Distributed Sediment Delivery Research Articles

Impact of land use/cover change (LUCC) on sediment connectivity in small watersheds based on a revised index algorithm

Soil erosion is an important cause of global land degradation and other ecological and environmental problems. Revealing the influence mechanism of land use/cover change (LUCC) on sediment yield can provide a scientific basis for efficient comprehensive and decision-making management of watersheds. As an important indicator of sediment yield and transport capacity, sediment connectivity has been widely studied in recent years. However, the existing index of sediment connectivity (IC) ignores the influence of upslope land use/cover on confluence and the corresponding changes in downslope sediment transport. Moreover, a formula describing the upslope and downslope components does not establish an effective correlation with existing soil erosion formulas. Therefore, the index is not closely related to the erosion process and does not reflect the physical process of sediment transport and sediment deposition. In addition, there have been few reports concerning the effect of LUCC on sediment connectivity inside (on-site impact) and outside (off-site impact) the changed patches. Consequently, by based on addition of the revised parameters of the effective confluence area (Ar) and the runoff velocity factor (v) of the sediment delivery distributed (SEDD) model, an improved sediment connectivity index (ICZQ) is proposed. The results indicate that ICZQ has a significant linear relationship with annual runoff depth or sediment yield modulus in small watersheds within 100 km2 in the Loess Plateau, except for feature years containing rainstorm events (daily rainfall exceeding 50 mm). Therefore, the runoff and sediment transport capacity of small watersheds can be characterized by ICZQ under the influence of LUCC and rainfall change. In 1982–2020, driven by LUCC with an enhancement in vegetation (forest and grass), the ICZQ decreased in 90% of the area and decreased by a significant or extremely significant level over 48% of the area. To better understand the effects of LUCC on sediment connectivity, we analyzed on-site and off-site impacts with rainfall remaining unchanged to control the variables. The contribution rates of the on-site and off-site impacts caused by LUCC on sediment connectivity in Lvergou were 61% and 39%, 48% and 52%, respectively, over two typical periods (1985–1990 and 2015–2020). Due to the large proportion that off-site impacts occupied in the sediment connectivity change, the impact of LUCC on sediment connectivity cannot be ignored, especially when the associated scale is relatively small. The present study provides a quantitative method for the optimization of land use/cover patterns, such as vegetation restoration in watersheds along with a reference for further revealing the impact mechanism of erosion and sediment yield in watersheds.

Introducing seasonal snow memory into the RUSLE

PurposeThe sediment supply to rivers, lakes, and reservoirs has a great influence on hydro-morphological processes. For instance, long-term predictions of bathymetric change for modeling climate change scenarios require an objective calculation procedure of sediment load as a function of catchment characteristics and hydro-climatic parameters. Thus, the overarching objective of this study is to develop viable and objective sediment load assessment methods in data-sparse regions.MethodsThis study uses the Revised Universal Soil Loss Equation (RUSLE) and the SEdiment Delivery Distributed (SEDD) model to predict soil erosion and sediment transport in data-sparse catchments. The novel algorithmic methods build on free datasets, such as satellite and reanalysis data. Novelty stems from the usage of freely available datasets and the introduction of a seasonal snow memory into the RUSLE. In particular, the methods account for non-erosive snowfall, its accumulation over months as a function of temperature, and erosive snowmelt months after the snow fell.ResultsModel accuracy parameters in the form of Pearson’s r and Nash–Sutcliffe efficiency indicate that data interpolation with climate reanalysis and satellite imagery enables viable sediment load predictions in data-sparse regions. The accuracy of the model chain further improves when snow memory is added to the RUSLE. Non-erosivity of snowfall makes the most significant increase in model accuracy.ConclusionThe novel snow memory methods represent a major improvement for estimating suspended sediment loads with the empirical RUSLE. Thus, the influence of snow processes on soil erosion and sediment load should be considered in any analysis of mountainous catchments.

