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Schematic illustration of the upslope and downslope components of connectivity for a reference pixel in watershed scale (adapted from Borselli et al. 2008)
Source publication
Purpose
Sediment connectivity is an emerging term that explains the connected transfer of sediment from all sources within a watershed to its outlet. Validation and further development of this concept require considerable supporting data. This research aims to investigate the relationship between the connectivity index (IC) and specific sediment yi...
Citations
... It is essential for the computation of the area and storage capacity of the reservoir. The TIN layer is characterized by three dimensions (x, y, and z) with a set of distinct triangles, signifies a computerized model of the dam bottom area consisting of randomly distributed vertices obtained from contour lines and point extents (Arabkhedri et al., 2021;Iradukunda et al., 2020;Mekonnen et al., 2022;Stoner et al., 2021). Figure 6c, ...
Dams are the source of power generation which also provide water supply for irrigation and other domestic needs. Siltation is the major issue, particularly in shortening the life span of the dams worldwide. Mizoram is highly fragile due to its undulating topography and loose sedimentary rock formations. Accumulated sediment is estimated to be high due to high runoff over steep slopes. This area lacks proper scientific studies on siltation estimation. An attempt was made in this study to estimate siltation at the micro-level in the Tuirial dam site, Kolasib district of Mizoram between 2016 and 2023 using advanced land observing satellite (ALOS) phased array type L-band synthetic aperture radar (PALSAR) digital elevation model (DEM) 2016, geographic information system (GIS) and remote sensing (RS) techniques, and by a bathymetry survey. The coordinates information and elevation data obtained from the bathymetry survey were interpolated for the generation of the triangulated irregular network (TIN) by interpolation. Again, in the same manner using ALOS PALSAR DEM at 12.5 m resolution, of the same bathymetry survey point elevation data was extracted for the generation of TIN. The total surface volume is computed as 17,295,827 m 3 in 2016, and 19,872,177 m 3 in 2023, and the rate of siltation is estimated to be 2,576,350 m 3 yr −1 .
... Although several studies have validated FSC in catchment scales by the field mapping-based analyses of storage (de)coupling and (dis)connectivity of the top sequences (Brown et al., 2013;Messenzehl et al., 2014;Pellegrini et al., 2021), they did not directly quantify the performance of IC. Previous research has shown that sediment connectivity or transport was positively correlated with the magnitude of the hydrological process (Arabkhedri et al., 2021;Wu et al., 2023;Zanandrea et al., 2021). Therefore, in this study, we evaluated the correlation between measured discharge and FSC to verify the accuracy of the IC RI and IC Rndvic results. ...
Linear landscape elements, such as man-made ditches and road networks, play a pivotal role in the transport of water and eroded sediments. Yet very few studies have focused on the variations in drainage flow paths disturbed by artificial linear landscapes and their contribution to flow and sediment connectivity (FSC). This study utilized the index of connectivity (IC) to examine and distinguish the impact of natural and artificial linear landscape elements (i.e., natural streams, man-made ditches, and road networks) on the spatial distribution of FSC. The method was employed in a typical agricultural terraced catchment of the Honghe Hani Rice Terraces World Heritage Site of China, based on two weight factors - roughness index (RI) and Rndvic factor. The results indicate that the incorporation of the linear landscape elements for the IC calculation remarkably affected the spatial distribution of FSC. Specifically, FSC values notably increased by closing the distance to linear landscape elements within a specific threshold. Moreover, in the confluence between natural and artificial linear landscape elements, the mean value of FSC was higher compared to scenarios without any or only one linear landscape element. In comparison, the presence of road networks only improved lateral connectivity by modifying the surface flow along east-west directions, while man-made ditches significantly influenced both longitudinal and lateral connectivity to a larger degree, especially in the terraced area. This finding underscores the effectiveness of ditch constructions as management practices for the regulation of water resources and facilitating the downstream transfer of sediment. Field observations and validation confirmed that Rndvic, which incorporates vegetation variable as a weight factor in the calculation of IC, yields more accurate and reliable maps of FSC than that of RI. This study holds far-reaching significance for water resources management and landscape sustainability within terrace-protected areas, providing invaluable insights for decision-makers.
