Omid Asadi Nalivan; Gholamreza Khosravi; Ehsan Alvandi
Abstract
Introduction
Watersheds, as key units of water resources management, play a fundamental role in supporting ecological processes, regulating the hydrological cycle, providing water, conserving soil, and sustaining the livelihoods of human communities. These natural systems are exposed to increasing pressures ...
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Introduction
Watersheds, as key units of water resources management, play a fundamental role in supporting ecological processes, regulating the hydrological cycle, providing water, conserving soil, and sustaining the livelihoods of human communities. These natural systems are exposed to increasing pressures from climate change, population growth, unsustainable exploitation, agricultural and industrial development, and land use changes. In such circumstances, the concept of watershed sustainability as the system's capacity to maintain optimal performance of ecological processes and environmental services in the long term has gained special importance. In addition to providing early warnings of environmental degradation, assessing the health and sustainability of watersheds can also identify the causes of existing problems. The Watershed Sustainability Index is one of the valid indicators that quantify the status of watershed sustainability. This index, due to its high flexibility and usability at different scales, is known as a suitable tool for planning and decision-making in sustainable watershed management. Therefore, the present study was conducted with the aim of assessing the sustainability of the Atrak River watershed and providing a comprehensive picture of its functional status and ecological sustainability. The strengths of the article include the breadth and comprehensiveness of the indicators used (four key dimensions of sustainability), the 10-year study period, which increases the validity of the results, and the spatial assessment of watersheds and prioritization of actions, which allows for targeted policymaking.
Materials and methods
The Atrak River watershed with an area of 819,000 hectares is located in Golestan Province. The watershed sustainability index, developed by developing the UNESCO-HELP model and using the PSR (pressure-state-response) causal model, is one of the few indicators designed specifically for watersheds, which evaluates the sustainability of the watershed in question numerically and using a formula in the form of four sub-indices of hydrology (qualitative and quantitative), environment, life (livelihood conditions and human development), and policy. In this method, taking into account the available information and data (10-year period), the values of the parameters in the three components of pressure, status, and response were collected to examine each of the sub-indices and converted into quantitative form in the scoring range from zero to one and in five categories (0, 0.25, 0.5, 0.75, 1). The indicators receive a score of one in the best condition and a score of zero in the worst condition. The final WSI value was classified into three categories of low, medium, and high through the arithmetic mean of the sub-indices.
Results and discussion
The results of the hydrology section showed that in all sub-watersheds, per capita available water decreased during the 10-year study period. Also, the three sub-watersheds of Chat, Dashli Borun, and Gomishan are in the weak category in terms of the pressure component, and only Maraveh Tapeh is in the medium category. This condition is also true for the status and response component. According to the results, the TDS level has increased in all sub-watersheds. The results indicate a critical situation in the water quality sector of the watershed. In general, the average results of the hydrological index varied between zero and 0.25. The environmental index showed that the trend of increasing agricultural land is visible in all four sub-watersheds. The highest increase in agricultural land occurred in the Chat sub-watershed and the lowest in the Gomishan sub-watershed. Also, the highest increase in population occurred in the Chat sub-watershed, which confirms the results of the increase in agricultural land. The results indicate a very bad situation of the EPI index in the two sub-watersheds of Maraveh Tapeh and Chat, and Dashli Borun is in the next rank, and the Gomishan sub-watershed has the best situation in this index. According to the final score results, the situation of Gomishan is better than other sub-watersheds in the environmental sector. In general, the average results of the environmental index varied between 0.33 and 0.5. The results of the life index showed that the status of this index in all sub-watersheds was average to high. In general, the average life index results varied between 0.75 and 0.83. The results of the Policy Index showed that based on the average scores, the status of this index in all sub-watersheds was poor. In general, the average Policy Index results for all sub-watersheds were 0.58. The final values of the WSI index showed that all sub-watersheds have a poor status in terms of sustainability in all four main indicators. According to the average scores (0.448), the Atrak watershed is in the low category in terms of sustainability.