Climate and Land Use Change Effects on Sediment Production in a Dry Tropical Forest Catchment

Understanding the natural and anthropogenic drivers that influence erosion and sediment transport is a key prerequisite for adequate management of river basins, where, especially in tropical catchments, there are few direct measurements or modeling studies. Therefore, this study analyzed the effect of human-induced land-use changes and natural ENSO (El Niño-Southern Oscillation) related changes in rainfall patterns on soil erosion and catchment-scale sediment dynamics with the SEDD (Sediment Delivery Distributed) model. In the 393 km2 Tonusco river basin, representative of tropical, mountainous conditions, daily rainfall data were used to quantify changes in rainfall erosivity and satellite images for the evaluation of cover factor changes between 1977 and 2015. The final model combined soil loss, calculated by RUSLE, with a sediment routing-based delivery ratio, that was calibrated and validated with data from the sediment load recorded at the basin outlet. The results detected a great reduction of the vegetation cover in the catchment during the last decade of from 79.5 to 29.5%, and the influence of important runoff and erosion events linked to La Niña episodes. Soil erosion rates were locally very high, of over 120 Mg ha−1yr−1, and sediment yields were estimated at the range of 6.17–8.23 Mg ha−1yr−1.

Evaluation of the SEdiment Delivery Distributed (SEDD) Model in the Shihmen Reservoir Watershed

The sediment delivery ratio (SDR) connects the weight of sediments eroded and transported from slopes of a watershed to the weight that eventually enters streams and rivers ending at the watershed outlet. For watershed management agencies, the estimation of annual sediment yield (SY) and the sediment delivery has been a top priority due to the influence that sedimentation has on the holding capacity of reservoirs and the annual economic cost of sediment-related disasters. This study establishes the SEdiment Delivery Distributed (SEDD) model for the Shihmen Reservoir watershed using watershed-wide SDRw and determines the geospatial distribution of individual SDRi and SY in its sub-watersheds. Furthermore, this research considers the statistical and geospatial distribution of SDRi across the two discretizations of sub-watersheds in the study area. It shows the probability density function (PDF) of the SDRi. The watershed-specific coefficient (β) of SDRi is 0.00515 for the Shihmen Reservoir watershed using the recursive method. The SY mean of the entire watershed was determined to be 42.08 t/ha/year. Moreover, maps of the mean SY by 25 and 93 sub-watersheds were proposed for watershed prioritization for future research and remedial works. The outcomes of this study can ameliorate future watershed remediation planning and sediment control by the implementation of geospatial SDRw/SDRi and the inclusion of the sub-watershed prioritization in decision-making. Finally, it is essential to note that the sediment yield modeling can be improved by increased on-site validation and the use of aerial photogrammetry to deliver more updated data to better understand the field situations.

Evaluating estimated sediment delivery by Revised Universal Soil Loss Equation (RUSLE) and Sediment Delivery Distributed (SEDD) in the Talar Watershed, Iran

The performance of the Revised Universal Soil Loss Equation (RUSLE) as the most widely used soil erosion model is a challenging issue. Accordingly, the objective of this study is investigating the estimated sediment delivery by the RUSLE method and Sediment Delivery Distributed (SEDD) model. To this end, the Talar watershed in Iran was selected as the study area. Further, 700 paired sediment-discharge measurements at Valikbon and Shirgah-Talar hydrometric stations between the years 1991 and 2011 were collected and used in sediment rating curves. Nine procedures were investigated to produce the required RUSLE layers. The estimated soil erosion by RUSLE was evaluated using sediment rating curve data by two methods including least squares and quantile regression. The average annual suspended sediment load was calculated for each sub-watershed of the study area using the SEDD model. Afterwards, a sediment rating curve was estimated by least squares and quantile regression methods using paired discharge-sediment data. The average annual suspended sediment load values were calculated for two hydrometric stations and were further evaluated by the SEDD model. The results indicated that the first considered procedure, which utilized 15-min rainfall measurements for the rainfall factor (R), and the classification method of SENTINEL-2 MSI image for the cover management factor (C), offered the best results in producing RUSLE layers. Furthermore, the results revealed the advantages of utilizing satellite images in producing cover management layer, which is required in the RUSLE method.

