes, and the reduction of riparian vegetation cover.
The highest morphological quality was observed in the upstream sections, characterized by gentle slopes, stable geological structures, and minimal human disturbance. In contrast, the construction of a dam in Reach 2 is the most significant factor disrupting longitudinal continuity, weakening channel dynamism, and causing a severe decline in MQI. The middle and downstream reaches are moderately stable but vulnerable, affected by agricultural activities, construction, and bank erosion.
Overall, the Soolachay River is in a semi-stable to relatively stable condition; however, the continuation of current human activities could rapidly disrupt this balance. To enhance morphological quality and ensure long-term ecological and hydromorphological stability, implementing integrated management strategies—including bed and bank stabilization, restoration of riparian vegetation, continuous monitoring of sedimentation, and regulating construction within the river corridor—is essential.
It is recommended that future studies employ artificial intelligence models and advanced spatial analyses to predict and monitor morphological and hydrological changes.
Keywords: anthropogenic interventions, Ardabil Province, hydromorphological quality, integrated river management, Morphological Quality Index (MQI), Sulachay River.