... The IC is widely applied in the field of hydrological connectivity because its calculations require less data and can assess connectivity in remote or vast areas [14,15]. Given this background, Arabkhedri et al. [16] explored the relationship between the IC and sediment yield in 11 catchments (Iran), demonstrating that the IC plays a key role in controlling sediment yield. Liu et al. [17] employed the IC to investigate the effects of land use/cover changes on the dynamics of hydrological connectivity. ...
Hydrological connectivity plays a major role in solving water resource and eco-environmental problems. However, this phenomenon has not been afforded the attention it deserves. The detailed analysis of connectivity in river systems could provide considerable insight into the structural and functional attributes of riverine landscapes. The current study used a graph theory approach and associated connectivity indicators to explore the characteristics and evolution of river systems and hydrological connectivity in a large catchment (Poyang Lake, China). The results revealed that the structure of the river system tended to be complex during 1990–2020, characterized by a dynamic evolution of tributaries in certain northern areas. Both river density and complexity exhibited an increasing trend by up to 15%, with the change rate after 2000 approximately twice as high as that of the preceding period. Overall, human activities across the catchment were more likely to play a key role in leading to significant changes in the quantity, morphometric, and structural characteristics of the river system. Additionally, the functional connectivity analysis indicated that the index of connectivity (IC) in the downstream catchment was stronger than that of the upstream vegetation areas, suggesting a strong contribution to the runoff sediment transport (r = 0.6–0.7). This study highlights the spatial and temporal evolution of both structural and functional connectivity in the large Poyang Lake catchment. The findings of this work will benefit future water resource management and applications by providing a strategy for protecting the surface hydrology and mass transport of large river basins under climate and land use changes.
... IC is widely applied in the field of hydrological connectivity because its calculations require less data and can assess connectivity in remote or vast areas [14,15]. Given this background, Arabkhedri et al. [16] explored the relationship between IC and sediment yield in 11 catchments (Iran), demonstrating that IC plays a key role in controlling sediment yield. Liu et al. [17] employed IC to investigate the effects of land use/cover changes on the dynamics of hydrological connectivity. ...
Hydrological connectivity plays a major role in solving water resource and eco-environmental problems. However, this phenomenon has not been afforded the attention it deserves. Detailed analysis of connectivity in river systems could provide considerable insight into structural and functional attributes of riverine landscapes. The current study used graph theory approach and associated connectivity indicators to explore the characteristics and evolution of river systems and hydrological connectivity in a large catchment (Poyang Lake, China). The results revealed that the structure of the river system tended to be complex during 1990-2020, characterized by a dynamic evolution of tributaries in certain northern areas. Both river density and complexity exhibited an increasing trend by up to 15%, with the change rate after 2000 approximately twice as high as that of the preceding period. Overall, human activities across the catchment are more likely to play a key role in leading to significant changes in the quantity, morphometric, and structure characteristics of the river system. Additionally, the functional connectivity analysis indicated that the index of connectivity (IC) in the downstream catchment is stronger than that of the upstream vegetation areas, suggesting a strong contribution to the runoff-sediment transport (r=0.6-0.7). This study highlights the spatial and temporal evolution of both the structural and functional connectivity in the large Poyang Lake catchment. The findings of this work will bene-fit future water resource management and applications by providing a strategy for protecting the surface hydrology and mass transport of large river basins under climate and land-use changes.
... Why sediment export varies so much between mountain catchments remains a very active research topic. In addition to catchment size, slope, land cover and geology, the sediment connectivity is increasingly highlighted as a key driving factor (Heckmann et al., 2018;Altmann et al., 2021;Arabkhedri et al., 2021). Recently, the concept of (sediment) connectivity has been introduced to describe the efficiency of sediment transfer from its sources to the river system and the links between sources and sinks of sediment such as lakes in the upstream areas of catchments (Fryirs, 2013). ...