Conclusions
Considering the results obtained and the low level of sustainability of the Atrak River watershed, it is necessary to take immediate and planned measures to improve the sustainability status. The most important management and applicable suggestions in the watershed include the following. Integrated water resources management, which will increase the efficiency of water use in the agricultural sector by using modern irrigation methods and consumption management in the drinking and industrial sectors. Improving the quality of water resources, including controlling and reducing the input of pollutants into surface and groundwater sources, can be done through the development of urban and rural wastewater treatment systems. Protecting and restoring natural vegetation by implementing projects to restore degraded rangelands and developing protected areas, which play a fundamental role in improving the sustainability status of the watershed. Strengthening environmental governance and policymaking and establishing coordination between organizations responsible for water, agriculture, and the environment to implement integrated watershed management are other important strategies for improving the sustainability of the Atrak watershed.
Mohammad Rostami; Akbar Kiasalari; Mohammad Reza Gharibreza
Abstract
Introduction
The construction of various structures for coastal protection is one of the strategies for dissipating wave energy in coastal areas. Permeable and floating protective structures are among the new coastal protection designs proposed to address the shortcomings of previous structures. In ...
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Introduction
The construction of various structures for coastal protection is one of the strategies for dissipating wave energy in coastal areas. Permeable and floating protective structures are among the new coastal protection designs proposed to address the shortcomings of previous structures. In the design and construction of such structures, piles and pipes are used as their foundations. Evaluating the pattern and extent of erosion around piles caused by wave interaction is essential for designing such structures. Therefore, in addition to structural design, hydrodynamic loading on the coastal protection structure and its foundation due to wave impact must be considered as a key criterion for foundation design in shallow waters. In coastal areas, waves undergo various processes such as wave refraction, wave shoaling, and wave breaking, which result from nonlinear interactions with the seabed. Moreover, energy transfer between different wave frequency components during the breaking process is highly nonlinear. Understanding the hydrodynamics involved is considerably more complex compared to breaking waves in deep waters. This complexity becomes particularly significant when wave breaking occurs exactly at the pile foundation, as the stability of permeable coastal structures depends on the stability of their foundations against erosion caused by marine currents.
Materials and methods
To evaluate the scour depth around cylindrical piles of coastal protection structures under impact pressure caused by wave breaking, an experimental study was designed. The experiment aimed to analyze how variations in wave characteristics such as wave height and period affect the research objectives. It is important to note that this study focused on breaking waves impacting the structure. The experiments were conducted in a two-dimensional wave channel at the Coastal Engineering Laboratory of the Soil Conservation and Watershed Management Research Institute. To create shallow water conditions and ensure wave breaking at the pile location, as well as to assess the resulting scour depth, a sloped surface and sediment reservoir were constructed in the central part of the main channel. The sediment reservoir, with a depth of 0.35 meters, was installed upstream of the sloped surface and filled with sand sediments. A cylindrical pile was placed at the center of the sediment reservoir. The wave channel was filled with water to a depth of 0.4 to 0.5 meters, and waves with varying heights and periods were generated using a wave paddle system. Trial and error was used to determine the exact location of wave breaking in relation to the pile. A total of 34 experiments were conducted under initial water depths ranging from 0.4 to 0.5 meters. Wave heights ranged from 0.05 to 0.14 meters, with wave periods between 2 to 7 seconds. After each experiment, the scour depth at the pile location was measured.
Results and discussion
In this study, wave characteristics, including wave height, breaking wave velocity, wavelength at the breaking point, breaker crest distance from the structure, and water depth at the breaking zone, as well as the maximum scour depth (S), were measured. Based on the measured values, the Keulegan–Carpenter number (KC) and the S/D ratio were determined. The results showed that as the KC number increases, the S/D ratio and scour depth also increase. Specifically, with increasing KC, the length of lateral vortices along the sides and behind the base of the cylindrical structure extends, exposing a larger portion of the seabed to scour and erosion. A regression analysis was established between these parameters, and the findings were compared with previous studies. A comparison of 34 experiments in the present study with the results of Sumer et al. (1992) indicated that the scour depth under wave-breaking conditions near the coastal protection structure was approximately 1.14 to 8.46 times greater than the scour depth caused by regular waves passing through the structure’s vicinity. On average, the scour depth due to wave breaking at the pile location was 2.4 times greater than that under normal wave conditions (Sumer et al., 1992). Additionally, comparing the results of this study with Dogan (2021) revealed that the scour depth under wave-breaking conditions near the coastal protection structure was approximately 1.31 to 2.85 times greater than the scour depth caused by regular waves. On average, the scour depth due to wave breaking at the pile location was 2.03 times greater than under normal wave conditions (Dogan, 2021).
