Volume Of Sediment Deposition Research Articles

Analisis Volume Sedimen Terhadap Pendangkalan Di Dalam Saluran Primer Jaringan Irigasi (Studi Kasus: D.I. Cipicung Subang)

Research conducted in the primary canal of D.I Cipicung, Subang Regency, experienced damage to the irrigation network. Damage to the D.I Cipicung irrigation canal network in the primary canal, so that research is needed to find out how much silting volume is caused by sediment deposition in the irrigation canal. The method in this study uses a mathematical method to determine the volume of sediment deposition in the channel. The results show that the volume of sediment in the primary canal in the Cipicung D.I irrigation network is Vq Primary = 16.24 m3 (difference in depth 0.64 m) or 0.16% of the length per section 50.5 m of the total length of the primary canal 300 m and the change in the cross section of the primary channel is A = 1.25 m2 or 27.11%. So that the results of these calculations, it is necessary to resolve by repairing the right side of the canal lining with construction, the entrance channel from the river to the primary canal needs to be built a gate, dredging of sediment is required in the primary canal, and maintenance is required so that the canal is routinely once a week or once a month so that the strong channel is not quickly damaged.
 Keywords: Sediment Siltation, Primary Canal, Irrigation Network Damage.

Assessment of sediment yield and deposition in a dry reservoir using field observations, RUSLE and remote sensing: Wadi Assarin, Oman

Soil erosion, sediment yield, and sediment transport associated with flash flooding in arid regions result in reservoir storage losses, decreased infiltration, high evaporation rates, and degradation of downstream channels. However, the lack of observational data from wadi systems and an empirical formula to compute sediment yield has hindered reservoir trapping evaluation, maintenance, and management. Therefore, this research aimed to estimate the annual soil loss in the upstream catchment area of a reservoir based on the Revised Universal Soil Loss Equation (RUSLE) with a remote sensing dataset. The sediment trapped in the Assarin Dam reservoir in Oman was estimated by coupling unmanned aerial vehicle (UAV) surveys with photogrammetry analysis to assess the reservoir siltation. Among the previous sediment trapping events, seven sets of field observation data were collected to investigate the relationship between soil loss at the catchment scale and sediment deposition volumes in the reservoir. The RUSLE method was applied to estimate soil erosion using independent factors such as rainfall erosivity, soil erodibility, topography, cover management and conservation practices. A remote sensing dataset and geographic information system (GIS) environments were used to analyse the quantitative and spatial distribution of the RUSLE parameters. Two drone surveys were conducted over the reservoir before and after a flash flood. The trapped sediment volume was estimated to be approximately 9,075 m3 (11,343 ton) per event, representing approximately 1.26 % of the total reservoir capacity. This computed volume was validated using measurements from monitored sediment scale bars sited throughout the Assarin Dam reservoir, yielding an accuracy of 79 %. From the RUSLE results, the annual soil erosion was estimated to be 196,599 ton/ha yr−1, of which approximately 5.8 % was trapped in the reservoir. Spatial-temporal variability in the rainfall patterns and the corresponding runoff discharges led to high sediment delivery at the outlet of the basin. After analysing available data from previous field surveys in Oman, a new formula for estimating the sediment yield in Wadi Assarin was developed. The results of this research, which represent the first of their type in the Middle East and North Africa (MENA) region, can support reservoir management practices and show that UAV-based photogrammetry is suitable for measuring trapped sediment volumes.

Transition from a transgressive to a regressive river-mouth sediment body in Tokyo Bay during the early Holocene: Sedimentary facies, geometry, and stacking pattern

