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Desertification and Land Degradation Processes
Published in Ajai, Rimjhim Bhatnagar, Desertification and Land Degradation, 2022
Waterlogged areas can be divided into two categories: (i) seasonal waterlogged areas – those areas where waterlogging exist in one cropping season only and (ii) perennial waterlogged areas – those areas where waterlogging occurs for the entire year. There could be two situations when land is waterlogged: (i) surface ponding, or accumulation of water on the surface and (ii) subsurface waterlogging. As discussed earlier, in subsurface waterlogging conditions, the soil profile is saturated with water. Soil profile gets saturated due to upward movement of water through capillary action and slowly blocks all the pore spaces in the soil. When all the soil pores get saturated, the free water stands on the ground surface (Figure 4.6) and sometimes it may appear as a water body. Surface waterlogging can also take place from the rainfall run-off water when water is not able to drain out due to insufficient natural drainage and or not able to percolate downward due to the presence of subsurface impervious layer. Land becomes unproductive under waterlogged conditions and may not be useful for growing crops.
Surface/shallow drainage systems
Published in Willem F. Vlotman, Lambert K. Smedema, David W. Rycroft, Modern Land Drainage, 2020
Willem F. Vlotman, Lambert K. Smedema, David W. Rycroft
Surface ponding is also caused by flatness and unevenness of the land surface, for under these conditions the water will only run off slowly. The excess water will collect in depressions leading to an unequally distributed infiltration load. Moreover, conditions for infiltration in depressions are poor as the soil structure deteriorates under the frequent ponding and the pores become clogged by sediments carried into them by water. The ponding thus becomes self-promoting. Better grading and smoothing of the land may solve part of the drainage problem.
Case Studies
Published in Patrick V. Brady, Michael V. Brady, David J. Borns, Natural Attenuation, 2018
Patrick V. Brady, Michael V. Brady, David J. Borns
Soil immobilization techniques include capping systems, vertical barriers, and horizontal barriers. Capping simply involves coverage of a contaminated site with a clay or synthetic membrane that is thought to be relatively impermeable. Additional effort may also be expended in grading or ditching a site to provide drainage or prevent ponding. Vertical barriers are used to prevent intrusion of uncontaminated water into, and contaminated water off of a site. Vertical barriers work best when they extend down to a horizontal, impermeable layer of rock beneath the zone of contamination (Smith et al., 1995). Slurry walls, grout curtains, sheet pile walls, and geomembrane curtains are the major types cited by Smith et al. (1995). Because slurry walls are thin, and placed in segments, the continuity of the barrier is often a major concern. Pile walls often leak between the joints. The distance of grout penetration varies for grout curtains, but can be relatively small (4.5 feet). Consequently, extensive efforts may be required. In any case, grout curtains are best for fractured rock. Grout curtains are expensive because they can generally only be injected into rocks made up of particles sand-size or larger. The details of emplacement as well as the advantages and disadvantages of each approach are examined in greater detail in (Smith et al., 1995). Horizontal barriers apparently remain a developing technology.
Hydraulic properties of stormwater biofilters during dry phase
Published in Urban Water Journal, 2021
Daniel Subramaniam, Asokarasa Janarth, Navakulan Ahilash, Mohan Sajeevan
Ponding zone is included in design specifications to provide temporary storage of stormwater runoff, to control overflow quantities and to provide head to initiate and facilitate infiltration process through the filter.