Change of wind flow speed in the protective belt-road system in the conditions of North Kazakhstan

The study results show the influence of roadside protective forest belts on the speed of the wind flow in the conditions of Northern Kazakhstan. The measurements of the wind flow speed took place on 15 trial plots over three periods of observations: leafless (winter), semi-foliated (spring) and foliated (summer) state of trees. On each trial plot, a profile located perpendicularly to the protective belt on both sides. The profile measurements were with access to the roadway, and in some cases crossing the highway. Measurements of wind speed at observation points (reclamation heights) located along the profile and at the control (open field) carried out synchronously using portable ATT-1002 anemometers. Measurement height for each point was equal to 0.5-1 m from the ground. The results of research were patterns of changes in wind flow velocities depending on seasons of the year in the “road-protective belt(s)” system. All examined belts perform their wind protection functions and have a significant impact on the wind mode in the “road-protective belt(s)” system, as well as territories adjacent to highway. This influence is closely dependent on the seasons of the year and reclamation-taxation characteristics of the studied stands. The range of wind-sheltering influence of forest strips reaches its greatest value in winds with approach angle as close as possible to 90° (heading perpendicularly to the belts). With change in the approach angle of the wind flow to the belts, their range of reclamation influence noticeably changes. With parallel arrangement of protective belts (on both sides of the road), a decrease in the average wind speed within the highway in winter period was from 57,0 to 96,5 %, in summer – from 59,0 to 75,0 %, in spring – from 31,0 to 86,0 %. With the decrease in the distance between protective belts and the road, the efficiency of reducing of the wind flow speed directly in the right-of-way of the highway road significantly rises.