Sedimentary facies, geometry, and stacking pattern transitions of river-mouth sediment bodies recording the turnaround from a transgressive estuary to a regressive delta system have not been sufficiently clarified in the Asian sedimentary record. In this study, the temporal and spatial distributions of sedimentary facies of the post-Last Glacial Maximum incised-valley fills (pLGMIVFs), including those recording delta initiation in the Tama River Lowland, on the west coast of Tokyo Bay, are described taking into account 14 sediment cores, 186 radiocarbon dates, and 8745 geotechnical borehole logs. The pLGMIVFs in the Tama River Lowland, which unconformably overlie Plio-Pleistocene deposits, can be divided into braided-river, meandering-river, estuary, and delta systems in an ascending order. The boundaries between the braided-/meandering-river or estuary systems and the estuary/delta systems correspond to a transgressive surface (20 ka) and a maximum flooding surface (8 ka), respectively. In the estuary system, the river-mouth sediment body, accumulated during 10–8 ka, gradually became smaller and coarser-grained landward; in contrast, the delta system's river-mouth sediment body became larger, finer-grained as it prograded seaward during the past 8 ky. With decelerating sea-level rise at 8 ka, the delta initiated as a sediment body, consisting of 5-m-thick, upward-coarsening sand and gravel beds, distributed in an area of 2 km wide and 2 km long in a funnel-shaped river mouth. This initial delta prograded locally in the subaqueous river mouth, with the saltmarsh spreading widely landward at the margins of the delta to the highest sea-level peak at 7 ka. This separation of subaqueous delta progradation and inland saltmarsh expansion occurred because the volume of sediment deposition was almost equal to the increase in accommodation space due to the 7 mm/yr sea-level rise during 8–7 ka.

Monsoon-influenced Deposition Systems in a Rhodolith Beach on Udo Island, Korea

Jeong, J.B.; Woo, H.J.; Jung, H.-S.; Park, H.N.; Kim, T.-J, and Lee, J.-H., 2021. Monsoon-influenced deposition systems in a rhodolith beach on Udo Island, Korea. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 41–45. Coconut Creek (Florida), ISSN 0749-0208. A beach on Udo Island, off the coast of Jeju Island, Korea was formed by long-term deposition of rhodoliths, which comprise more than 99% of all deposits on the beach. This phenomenon is very rare on the global scale. This rhodolith beach in 2004 was designated a natural monument to preserve its geoheritage. However, to date, no geological studies have been conducted to examine its sedimentary mechanisms and properties. Recent tourist developments and climate change have raised the possibility of erosion on the rhodolith beach. The objective of the present study was to examine the evolution and sedimentation characteristics of this beach through analysis of grain size and aerial photographs, and seasonal beach surveys. Geomorphologically, the beach is divided into reef areas to the north, with high altitudes and rocks mainly distributed along the coastline, and sandy beach to the south, which is strongly affected by waves and tidal currents. Particle sizes decrease toward the upper part of the beach, with gravel-sized sediments in the south and sand-sized sediments in the north. The mean grain size of deposited sediments increases from spring to autumn. In spring, the beach experiences greater erosion in the north and deposition in the south, whereas in summer, the opposite trends are seen. The sediment deposition volume is largest in autumn. There is also annual variation, where the beach was dominated by erosion in three recent years due to a decrease in sediment volume toward the south. The beach increased in volume from 1985 to 2003, and decreased thereafter. Due to the influence of the East Asian Monsoon, the beach experiences typhoons in summer and north-northwesterly waves and tidal currents in autumn and winter. However, erosion occurs in in the south due to a lack of berm for rhodoliths deposition.

Efficiency of Pressurized Rock Traps for Unlined Hydropower Tunnels

Pressurized rock traps are constructed in many hydropower plants to stop sand and gravel from being transported through the turbines. Pressurized rock traps are typically located in the downstream end of unlined headrace tunnels, where the tunnel itself may be one of the sediment sources. This state-of-the-art review presents an overview of research on pressurized rock traps from both publicly available sources and unpublished sources. Limited scientific literature exists on rock traps, and most of the existing literature has previously been unavailable for an international audience. Based on this review, it is concluded that pressurized rock traps should be built with the flow area and sediment deposition volume separated by plates or ribs. Without any separation measures, the sediments risk being re-entrained due to turbulence. This review is separated into three sections: (1) sediment problems and sources of sediments, (2) theory for pressurized rock traps, and (3) design of pressurized rock traps. The recommended design for new pressurized rock traps, including a design flow chart, is provided. Finally, a recommended solution for rebuilding existing pressurized rock traps with an open design into a closed design is also presented.