The ability to understand and predict coarse-sediment transport in torrent catchments is a key element for the protection against and prevention of the associated hazards. In this study, we collected data describing sediment supply at 99 torrential catchments in the northern French Alps. The sample covers a wide range of geomorphic activity: from torrents experiencing debris flows every few years to fully forested catchments exporting small bed load volumes every decade. These catchments have long records of past events and sediment supply to debris basins. The mean annual, the 10-year return period and the reference volume (i.e., the 100-year return level or the largest observed volume) of sediment supply were derived for the studied torrents. We examined the relationships between specific sediment supply volumes and many explanatory variables using linear regression and random forest approaches. Results showed that the ratio of sediment-contributing area (bare soil or rock) to catchment area is the most important predictor of the specific sediment production volumes (m3 km−2). Other variables such as the Melton index or the indices of sediment connectivity also have an influence. Several predictive models were developed in order to estimate the sediment supply in torrents that are not equipped with debris basins.
... Their results showed that contour trenching significantly declined runoff rate, soil erosion, and soil nutrient loss (e.g., organic carbon, N, P, and K). Although the concept of sediment connectivity is widely used in the literature as a basis for scrutinizing the influence of anthropogenic activities and landscape changes (e.g., Heckmann et al. 2018;Persichillo et al. 2018;Hooke and Souza 2021;Arabkhedri et al. 2021;Najafi et al. 2021;Zanandrea et al. 2021), it has not been applied to evaluate the performance of soil conservation practices. ...
Purpose
Although contour trenching is one of the widely used nature-based solutions for soil conservation around the world, its efficiency has not been quantitatively investigated. This study aimed to scrutinize the performance of the contour trenching program, a nature-based solution and common soil erosion prevention measure in hillslopes of a data-scarce region based on the sediment connectivity approach.
Materials and methods
Six different hillslopes (A–F) were selected in the Khamsan watershed in Iran, a representative area where contour trenching has been implemented. The sediment connectivity map of each hillslope was generated using the index of connectivity (IC) based on two real scenarios: with (scenario I) and without (scenario II) contour trenching. Two different field-based validation methods were applied on the base of (i) in situ measurements of the sediment depth in contour trenches and Pearson’s correlation analysis, and (ii) field index of connectivity (FIC). The validity of the sediment connectivity results was verified using both validation approaches. The sediment connectivity in two scenarios was compared and the impact of the contour trenching was analyzed. The performance of the contour trenching program was quantitatively determined for each hillslope.
Results and discussion
The results revealed that contour trenching significantly affected sediment routing and reduced the IC values of all selected hillslopes. The differences in IC value between the two scenarios (∆IC) for hillslopes A, B, C, D, E, and F were found to be 22.6%, 11.27%, 14.69%, 5.83%, 15%, and 7.27%, respectively. Therefore, the spatial pattern of sediment connectivity also differed significantly after implementing contour trenching. Furthermore, Pearson’s correlation coefficients revealed that the sediment connectivity and the sediment depth in contours in all hillslopes had a significant negative relationship, resulting in confirming the validity of the sediment connectivity results for all six hillslopes in the current study.
Conclusion
Contour trenching significantly reduced the sediment connectivity on all six hillslopes studied. Furthermore, in situ measurements of the sediment depth in contour trenches should be conducted to verify the simulation of sediment connectivity. The proposed methodology can be applied in other data-scarce regions to evaluate the performance of the contour trenching program.
... Why sediment export varies so much between mountain catchments remains a very active research topic. In addition to catchment size, slope, land cover and geology, the sediment connectivity is increasingly highlighted as a key driving factor (Heckmann et al., 2018;Altmann et al., 2021;Arabkhedri et al., 2021). Recently, the concept of (sediment) connectivity has been introduced to describe the efficiency of sediment transfer from its sources to the river system and the links between sources 45 and sinks of sediment such as lakes in the upstream areas of catchments (Fryirs, 2013). ...