Conclusions
In general, when coastal currents interact with waves, if the waves do not break, the depth of scour decreases. However, if the wave in question propagates in the direction of the coastal current and breaks, the increased turbulence and resulting shear stress near the seabed at the breaking zone lead to an increase in scour depth. If wave breaking occurs at the site of the coastal structure, the extent of erosion and scour will exceed the values reported in previous studies. The results of the present study indicate that wave breaking causes approximately a 2.4-fold increase in scour depth compared to the passage of regular, non-breaking sea waves around a cylindrical pile structure. Therefore, marine structure designers must carefully consider this issue. An inaccurate estimation of the scour depth at the foundation of coastal protection structures based solely on the theory of regular wave passage near a cylindrical pile may lead to incorrect foundation depth calculations, affecting the overall stability of the structure. If the findings of this study are not taken into account, instability conditions could arise for the marine structure, especially when wave breaking occurs near the foundation.
Parviz Abdinejad; Asghar heidari
Abstract
Introduction
According to the climatic conditions in most areas of Zanjan province, watersheds are faced with inappropriate temporal and spatial distribution of rainfall and seasonal water shortage in spring and summer. The use of water catchment systems and super absorbent materials is one of the proposed ...
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Introduction
According to the climatic conditions in most areas of Zanjan province, watersheds are faced with inappropriate temporal and spatial distribution of rainfall and seasonal water shortage in spring and summer. The use of water catchment systems and super absorbent materials is one of the proposed methods for supplying the water needed by seedlings for the construction of rainfed gardens in sloping lands to prevent erosion in these lands and their proper exploitation.One of the strategies that can increase the efficiency of rainwater harvesting is to assist in the establishment and adaptation of seedlings planted on steep soils, using super absorbent materials at the bottom of these seedlings. The use of these materials increases the tolerance of horticultural crops under drought stress and preserves soil moisture. Therefore, feasibility of establishment of fruit trees and development of these orchards using moisture-absorbing materials seem necessary through the application of intake surface systems. accordingly, this study was conducted to evaluate the effect of super absorbent materials on diameter growth of two type trees in rain water harvesting systems .in this way, it is possible to study the simultaneous use of super absorbent and super absorbent materials to create dryland orchards in sloping lands.
Materials and methods
In this study, the effect of application superabsorbent material on growth of rain-fed trees in managed rainwater harvesting systems was investigated and application or non-application of superabsorbent as main treatment, three management treatments including: 1) no change at the level of system, 2) Trench collection and vegetation cover of the system level and 3) Semi-insulated treatment as sub-treatments (in the three repetitions) and Was examined with randomized complete block design two fruit tree including almond and apricot as sub-treatments in a split plot design. During the design, tree growth indices including changes in diameter, height and canopy of seedlings were measured in different treatments of rain water harvesting.
Results and discussion
Based on the results of chemical analysis of soil samples in the research area, the average electrical conductivity (ds/m) was 0.44, the average soil organic matter was 0.88 percent, lime or neutralizable carbonates was 0.66 percent, potassium was 1.42 (mg/kg), carbonate was 2.22 (mg/kg), and bicarbonate (meq/lit). During the implementation of the project, growth indices including changes in diameter, height, and canopy cover of seedlings were measured over a five-year period. Based on the results obtained, the maximum and minimum diameter growth rates of almond seedlings in the treatments with and without superabsorbent were 1.4 and 0.35 cm and 1.2 and 0.3 cm, respectively, and this rate for apricot seedlings was 1.4 and 0.2 cm, and 0.9 and 0.2 cm, respectively, without superabsorbent. Accordingly, the surface treatment of the catchment surface system with vegetation cover had the lowest amount of diameter growth in almond and apricot seedlings, and the insulated treatment had the highest diameter growth. This situation actually indicates the effect of creating a catchment surface system with different coverage levels in creating different amounts of runoff and, as a result, differences in the diameter growth of the planted seedlings. The existence of significant differences between treatments and blocks in the diameter growth of almond and apricot seedlings compared to the year in the experimental treatments with and without superabsorbent at the one percent level indicates the effectiveness of the operations carried out in each of these treatments. However, the analysis of variance of the factors affecting the diameter growth values of seedlings showed that the presence of superabsorbents did not have a significant effect on their growth.