Quantifying Sediment Deposition Volume in Vegetated Areas with UAV Data

Floods are frequent hydro-meteorological hazards which cause losses in many parts of the world. In hilly and mountainous environments, floods often contain sediments which are derived from mass movements and soil erosion. The deposited sediments cause significant direct damage, and indirect costs of clean-up and sediment removal. The quantification of these sediment-related costs is still a major challenge and few multi-hazard risk studies take this into account. This research is an attempt to quantify sediment deposition caused by extreme weather events in tropical regions. The research was carried out on the heavily forested volcanic island of Dominica, which was impacted by Hurricane Maria in September 2017. The intense rainfall caused soil erosion, landslides, debris flows, and flash floods resulting in a massive amount of sediments being deposited in the river channels and alluvial fan, where most settlements are located. The overall damages and losses were approximately USD 1.3 billion, USD 92 million of which relates to the cost for removing sediments. The deposition height and extent were determined by calculating the difference in elevation using pre- and post-event Unmanned Aerial Vehicle (UAV) data and additional Light Detection and Raging (LiDAR) data. This provided deposition volumes of approximately 41 and 21 (103 m3) for the two study sites. For verification, the maximum flood level was simulated using trend interpolation of the flood margins and the Digital Terrain Model (DTM) was subtracted from it to obtain flooding depth, which indicates the maximum deposition height. The sediment deposition height was also measured in the field for a number of points for verification. The methods were applied in two sites and the results were compared. We investigated the strengths and weaknesses of direct sediment observations, and analyzed the uncertainty of sediment volume estimates by DTM/DSM differencing. The study concludes that the use of pre- and post-event UAV data in heavily vegetated tropical areas leads to a high level of uncertainty in the estimated volume of sediments.

Landscape Change and Vegetation-Channel Interactions in an Estuarine System

We examine the extent of land cover change and sedimentation within the Tijuana River Estuary due to the significant development within Mexico that has increased sedimentation that could alter estuary elevation. We examined aerial imagery to determine major changes in estuary land cover over time (1995–2016), examined sedimentation patterns by calculating vegetation roughness of two dominant lower marsh species: Salicornia pacifica and Spartina foliosa and directly measured sediment deposition within plant stands at multiple elevations and determined how vegetation may be interrupting flow and affecting deposition. Upper elevation scrub has increased slightly through time while marsh area has decreased. Plant roughness for S. foliosa was significantly higher and, based on modeling, each species creates different water surface and channel velocity conditions that could alter deposition patterns. Vegetation inventories and sediment size deposition analysis within vegetation patches show that S. foliosa occupies those areas closest to the channel, is most frequently inundated, and has the smallest sediment sizes present. Sediment size increases with distance from the channel and where it becomes more commonly dominated by S. pacifica. These areas, typically 0.5-1 m above channel bottom elevation, experience the highest volume of sediment deposition. Modeling and direct measurements of deposition indicate that water velocity is impacted by plant stands and deposition is occurring in areas close to the channel. Because these deposition patterns may eventually result in changes in estuary elevation, continual monitoring should be carried out to determine how vegetation-induced sediment behavior, combined with anthropogenic land-use change and sea level rise, influence estuary elevation and land cover.

Depocentre transfer in the Lingdingyang estuary: Interferences from natural and anthropogenic forcings

Estuarine morphodynamic processes caused by the combined effects of global and coastal environmental processes and human activities significantly influence the sustainable development of estuaries. Based on the bathymetric and boundary data extracted from multi-year digital charts for the Lingdingyang estuary (LE), South China, and in situ observations of the main hydrological stations, the spatiotemporal variations of depocentres in the LE and possible contributing factors are analysed. The results indicate that the spatial evolution of the morphology of the LE features shoal-deposition and channel erosion, and that the temporal evolution (1955–2015) presents a general pattern of alternating erosion and sediment deposition. A pattern of multi-depocentres exists in the LE, and the evolution of the depocentres can be divided into three general stages: i) a stage dominated by natural processes (1955–1989), ii) a stage dominated by highly-intensive reclamation (1989–2006), and iii) a stage dominated by large-scale channel dredging or sand mining (2006–2015). The transfer path of depocentres in the eastern and middle shoals traversed mainly from a north-westerly to south-easterly direction, while the transfer path of depocentres in the western shoal shows a clockwise spiral transfer feature. The large reduction of sediment supply from upstream river after the 1980s, resulted in an overall decrease in the mean annual sediment deposition volume in the LE from ~0.61 million m3/year (1989–1998) to ~0.29 million m3/year (2012–2015). The mean annual sediment deposition rate of the LE over time (i.e. 1955–2015) fluctuates in an oscillating manner rather than a linearly declining trend. Large to extreme flood (e.g. flood events of ‘94.6’, ‘98.6’ and ‘08.6’) led to higher sediment deposition rates and larger deposition volumes in the LE during the periods 1989–1998 and 2006–2008. The position of the four outlets were significantly pushed outwards by highly-intensive reclamation between 1989 and 2006, thus resulting in the bifurcation of runoff (in the Jiaomen and Hengmen outlets) and the formation of new artificial ‘outlets’ in the new channels. These great variation of the outlets induced the depocentres to transfer southeast or southwest during the period 1989–2006. A large number of temporary depocentres formed as a result of large-scale sand mining, were located in the middle shoal from 2006 to 2015. In addition, the enhancement of tidal dynamics combined with the great reduction of sediment supply from upstream river, actuated the continued transfer of the depocentres in the eastern, middle, and western shoals to the northwest or northeast after 2006. It is expected that our findings can provide a scientific foundation for port engineering construction, channel development, and the use of the tidal flat zone in the LE. Our conclusions provide a reference for other estuaries that are subject to similar anthropogenic activities.

