Seyed Hamidreza Sadeghi *1 
, Fatemeh Abdulbaghi1 , Fatemeh Hasanpour1 , Ali Nouri1 , Fatemeh Esmailzadeh Ashini1 , Negin Rashidi1 , Masoumeh Hamzeh1 , Arasteh Payfeshordeh1 , Fatemeh Tavakoli1 , Sahar Mousavian1 , Mehdi Khairparast1 , Somaye Zare1 , Mostafa Zabihi Seilabi1
, Fatemeh Abdulbaghi1 , Fatemeh Hasanpour1 , Ali Nouri1 , Fatemeh Esmailzadeh Ashini1 , Negin Rashidi1 , Masoumeh Hamzeh1 , Arasteh Payfeshordeh1 , Fatemeh Tavakoli1 , Sahar Mousavian1 , Mehdi Khairparast1 , Somaye Zare1 , Mostafa Zabihi Seilabi1
1- Tarbiat Modares University
Abstract: (155 Views)
Extended Abstract
Introduction and Objective: Soil erosion is defined as separating soil particles from their original location and moving to other places through various processes and deposition. Soil erosion and sediment yield are the most critical problems in most regions of the world, which causes a decrease in soil productivity, an increase in floods, a decrease in the health of water systems, and an increase in sedimentation in dam reservoirs. A model of potential sediment delivery to the waterway network is essential to manage soil erosion and sediment yield and identify sources of sediment yield. As a result, the estimation of sediment yield at the watershed, sediment yield areas, its delivery patterns from sources to the network, and finally, depositing it in reservoirs are needed for soil erosion management. The sediment connectivity index is one of the most important methods and characteristics of watershed sediment yield. Sediment connectivity is an emerging concept that helps us better understand the processes occurring in the watershed area that affect water flow and sediment movement differently. This index explains the degree of connection of the sediment flow throughout the watershed, especially between the sediment source and the downstream area, and expresses the sediment delivery ratio.
Material and Methods: The study aims to compare and evaluate the spatial changes of the connectivity index at the scale of a small watershed. The term connectivity describes the relationship between the sources of runoff and sediment yield in the mirage (upstream) of watersheds and the corresponding reservoirs downstream. Sediment connectivity indicates the connectivity or non-connectivity of runoff and sediment paths at a particular time and in a system under detachment, transportation, and sedimentation processes. This study was conducted in the Shazand Watershed in Markazi Province, Iran. To investigate the spatial pattern of sediment yield in the watershed and the sediment connectivity map of the watershed, the Sediment Delivery Ratio model, the method presented by Borsley et al., and the definition of the connectivity index were used. The sediment connectivity index is a type of hydrological connectivity that examines the potential of moving sediment particles throughout the watershed system using topographical and other characteristics of the watershed. This index can be calculated in the GIS software environment and based on the main elements of the hydrological connectivity index, such as land-use (as a dynamic element) and topographic characteristics (as a static element). The sediment connectivity index consists of two parts, including upstream and downstream. To calculate the connectivity index, the distance from the sediment source (or the end of the range or the connectivity to the main waterway), the characteristics of the sediment movement path, factors affecting the cumulative flow of runoff, and local conditions in each part. The more positive the connectivity index is, and it tends to the positive side of infinity, the higher the probability of structural connectivity for sediment transport. In contrast, the more it tends to the negative side of infinity, the more the connectivity probability will decrease.
Results: The results showed that the sediment connectivity index in different sub-watersheds ranged from -7.108 to 1.400. For this purpose, slope and land-use/ cover maps were used. Comparing the land-use map with the sediment connectivity index shows the role of human disturbance in the natural functioning of ecosystems and natural systems. According to slope and land-use/ cover maps, mountainous and highland areas, due to the naturalness of the areas and rainfed lands by human interventions, had the minimum and the maximum sediment connectivity to the downstream area. In addition, the lowland areas mainly had the minimum connectivity index, and the steep highlands had the maximum connectivity index. One of the main factors affecting connectivity is the type of vegetation that affects the movement of particles. So, in areas without vegetation or with little coverage, connectivity increases and leads to more runoff yield. However, more infiltration occurs in areas with dense vegetation, leading to less runoff generation and, ultimately, a lower possibility of sediment connectivity. Based on the results and the concept of the sediment connectivity index, the smaller its value is, the lower the probability of sediment transportation. In general, considering the connectivity index and its distribution can be important for prioritizing areas in terms of soil erosion and sediment management.
Conclusion: Recently, sediment connectivity has been used more in the studies of soil erosion and sedimentation of watersheds. Due to the novelty of connectivity concepts in watersheds, further investigation of sediment connectivity and related concepts is necessary. The review of various research on the sediment connectivity index showed that despite the extensive progress in recent years, there still needs to be a comprehensive framework to achieve a uniform understanding of the performance and fluvial behavior and the various associated processes. Therefore, considering the importance of conserving the country's water and soil resources and providing suitable solutions for policy making for sediment management in the watersheds, a specific framework in planning related to sediment monitoring and control and accurate and up-to-date statistics and information are crucial. It is necessary to show the status of the watershed, especially the critical and sensitive watersheds, in terms of erosion and sediment yield. According to the present research results and an understanding of the sediment connectivity index, the proposed concept can be used as an effective tool for the sustainable management of watersheds.