Assessing sediment connectivity in dendritic and parallel calanchi systems

Calanchi, a type of Italian badlands created by a combination of water erosion processes and environmental constraints controlling their development, is a striking example of long-term landscape evolution. Sediment connectivity can be defined as the degree to which a system facilitates the fluxes of sediments through itself. The goal of this research is testing the use of simple morphometric variables for assessing sediment connectivity of calanchi landforms distinguishing between dendritic and parallel systems. For detecting the morphological characteristics controlling the sediment connectivity of calanchi basins, literature data (146 calanchi basins) and measurements carried out in two areas located in Sicily (Italy) (119 calanchi basins) were examined. Application of Hack's law to the investigated calanchi basins, carried out distinguishing between landforms with dendritic and parallel systems, demonstrated that a calanco basin with a dendritic system has an exponent (k = 0.49) which is close to that (k = 0.55–0.60) typical of a river basin. The analysis also showed that Melton number assumes only for calanchi basins with a dendritic system a value (0.648) which is similar to that of the river case (0.694). For establishing calanchi hillslope connectivity, the hillslope sediment transport efficiency was also measured by the travel time, which is the ratio between the length and the square root of the hillslope steepness of each cell of the calanchi DEM, and the corresponding sediment delivery ratio.The concept of sediment delivery ratio of each hillslope cell SDRi was used as a measure of sediment connectivity since low values of this ratio imply a lack of connectivity (structural and/or hydrological). For each calanco the cumulative frequency distribution of the travel time allowed both to test the applicability of the exponential relationship used in SEdiment Delivery Distributed (SEDD) model to calculate SDRi and to estimate the coefficient β appearing in this relationship. Finally, the median travel time and the sediment delivery ratio SDRM of each calanco basin were calculated to evaluate the structural connectivity at calanchi basin scale. The analysis demonstrated that both a dendritic system has median travel time values less than those of a parallel system and that SDRM values of a dendritic system are higher than those of a parallel one. In conclusion, sediment connectivity of a dendritic system is higher than that of a parallel one.

Modelling sediment delivery using connectivity components at the experimental SPA2 basin, Sicily (Italy)

Sediment delivery ratio can be used as a measure of sediment connectivity and it can be linked to the structural connectivity (morphological unit, slope length, slope steepness, travel time) of a basin and to the functional connectivity (rainfall-runoff processes at morphological unit scale). In this paper the sediment connectivity approach was applied at basin scale both using Sediment Delivery Distributed (SEDD) model, which takes into account the hillslope sediment transport, and sediment yield measurements carried out at SPA2 experimental basin (Sicily, Italy). The expression of the sediment delivery ratio SDRi of a morphological unit was modified for highlighting two components corresponding to the structural (SDRF,i) and functional (SDRF,i) sediment connectivity, respectively. For SPA2 basin the frequency distribution of the travel time of each morphological unit was used to estimate the coefficient βL of the structural component of the sediment delivery ratio of each morphological unit. Then, using the sediment yield measurements carried out at the outlet of the experimental SPA2 basin in the period April 2000-March 2015, the SEDD model was calibrated at event scale for estimating the coefficient βF of the functional component of the sediment delivery ratio. At event scale the developed analysis stated that the functional connectivity is dependent on the magnitude of erosion events. Intermediate and high events, which were characterized by the lowest values of the functional coefficient, determine a more high functional connectivity and are characterized by a more efficient sediment transport along the hillslopes. Finally, at annual scale, the model was calibrated for the period 2000–2015 and relationships for estimating the coefficient βF,a of the functional component of the sediment delivery ratio taking into account the intensity of erosion events occurring in each year were determined. At annual scale, the analysis demonstrated that the functional coefficient was always greater than the landscape coefficient and the sediment connectivity was always controlled by the low values of the functional component.

