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Desert, Desertification and Land Degradation
Published in Ajai, Rimjhim Bhatnagar, Desertification and Land Degradation, 2022
After the soil is eroded, it gets deposited at the other place, again through two means, water and wind. After the erosion and transportation, the eroded material gets deposited to form dunes and loess. Dunes are wind-blown sand mounds usually deposited near their source. The size, shape and arrangement of dunes depend on sand supply, direction, the velocity of the prevailing wind and the amount of vegetation. Barchan, longitudinal, transverse, parabolic and star dunes are some of the types of sand dunes. Barchan dunes are crescent-shaped dunes in the downwind direction, opposite to the upwind direction of parabolic dunes. They are formed when sand moves across the pavement. Transverse dunes are perpendicular to wind direction, formed in regions of abundant sand-like beaches. Longitudinal dunes are formed parallel to wind direction especially in the areas of limited sand. Figure 2.9 shows different kinds of sand dunes as captured on satellite images. Loess, too, is deposition by wind but at faraway places, particularly from dry to wet. It consists of layers of windblown silt and clay composed of quartz, feldspar, mica and calcite.
Petroleum Migration and Accumulation
Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021
Aeolian sandstone reservoirs are found in wind zone areas of desert and coastal belts. Aeolian sandstone rock formed by wind contains the maximum amount of sand particles compared to other types of sandstone reservoir rock. The wind can carry sand particles from one place to another far off or to a very short distance. The wind can hold up only small particles of sand less than 0.06 mm in size. When the wind carrying sand particles slows down or stops, the sand particles are released and deposited on land, forming sand dunes. The sand dune is a hillock of well-sorted fine-grained sand particles. The geometry and size of dune are controlled by the speed and direction of the blowing wind which depend on the weather conditions. Different layers (cross bed) with specific geometrical shapes of sand are formed in the dune, due to variation of wind velocity. The layers are flat (horizontal) at the bottom and slanting towards the top forming the crest (peak). The crest of dune is either parallel to the wind direction (longitudinal dune) or perpendicular to the wind direction (transverse dune) or a combination rounded shape.
Small Unmanned Aerial Systems (sUAS) and Structure from Motion for Identifying, Documenting, and Monitoring Cultural and Natural Resources
Published in J.B. Sharma, Applications of Small Unmanned Aircraft Systems, 2019
Marguerite Madden, Thomas Jordan, Sergio Bernardes, Cari Goetcheus, Kristen Olson, David Cotten
Due to their high intensity winds, hurricane impacts on coastal areas often include drastic alterations of physical and chemical environmental conditions that sustain key coastal ecosystems. Strong winds can totally or partially remove vegetation (e.g., uproot trees and/or break trunks and limbs), change salinity of water available to root systems, increase exposure to salt spray, and change the spatial distribution of sand dunes and associated biota. These impacts are particularly critical considering that climate projections indicate hurricanes, such as those that have affected the United States in recent years, may become more frequent and intense, resulting from the warming of ocean waters and the atmosphere. Thus, understanding vegetation responses to these extreme events is required to understand how extreme events linked to future climate scenarios may impact important ecosystems. This section describes sUAS-based strategies to assess environmental damage caused by extremes events, including damage to vegetation and shoreline erosion.
Evaluating and tracking investments in natural infrastructure to reduce coastal flooding hazards
Published in Sustainable and Resilient Infrastructure, 2022
Carson Ezra Young, Shannon E. Cunniff, William C. McDow
Urban planners, floodplain managers, and environmental groups have suggested that landscape-scale planning and implementation of coordinated flood and storm damage reduction systems – that include both natural and gray infrastructure – are needed to cope with increasing flooding threats (Cunniff, 2019; Dow et al., 2013; Jones et al., 2012; Jongman, 2018; Opperman, 2014; Smith et al., 2017; Spalding et al., 2014; Sutton-Grier et al., 2015; Van Wesenbeeck et al., 2013). Floodplain managers have long advocated for riparian corridors with forests, wetlands, and undeveloped open space to reduce flood and storm damages (e.g., Federal Emergency Management Agency, 1994). Maintenance and restoration of vegetated dunes to capture sand and reduce the impact of coastal storm waves and surge is a well-accepted strategy employed by the US Army Corps of Engineers and coastal communities.
Sustainable hard and soft measures for coastal protection – Case studies along the Indian Coast
Published in Marine Georesources & Geotechnology, 2022
Vallam Sundar, Sannasi Annamalaisamy Sannasiraj, Sukanya Ramesh Babu
Kumar and Hota (2014) have reported in detail the geomorphology, flora and hydrogeology of the coastal sand dunes and anthropogenic impact on sand dunes (Figure 11) from the region of Gopalpur (19°00′ and 19°50′ N and 84° 40′ to 85° 12′ E), along the southern coast of Odisha. The study of Sridhar and Bhagya (2007) examined the composition and distribution from coastal sand dunes revealed a total of 338 species along the coast of India. Coastal sand dunes are important sites for a variety of flora, fauna, and microbes. Their stability is enhanced by vegetation over it.
Change detection, risk assessment and mass balance of mobile dune fields near Dunhuang Oasis with optical imagery and global terrain datasets
Published in International Journal of Digital Earth, 2020
Chao Ding, Guangcai Feng, Mingsheng Liao, Lu Zhang
In the common sense, the threats of mobile sand dunes can be classified into the dune encroachment and the erosion of windblown sand (Bagnold 1941). Thus, many sand-control facilities have been constructed to resist local landscapes from these threats. To some extent, the quantification of dune migration can also indicate the activity of windblown sand transport. Here, we intend to evaluate the potential threats of dune migration on surrounding natural/cultural heritage sites and river catchment, such as Crescent spring, Mogao Grottoes, and Dang river.