Document Type : Research Article
Authors
1
Department of Physical Geography, Faculty of Social Sciences, University of Mohaghegh Ardabili, Ardabil, Iran
2
Department of Natural Resources, Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran
Abstract
The aim of this study is to assess the geomorphological quality of the Nirchai River in Ardabil Province. To achieve this objective, the Morphological Quality Index (MQI), which is based on functional and artificial factors and is used to evaluate the condition and morphological stability of river systems, was employed. First, the river network was divided into six homogeneous reaches based on total channel length and the geomorphic quality index method. Subsequently, the relevant morphological indicators, including bank stability, channel pattern, cross‐sectional changes, sedimentation potential, and compatibility with the surrounding environment, were calculated. The MQI criteria consist of thirteen functional indicators and twelve artificial indicators. According to the results, the MQI of the Nirchai River effectively reflects the geomorphological conditions. Reach 2, with an excellent score of 0.85, falls within the very good class, indicating its morphological stability due to minimal human intervention. In the following ranks, Reach 4 (0.54) and Reach 3 (0.62) fall into the moderate class. Ultimately, Reach 6, with the lowest score (0.43), is classified as having very poor quality, which is directly attributed to excessive human interventions and extensive artificial alterations to the river channel as a result of urban development in Nir. Therefore, it is concluded that Reach 2, with the highest score, has the best geomorphological quality and greater morphological stability compared to the other reaches, whereas Reach 6, with the lowest score, represents the poorest condition. Finally, it is recommended that future studies evaluate temporal changes in the MQI of the Nirchai River using satellite data.
Introduction
River flow regimes are among the most fundamental drivers of river evolution. Beyond their roles in runoff conveyance and sediment transport, rivers provide essential ecological functions by supporting aquatic habitats, interacting laterally with riparian ecosystems, and forming longitudinal corridors that connect terrestrial and marine environments (Downs & Gregory, 2014).
The necessity of investigating the Nirchai River arises from the increasing hydromorphological pressures imposed on this river system as a result of land‑use changes, excessive substrate extraction from the riverbed, and recent climatic transformations. These pressures have contributed to the degradation of channel morphology, intensification of bank erosion, and progressive deterioration of riparian ecosystems. Despite its environmental and socio‑economic importance, the Nirchai River has not previously been evaluated using a standardized geomorphological assessment framework.
Accordingly, the application of the Geomorphological Quality Index (MQI) a quantitative and standardized method for assessing river morphological quality and stability is particularly warranted. The present study represents the first application of the MQI method to the Nirchai River, with the primary objective of evaluating its geomorphological quality and identifying reaches most affected by human intervention.
Material and Methods
In terms of research design, this study is descriptive–analytical and, with respect to its objectives, constitutes applied research. Primary data were collected through comprehensive library studies and detailed field surveys conducted along the course of the Nirchai River. Initially, geomorphic data (including topographic and geomorphological maps and aerial imagery), geological information, climatic records, and hydrological data such as discharge statistics from the Nirchai hydrometric station and information on tributaries and water resources were compiled to define reference conditions and establish the core components required for MQI calculation. Subsequently, anthropogenic pressures and engineering structures along the riverbanks were systematically documented.
Spatial analyses and extraction of geometric parameters were carried out using ArcGIS and Google Earth imagery. Quantitative calculations of the Geomorphological Quality Index (MQI) and the associated Pressure Index (IP), along with statistical processing of the results, were performed using Microsoft Excel. The MQI method applied in this study is based on a set of functional (F1–F11) and artificial (A1–A12) indicators, which collectively quantify the morphological status and stability of the river system.
Results and Discussion
Analysis of Index Data Across Different River Reaches
In light of the results presented in Table 3, the data pertaining to the scores of various indices across diverse reaches provide a robust opportunity to investigate the trend of performance changes and to identify the factors influencing the improvement or degradation of performance quality. This analysis is predicated upon data collected from six distinct reaches, with scores assigned to indices ranging from F1 to A12, ultimately leading to the derivation of the Geomorphological Quality Index (MQI).
Descriptive Analysis and Overall Data Trend
The aggregate score across all questionnaire items has increased from 53 in the initial reache to 82 in the sixth reache. This ascending trend signifies an overall improvement in the collective performance of the indices over time. Similarly, the total score for Class C criteria has advanced from 37 to 57, corroborating the positive trajectory in the overall quality index.
Index fluctuations across the reaches are varied; certain indices, notably A3 and A10, have maintained consistently high and stable scores across all periods, indicating sustained optimal performance. Conversely, indices such as F11 and F12 experienced a noticeable score decrement in the latter reaches, necessitating more rigorous investigation and follow-up.
Temporal Trend Analysis and Index Variation
An examination of the score variations across the time intervals reveals that a number of indices exhibited a statistically significant upward trend. For instance, index F7 increased from a score of zero in the first reach to five in subsequent reach, denoting substantial amelioration. Furthermore, key indices within Group A, particularly A3 and A10, have consistently attained high scores, positioning them as pivotal determinants of the Geomorphological Quality Index. This escalating trend suggests the positive impact of implemented interventions or favorable environmental factors on index quality enhancement, thereby guiding the development of future planning strategies.
Correlation Analysis with Overall Performance
A correlation assessment between the scores of each individual index and the total score of all questions, as well as Class C, demonstrated that specific indicesnamely A3, A10 and F7 exhibit a strong positive correlation with overall performance. These indices play a pivotal role in the comprehensive performance enhancement, and focused attention on them can significantly amplify the efficacy of upgrading programs.
Index Classification and Cluster Analysis
The classification of indices based on their functional attributes and temporal variations enables the identification of groups sharing analogous characteristics. Cluster analysis revealed three distinct groupings: one cluster comprised indices with high performance and an increasing trend (e.g., A3, A10, and F7); a second cluster consisted of indices with moderate scores and limited fluctuation; and the third cluster was composed of indices demonstrating low performance or severe volatility.
Summary of Scores and Geomorphological Assessment of Nirchai River Reaches
As presented in Table 4, Reach 2 records the highest MQI coefficient (0.85) and is classified in the “very good” category, indicating the highest level of geomorphological quality and morphological stability among the studied reaches. Reaches 1 and 6, both with a coefficient of 0.43, fall within the poor to very poor category, reflecting intense human interference and extensive artificial alterations. Reach 5, with a coefficient of 0.75, is classified as good, while Reaches 3 and 4 occupy an average quality class.
Conclusion
This study provides a comprehensive assessment of the geomorphological quality and morphological stability of the Nirchai River using the Geomorphological Quality Index (MQI). The results derived from field observations and satellite imagery indicate that Reach 2, with an MQI value of 0.85, exhibits the highest morphological stability and is categorized as having very good geomorphological quality. In contrast, reaches 1 and 6, with MQI values of 0.43, are classified as poor, reflecting substantial human intervention within the river channel and adjacent areas.
These anthropogenic disturbances contribute to increased sediment production, channel instability, and accelerated erosion processes. The findings emphasize the necessity of implementing targeted river management and restoration strategies, particularly in reaches experiencing severe human pressure, to improve geomorphological conditions and ensure the long‑term stability of the Nirchai River system.
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