The ability to understand and predict coarse sediment transport in torrent catchments is a key element for the protection and prevention against the associated hazards. In this study, we collected data describing sediment supply at 99 torrential catchments in the Northern French Alps. The sample covers a wide range of geomorphic activity: from torrents experiencing debris flows every few years to fully forested catchments exporting small bedload volumes every decade. These catchments have long records of past events and sediment supply to debris basins. The mean annual, the 10-year return period and the reference volume (i.e. the 100-year return level or the largest observed volume) of sediment supply were derived for studied torrents. We examined the relationships between specific sediment supply volumes and many explanatory variables using linear regression and random forest approaches. Results showed that the ratio of sediment contributing area (bare soil) to catchment area is the most important predictor of the sediment production specific volumes (m3/km2). Others variables such as the Metlon index or the indices of sediment connectivity have also an influence. Several predictive models were developed in order to estimate the sediment supply in torrents that are not equipped with debris basins.
... On the one hand, soil erosion destroys soil and water resources, reduces soil fertility and cultivated land, and causes land degradation and loss of biodiversity; on the other hand, it silts up river beds and reduces the effective storage capacity of reservoirs, leading to droughts and floods and sandstorms (Dai and Lu 2010;Marques et al. 2008;Xu et al. 2021;Yang et al. 2020;Zhou et al. 2016). Therefore, the prevention and control of soil erosion and sediment yield is the focus of watershed planning and management, and the estimation of soil erosion rate and river erosion sediment yield is the primary factor to be considered to achieve environmental sustainability inland and river system management (Arabkhedri et al. 2021;Xin et al. 2012;Zhang et al. 2014). ...
Soil erosion and sediment yield in watersheds are comprehensively affected by land use/cover changes and climatic factors. The current sediment yield index (SYI) model incorporates parameters of area (A), delivery ratio (DR), and curve number (CN), which reflect the character of underlying surface conditions, while the impact of rainfall intensity on sediment yield could not be properly considered. This study aims to improve the current SYI model by introducing rainfall-related factors such as rainfall erosivity (R) and applying it to estimate the sediment yield of river basin. Taking the Dongjiang River basin, South China, as a case study, the performances of the improved simplified SYI model (SYI-CN + R) were compared and demonstrated at multi-spatiotemporal scales. The results showed that (1) compared with the SYI model which only has the parameter CN (SYI-CN), the model SYI-CN + R achieves better simulation performances at yearly (the efficiency coefficient (CE) is 81% in the whole basin and 62% in the sub-basin) and half-month (CE is 69% in the whole basin and 57% in the sub-basin) time scales. (2) On the basin scale, the simulation performance in the whole basin is better overall compared to that in the sub-basin, and the model SYI-CN + R at the half-month time scale is more suitable for the sediment yield simulation in the Dongjiang River basin, with higher value of correlation coefficient (CC) of 87% and 83% for the whole basin and the sub-basin, respectively. And (3) the values of CN and R have an obvious spatial gradient in the whole basin, showing an increasing trend from northeast to southwest as a whole, with larger values concentrated in the lower reaches and smaller values in the middle and upper reaches. This study extends the application and improves the performance of the SYI model, and provides a basis for soil and water conservation in a river basin with fewer observation data.
... Likewise, the Hazaribagh township area situated in the southwest corner of the catchment is well connected with the streams (Fig. 11). The range of IC values of this catchment was found to range from very low to moderate on comparing with other similar studies (Arabkhedri et al., 2021;Zhao et al., 2020). ...
