Thirty coastal nabkhas were selected for morphometrical measurements. The studied nabkhas were mostly elongated, with an average total length of about 12.9 m, an average width of 3.4 m, and an average height of 1.2 m. Optical porosity of nabkha shrub crown was measured and no apparent relationship with the horizontal size of trapped wind laden sand was found. A simple wind tunnel experiment was carried out to investigate the horizontal wind-flow distribution across a pro-typed shrub. The results of the experiment reveal ed that the degree of wind sheltering m ight extend up to a downwind distance approximately equal to 4.5 times the height of the shrub, where an effective velocity recovery start ed .
KeywordsNabkhasSedimentPorosityWind Tunnel
K. Ardon, H. Tsoar and D. G. Blumberg, “Dynamics of Nebkhas Superimposed on a Parabolic Dune and Their Effect on the Dune Dynamics,” Journal of Arid Environments, Vol. 73, No. 11, 2009, pp. 1014-1022. http://dx.doi.org/10.1016/j.jaridenv.2009.04.021
A. Tengberg and D. L. Chen, “A Comparative Analysis of Nebkhas in Central Tunisia and Northern Burkina Faso,” Geomorphology, Vol. 22, 1998, pp. 181-192. http://dx.doi.org/10.1016/S0169-555X(97)00068-8
F. I. Khalaf, R. Misak and A. Al-Dousari,” Sedimentological and Morphological Characteristics of Some Nabkha Deposits in the Northern Coastal Plain of Kuwait, Arabia,” Journal of Arid Environments, Vol. 29, No. 3, 1995, pp. 267-292. http://dx.doi.org/10.1016/S0140-1963(05)80107-7
P. A. Hesp, “Ecological Processes and Plant Adaptations on Coastal Dunes,” Journal of Arid Environments, Vol. 21, No. 2, 1991, pp. 165-191.
R. Cooke, A. Warren and A. Goudie, “Desert Geomorphology,” UCL Press Limited, University College London, London, 1993.
S. J. Lee, K. C. Park and C. W. Park, “Wind Tunnel Observations about the Shelter Effect of Porous Fences on Sand Particle Movements,” Atmospheric Environment, Vol. 36, No. 9, 2002, pp. 1453-1463. http://dx.doi.org/10.1016/S1352-2310(01)00578-7
J. M. Al-Awadhi, A. Al-Hellal and A. Al-Enezi, “Sand Drift Potential in the Desert of Kuwait,” Journal of Arid Environments, Vol. 63, No. 2, 2005, pp. 425-438. http://dx.doi.org/10.1016/j.jaridenv.2005.03.011
L. I. Zhizhong, W. U. Shengli, D. L. Janis, G. E. Lin, H. E. Mudan, W. Xiaofeng, J. Jianhui, L. Jinwei, L. I. Wanjuan and M. A. Rong, “Wind Tunnel Experiments of Air Flow Patterns over Nabkhas Modeled after Those From the Hotan River Basin, Xinjiang, China (II): Vegetated,” Earth Science China, Vol. 2, No. 3, 2008, pp. 340-345.
P. F. Grant and W. G. Nickling, “Direct Field Measurement of Wind Drag on Egetation for Application to Windbreak Design and Modelling,” Land Degradation and Development, Vol. 9, No. 1, 1998, pp. 57-66. http://dx.doi.org/10.1002/(SICI)1099-145X(199801/02)9:1 3.0.CO;2-7
F. I. Khalaf and D. Al-Ajmi, “Aeolian Processes and Sand Encroachment Problems in Kuwait,” Geomorphology, Vol. 5, No. 2, 1993, pp. 111-134. http://dx.doi.org/10.1016/0169-555X(93)90042-Z
A. Al-Enezi, K. Pye, R. Misak and S. Al-Hajraf, “Morphologic Characteristics and Development of Falling Dunes, Northeast Kuwait,” Journal of Arid Environments, Vol. 72, No. 4, 2008, pp. 423-439. http://dx.doi.org/10.1016/j.jaridenv.2007.06.017
J. M. Al-Awadhi and R. M. Misak, “Field Assessment of Aeolian Sand Processes and Sand Control Measures in Kuwait,” Kuwait Journal for Science and Engineering, Vol. 27, No. 1, 2000, pp. 156-176.