Conclusions
Based on the results of this study and other researchers, the significance of the effect of superabsorbent materials on plant growth in the use of superabsorbent materials is not a general and permanent state and depends on the climatic conditions of the region, the type of soil and its texture, the type of plant, and even the topographic conditions and slope of the planting site. Considering the results of this research and the results of others, it can be argued that the effect of super absorbent materials on the growth of each plant or seedling should be investigated and evaluated in the desired area and an opinion should be expressed based on that.
Vahid Payravand; Ali Salajegheh; Mohammad Reza Sayyadi
Abstract
IntroductionSustainable water resources management in arid and semi-arid regions such as Iran is a critical challenge for ensuring food security and environmental protection. While surface dams have traditionally been effective, they face issues such as high evaporation, sedimentation, and ecological ...
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IntroductionSustainable water resources management in arid and semi-arid regions such as Iran is a critical challenge for ensuring food security and environmental protection. While surface dams have traditionally been effective, they face issues such as high evaporation, sedimentation, and ecological impacts, highlighting the need for alternative solutions. Underground dams reduce water loss and preserve water quality, offering significant potential for improving groundwater management. However, their implementation in Iran encounters technical, social, economic, and institutional challenges. This study uses a grounded theory approach to develop a practical management framework for underground dam implementation, aiming to optimize water use while ensuring the long-term sustainability and efficiency of these infrastructures. Materials and methodsThis qualitative study was conducted using Strauss and Corbin’s grounded theory approach, involving 14 experts in watershed management and underground dams with at least 15 years of experience, selected through purposive and snowball sampling. Data were collected via semi-structured interviews until theoretical saturation was achieved. Analysis followed open, axial, and selective coding, resulting in 201 open codes, organized into 49 axial codes and 22 main categories. Data validity and reliability were ensured through expert evaluation, coder agreement, and triangulation methods, leading to the development of a final paradigmatic model for managing the implementation of underground dams. Results and discussionThis study aimed to develop a paradigmatic model for the management of underground dam implementation in Iran and to analyze the factors affecting project success, based on Strauss and Corbin’s Grounded Theory approach. To achieve this, 14 experts and executive managers with 15–35 years of experience, including faculty members and senior managers of national natural resource organizations, participated in the study, providing a diverse and robust basis for qualitative analysis. Through open coding, 201 initial concepts were identified, which, after organization into axial and selective codes, led to the extraction of five core components of the paradigmatic model: causal conditions, contextual conditions, intervening conditions, strategies, and consequences. The causal conditions, including inefficiency of surface dams, threats to livelihoods, and water security risks, acted as the main drivers for adopting underground dams, while contextual conditions such as geological and site characteristics, technical specifications, functional and economic capacities, and local experience created a supportive operational environment for project implementation. Moreover, intervening conditions, including policies, legal frameworks, operational challenges, social participation, and economic justification, played a moderating role affecting the success of strategies and outcomes. Strategy analysis revealed that comprehensive planning, technological development, stakeholder engagement, socio-economic decision-making, training and capacity-building, adoption of innovative technologies, and resource management are critical for achieving underground dam objectives, and coordinated implementation of these strategies enhances management effectiveness, reduces risks, and improves water resource sustainability. Finally, the consequences were identified across five domains: water resource protection and sustainability, economic efficiency and technology acceptance, sustainable agricultural development and water supply, ecological balance and social impacts, and overall project sustainability, demonstrating that simultaneous consideration of causal, contextual, and intervening factors along with coordinated strategies is key to project success. Therefore, the extracted paradigmatic model explains the dynamic interactions among factors and their effects on strategies and outcomes, offering a robust framework for decision-making and policy planning in water resource management in dry and semi-arid regions of Iran, while aligning with international studies and contributing novel insights by integrating technical, managerial, economic, and social dimensions and emphasizing the moderating role of intervening conditions and economic consequences. ConclusionsUnderground dams in Iran can be considered a complementary, context-specific option whose success depends on technical, social, economic, and institutional factors. Inefficiencies of surface dams and threats to water security justify their use, while suitable geological conditions enable implementation. Strategies such as comprehensive planning, technology development, stakeholder engagement, and education can lead to sustainable water management, agricultural development, and economic resilience. This study provides a paradigm model offering a framework for decision-making and management of underground dams, serving as a foundation for future research and water resource planning.