Introduction and Objective: Soil erosion is defined as separating soil particles from their original location and moving to other places through various processes and deposition. Soil erosion and sediment yield are the most critical problems in most regions of the world, which causes a decrease in soil productivity, an increase in floods, a decrease in the health of water systems, and an increase in sedimentation in dam reservoirs. A model of potential sediment delivery to the waterway network is essential to manage soil erosion and sediment yield and identify sources of sediment yield. As a result, the estimation of sediment yield at the watershed, sediment yield areas, its delivery patterns from sources to the network, and finally, depositing it in reservoirs are needed for soil erosion management. The sediment connectivity index is one of the most important methods and characteristics of watershed sediment yield. Sediment connectivity is an emerging concept that helps us better understand the processes occurring in the watershed area that affect water flow and sediment movement differently. This index explains the degree of connection of the sediment flow throughout the watershed, especially between the sediment source and the downstream area, and expresses the sediment delivery ratio.
Material and Methods: The study aims to compare and evaluate the spatial changes of the connectivity index at the scale of a small watershed. The term connectivity describes the relationship between the sources of runoff and sediment yield in the mirage (upstream) of watersheds and the corresponding reservoirs downstream. Sediment connectivity indicates the connectivity or non-connectivity of runoff and sediment paths at a particular time and in a system under detachment, transportation, and sedimentation processes. This study was conducted in the Shazand Watershed in Markazi Province, Iran. To investigate the spatial pattern of sediment yield in the watershed and the sediment connectivity map of the watershed, the Sediment Delivery Ratio model, the method presented by Borsley et al., and the definition of the connectivity index were used. The sediment connectivity index is a type of hydrological connectivity that examines the potential of moving sediment particles throughout the watershed system using topographical and other characteristics of the watershed. This index can be calculated in the GIS software environment and based on the main elements of the hydrological connectivity index, such as land-use (as a dynamic element) and topographic characteristics (as a static element). The sediment connectivity index consists of two parts, including upstream and downstream. To calculate the connectivity index, the distance from the sediment source (or the end of the range or the connectivity to the main waterway), the characteristics of the sediment movement path, factors affecting the cumulative flow of runoff, and local conditions in each part. The more positive the connectivity index is, and it tends to the positive side of infinity, the higher the probability of structural connectivity for sediment transport. In contrast, the more it tends to the negative side of infinity, the more the connectivity probability will decrease.
Results: The results showed that the sediment connectivity index in different sub-watersheds ranged from -7.108 to 1.400. For this purpose, slope and land-use/ cover maps were used. Comparing the land-use map with the sediment connectivity index shows the role of human disturbance in the natural functioning of ecosystems and natural systems. According to slope and land-use/ cover maps, mountainous and highland areas, due to the naturalness of the areas and rainfed lands by human interventions, had the minimum and the maximum sediment connectivity to the downstream area. In addition, the lowland areas mainly had the minimum connectivity index, and the steep highlands had the maximum connectivity index. One of the main factors affecting connectivity is the type of vegetation that affects the movement of particles. So, in areas without vegetation or with little coverage, connectivity increases and leads to more runoff yield. However, more infiltration occurs in areas with dense vegetation, leading to less runoff generation and, ultimately, a lower possibility of sediment connectivity. Based on the results and the concept of the sediment connectivity index, the smaller its value is, the lower the probability of sediment transportation. In general, considering the connectivity index and its distribution can be important for prioritizing areas in terms of soil erosion and sediment management.
Conclusion: Recently, sediment connectivity has been used more in the studies of soil erosion and sedimentation of watersheds. Due to the novelty of connectivity concepts in watersheds, further investigation of sediment connectivity and related concepts is necessary. The review of various research on the sediment connectivity index showed that despite the extensive progress in recent years, there still needs to be a comprehensive framework to achieve a uniform understanding of the performance and fluvial behavior and the various associated processes. Therefore, considering the importance of conserving the country's water and soil resources and providing suitable solutions for policy making for sediment management in the watersheds, a specific framework in planning related to sediment monitoring and control and accurate and up-to-date statistics and information are crucial. It is necessary to show the status of the watershed, especially the critical and sensitive watersheds, in terms of erosion and sediment yield. According to the present research results and an understanding of the sediment connectivity index, the proposed concept can be used as an effective tool for the sustainable management of watersheds.
Keywords: Integrated watershed management, Sediment connectivity, Soil erosion, Sediment management.
Type of Study: Research |
Subject:
فرسايش خاک و توليد رسوب
Received: 2024/02/7 | Accepted: 2024/05/5
Received: 2024/02/7 | Accepted: 2024/05/5
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