Assessing response of sediment load variation to climate change and human activities with six different approaches

Understanding the relative contributions of climate change and human activities to variations in sediment load is of great importance for regional soil, and river basin management. Considerable studies have investigated spatial-temporal variation of sediment load within the Loess Plateau; however, contradictory findings exist among methods used. This study systematically reviewed six quantitative methods: simple linear regression, double mass curve, sediment identity factor analysis, dam-sedimentation based method, the Sediment Delivery Distributed (SEDD) model, and the Soil Water Assessment Tool (SWAT) model. The calculation procedures and merits for each method were systematically explained. A case study in the Huangfuchuan watershed on the northern Loess Plateau has been undertaken. The results showed that sediment load had been reduced by 70.5% during the changing period from 1990 to 2012 compared to that of the baseline period from 1955 to 1989. Human activities accounted for an average of 93.6 ± 4.1% of the total decline in sediment load, whereas climate change contributed 6.4 ± 4.1%. Five methods produced similar estimates, but the linear regression yielded relatively different results. The results of this study provide a good reference for assessing the effects of climate change and human activities on sediment load variation by using different methods.

Computing spatially distributed sediment delivery ratios: inferring functional sediment connectivity from repeat high‐resolution digital elevation models

AbstractHigh‐resolution digital elevation models (DEMs) from repeat LiDAR (light detection and ranging) or SfM (structure from motion) surveys have become an important tool in process geomorphology. The spatial pattern of negative and positive changes of surface elevation on raster DEMs of difference (DoD) can be interpreted in terms of geomorphic processes, and has been used for morphological budgeting. We show how the application of flow routing algorithms and flow accumulation opens new opportunities for the analysis of DoD. By accumulating the values of the DoD along downslope flowpaths delineated on a DEM, these algorithms lend themselves to computing the net balance, i.e. sediment yield (SY), for the contributing area of each cell. Doing the same for the negative subset of the DoD yields a minimum estimate of erosion (E) within the contributing area. The division of SY by E yields (a maximum estimate of) the sediment delivery ratio (SDR), that is the proportion of material eroded within the contributing area of each cell that has been exported from that area. The resulting SDR is a spatially distributed measure of functional sediment connectivity. In this letter, we develop the computationally simple approach by means of an example DoD from a lateral moraine section in the Upper Kaunertal Valley, Austrian Central Alps. We also discuss advantages, assumptions and limitations, and outline potential applications to connectivity research using field‐, laboratory‐, and model‐based DoD. Copyright © 2018 John Wiley & Sons, Ltd.

Estimating Sediment Delivery Ratios for Grassed Waterways using WEPP

AbstractGrassed waterways (GWWs) transport sediment and nutrients from upland source areas to receiving waters. Watershed planners have a critical need to understand GWW sediment delivery to optimally target source area management practices. Better physically based tools are needed to estimate sediment delivery by GWWs. This study developed several distributed sediment delivery ratio (SDR) regressions for GWWs using the process‐based Water Erosion Prediction Project (WEPP) model to provide simple equations to estimate sediment delivery for planning applications. Water Erosion Prediction Project was calibrated and validated for runoff and sediment yield for large 30.2‐ha and smaller 5·7‐ha nested watersheds with terraces and a common GWW outlet. A crop rotation of corn, oat and alfalfa and fall tillage using chisel plow were used in the nested watersheds. A hypothetical management case without terraces using corn, oat and alfalfa rotation with chisel plow as fall tillage was also evaluated for the 5·7‐ha watershed and the GWW. The length, slope, Manning's roughness coefficient and infiltration rate for the GWW were varied and SDRs calculated for 30 representative (in terms of daily rainfall) days over a 20‐year period of simulated climate. Regressions were developed for the existing (terraced) and hypothetical (non‐terraced) management scenarios for early (April–July), late (August–October) and full (April–October) growing seasons. Equations developed for the non‐terrace watershed had higher R2 values compared to the terraced watershed suggesting that channel and rainfall parameters were better able to explain the variation in SDR for the non‐terraced watershed. Manning's roughness coefficient was the most significant parameter for predicting SDR for both the terraced and non‐terraced watersheds. The equations developed here can be used to estimate SDRs for watersheds that are drained via GWWs having similar physical characteristics: slope (1–5%), Mannings's roughness coefficient (0·1–0·3), length (0·15–1 km) and infiltration rate (0·025–25 mm h−1). The SDRs can be used to estimate sediment yield, which is an essential element for making land management decisions but is rarely measured. Copyright © 2017 John Wiley & Sons, Ltd.