Mohammad Rostami Khalaj; Hamze Noor; Ali Bagheryian Kalat
Abstract
Introduction
Drought propagation, defined as the transfer of moisture deficits from meteorological to hydrological drought, represents a central topic in water resources management, particularly in arid and semi-arid regions. Understanding the spatial patterns of drought propagation and identifying ...
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Introduction
Drought propagation, defined as the transfer of moisture deficits from meteorological to hydrological drought, represents a central topic in water resources management, particularly in arid and semi-arid regions. Understanding the spatial patterns of drought propagation and identifying the controlling factors are essential for designing risk-reduction strategies and achieving sustainable management of aquifers and surface runoff. Considering the sensitivity of catchments to climatic stress in eastern Iran, this study aims to analyze the spatial dynamics of drought propagation and assess the influence of catchment environmental characteristics in Khorasan Razavi Province.
Materials and methods
This study utilized data from 46 catchments over a 29-year period (April 1988 to September 2016). Meteorological and hydrological droughts were identified using the standardized precipitation index (SPI) and the standardized streamflow index (SSI), respectively. Drought events were extracted using a threshold of SPI or SSI ≤ –1, and paired events were determined. For each event, the intensity and severity of both meteorological and hydrological droughts were calculated, followed by the derivation of drought propagation ratios and their normalized forms. A set of physiographic and climatic catchment variables-including slope, normalized difference vegetation index (NDVI), precipitation seasonality index (Ps), snow fraction (fₛ), aridity index (Ai), and available water capacity (AWC)—were averaged at the catchment scale and analyzed using Pearson correlation to assess their relationships with drought propagation ratios.
Results and discussion
Spatial analyses indicated that the mean meteorological drought intensity ranged from 0.23 to 2.17, with an average of approximately 2.1, whereas hydrological drought intensity ranged from 0.14 to 1.16, with a mean of 0.65. The coefficient of variation (CV) was 63% for hydrological drought intensity and 37.7% for meteorological drought, indicating greater spatial variability in hydrological drought. At the catchment level, 54% of the catchments exhibited a reduction in propagation intensity, and 67% showed a decrease in propagation severity. The mean propagation intensity and severity ratios were –0.03 and –0.1, respectively, suggesting a general attenuation of drought effects during the transfer from meteorological to hydrological systems. Significant negative correlations between meteorological drought characteristics and propagation ratios (r = –0.48 for intensity and r = –0.67 for severity) indicate that stronger meteorological drought events tend to experience greater attenuation during propagation; that is, high-intensity meteorological drought does not always translate into equally severe hydrological drought. Among environmental factors, NDVI showed a significant negative relationship with both propagation ratios, and AWC was negatively correlated with the severity propagation ratio. In contrast, precipitation seasonality (Ps) and aridity index (Ai) did not exhibit significant correlations with propagation ratios, while snow fraction (fₛ) showed only a weak negative correlation with propagation intensity. Catchment slope also showed no significant relationship with propagation ratios. These patterns suggest that, in Khorasan Razavi, intrinsic catchment characteristics—particularly vegetation cover and soil water storage capacity—play a key role in attenuating drought propagation.
Conclusions
The results of this study indicate that drought propagation in the 46 catchments of Khorasan Razavi is predominantly characterized by a reduction in both intensity and severity, with 54% of catchments showing decreased propagation intensity and 67% exhibiting reduced severity. The mean propagation ratios for intensity and severity were –0.03 and –0.1, respectively. Meteorological drought intensity and severity emerged as the strongest controls on drought propagation, showing significant negative correlations with propagation ratios. Among environmental factors, vegetation cover (NDVI) and soil water storage capacity were the most influential in mitigating drought propagation, whereas climatic indices had no significant impact.
