Investigation of Typological Changes in the Riparian Vegetation of Jajrood River Emphasizing the Anthropogenic Impacts

ABSTRACT
Understanding the interactions among components of the river system in response to external drivers is essential for advancing sustainable river environment management. This study aims to investigate the changes in the typology of riparian vegetation along the Jajrood River during the period from 1988 to 2023. In this research, analog aerial photographs from 1988 and UltraCam images from 2023 were used. The GUS method was applied to segment the river based on geoforms. According to the river's geomorphological analysis, five 800-meter reaches were identified, and the confinement type of the left and right banks, stability, sediment types, slope, and elevation of each reach were examined. The Jajrood River was divided into five geomorphic reaches. Subsequently, a number of quasi-parallel cross-sections were drawn at suitable intervals along the river. Typological classification of vegetation in each cross-section included the river channel, grassland, tall and short woody vegetation, sedimentary islands, marginal sediment deposits, human-made features, and vegetated islands. The vegetation change analysis indicates a reduction in riparian grassland typology in 2023 compared to 1988. The area of vegetated islands within the river channel decreased from 165,415 square meters in 1988 to 265,633 square meters in 2023. Typologies of marginal sediment deposits and human features increased in 2023 compared to 1988, indicating land use change and encroachment into riparian lands along the Jajrood River.
 
Extended Abstract
Introduction
Rivers operate as hierarchical systems, where large-scale processes and structures profoundly influence local dynamics. Over the past five decades, this understanding has evolved, with geomorphologists increasingly embracing an interdisciplinary approach—integrating geology, biology, and ecology—to conceptualize rivers as interconnected ecosystems. Floodplain environments, in particular, depend on the continuous exchange of water, nutrients, and sediments, which sustains their biodiversity and enhances ecological resilience. Similarly, although coastal zones are spatially limited, they play a crucial role in water filtration, biodiversity conservation, and overall ecosystem stability.
Ensuring environmental sustainability in these vital systems is essential for maintaining their ecological functions. However, human activities have significantly disrupted their balance. Dam construction alters natural flow regimes, restricting the downstream transport of sediments and nutrients. Agricultural practices contribute to habitat degradation and pollution, while industrialization introduces harmful contaminants that degrade water quality and aquatic ecosystems. Moreover, climate change compounds these challenges by shifting precipitation patterns, increasing the frequency of extreme weather events, and driving changes in vegetation and species composition.
These anthropogenic impacts have led to reduced biodiversity and compromised ecosystem functions. To counter these effects, it is crucial to implement sustainable land-use practices, restore degraded habitats, and develop adaptive management strategies that address both human needs and ecological integrity. In Iran, rivers like the Jajrood River have faced significant ecological changes due to dam construction, tourist overcrowding, encroachment on riverbanks, and the cutting of riparian trees. These changes have damaged the geomorphic and ecohydrological patterns of the river, emphasizing the urgent need to incorporate environmental sustainability into river management practices to prevent further degradation of its ecosystems.
This study aimed to examine changes in the riparian vegetation typology of the Jajrood River between 1988 and 2023, considering both human and natural impacts.
 
Methodology
This study utilized analog aerial photographs from 1988 and UltraCam images from 2023 to assess changes in river morphology and riparian vegetation. The data were processed and mosaicked, then georeferenced using ENVI software. Georeferencing accuracy was enhanced by selecting 30 to 80 ground control points, which helped minimize RMS error and ensured reliable spatial alignment. The river typology was examined using the GUS (Geomorphic Unit Survey) method, which integrates geomorphic and ecological parameters to describe river morphology and functions. This method categorizes river types based on confinement degree, bed material, and channel planform, offering a comprehensive framework for understanding river dynamics. Semi-parallel cross-sections were established along the river, allowing for systematic analysis of key features such as river channels, grasslands, woody vegetation, sediment islands, riparian sediment loads, and human-made structures. Land cover changes were evaluated by overlaying classified maps in ArcGIS software, focusing particularly on woody vegetation (shrubs and trees) due to their critical role in biogeomorphological feedbacks. The comparison of data from 1988 and 2023 facilitated an in-depth investigation of structural and dynamic changes in vegetation. This integrative methodology provided a robust platform for analyzing spatial and temporal patterns, highlighting significant transformations in the study area over 35 years.
 
Results and Discussion
The GUS method was used to analyze the Jajrood River typology. Due to the length of the study area (20 km) and the large diversity of habitat units (63 subunits and 35 main units), the river was divided into five segments of 800 to 1000 meters. These segments were differentiated based on geomorphic features, elevation, and slope, and geomorphic units were mapped for each segment using the GUS method criteria. River stability was examined by comparing satellite images and aerial photographs in ArcGIS. In the various segments, specific features such as branches, sediments, and vegetation types were identified. In the first segment, the river had a 12% slope and an elevation of 1363 meters, showing bed and bank erosion and sediment transfer from upstream. In the second segment, with a lower slope, erosion and sediment transfer from upstream were also observed. The third segment showed more branching and a wider bed. The fourth segment showed more human impact, and the fifth segment showed sediment deposition and the increase of sediment and vegetative islands. Between 1988 and 2023, the Jajrood River underwent notable transformations in riparian vegetation typology, driven largely by human activities and land use changes. A marked decrease in the river channel area was observed, accompanied by an increase in sediment and vegetative islands, highlighting shifts in geomorphic processes and sediment deposition patterns. Simultaneously, agricultural and residential areas expanded significantly, encroaching upon natural habitats and exerting increased pressure on the river ecosystem. One of the most critical changes was the reduction in woody vegetation, which plays a key role in stabilizing riverbanks and supporting biodiversity. In certain segments, the percentage of woody riparian vegetation declined dramatically, replaced by expanding areas of grasslands and vegetative islands. While the increase in vegetative islands may indicate adaptive responses to altered sediment dynamics, the loss of woody vegetation reflects disruptions in biogeomorphological feedbacks crucial for maintaining ecosystem stability.
 
Conclusion
The observed decrease in the Jajrood River channel area and riparian vegetation, coupled with an increase in human land uses such as agricultural expansion and the proliferation of human-made features, signifies profound alterations in the river ecosystem. These changes reflect escalating anthropogenic pressures that jeopardize the river's ecological integrity. The expansion of sediment and vegetative islands, alongside the reduction in grassland typology, underscores shift in the river's geomorphological and ecological dynamics, which are likely driven by both natural processes and human interventions. These findings point to the urgent need for sustainable management practices that prioritize the river's ecological balance. Effective strategies could include implementing riparian buffer zones, regulating land-use activities, and enhancing community engagement in conservation efforts. Addressing sediment management and promoting native vegetation restoration are also critical steps to mitigate these impacts and foster a resilient river ecosystem. The study’s results serve as a wake-up call for policymakers and stakeholders to integrate environmental sustainability into development plans. By adopting holistic approaches that balance human needs with ecological preservation, the Jajrood River’s health can be safeguarded, ensuring its ecological functions and services continue to benefit both the environment and local communities.
 
Funding
There is no funding support.
 
Authors’ Contribution
All of the authors approved the content of the manuscript and agreed on all aspects of the work.
 
Conflict of Interest
Authors declared no conflict of interest.
 
Acknowledgments
We are grateful to all the scientific consultants of this paper.