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The Range of Environmental and Social Concerns
Published in Karlheinz Spitz, John Trudinger, Mining and the Environment, 2019
Karlheinz Spitz, John Trudinger
Erosion is a common problem associated with land clearing and earthworks (excavation, transportation, and placement of soil and/or rock). This applies particularly in mining where large areas are cleared of vegetation, and huge volumes of soil and rock are removed and stored (environmental impacts of erosion are detailed in Chapter Twenty Five). Also, the most erodible material of all is topsoil, which, as discussed in Chapter Twenty Six, represents a valuable resource that usually warrants conserving. However, without application of stringent safeguards, topsoil from disturbed land will end up in nearby streams causing short-term or long-term degradation to aquatic habitats. Erosion of waste rock piles by runoff after heavy rainfall also transports soil and rock materials into nearby streams. Increased turbidity in natural waters will reduce the light available to aquatic plants for photosynthesis. Increased sediment loads can also smother benthic organisms in streams, eliminating important food sources for predators and decreasing available habitat for fish to migrate and spawn (Johnson 1997b). Some eroded materials are simply toxic due to their high metal content, or become so after contact with air, which causes oxidation of sulphide minerals.
Water Drop Algorithm
Published in Nazmul Siddique, Hojjat Adeli, Nature-Inspired Computing, 2017
The specific characteristics of the sediment load are another key factor influencing channel form and process. The load is the total amount of sediment being transported. There are three types of sediment load in the river: dissolved, suspended, and bed load, as shown in Figure 6.3. The dissolved load is made up of the solutes that are generally derived from chemical weathering of bedrock and soils. Fine sands, clay, and silt are typically transported as suspended load. The suspended load is held up in the water column by turbulence. The bed load is made up of sands, gravel, cobbles, and boulders. Bed load is transported by rolling, sliding, and bouncing along the bed of the channel (Allan, 1995). While dissolved and suspended loads are important components of the total sediment load, in most river systems, the bed load is what influences the channel morphology and stability (Kondolf et al., 2002).
Wind action and arid regions
Published in F.G. Bell, Geological Hazards, 1999
Movement of sediment on slopes is caused primarily by run-off, supplemented by raindrop impact and splash erosion. High run-off associated with torrential rainfall can flush sediment from gullies. Small fans may develop at the exits from gullies, spreading into stream channels. This, in turn, may lead to the formation of gravel sheets, lobes and bars on the one hand and/or bank erosion on the other. Major flows can transport massive quantities of sediment, which when deposited raises valley floor levels. Channels are frequently flanked by terraces, which provide evidence of previous flood events. Sediment load increases downstream as slopes and tributaries contribute more load, and as water is lost by infiltration. Hence, the lower reaches of streams are dominated by deposition. The deposits exhibit some lateral grading in that the larger material, that is, the bedload, is deposited first, the suspended sediment being carried further downstream. Individual flood deposits also tend to show an upward fining sequence. In fact, the surface of channel deposits may consist of a thin layer of sandy or silty material, which can affect infiltration. An important factor to be borne in mind is that the annual sediment yield in such regions is highly variable.
A total load approach to predict bed load transport of Indian alluvial river
Published in ISH Journal of Hydraulic Engineering, 2018
Sahita Ibopishak Waikhom, Sanjaykumar Madhusudan Yadav
Sediment transport in natural rivers has been widely studied in the past few decades. The subcommittee on Sediment Terminology of the American Geophysical Union has defined various loads (sediments) carried by a stream as bed load, suspended load, wash load, etc., and stated that the total load is the sum of the bed load, suspended load and wash load (Vanoni 1975).The wash load is material sourced from erosion of cohesive river banks and surface erosion in the catchment and usually is finer than 0.062 mm (Knighton 1998). Sediment in the wash load is transported in suspension by turbulent eddies in the flow and generally moves at the same rate as the flow (Edwards and Glysson 1999). These particles pass through the river system relatively unrelated to the hydraulic condition in a given reach and are independent of the discharge in stream (Roger, 2008). Thus, the total load carried by the stream is considered as the sum of suspended load and bed load transported per unit time per unit width of channel, not including wash load. The partitioning of the total sediment load of a river into suspended load and bed load is a key factor in fluvial geomorphology, sedimentation engineering and sedimentology. An appropriate assessment of the partitioning requires both short- and long-term measurements (Turowski et.al 2010). In a fluvial system, the analysis of short- (single flood event) and long-term (year of decade) evolution of total load and its partitioning may be a valuable support for applications such as hazard assessment, infrastructure design, reservoir management, environmental engineering and planning for climate or land use changes (Rainato 2016).
Towards an evaluation of bedload transport characteristics by using Doppler and backscatter outputs from ADCPs
Published in Journal of Hydraulic Research, 2021
Slaven Conevski, Massimo Guerrero, Colin D. Rennie, Nils Ruther
Sediment transport measurements are essential for understanding river morphology, design of hydraulic structure, environmental assessment, and flood hazard mapping. The sediment flux in streamflow can be characterized as suspended sediment load and bedload, depending upon whether the advection of the particles occurs as a suspension in the water column or close to the bed (Parker, 2004). The lack of frequent and continuous measurements of these sediment fluxes complicates the accurate prediction of river morphology changes, as well as the development, calibration, and validation of numerical models and analytical formulas.
Ice in reservoirs and regulated rivers
Published in International Journal of River Basin Management, 2022
Mikko Huokuna, Mike Morris, Spyros Beltaos, Brian C. Burrell
During the breakup of river-ice covers, rising discharge and moving ice, and the highly dynamic waves that form upon ice-jam release, increase the potential for erosion (Burrell and Beltaos 2019). Concentrations of suspended sediment can increase sharply due to the greater erosive capacity during ice breakup, as illustrated in Figure 9. Sediment loads can have important implications with respect to the infilling of reservoirs, channel morphology, soil development, and biogeochemical cycling of pollutants and nutrients (Burrell and Beltaos 2019).