Negar Arjmand; Alireza Sepahvand; Omid Rahmati
Abstract
Introduction
Today, the study of gully erosion is of great importance due to sediment production and numerous damages resulting from human activities. Many natural factors have been reported as controlling factors of gully erosion. Among the geo-environmental factors that control the critical conditions ...
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Introduction
Today, the study of gully erosion is of great importance due to sediment production and numerous damages resulting from human activities. Many natural factors have been reported as controlling factors of gully erosion. Among the geo-environmental factors that control the critical conditions for the occurrence and development of gully erosion, primarily related to topography, lithology, rainfall, soil, and land use, other studies have stated that surface runoff is one of the main factors affecting the occurrence of gully erosion. Identifying the factors affecting the occurrence of gully erosion and its zoning is one of the essential and important tools for controlling and managing this phenomenon. Gully erosion is a significant threat to the state of ecosystems worldwide; consequently, developing gully erosion susceptibility maps is essential. Therefore, this research was conducted to mapping the susceptibility of gully erosion occurrence using artificial intelligence models of the Multilayer Perceptron (MLP) neural network, Maximum Entropy (MaxEnt), and Flexible Discriminant Analysis (FDA) in Al-Shatr city.
Materials and methods
The study area is located in the central part of the Zagros mountain range in Lorestan Province, Iran, within the Karkheh sub-basin. Alashtar County covers an area of 1,523.55 km², situated between longitudes 48°30′52″E to 48°03′38″E and latitudes 34°01′21″N to 33°44′37″N. The basin has an average annual precipitation of approximately 570 mm and features a semi-arid, cold climate. To map gully erosion susceptibility and identify the most effective model, three artificial intelligence models were employed: Multi-Layer Perceptron (MLP), Maximum Entropy (MaxEnt), and Flexible Discriminant Analysis (FDA). Twelve environmental factors were used as input variables: slope, aspect, precipitation, distance from roads, distance from rivers, distance from faults, soil type, land use, geological formation, Topographic Wetness Index (TWI), Topographic Position Index (TPI), and Normalized Difference Vegetation Index (NDVI). The output variables consisted of gully and non-gully points. A total of 151 points (89 gully and 62 non-gully locations) were collected. Seventy percent of the data were used for model training, while the remaining 30% were reserved for validation. Model performance was evaluated using the Relative Operating Characteristic (ROC) curve to assess predictive accuracy.
Results and discussion
The results showed that the MLP model, with AUC values of 0.98 in the training phase and 0.92 in the validation phase, had the best performance in predicting gully erosion susceptibility. This was followed by the FDA (AUC = 0.87) and MaxEnt (AUC = 0.5) models, respectively. Analysis of the influencing factors revealed that most gullies were located in precipitation classes of 600-700 mm, distances greater than 300 meters from faults, roads, and rivers, slope classes of 0-5% and 5-15%, northern aspects, dry farming land use, and geological formations of old alluvium and marls. Furthermore, a direct relationship was observed between the TWI index and gully occurrence, while an inverse relationship was found for the NDVI index. Finally, the gully erosion map was prepared using the MLP model.
Conclusions
Given that gully erosion is an advanced form of water erosion, identifying its driving factors and mapping its susceptibility are crucial for effective control and management. This study aimed to identify key factors influencing gully erosion and develop machine learning models to map susceptibility in Shastar County. Results indicate that the Artificial Neural Network (MLP) model performed best, achieving an AUC of 0.92, followed by FDA (AUC = 0.87) and MaxEnt (AUC = 0.50). These findings provide valuable insights for planners and researchers regarding the factors driving gully erosion. Future research should explore additional machine learning techniques and incorporate other influential factors to further improve prediction accuracy.
Ahmadreza Karimipour; Saleh Yousefi; Sara Mardanian
Abstract
Introduction
The phenomenon of land subsidence, as a global challenge, has affected many plains and metropolitan areas, including various regions of Iran. This phenomenon is primarily caused by the uncontrolled exploitation of groundwater resources and geological factors, which can lead to serious consequences ...
