Siltation

About: Siltation is a research topic. Over the lifetime, 1420 publications have been published within this topic receiving 20983 citations.

Modeling of Soil Loss by Water Erosion and Its Impacts on the Cantareira System, Brazil

Abstract: The Cantareira System is one of the largest water supply systems in the world, supplying about half of the water consumed by 22 million inhabitants in the Metropolitan Region of São Paulo, in southeastern Brazil. In this scenario, in view of climate change, silting is a serious environmental threat and a major challenge to the sustainability of water reservoirs. Therefore, identifying the provenance of sediments is an essential tool to support soil conservation policies, slowing erosion processes and mitigating the deposition of sediments in water reservoirs. Thus, this study aimed to model soil losses—sediment production, by water erosion in the Cantareira System, based on the RUSLE model—Revised Universal Soil Loss Equation, GIS—Geographic Information System and SR—Remote Sensing. The work was conducted on data obtained from online platforms of Brazilian public institutions. The results indicate an average rate of soil loss of 13 Mg ha−1 yr−1, which corresponds to an annual loss of 3 million tons, of which 22% reaches water bodies. The data also show that: (1) in 66 % of the Cantareira System, soil losses are below the soil loss tolerance limits, and, in 34% of the region, water erosion is compromising the sustainability of water and soil resources; (2) the areas with the greatest soil losses are predominantly located in planted forests, agricultural crops and non-vegetated areas; and (3) sectors with high rates of soil loss require the adoption of conservationist practices aimed at reducing sediment production rates and thereby increasing supply and improving water quality.

Assessing Soil Erosion by Monitoring Hilly Lakes Silting

Abstract: Soil erosion continues to be a threat to soil quality, impacting crop production and ecosystem services delivery. The quantitative assessment of soil erosion, both by water and by wind, is mostly carried out by modeling the phenomenon via remote sensing approaches. Several empirical and process-based physical models are used for erosion estimation worldwide, including USLE (or RUSLE), MMF, WEPP, PESERA, SWAT, etc. Furthermore, the amount of sediment produced by erosion phenomena is obtained by direct measurements carried out in experimental sites. Data collection for this purpose is very complex and expensive; in fact, we have few cases of measures distributed at the basin scale to monitor this phenomenon. In this work, we propose a methodology based on an expeditious way to monitor the volume of hilly lakes with GPS, sonar sensor and aquatic drone. The volume is obtained by means of an automatic GIS procedure based on the measurements of lake depth and surface area. Hilly lakes can be considered as sediment containers. Time-lapse measurements make it possible to estimate the silting rate of the lake. The volume of 12 hilly lakes in Tuscany was measured in 2010 and 2018, and the results in terms of silting rate were compared with the estimates of soil loss obtained by RUSLE and MMF. The analyses show that all the lakes measured are subject to silting phenomena. The sediment estimated by the measurements corresponds well to the amount of soil loss estimated with the models used. The relationships found are significant and promising for a distributed application of the methodology, which allows rapid estimation of erosion phenomena. Substantial differences in the proposed comparison (mainly found in two cases) can be justified by particular conditions found on site, which are difficult to predict from the models. The proposed approach allows for a monitoring of basin-scale erosion, which can be extended to larger domains which have hilly lakes, such as, for example, the Tuscany region, where there are more than 10,000 lakes.

Comparative Studies between Urbanization and Dam Settlement Processes

Abstract: The city of Viamao is located in the metropolitan region of Porto Alegre, in the Rio Grande Sul State, southern Brazil. The Mae d'Agua dam was built in 1962 and, due to the lack of urban planning during the last forty years, received large discharges of sediments and contaminants (organic and/or inorganic). This study aimed to use the geochronology technique using the lead element 210 (210Pb) through the cores of sediments sampled from the Mae D'agua dam and to establish the chronology of the sedimentary layers over the last four decades, in addition to the characterization of the sedimentation processes in the Mae D'Agua reservoir and to size the sediment volumes silted in the reservoir in the current scenario, year 2014 (year of sampling) and thus, to present the total sediment concentrations during the 40-year silting. The sediment column, bathymetry, bibliographical references and GIS resources were used to infer the process of urbanization and sedimentation process of the dam, and representative samples were collected in June 2014, using sediment cores distributed in the dam area. The sediment cores were extracted through the "Piston core" sampler. With the results obtained, graphs and tables were generated to create the mathematical models and later the sedimentation maps, establishing correlations with the sedimentation geochronology studies during the last four decades (layers of sedimentation generated in each of these periods). There were periods with high sedimentation rates, mainly during the acceleration of the process of urbanization of the basin resulting in a total sediment volume of 44% of the useful volume of the project, which drastically reduces the capacity of the Mae d'Agua dam. Keywords: Urban dams, Sediments, Sedimentation of dams.

Development of longitudinal profile of the lower yellow river

Abstract: An exhaustive study on the short period evolution of the Yellow River mouth and the long term siltation distribution along the river course as well as the variation of longitudinal profile has not revealed that the parallel aggradation of the Yellow River bed and the siltation along the river course are caused by the estuarine deposit. Theoretically, all the changes of river profiles undergo a process of deplanation. By conceptualized flume test analysis the formation and the evolution of equilibrium profile without silting up are discussed, and it is verified that a great mount of silt deposit will severely appear in a long period till the silt stable profile is formed. The reasons for the continuous siltation between the high sediment concentration of the river resulting in the wide and shallow riverbed and the sorting of deposition on the river and the low height of the levee system resulting in a gentle riverbed slope. Hence the river is incapable of carrying away the large amount of sediment load.

Determination of Farm Level Soil Erosion Using the Revised Universal Loss Equation (RUSLE)

Abstract: The authors present this investigation concerning estimate of soil loss at a corn farm. Soil erosion is an enormous concern particularly in sloping agricultural lands. Heavy siltation of any river system after a heavy rain event upstream is indicative of soil erosion. However, it is difficult to convince farmers of the urgency to initiate soil erosion control measures at the individual farm level without providing estimates of soil loss. The objectives of this study were a) to generate terrain or digital elevation models (DEMs); and b) to estimate the extent of soil erosion in a representative cornproducing farm using the Revised Universal Soil Loss Equation (RUSLE). DEMs were generated by extracting data from Google Earth (GE), and conducting a topographic profiling using dual frequency survey-grade Global Positioning System (GPS) receivers on a representative corn-growing farm in Claveria, Misamis Oriental, Philippines. The annual amount of soil erosion estimated by the RUSLE for the modeled corn farm was 16 mTha-1 (4.08 cm) using GE DEM. On the other hand, the use of GPS-derived DEM had about 340% higher estimated soil loss at 55 mTha1 (12.85 cm).The GE elevation was higher than GPS in 22% of the land area while 77% of the study land area had GPS elevation higher than GE. The soil erosion figures obtained in the study serve as an objective starting point in exploring ways and means to mitigate the loss of soil which is an agricultural resource of vital importance, thereby contributing to agricultural sustainability and productivity.