'Re-designing and Operational Analyses of the Sediment Transport Control in Irrigation Canal Network'

The purpose of this research was to improve the existing design of the irrigation canals in Punjab. The design of an entire canal network is a tiresome and laborious work, where engineers spend months to design canals. Over the years, engineers and agriculturists in the Punjab have been trying to find a solution to the sediment transport problem which occurs in existing irrigation system. To address these problems, the canals can be analyzed to point out the flaws in design and operation mechanism. This study used a Physics based mathematical model, which can aid the engineers to design and analyze the canals on scientific basis. The research evaluated the existing design of BRBD link canal using SETRIC (Sediment Transport in Irrigation Canals) model based on Saint Venant shallow water equation and also, compared the sediment deposition’s result under various maintenance conditions for both Brownlie and Engelund Hansen predictor methods. The data related to BRBD canal, including its cross-sectional properties, hydraulics and sediment parameters were acquired from the Irrigation Department, Lahore. The paper also described the problem which exists in design and operation of the canal by comparing it with original field data. The BRBD canal achieved a regime condition in 1.5 years. The results of sediment deposition produced by Brownlie predictor were more accurate than Engelund Hansen. The sediment deposition volume for Reach 2 was about 593084 m3, whereas for Reach 1 Brownlie method predicted a sediment deposition of 26675 m3 and it was discovered that this large volume of sediments were deposited due to cross-sectional anomalies along the canal such as the geometry of Reach 2 varied abruptly; at one section the width was 21.54 m and the very next section it faced a contraction and reduced to 16.46 m and at RD 372+638, the width of channel expanded to 45.72 m, which then reduced to 43.28 m. ​Thus, to make possible efficient flow of water in BRBD Link canal and to decrease the sediment volume, the canal’s cross-sections were redefined. After this, the canal was remodeled on SETRIC by providing gradual changes in geometry rather than abrupt changes, which showed positive results, and sediment deposition was reduced by 35.25 %. If further modifications are made in the geometry of BRBD canal, the sediment deposition can be minimized which can help in saving billions of tax payer money spent on “Bhal Safai” and maintenance.

Dynamic relations for the deposition of sediment on floodplains and point bars of a freely-meandering river

Fluvial features such as floodplains and point bars are built by sediment deposition and sculpted by erosion. Long-term measurements (38 yr) of the cross-section topography of active floodplains and point bars along the freely-meandering Powder River in southeastern Montana, USA (mean daily discharge of 12.5 m3 s−1), were used to develop dynamic relations between annual sediment deposition and peak-flood discharge. Five floodplain sections and five point-bar sections were selected from 24 cross sections along a 90-km study reach. At each cross section the sediment deposition volume per unit streamwise distance was computed as the difference between two topographic surveys made in consecutive years.Snowmelt floods were found to be the dominant annual process. However, other processes such as flash floods, ice breakup floods, and autumnal floods were important episodically. The dynamic relations were linear for both fluvial features. The snowmelt deposition-discharge relations showed, in general, that point bars were about two times more efficient at trapping sediment than floodplains. Each relation had a discharge threshold that must be exceeded before sediment was deposited. Although these discharge thresholds for floodplains and point bars had essentially the same mean value (69 and 71 m3 s−1, respectively), they represented different processes. Thresholds for other rivers will probably differ from those for Powder River because of different channel geometry and sediment characteristics.