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Introduction
The phenomenon of land subsidence, as a global challenge, has affected many plains and metropolitan areas, including various regions of Iran. This phenomenon is primarily caused by the uncontrolled exploitation of groundwater resources and geological factors, which can lead to serious consequences such as damage to infrastructure and the destruction of agricultural lands. Recent advances in remote sensing have enabled more accurate monitoring of this phenomenon, utilizing various techniques such as PS-InSAR and CPT. In addition to remote sensing, machine learning algorithms have also been used in various studies to predict subsidence. Accordingly, employing a suitable model with high accuracy in this field is of great importance. The AdaBoost model, due to its high capability in addressing the complex nonlinear relationships governing the subsidence phenomenon, can play an effective role in zoning subsidence risk levels, thereby contributing to risk management and land-use planning in a region.
Materials and methods
This study was conducted in Chaharmahal and Bakhtiari province, located in the heart of the Zagros Mountains. Initially, thirty factors related to land subsidence were considered, encompassing topographic (elevation, slope, aspect, curvature, TWI, TPI, TRI), hydrological (distance from rivers, flow accumulation), geological (distance from faults, lithology), environmental (vegetation cover, land moisture index, land use), and climatic parameters (temperature, precipitation, snow depth). To avoid multicollinearity, a correlation matrix analysis was performed, leading to the removal of seven variables with a correlation coefficient greater than 0.7. Subsequently, 23 variables were retained for modeling. The AdaBoost algorithm was trained on 2,352 samples (1,859 subsidence and 493 non-subsidence) and validated on an independent test set of 772 samples (536 subsidence and 236 non-subsidence). The model's performance was assessed using the Area Under the Curve (AUC), Precision, Recall, and Kappa coefficient metrics.
Results and discussion
The data of the obtained statistical indices for the Area Under the Curve (AUC), model accuracy (Precision), Recall index (Recall), and Kappa coefficient (0.974, 0.936, 0.981, and 0.855, respectively) in evaluating the AdaBoost model indicate the model's highly desirable performance in predicting subsidence risk. Based on the classification obtained in the final subsidence risk zoning map, the study area was categorized into five classes: very low risk, low risk, moderate, high, and very high. The results showed that the plains of Boroujen and Shahrekord are at the highest risk, respectively, while limited parts of the Lordegan plain fall into the very high-risk category. Other plains in the province are mainly faced with low to moderate risk levels. Furthermore, the results indicated that 36% of the province is exposed to moderate subsidence risk.
Conclusions
The findings of this study demonstrate that the AdaBoost model is an effective tool for zoning land subsidence risk in Chaharmahal and Bakhtiari Province. According to the SHAP analysis, the three main parameters influencing subsidence, in order of importance, are: land slope angle, surface sand percentage, and groundwater level fluctuations. It was further established that an inverse relationship exists between land slope and subsidence intensity, meaning areas with gentler slopes exhibit greater vulnerability to this phenomenon. Conversely, a decline in the groundwater level and its fluctuations have a direct correlation with increased subsidence, while a higher surface sand percentage exerts a mitigating effect on subsidence occurrence. The results underscore the necessity for proper management of groundwater resources. The subsidence risk zoning map and the evaluation charts presented in this study can serve as practical tools for preventing and mitigating damages caused by land subsidence.
Rouhangiz Akhtari; Hamidreza Hajipoor; Mojtaba Saneie; Mohammadreza Gharibreza
Abstract
Introduction
Seasonal floods in mountainous regions of Iran are a major challenge for water resources management and the protection of rural communities. This study evaluates the effectiveness of check dams in reducing seasonal flood impacts in the Sijan watershed, Alborz Province, Iran. The watershed ...
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Introduction
Seasonal floods in mountainous regions of Iran are a major challenge for water resources management and the protection of rural communities. This study evaluates the effectiveness of check dams in reducing seasonal flood impacts in the Sijan watershed, Alborz Province, Iran. The watershed was selected because of its high flood potential, the occurrence of destructive debris floods (including the 2015 event), and the importance of Sijan village as a popular tourist destination. In 2018, the Forests, Rangelands and Watershed Management Organization of Iran constructed one masonry check dam and four gabion check dams along the main channel upstream of the village to reduce debris flood hazards. The main objective of this research was to simulate the historical flood event and evaluate the effectiveness of these structures in modifying flood hydrographs. Because the stream is seasonal and hydrometric data are limited, a physical model was used as the main research tool. This paper presents the results of the first stage of the study, which focuses on evaluating the effects of the check dams on runoff flood hydrographs (clear water flow without sediment).