Testing the Modified Sediment Delivery Model (MOSEDD) at SPA2 Experimental Basin, Sicily (Italy)

AbstractA new version of a spatially distributed sediment delivery model taking into account the hillslope sediment transport efficiency, named MOSEDD, is presented. This model gives estimates of basin sediment yield at event scale, which are more reliable than those obtained by the original SEDD. For SPA2 basin discretized into morphological units, four different calculation schemes of MOSEDD, including the original SEDD version, were applied. All parameterization schemes of the model were calibrated using 15 events measured at the outlet of the experimental basin in the period February 2005–February 2010. The model calibration was used to determine a relationship between the coefficient βe of the model and the erosivity factor. For the model validation, other six measured events, collected in the period March 2010–February 2014, were used. At event scale, the comparison between measured sediment yield values and calculated ones showed that the three calculation schemes of MOSEDD using a rainfall–runoff erosivity factor (MODB, MODC and MODD) have the best performance in estimating sediment yield with respect to the original version of SEDD. The analysis was also developed at annual scale, for the period 2005–2014, and a relationship between the annual value of the coefficient, βa, of the model and the corresponding erosivity factor was established. This last analysis showed that the sediment delivery distributed approach has also a good predictive ability at annual scale. Copyright © 2016 John Wiley & Sons, Ltd.

Soil Erosion and Sediment Yield Analysis Using Prototype & Enhanced SATEEC GIS System Models

Rapid propagation of soil erosion is a severe worldwide problem because of its economic and environmental impacts. Thus various efforts have been made to evaluate soil erosion and sediment yield spatially and temporarily to develop effective soil erosion best management practices. To effectively estimate soil erosion and to establish soil erosion management plans, many computer models have been developed and used. In the past couple of decades, these soil erosion models have been integrated with Geographic Information System (GIS) for spatiotemporal analysis of generation and transport of soil erosion and sediment. The Revised Universal Soil Loss Equation (RUSLE) has been used in many countries, and input parameter data for RUSLE have been well established over the years. Thus, the GIS-based Sediment Assessment Tool for Effective Erosion Control (SATEEC) was developed to estimate soil loss and sediment yield for any location within a watershed using RUSLE and a spatially distributed sediment delivery ratio. In this paper SATEEC GIS System Ver.1.6 and version 1.8 were used for estimation of soil erosion and sediment yield. Moore & Burch ‘LS’ factor method and slope based SDR were used for estimation of soil erosion and sediment yield. The simulation results are reveals that SATEEC ver.1.6 exhibits 3 times more in quantity of soil erosion and sediment yield to SATEEC ver. 1.8.

Use of Caesium-137 Measurements and Long-Term Records of Sediment Load to Calibrate the Sediment Delivery Component of the SEDD Model and Explore Scale Effect: Examples from Southern Italy

AbstractSoil erosion has become a serious environmental problem in southern Italy, where annual soil loss associated with extreme rainfall events can reach 100–150 t ha−1. In order to predict rates of soil loss and sediment yields, to inform the development of effective erosion and sediment control strategies in these areas, several prediction models have been utilized in recent years. Most of these models are based on the universal soil loss equation (USLE) or revised universal soil loss equation (RUSLE). However, they require calibration and validation if they are to be used to provide reliable estimates of soil erosion and sediment yield. The use of fallout Cs137 measurements affords a useful means of assembling spatially distributed information on soil redistribution rates, which can be used to calibrate and validate sediment yield models. This paper reports a study in which Cs137 measurements have been used to calibrate the sediment delivery component of the sediment delivery distributed (SEDD) mode...

Geographic information system-coupling sediment delivery distributed modeling based on observed data.

Spatially distributed sediment delivery (SEDD) models are of great interest in estimating the expected effect of changes on soil erosion and sediment yield. However, they can only be applied if the model can be calibrated using observed data. This paper presents a geographic information system (GIS)-based method to calculate the sediment discharge from basins to coastal areas. For this, an SEDD model, with a sediment rating curve method based on observed data, is proposed and validated. The model proposed here has been developed using the combined application of the revised universal soil loss equation (RUSLE) and a spatially distributed sediment delivery ratio, within Model Builder of ArcGIS's software. The model focuses on spatial variability and is useful for estimating the spatial patterns of soil loss and sediment discharge. The model consists of two modules, a soil erosion prediction component and a sediment delivery model. The integrated approach allows for relatively practical and cost-effective estimation of spatially distributed soil erosion and sediment delivery, for gauged or ungauged basins. This paper provides the first attempt at estimating sediment delivery ratio based on observed data in the monsoon region of Korea.

