Wind flow and sediment flux profiles for vegetated surfaces in a wind tunnel and field-scale windbreak

Abstract

Abstract Despite many studies describing wind speed and sediment flux profiles in various situations, wind tunnel observations in the presence of live vegetation are infrequent and rarely combined with field measurements. To investigate the structure of wind speed and sediment flux profiles in morphologically different vegetation and various plant densities, wind velocity and sediment flux profiles were obtained over a multi-row windbreak in an arid environment and over unplanted surfaces and canopies of two types of plants in a wind tunnel. Although the two plant types in the wind tunnel have different morphology, the profiles of wind velocity and sediment flux showed structures similar to those for other plant types reported in previous studies which indicates that profile structures are likely common for homogeneous canopies even with different plant morphology and in various wind velocities. The horizontal profiles of wind speed and vertical profiles of sediment flux in the wind tunnel closely matched the profiles in the field-scale windbreak. The vertical profiles of wind speed within the wind-tunnel vegetation exhibited a deflection which was not reflected within the multi-row windbreak where profiles were nearly uniform without inflections, which was likely a response to different plant spacing and patterns. Wind-tunnel vegetation reduced wind speed significantly even in low density. Lowest wind speeds were observed beyond the wind-tunnel canopies and at the beginning of the windbreak. No difference in the size of the sheltered zone is observed between the two plant types in the wind tunnel either in different wind velocities or in various density configurations, or within the windbreak in various wind speeds and different dust storm events. The sheltered area was greater for the windbreak than for the wind-tunnel canopies, suggesting that wind tunnel studies may under-estimate the sheltered area afforded by a multi-row windbreak.