Eurocode standard recommends using fundamental basic wind velocity (characteristic velocity) as the design value in civil engineering. There are different approaches to estimate this value depending on the climate features of the given area and the quality of environmental data. The estimation of the characteristic value requires statistical analysis of historical data regarding wind velocities measured throughout the country at meteorological stations. The results of the analysis are probability density distributions of this random variable for each meteorological station. On this basis, values of characteristic wind velocity with a mean return period of 50 years are determined. The zones with uniform velocities are delineated on the map of the country. In the case of Poland the last evaluation of wind zones took place over 15 years ago. Higher quality of measurement data on the one hand, and the introduction of the second generation of Eurocode standards on the other hand, create a need to check and update these zones. This work presents theoretical basis for the estimation of characteristic values of random variables in the context of wind velocity, comprehensively reviews practical methods used for this purpose and summarizes current situation in Poland, finally discusses the issues related to the heterogeneity of wind data, illustrating them with an example.

Oxbow lakes occurring in floodplains are those natural elements that are subject to rapid changes, which may lead to their disappearance. These are extremely valuable ecosystems and landscape components, as well as water management units. However, they quickly disappear if they are not periodically fed with river water, which takes place especially when rivers are embanked. Such a situation occurs, among others in Warsaw, in the Vistula valley. There are many opportunities for the reactivation of oxbow lakes, including through technical activities. It is not always possible to restore the naturalvalues of the valley in urbanized areas, however, oxbow lakes can then also play a recreational role and they can fulfill an important task in improving the quality of life, being also an important element of the public space system. The author has carried out research related to land development projects of the new district located in the Vistula River valley in Warsaw (the Siekierkowski Arc). Many different design solutions have been proposed, taking as a leitmotiv the restoration of oxbow lakes, for example: (1) reconstruction of the water channel in the former watercourse with the boulevard along its fragment and with the public park in another part, (2) water supplying of the existing oxbow lake through the green and blue infrastructure system. The author presents few urban designs carried out under her direction for this area and shows that creative reactivation of oxbow lakes can improve water conditions, and be beneficial for the introduction of a new, attractive development.