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Soils, rocks, and groundwater
Published in Rodrigo Salgado, The Engineering of Foundations, Slopes and Retaining Structures, 2022
Alluvial soils are deposits of interlayered gravel, sand, silt, and clay. They form as rivers carry and deposit particles of varying sizes, depending on the water velocity, which changes across time and space. Locally, at a river cross section, water velocity drops with distance from the center of the river. It also varies seasonally, as the river expands laterally to occupy its flood plain during rainy seasons and shrinks during drier periods (Figure 3.8). As a result, the river tends to deposit soils on the inside of a bend and to remove soil from the outside. This, over time, increases the sharpness of the bend (Figure 3.9b); this process may go so far that eventually it becomes easier for the river to cut across the soil, leaving the bend behind as an abandoned oxbow lake (Figure 3.9c). The water velocity also varies along the axis of the river. Closer to its source, it tends to be steeper, and water velocities, higher. As the river approaches its delta, velocities drop substantially, and the river deposits larger volumes of soil (which tends to be made up of finer particles).
Assessment of Effectiveness of DRASTIC Model
Published in Prashant Kumar, Praveen K. Thakur, Sanjit K. Debnath, Groundwater Vulnerability Assessment and Mapping Using DRASTIC Model, 2019
Prashant Kumar, Praveen K. Thakur, Sanjit K. Debnath
The physical characteristics of an aquifer together with its hydraulic conductivity also have a large influence on the level of vulnerability determined by the DRASTIC model. Fatehgarh Sahib district is underlain by an extensive shallow aquifer in alluvial sediments (Saigal 2007; Water Resources and Environment Directorate Punjab 2009, 2011). According to Park et al. (2007) alluvial deposits are very good for supplying water to many rural agricultural areas due to the water holding characteristics of these materials. Both the hydraulic conductivity and the porosity of sediments materials can affect in a shallow alluvial aquifer and can have a large influence on its vulnerability to contamination. The bigger the openings/fracture size, the higher will be the pollution potential as the particular aquifer will have a higher permeability and lower attenuation potential (Umar et al. 2009). In this study, a rating of 8 has been assigned for the aquifer type in the final calculation of vulnerability index of contamination because area aquifer material is almost homogeneous throughout the district. The alluvial aquifer in the Fatehgarh Sahib district has a thickness of about 20 m and is comprised of clay and fine sand.
Flood Risk in the UK: Evidence of Change and Management Responses
Published in Zbigniew W. Kundzewicz, Changes in Flood Risk in Europe, 2019
Groundwater floods occur in unconfined aquifers and alluvial sediments overlying impermeable ground, and can be particularly damaging by virtue of the duration of flooding, resulting from the slow decline of elevated groundwater levels. England’s chalk aquifer has accounted for the large majority of groundwater flooding events that have been recorded in the recent past. However, other aquifers contain significant amounts of groundwater and have the potential to cause flooding. Groundwater floods tend to occur when prolonged extreme rainfall is coupled with above-average antecedent groundwater levels, such as those which took place during winter/spring of 2000/01 when the rainfall for the eight-month period starting in September 2000 was 166% of the long-term average (Marsh & Dale, 2002). Based on analysis of hydrogeological conditions, it is estimated that 1.6 million properties are at flood risk in England and Wales (Jacobs, 2004; Morris et al., 2007).
Improved water management is central to solving the water-energy-food trilemma in Lao PDR
Published in International Journal of Water Resources Development, 2021
Matthew McCartney, Jake Brunner
There are limited data or specific information, but water pollution, particularly from the agricultural and mining sectors, is widely perceived to be an increasing threat to both ecological and human health, particularly in sub-basins where these activities are concentrated and in communities that continue to depend on untreated river water for domestic supplies. In relation to mining (i.e. alluvial gold mining as well as sand and gravel abstraction), particular concerns relate to mining methods and their impacts on water quality and turbidity, as well as erosion of riverbeds and banks. Communities in southern Lao PDR have complained of water pollution from gold mining (Radio Free Asia, 2013). As a consequence of environmental and social concerns, including water pollution, in 2012 the government implemented a four-year nationwide moratorium on new mining projects which, despite pressure from mining companies, was extended in 2016 (Vientiane Times, 2016).
Hazards assessment of the intake of trace metals by common mallow (Malva parviflora K.) growing in polluted soils
Published in International Journal of Phytoremediation, 2019
Tarek M. Galal, Zeinab A. Shedeed, Loutfy M. Hassan
Plant, soil, and irrigation water samples were collected from polluted and un-polluted sites. The polluted site (29°44'9.43" N and 31°17'26.61" E) was located at south Cairo Governorate, where agricultural soils are irrigated with polluted water from El-Hajir and El-Khashab canals receiving a lot of industrial discharges, anthropogenic wastes, car washing wastes and sewage discharges. This site, which extends along the River Nile and characterized by alluvial soils, comprises many agricultural activities including cultivation of vegetables. The high soil water level as well as the high proportion of air and water pollutants, and creeping urbanization may increase the risk of desertification of this area. Besides, the un-polluted (reference) site (29°50'37.05" N and 31°15'47.55" E) was located at south Giza Governorate and irrigated from El-Ebrahemia canal, a branch from the River Nile that does not receive industrial or municipal wastes (Elawa 2015). This site stretches along the Nile River, so agricultural soil in this region was formed as a result of Nile silt sedimentations and the soil is thus considered as alluvial. The agricultural activities in the study site were restricted mainly for the cultivation of vegetables.