Correlating check dam sedimentation and rainstorm characteristics on the Loess Plateau, China

On the Loess Plateau, China, check dams are necessary for soil and water conservation. In this study, the relationships between check dam sedimentation and storm characteristics were investigated, and rainstorm events for an area of data scarcity were reconstructed using optimal regression models. Four typical check dams of the Loess Plateau (the Shipanmao, Hualiang, No. 3 Guandigou, and No. 4 Guandigou dams) were selected for case studies. Soil profiles behind the four dams were divided into 21, 25, 31, and 31 layers, respectively. The one-to-one link between sediment layers and corresponding storm characteristics were considered based on the peak fallout of 137Cs and on the principle that higher flow corresponds to higher sediment deposition volume. Analysis showed that the layered sediment volume (V) was closely related to rainfall erosivity (R), and to the maximum rainfall intensity over 30min (I30). A statistically significant power regression model between V and R was observed, along with an exponential regression model between V and I30. Based on the power regression model between V and R, a new approach was developed in order to reconstruct rainfall erosivity in rainfall data-scarcity areas. Different hysteresis patterns (counterclockwise, clockwise, and hybrid) at the single storm scale were observed between V and R for the Shipanmao dam deposition wedge (depositional area behind a dam), and these impacted differently on the scale reconstruction results. However, the distance between the reconstructed dams and the known dams had an even stronger influence. The scale method developed in this study was shown to perform well and was able to reconstruct rainstorm events for adjacent regions with similar climatic and geomorphological conditions. Furthermore, the results of this study have improved our understanding of single rainstorm dynamics and soil erosion mechanisms on the Loess Plateau.

Influence of flocculation on sediment deposition process at the Three Gorges Reservoir.

By comparing the original particle gradation of sediment from the Three Gorges Reservoir with the single particle gradation, the differences in these two particle gradations showed that there is sediment flocculation in the Three Gorges Reservoir, which can accelerate the sediment deposition rate in the reservoir. In order to determine the influence of flocculation on the sediment settling velocity, sediment was collected at the Three Gorges Reservoir, and the indoor quiescent settling experiment was performed to study the mechanism of sediment flocculation. The experimental results showed that sediments aggregated from single particles into floccules in the settling processes. The single particles smaller than 0.022 mm will participate in the formation of floccules, which accounts for 83% of the total amount of sediment in the Three Gorges Reservoir. Moreover, the degree of sediment flocculation and the increase in sediment settling velocity were directly proportional to the sediment concentration. Taking the average particle size and the median particle size as the representative particle size, respectively, the maximum flocculation factors were calculated to be 3.4 and 5.0. Due to the sediment flocculation, the volume of sediment deposition will increase by 66% when the mass settling flux factor of total sediment had a maximum value of 1.66, suggesting that flocculation has a significant influence on the sediment deposition rate in the Three Gorges Reservoir.

Prediction of sediment inflows to Angereb dam reservoir using the SRH‐1D sediment transport model

AbstractAngereb Dam, located in Ethiopia, was constructed in early 1994 as a water supply for the town of Gondar up to the year 2020. The reservoir could not achieve this objective, however, because of significant sedimentation problems. Accordingly, one objective of this study was to simulate the historical reservoir sedimentation pattern, as well as predict the near future (until 2015) sedimentation pattern of Angereb Reservoir. The Sedimentation and River Hydraulics one‐dimensional model (SRH‐1D), version 2.6, was used for this purpose. Another objective was to propose possible mitigation measures to reduce the quantity and rate of sedimentation in the reservoir. There was generally good agreement between measurements and model simulations, with the observed trends being well simulated. The exception was that the model tended to overpredict the sediment deposition volumes in the upstream reaches of the reservoir. The two mitigation alternatives for addressing the sedimentation problem, namely managing sediments in the watershed and flushing sediment through the dam bottom outlet, appear to be technically feasibility, with a predicted reduction of the volume of deposited sediment between 63 and 80% be achievable.

Evaluation of reservoir sedimentation using data driven techniques

The sedimentation is a pervasive complex hydrological process subjected to each and every reservoir in world at different extent. Hydrographic surveys are considered as most accurate method to determine the total volume occupied by sediment and its distribution pattern in a reservoir. But, these surveys are very cumbersome, time consuming and expensive. This complex sedimentation process can also be simulated through the well calibrated numerical models. However, these models generally are data extensive and require large computational time. Generally, the availability of such data is very scarce. Due to large constraints of these methods and models, in the present study, data driven approaches such as artificial neural networks (ANN), model trees (MT) and genetic programming (GP) have been investigated for the estimation of volume of sediment deposition incorporating the parameters influenced it along with conventional multiple linear regression data driven model. The aforementioned data driven models for the estimation of reservoir sediment deposition were initially developed and applied on Gobindsagar Reservoir. In order to generalise the developed methodology, the developed data driven models were also validated for unseen data of Pong Reservoir. The study depicted that the highly nonlinear models ANN and GP captured the trend of sediment deposition better than piecewise linear MT model, even for smaller length datasets.