Soil erosion risk assessment of the Keiskamma catchment, South Africa using GIS and remote sensing

This paper examines the soil loss spatial patterns in the Keiskamma catchment using the GIS-based Sediment Assessment Tool for Effective Erosion Control (SATEEC) to assess the soil erosion risk of the catchment. SATEEC estimates soil loss and sediment yield within river catchments using the Revised Universal Soil Loss Equation (RUSLE) and a spatially distributed sediment delivery ratio. Vegetation cover in protected areas has a significant effect in curtailing soil loss. The effect of rainfall was noted as two pronged, higher rainfall amounts received in the escarpment promote vegetation growth and vigour in the Amatole mountain range which in turn positively provides a protective cover to shield the soil from soil loss. The negative aspect of high rainfall is that it increases the rainfall erosivity. The Keiskamma catchment is predisposed to excessive rates of soil loss due to high soil erodibility, steep slopes, poor conservation practices and low vegetation cover. This soil erosion risk assessment shows that 35% of the catchment is prone to high to extremely high soil losses higher than 25 ton ha−1 year−1 whilst 65% still experience very low to moderate levels of soil loss of less than 25 ton ha−1 year−1. Object based classification highlighted the occurrence of enriched valley infill which flourishes in sediment laden ephemeral stream channels. This occurrence increases gully erosion due to overgrazing within ephemeral stream channels. Measures to curb further degradation in the catchment should thrive to strengthen the role of local institutions in controlling conservation practice.

Assessment of soil erosion and sediment yield in Liao watershed, Jiangxi Province, China, Using USLE, GIS, and RS

Soil erosion by water is a serious problem all over the world. In China, about 1 790 000 km2 of land suffers from water erosion, which accounts for 18.3% of China’s total area. This study was conducted in the Liao (潦) watershed in Jiangxi (江西) Province to assess annual soil erosion and sediment yield using the Universal Soil Loss Equation (USLE). A geographic information system (GIS) was used to generate maps of the USLE factors, which include rainfall erosivity (R), soil erodibility (K), slope length and steepness (LS), cover (C), and conservation practice (P) factors. By integrating these factors in a GIS, a spatial distribution of soil erosion over the Liao watershed was obtained. The soil erosion was found to vary from nil for flat and well-covered areas to more than 500 t/ha/a in mountainous places with sparse vegetation. The average soil erosion is 18.2 t/ha/a with a standard deviation of 109.3 t/ha/a. The spatial distribution of erosion classes was estimated. About 39.5% of the watershed is under the tolerant erosion rate, and 60.5% of the study area experienced erosion to different extents. A spatially distributed sediment delivery ratio (SDR) module was developed to account for soil erosion and deposition. It was found that the SDR value at the outlet of the Liao watershed was 0.206, and the sediment yield was 1.32 million t/a, which was 20% higher than the measured sediment. The results can be used to identify the soil erosion hot spots and develop the best soil erosion management practices and help estimate the quantity of soil that was transported into the downstream Poyang (鄱阳) Lake.

Topographic uncertainty and catchment-based models

Topographic attributes are key parameters in numerous models to assess sediment or nutrient input into surface waters. A broad range of digital elevation models (DEM) and algorithms bring, however, uncertainty to topographic interpretations. This may raise the question whether empirical, semi-distributed models can cope with such uncertainty. In this study, primary and complex topographic attributes related to soil loss and distributed sediment delivery were computed from DEM with cell widths between 10 and 1,000 m. Correlation and regression analyses were conducted with average values of the catchments of 138 German gauges spanning different terrain. Two slope, single-flow routing and slope-length algorithms were also included to evaluate their effects. Although either choice mostly induces significant changes of catchment means of slope, flow length, slope-length factor and sediment delivery ratio (SDR), Spearman's rank correlation coefficients are generally above 0.9. It is suggested from the data that linear or slightly curved functions are suitable to adapt average topographic attributes computed from differently resolved DEM or by different methods. Empirical catchment-based models can thus cope with topographic uncertainty and model users may implement these equations to compare model outputs. However, the catchment delineation and stream definition may constrain their application.

