The article describes the effect of substrate roughness on the generation of air flow resistance and the occurrence of kinetic friction. These are the two main factors influencing reduction in wind speed, lack of ventilation in built-up areas, and stagnation of pollution over areas with high substrate roughness. The work presents the results of the authors' own measurements in the field, carried out using WindLog and CHY 361 anemometers, in two different types of atmospheric conditions - sunny and rainy weather. The measurements were taken on a stretch of the Rudawa River, located on the Cracow city limits. Wind speed was measured at all established measurement points. The immediate surroundings of the points varied in terms of how densely the areas were built up. The effect of changes in the shape and equivalent diameter of the measurement profile on the magnitude of flow resistance and friction was also tested. The results of the study indicate that the best type of arrangement for buildings around the valley of the Rudawa River is a latitudinal configuration. The lack of buildings on the path along which the airstream flows creates suitable conditions for ventilation of the city, and thus for clearing the air ...