Estimating sediment deposition volume in a reservoir using the physiographic soil erosion-deposition model

A traditional way to estimate the amount of sediment deposition in a reservoir is simply based on the variation in the elevation measurements made at different times. In the present study, a physiographic soil erosion-deposition (PSED) model is applied to Tseng-Wen reservoir watershed to compute the discharge and sediment concentration into the reservoir, and the deposition volume. The PSED model is verified using three storm events and then compared to the historic data recorded at the hydrological stations in the reservoir watershed, which shows close agreement between the simulated and recorded values of the flow discharge into the reservoir and the corresponding sediment yield. The numerical simulation was also conducted for all rainfall events from 1996 to 2001 to estimate the annual sediment deposition volume in the reservoir. Similarly, the simulated result was compared to that obtained from the cross-section elevation measurement. It is found that some measured data points had large uncertainty or were questionable. On the contrary, the model results and the measured data that renders the model credible. Therefore, regardless of the estimation for the flow discharge into the reservoir induced by a single rainfall event, the sediment yield, or the sediment deposition, the PSED model has successfully demonstrated its ability.

Effect of Shallowness on Sediment Deposition in Recirculation Zones

Various hydrodynamic and sediment deposition experiments were conducted on a purpose-built, wide, shallow water table using a range of incoming flow and bed roughness conditions, including five flow rates, different inflow sediment concentrations, and different artificial roughness coefficients generated by four transverse string intervals. A recirculation zone was created behind a 0.5-m-wide backward-facing step on the left side of the table. Surface velocities, sediment concentrations, and processes and features of sediment deposition in recirculation zones were measured. Experimental results indicate that (1) as the value of the shallow stability parameter increased from 0.033 to 0.47, the length of the recirculation zone decreased to less than half, but the corresponding area and volume of sediment deposition increased about four times, and (2) it is the strength of the mixing layer rather than the size of the recirculation zone that dominates the process of sediment deposition as well as the final deposition feature.

An empirical model of sediment deposition processes in Lake Kerkini, Central Macedonia Greece

The deposition processes in Kerkini Reservoir, since 1933, are examined in this paper. Built on the course of River Strymonas at the plain of Serres for anti-flooding control, it was gradually developed as a multipurpose reservoir for irrigation and a very important international wetland protected by the Ramsar Treaty. The deposition into Lake Kerkini is caused by the high rates of sediment transport by River Strymonas from the Bulgarian, Serbian and Former Yugoslav Republic of Macedonia territory drainage basin of Kerkini of 11,600 km(2). The life expectancy of the original reservoir was approximately 40 years. The sediment transport and the deposition volumes and rates were high during the first stages of Kerkini operation due to deforestations and stockbreeding activities against forested and agricultural areas in southwestern Bulgaria before World War II, which intensify erosion and deposition phenomena in Kerkini's catchment. They were gradually reduced due to the anti-erosion hydraulic works, extended reforestations mainly in the period 1962-1977, and the natural processes of Strymonas-Kerkini hydrosystem to attain its equilibrium. Based on six systematic bottom surveys of the reservoir from 1933 to 1991, two empirical formulas of the total deposition volume (Sigma V(s)) and the deposition rates (DeltaSigma V(s)/DeltaSigma t) through time (Sigma t) were developed. The results have been compared with other catchments of the broader Balkan area concerning the erosion, sediment yield, sediment deposition volumes, and rates, and it was found in accordance with the measured data. The obtained empirical model was used to estimate the life expectancy of the new rebuilt reservoir of Kerkini in 1984; in the case of natural processes, these do not change dramatically in the transboundary Lake Kerkini catchment. The deposition processes of Kerkini were the major causes of its development into an internationally important wetland and biotope. Kerkini offers development opportunities for scientific research, environmental education, ecotourism, and recreation activities.