Evaluation of the SEDD model for predicting sediment yield at the Sicilian experimental SPA2 basin

AbstractIn this paper a spatially distributed model of the hillslope sediment delivery processes, named the sediment delivery distributed (SEDD) model, is initially reviewed; the model takes into account the sediment delivery processes due to both the hillslope sediment transport and the effects of slope curvature.Then the rainfall and sediment yield events measured at the experimental SPA2 basin, in Sicily, are used both to calibrate the SEDD model and to verify the predictive capability of the distributed sediment delivery approach at event scale.For the SPA2 basin discretized into morphological units and stream tubes, the SEDD model is calibrated at event scale using the measurements carried out at the outlet of the experimental basin in the period December 2000–January 2001. The model calibration is used to determine a relationship useful for estimating the unique coefficient βe of the model by rainfall erosivity factor Re at event scale.To test the predictive capability of the βe = f(Re) relationship, 20 events measured in the period September 2002–December 2005 are used; the comparison between measured sediment yield values and calculated ones for all monitored events shows that the sediment delivery distributed approach has a good predictive ability at event scale.The analysis also shows that estimating βe by the relationship βe = f(Re) gives a better agreement between measured and calculated sediment yields than obtained with the median value βe,m of all 27 calculated βe values.Finally the analysis at annual scale, for the period 2000–2005, allows the estimation of the median value βa,m representative of the annual behaviour. This analysis shows that the sediment delivery distributed approach also has a good predictive ability at annual scale. Copyright © 2006 John Wiley & Sons, Ltd.

Modelling the impact of land cover changes in the Czech Republic on sediment delivery

At present large collective fields in the Czech Republic are being split up into smaller spatial units. Moreover, a large number of former state farms are abandoned, resulting in an increase of the area of set-aside land. Between 1990 and 2000 the area of pasture land in the Czech Republic increased 150%. The ongoing landscape dynamics has a significant impact on soil erosion and sediment delivery to rivers and reservoirs. In some cases sedimentation records in retention ponds at the outlet of rural drainage basins show a 75% decrease of the mean annual sediment export since 1990. It may be expected that the EU enlargement will be a significant driver for future land cover change in Central and Eastern Europe. In this paper some possible land cover change scenarios for rural areas in the Czech Republic were considered. Next, these scenarios were used as an input for a spatially distributed sediment delivery model in order to evaluate their impact on soil erosion and sediment delivery. The results show that the spatial pattern of land cover change seems to be more important than the percentage of land cover change, which encourages the development and application of spatially explicit land cover change models.

GIS-based sediment assessment tool

Accelerated soil erosion is a worldwide problem because of its economic and environmental impacts. To effectively estimate soil erosion and to establish soil erosion management plans, many computer models have been developed and used. The Revised Universal Soil Loss Equation (RUSLE) has been used in many countries, and input parameter data for RUSLE have been well established over the years. However, RUSLE cannot be used to estimate the sediment yield for a watershed. Thus, the GIS-based Sediment Assessment Tool for Effective Erosion Control (SATEEC) was developed to estimate soil loss and sediment yield for any location within a watershed using RUSLE and a spatially distributed sediment delivery ratio. SATEEC was enhanced in this study by developing new modules to: 1) simulate the effects of sediment retention basins on the receiving water bodies, 2) estimate the sediment yield from a single storm event, and 3) prepare input parameters for the Web-based sediment decision support system using a GIS interface. The enhanced SATEEC system was applied to the study watershed to demonstrate how the enhanced system can be effectively used for soil erosion control. All the procedures are fully automated with Avenue, CGI, and database programming; thus the enhanced SATEEC system does not require experienced GIS users to operate the system. This easy-to-operate SATEEC system can be used to identify areas vulnerable to soil loss and to develop efficient soil erosion management plans.