The effectiveness of a multi-row Tamarix windbreak in reducing aeolian erosion and sediment flux, Niatak area, Iran

摘要

Windbreaks are barriers that are widely used to reduce wind speed and aeolian erosion. Most windbreak studies have been done in wind tunnels and generally used rigid objects rather than live plants and most of these studies report on the modification of the flow field and not on the effectiveness at reducing sediment transport. A series of experiments were conducted to monitor the effectiveness of a fourteen-rows Tamarix windbreak in the field and in particular to measure the reduction in sediment erosion and transport. Over the course of six dust storm events, with mean wind speed ranging from 9.4 to 18.2 ms~(-1), sediment flux and wind speed were measured at seven heights (z/h = 0.05, 0.1, 0.2, 0.4, 0.8, 1.4 and 1.8 where h is the mean height of the windbreak) at five locations upwind (x = - 100 m), within (x = 100 and 256 m) and downwind (x = 448 and 560 m) of the windbreak. Largest reduction of sediment flux (a reduction of 50%) was observed at the end of the windbreak (x = 256 m). The decrease in silt and clay component is quite uniform but the relative concentration of sand (＞100 μ) generally decreases within the windbreak and remained lower downwind of the windbreak compared to the upwind value in two of the three events for which sediment size data are available. The windbreak is effective in aeolian erosion control under a variety of dusty conditions and, in general, the potential of the windbreak is optimum due to its optimal porosity (39%) and structure (multiple-row design). Because Tamarix withstand harsh conditions, it is optimal to use it as a windbreak for wind and blown-sediment control in arid regions.