J. M. Al-Awadhi and A. M. Al-Dousari, “Morphological Characteristics and Development of Coastal Nabkhas, North-East Kuwait,” International Journal of Earth Sciences (Geologische Rundschau), Vol. 102, No. 3, 2013, pp. 949-958. http://dx.doi.org/10.1007/s00531-012-0833-9
X. Wang, T. Wang, Z. Dong, X. Liu and G. Qian, “Nebkha Development and Its Significance to Wind Erosion and Land Degradation in Semi-Arid Northern China,” Journal of Arid Environment, Vol. 65, No. 1, 2006, pp. 129-141. http://dx.doi.org/10.1016/j.jaridenv.2005.06.030
P. Hesp and A. McLachlan, “Morphology Dynamics, Ecology and Fauna of Arctotheca Populifolia and Gazania Rigens Nabkha Dunes,” Journal of Arid Environments, Vol. 44, No. 2, 2000, pp. 155-172. http://dx.doi.org/10.1006/jare.1999.0590
A. J. Dougill and A. D. Thomas, “Nebkha Dunes in the Molopo Basin, South Africa and Botswana: Formation Controls and Their Validity as Indicators of Soil Degradation,” Journal of Arid Environments, Vol. 50, No. 3, 2002, pp. 413-428. http://dx.doi.org/10.1006/jare.2001.0909
K. K. Bofah and K. G. Al-hinai, “Field Tests of Porous Fences in The Regime of Sand-Laden Wind,” Journal of Wind Engineering and Industrial Aerodynamics, Vol. 23, 1986, pp. 309-319. http://dx.doi.org/10.1016/0167-6105(86)90051-6
J. E. Cermak, “Advances in Physical Modeling for Wind Engineering,” Journal of Engineering Mechanics, ASCE, Vol. 113, No. 5, 1987, pp. 737-756. http://dx.doi.org/10.1061/(ASCE)0733-9399(1987)113:5(737)
M. D. Perera, “Shelter Behind Two-Dimensional Solid and Porous Fences,” Journal of Wind Engineering and Industrial Aerodynamic, Vol. 8, No. 1-2, 1981, pp. 93-104. http://dx.doi.org/10.1016/0167-6105(81)90010-6
G. M. Heisler and D. R. DeWalle, “International Symposium on Windbreak Technology,” Reprinted from Agriculture, Ecosystems and Environment, Vol. 22-23, pp. 41-69, Elsevier Science Publishers BV, Amsterdam, 1988.
S. J. Lee, K. C. Park and C. W. Park, “Wind Tunnel Observations about the Shelter Effect of Porous Fences on Sand Particle Movements,” Atmospheric Environment, Vol. 36, No. 9, 2002, pp. 1453-1463. http://dx.doi.org/10.1016/S1352-2310(01)00578-7
P. A. Taylor, “Turbulent Wakes in the Boundary Layer,” In: W. L. Steffen and O. T. Denmead, Eds, Flow and Transport in the Natural Environment: Advances and Applications, Springer-Verlag, Berlin, 1988, pp. 270-292. http://dx.doi.org/10.1007/978-3-642-73845-6_17
J. M. Al-Awadhi (Abdullah), “Sand Transport and Deposition over Nonerodible Elements,” Ph.D. Thesis, University of Aberdeen, Aberdeen, 1996.
D. A. Gillette and P. H. Stockton, “The Effect of Non-Erodible Particles on Wind Erosion of Erodible Surfaces,” Journal of Geophysical Research, Vol. 94, No. D10, 1989, pp. 12885-12893. http://dx.doi.org/10.1029/JD094iD10p12885
L. K. Marshall, “Drag Measurements in Roughness Arrays of Varying Density and Distribution,” Agricultural Meteorology, Vol. 8, 1971, pp. 269-292. http://dx.doi.org/10.1016/0002-1571(71)90116-6
L. Lyles, R. L. Schrandt and N. F. Schneidler, “How Aerodynamic Roughness Elements Control Sand Movement,” Transactions, American Society Agricultural Engineers, Vol. 17, No. 1, 1974, pp. 134-139. http://dx.doi.org/10.13031/2013.36805