The soil erosion and sediment yield on the Chota Nagpur Plateau, India have been greatly affected over the years by ever increasing anthropogenic influences and associated land-use/land-cover (LULC) changes. This study coupled a CA-Markov model with the Geospatial Interface for Water Erosion Prediction Project (GeoWEPP) model along with sediment connectivity index (IC) to estimate the decadal-scale soil erosion and sediment yield changes in a representative catchment of Chota Nagpur Plateau for 2001–2040 period. This LULC- Erosion-IC modeling approach in the Konar catchment has revealed (i) concerning patterns of conversions of bare lands and grasslands to agricultural fields and (ii) dominance of the new agricultural lands in the areas with higher connectivity. Results indicated that around 11 % and 13 % of the total catchment area undergoing agriculture will be in the highly erodible and highly connected category respectively by 2040. The corresponding mean erosion rates showed a significant increase for agricultural lands [from 26 to 35 T/Ha/Y], built up areas [from 43 to 48 T/Ha/Y], and bare lands [from 30 to 36 T/Ha/Y] during the time period of 2001 to 2040. The evaluation of mean connectivity values showed future expansions of forests (through agro-forestry, i.e. ∼2400 ha) with low connectivity by 2040. A strong linkage between increased future sediment yield and changing LULC patterns (around +6 % and +8 % of the built up area and agricultural lands and −5% and −9% of bare lands and grasslands respectively) can be observed by 2040. These changes are directly attributed to the sediment yield in the region with approximately 59 % and 97 % increase during 2001–2020 and 2020–2040 periods respectively. This study provided a good understanding of general trends in erosion and sediment yield in the Chota Nagpur Plateau and the influence of ongoing efforts in agro-forestry components and land use change dynamics.
... Sediment connectivity includes both structural and functional connectivity: structural connectivity is a potential physical connection between patches of the watershed system (Najafi et al., 2021), and functional connectivity highlights the actual consequences of mechanical processes involved in erosion, transport, and deposition (Pearson et al., 2020). A previous study demonstrated a significant positive correlation between sediment yield and sediment connectivity based on the observations of 11 sub-watersheds (Arabkhedri et al., 2021). Regions with high sediment connectivity have a high probability of eroding sediment loads reaching the watershed outlet because of low barrier levels (Masselink et al., 2016). ...
... The Digital Elevation Model (DEM) from ASTER GDEM V3 data products, with a spatial resolution of 30 m, was used to calculate topographic factors, accumulated flows, and flow directions. The soil maps from the second national soil survey data were transformed into 30-m resolution raster layers, according to relevant studies on the effect of data resolution on connectivity estimation (Arabkhedri et al., 2021). The main soil parameters used were soil unit symbol, texture class, available water storage capacity, relative proportion of different grain sizes, and organic matter. ...
Sediment connectivity quantifies the intermediate processes between initial erosion and the corresponding sediment yield. However, fully capturing the variations in sediment connectivity at the event scale and revealing their impact on watershed sediment sources remains challenging. Herein, we established an event-based model to assess sediment connectivity by integrating runoff factors. The spatiotemporal variability of sediment connectivity was evaluated for 58 rainfall events in three heterogeneous watersheds. The degree of sediment connectivity served as an indicator to quantify the proportion of potential sediment transport from units to the watershed outlet, with 1 indicating that the eroded sediment can be fully connected and 0 indicating that it cannot be transported. Moreover, the controls of sediment connectivity on watershed sediment sources and yield were determined. Our results indicated that the watersheds with poor vegetation and dense gullies were characterized by high sediment connectivity during all the rainfall events. The connectivity degree was below 0.5 in approximately 80% of the watershed area, suggesting that most of the eroded sediment was deposited. Rainfall amount and duration dominated the degree of connectivity of the distal hillslopes, while rainfall intensity exerted a primary control on the transport of sediments from riverbanks to the outlet. In addition, the increase of mismatched area between sediment connectivity and erosion resulted in the decrease of sediment yield. The interaction between sediment connectivity and erosion effectively explained the spatial patterns of sediment sources (p < 0.05). Our work confirmed that the coupled erosion model and sediment connectivity predicted the sediment yield accurately. The predictions for different watersheds portrayed that the Nash-Sutcliffe efficiency and Willmott’s agreement index were greater than 0.70 and 0.89, respectively. These findings revealed the role of sediment connectivity and are the critical basis to identify watershed-specific sediment management practices.