Materials and methods
A direct physical modelling approach was used to investigate the influence of check dams on flood peak reduction and peak delay. Field investigations were carried out along a 700 m reach of the Sijan stream after the construction of the check dams. A detailed topographic survey at a scale of 1:1000 was then conducted. Due to laboratory space limitations, a 168 m section containing three 1 m high check dams was selected for modelling. A 1:10 scale physical model was built at the Soil Conservation and Watershed Management Research Institute following geometric and dynamic similarity principles. To eliminate infiltration effects, the channel bed and banks were made impermeable. The experiments considered two main factors: channel condition and inflow hydrograph characteristics. Three channel conditions were tested: (1) no check dams, (2) empty check dams, and (3) sediment-filled check dams. Flow conditions included both steady flow for stage-discharge calibration and unsteady triangular hydrographs for flood simulation. The time to peak was examined under three conditions: shorter than, equal to, and longer than the watershed concentration time. Peak discharges were selected below the estimated 10-year flood because of laboratory limitations. Hydraulic variables were measured using standard weirs, and all experiments were video recorded to improve measurement accuracy. The analysis focused on three hydraulic indicators: peak discharge reduction, delay in peak arrival time, and changes in flood base duration. In total, 90 experiments were conducted, and the outlet hydrographs were recorded using a sharp-crested rectangular weir.
Results and discussion
The results demonstrate that 1 m high check dams significantly modify flood hydrographs under different hydrological conditions using clear water over a rigid, non-erodible bed. In the natural channel without check dams, increasing inflow discharge reduced both peak attenuation and peak delay. Empty check dams showed the highest efficiency for floods with peak discharges below 4.74 m³/s (approximately corresponding to return periods of less than five years). Under these conditions, the dams temporarily stored runoff and effectively attenuated the flood hydrograph. However, as flood magnitude increased or the dams became filled with sediment, their storage capacity decreased, resulting in lower flood mitigation performance. The experiments showed that empty check dams reduced peak discharge by up to 28% and increased the time to peak by up to 36% during small and moderate floods. In addition, the ratio between watershed concentration time (tc) and flood time to peak (Tp) was identified as a key parameter controlling dam performance. For floods with short hydrograph duration (Tp < tc), representing intense short-duration storms, the dams achieved their highest efficiency, reducing peak discharge by up to 22.5% and increasing peak delay by up to 43%. Their effectiveness gradually decreased as flood return period and hydrograph duration increased. The results indicate that the design of check dam systems should consider watershed hydrological characteristics, including flood return period, hydrograph shape, time to peak, and sediment accumulation, to maximize flood reduction efficiency. Three empirical equations based on dimensional analysis were developed to quantify the effects of check dams on flood hydrograph characteristics. These equations showed good predictive performance, with coefficients of determination (R²) ranging from 0.81 to 0.92. However, their application to other watersheds requires local calibration.
Conclusions
The physical model results also identified the ratio tc/Tp as a practical indicator for evaluating check dam performance. When tc/Tp > 1, floods have a short time to peak and a narrow hydrograph. Under these conditions, check dams provide temporary storage, increase backwater effects, enhance local turbulence and energy dissipation, and significantly reduce peak discharge while delaying flood propagation. When tc/Tp ≈ 1, the inflow hydrograph is well balanced with the storage capacity of the dams, resulting in effective but moderate flood attenuation. When tc/Tp < 1, floods have a longer duration, and the available storage behind the dams gradually becomes full. Consequently, the proportion of dissipated flow energy decreases, leading to lower reductions in peak discharge and smaller delays in flood timing. Overall, the findings demonstrate that check dam performance depends not only on the structural characteristics of the dams but also on watershed hydrology, particularly the tc/Tp ratio. Therefore, in watersheds with short concentration times, check dams are particularly effective for mitigating flash floods and should be designed to maximize temporary storage and energy dissipation. In contrast, in watersheds with longer concentration times, combining check dams with larger storage facilities and other watershed management measures is likely to provide better flood mitigation. The study also highlights the importance of considering long-term sediment deposition during the design and maintenance of check dams, as sediment accumulation significantly reduces their storage capacity and hydraulic performance over time.
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