Vegetation and topographic controls on sediment deposition and storage on gully beds in a degraded mountain area

AbstractActive gully systems developed on highly weathered or loose parent material are an important source of runoff and sediment production in degraded areas. However, a decrease of land pressure may lead to a return of a partial vegetation cover, whereby gully beds are preferred recolonization spots. Although the current knowledge on the role of vegetation on reducing sediment production on slopes is well developed, few studies exist on the significance of restoring sediment transport pathways on the total sediment budget of degraded mountainous catchments. This study in the Ecuadorian Andes evaluates the potential of vegetation to stabilize active gully systems by trapping and retaining eroded sediment in the gully bed, and analyses the significance of vegetation restoration in the gully bed in reducing sediment export from degraded catchments. Field measurements on 138 gully segments located in 13 ephemeral steep gullies with different ground vegetation cover indicate that gully bed vegetation is the most important factor in promoting short‐term (1–15 years) sediment deposition and gully stabilization. In well‐vegetated gully systems ( ≥ 30% of ground vegetation cover), 0.035 m3 m–1 of sediment is deposited yearly in the gully bed. Almost 50 per cent of the observed variance in sediment deposition volumes can be explained by the mean ground vegetation cover of the gully bed. The presence of vegetation in gully beds gives rise to the formation of vegetated buffer zones, which enhance short‐term sediment trapping even in active gully systems in mountainous environments. Vegetation buffer zones are shown to modify the connectivity of sediment fluxes, as they reduce the transport efficiency of gully systems. First calculations on data on sediment deposition patterns in our study area show that gully bed deposition in response to gully bed revegetation can represent more than 25 per cent of the volume of sediment generated within the catchment. Our findings indicate that relatively small changes in landscape connectivity have the potential to create strong (positive) feedback loops between erosion and vegetation dynamics. Copyright © 2009 John Wiley & Sons, Ltd.

Foredune vegetation patterns and alongshore environmental gradients: Moçambique Beach, Santa Catarina Island, Brazil

AbstractThis paper examines patterns of foredune vegetation along an embayment in southern Brazil and the relationships between variations in percent cover and diversity, and environmental factors such as beach/surfzone type and exposure to wind and wave energy. The study was conducted on Moçambique Beach, Brazil, which displays significant alongshore variations in exposure to the prevailing winds and waves, beach/surfzone morphodynamic type, type and dimensions of the dune systems and foredune vegetation cover and diversity. Two vegetation surveys were carried out in contiguous 1 m2 quadrats across the foredune. The presence/absence, percent cover of the species, diversity and similarity between the vegetation of the profiles surveyed and their relation with environmental conditions are examined. The results show that the vegetation cover decreases from south to north, possibly reflecting the increasing exposure to wind and wave energy. Distinct patterns of species distributions occur along Moçambique beach, such that different plant species are dominant on the southern, middle and northern ends of the beach. A cluster analysis demonstrated two associations: the first one is represented by the profiles located in the lower energy zone of the beach, and the second association is represented by the profiles more exposed to wind and wave energy, sediment deposition and salt spray. The diversity of species decreases northwards, possibly influenced by the surfzone type, number of breaking waves and degree of aeolian transport. The presence/absence of the species and the vegetation cover on the foredune reflect the varying levels of exposure of the beach and foredune to the winds and waves and also reflect the volume of sediment deposition on the foredune and the beach mobility determined by the morphodynamic beach/surfzone type. Copyright © 2008 John Wiley & Sons, Ltd.

Reconstructing ancient topography through erosion modelling

One of the main aims of geomorphology is to understand how geomorphic processes change topography over long time scales. Over the last decades several landscape evolution models have been developed in order to study this question. However, evaluation of such models has often been very limited due to the lack of necessary field data. In this study we present a topography based hillslope erosion and deposition model that is based on the WATEM/SEDEM model structure and works on a millennial time scale. Soil erosion, transport and deposition are calculated using slope and unit contributing area. The topography is iteratively rejuvenated by taking into account modelled erosion and deposition rates, thereby simulating topographic development backwards in time. A first attempt has been made to spatially evaluate the model, using detailed estimates for historical soil erosion and sediment deposition volumes, obtained from an augering campaign in a small catchment in the Belgian Loess Belt. The results show that the model can simulate realistic soil redistribution patterns. However, further research is necessary in order to deal with artificial flaws that cause routing problems and significantly influence results. Common problems and issues related to this type of backward modelling are also discussed.