Introduction

Rivers have garnered increasing attention due to their role in delivering diverse ecosystem services. In recent decades, river morphology has undergone frequent alterations as a result of climate change and anthropogenic factors. In Iran, rivers have been subjected to significant pressures due to extensive human interventions, including sand and gravel mining, dam construction, channel diversion, bank stabilization, and water resource exploitation.

A key tool in this field is the Revised Morphological Quality Index (rMQI), developed to enable a more precise analysis of riverine physical processes. This index provides a comprehensive assessment of a river's physical condition by evaluating three critical aspects: the intensity of anthropogenic pressures, the degree of morphological alterations, and the ecological and geomorphological functionality of the river.

The objective of this study is to understand the dynamic processes shaping the channel and the morphological changes of the Vaz, and Hajimahrud Hablehrud, and Shahrud rivers over time. Using the Revised Morphological Quality Index (rMQI) method—based on the Human Pressure Index, Channel Form Adjustment Index, and Meandering Functionality Index—the morphological quality of the studied rivers was assessed. The findings of this research can inform decision-making processes aimed at mitigating environmental risks and optimizing river management practices.



Methodology

T he rivers studied in this research include the Vaz River and Hajimahrud (Chamestan, Nour), the Hablehrud River (Garmsar), and the Shahrud River (Rajaei Dasht-e Alamut). To collect high-resolution morphometric data, field surveys and unmanned aerial vehicles (UAVs), or drones (using stereoscopic imaging or short-range photogrammetry), were employed for image acquisition. Based on field surveys and the use of a digital elevation model (DEM), morphometric parameters of the channel, channel characteristics, and human interventions were recorded and derived.

The revised Morphological Quality Index (rMQI) method was used to assess the morphological quality of the studied rivers. This method evaluates the qualitative status of rivers by applying and measuring a set of indicators, including Pressure Indicators (PI) and Channel Adjustment and Functioning Indicators (AI). The rMQI method examines the morphological quality status based on 12 human pressure indicators and 21 channel alteration indicators, consisting of 10 channel form adjustment indicators and 11 functional indicators.



Results

Through field surveys and processing of drone-captured images at different time intervals, the relevant indicators for each river segment were identified. Subsequently, measurements, calculations, and data scoring were performed using the rMQI method.



Hajimahrud River: The values obtained from the pressure index parameters in the first and second segments were 37.5 % and 42.19 %, respectively, while the channel adjustment change/trend indicators in the first segment were 70 % and 70 % in the second segment. Based on these data, the rMQI values were calculated as 45.18 % for the first segment and 47.53 % for the second segment. The morphological quality of both segments of the Vaz River was assessed as moderate.





Vaz River: The study area along the Vaz River was divided into two segments. The values obtained from the pressure index parameters in the first and second segments were 31.25% and 54.39%, respectively, while the channel adjustment change/trend indicators in the first segment were 54.39% and 51.75% in the second segment. Based on these data, the rMQI values were calculated as 42.82% for the first segment and 41.5% for the second segment. The morphological quality of both segments of the Vaz River was assessed as moderate.

Hablehrud River:The study area along the Hablehrud River was divided into three segments. The values obtained from the pressure index parameters were 7.87% in the first segment, 28.75% in the second, and 15.63% in the third. The channel adjustment change/trend indicators were 64.91% in the first segment, 60.53% in the second, and 67.54% in the third. Based on these data, the rMQI values were calculated as 36.39% for the first segment, 44.64% for the second, and 41.58% for the third. The morphological quality of all three segments of the Hablehrud River was assessed as moderate.

Shahrud River: The study area along the Shahrud River was divided into two segments. The values obtained from the pressure index parameters were 20.31% in the first segment and 25% in the second, while the channel adjustment change/trend indicators were 30.7% in both segments. Based on these data, the rMQI values were calculated as 25.51% for the first segment and 27.85% for the second. The morphological quality of both segments of the Shahrud River was assessed as good.

Discussion and Conclusion

The assessment of the morphological quality of the studied river sections using the rMQI method revealed that the examined reaches of the Vaz River and Hajimahrud exhibit moderate quality. This condition is attributed to the presence of three severe and one moderate anthropogenic pressure, as well as unfavorable morphological alterations and channel functionality. Similarly, the studied reaches of the Hablehrud River were found to be in a comparable state to those of the Vaz River, resulting in a moderate morphological quality. In contrast, the examined sections of the Shahrud River demonstrated good morphological quality, owing to minimal human pressures and favorable conditions in channel planform dynamics and functionality over time. The superior morphological quality of the Shahrud River may be linked to the absence of intensive management and exploitation pressures. These studied reaches are located in mountainous areas, distant from densely populated urban and rural settlements.

The findings from the Vaz, Hajimahrud, Hablehrud, and Shahrud Rivers indicate that human interventions—such as sand and gravel mining, channelization, and unsustainable water extraction—have significant adverse impacts on the hydrogeomorphological conditions of rivers.