The ecological water quality in rivers and streams is influenced both by the morphological factors (within the watercourse channel and by the dynamic factors associated with flow), as well as biological factors (connected with the flora and fauna characteristic of its specific area). This paper presents an analysis of the effect of river channel shading by trees and shrubs on hydromorphological changes in a selected reach of the Wełna River, Poland. The analysis was conducted on two adjacent cross-sections (one in a reach lined with trees, the other in an open area with no tree or shrub vegetation). Data were collected during field surveys in the years 2014 and 2019. According to the Water Framework Directive, the Wełna River represents a watercourse with small and average-sized watershed areas, with sand being the dominant substrate of the river bottom. Flow volume, distributions of velocity in the sections, as well as substrate grain-size characteristics and river bottom morphology, were determined based on field measurements. In the study, the leaf area index (LAI) of vegetation was measured in the reach lined with trees, while the number and species composition of macrophytes were determined in the investigated river reaches. Moreover, a digital surface model (DSM) and Geoinformation Information System GIS tools were used to illustrate variability in shading within the tree-lined reach. The DSM model was based on Light Detection and Ranging (LIDAR) data. The results of this study enable us to establish the relationship between river shading by vegetation covering the bank zone, and changes in hydromorphological parameters of the river channel.

The key challenge for sustainable water management is to carry out a proper assessment of the technical condition of hydrotechnical constructions. Maintaining them in a good state is a prerequisite for ensuring the safety of objects, as well as adjacent areas. This paper compares the results of field research obtained by three methods to assess the technical condition of structures located on the Wełna River. The main objective is to determine the differences between the methods and to indicate the most important assessment elements and criteria. Moreover, it was checked if the Analytic Hierarchy Process (AHP) can be used to carry out the correct assessment of hydrotechnical construction. An assessment that will be based on the hierarchy of factors, which is not often used in other methods. The AHP was applied for the first time to assess the technical condition of hydrotechnical constructions. Based on AHP, three variants of different weights for factors, including exploitation problems and damage to construction elements, were selected. The new variants developed by the authors allow for a more accurate, multifactor assessment. The use of scales to determine the importance of individual elements contributes to the actual representation of the technical condition of the object, which is often over- or underestimated by other assessment methods. The analysis shows that the AHP method is a useful tool to support the assessment of the technical condition of hydrotechnical construction. The use of AHP as a universal assessment method will compare the technical condition of hydrotechnical constructions located all over the world.

The aim of the following study was to compare a few methods of river regulations and indicate the one which fully meets technical regulative standard and concurrently ensures protection of the watercourse ecosystem. According to the sustainable development rules it is of the most importance in every human activity to compromise between developmental and environmental needs of current and future generations. Therefore, both technical criteria related to flood safety and environmental ones were taken into consideration in the analysis. Field study was conducted in vegetation stage between 2008 and 2014 in small and medium lowland watercourses in Lower Silesia. The research comprised of measurements and descriptions of selected technical and environmental elements of a complex system of the watercourse river bed. Basing on obtained results a multicriterial assessment of the effects of the works was conducted. In order to assess the results an Analytic Hierarchy Process (AHP) was used in the study. It facilitated the creation of linear ranking of river beds and indicate the most optimal solution in terms of sustainable development. Such methods have not been applied in solving problems connected with river regulation. That’s why this study aims also at checking the utility of this method in decision making in both planning and regulation works realization. Results of the study indicate high usefulness of AHP method in the decision-making process.

Increasing water demand, combined with unfavourable climate change, creates a need for well-thought-out water management. Such goals are realised thanks to appropriate hydrotechnical infrastructure, the efficiency and functionality of which depend on its technical condition. In the literature, there is no method for the assessment of the technical condition of small damming structures, including sluice gates. The aim of this article was to present the possibility of using the multi-criteria AHP decision support method to assess the technical condition of small damming structures. The assessment included both concrete elements (spillways, abutments, and apron) and steel elements (gates and hoisting equipment). The analyses considered the effects of growing vegetation, the condition of concrete surfaces (e.g., cracks, cavities, exposed rebar) and steel elements (corrosion, deterioration). A hybrid method was used to study the assessment of the technical condition of water structures. It consisted of a modified Zawadzki’s method and weights which were determined by different groups of respondents with industry backgrounds (university students and experts) using the AHP method. The obtained results show that the factors related to the holes and corrosion of the gate elements had the highest value of the matrix solution vector. The last level of the tree structure indicated that the condition of the spillway and gate is the most important factor in the technical condition assessment. As the assessment considers commonly available parameters, the proposed method is universal and can be used in the assessment of other structures of this type in different regions of the world, which is important in terms of their functioning, planned repairs, and optimal use in water resource management.

Willow bush growing in floodplains is a dominant form of vegetation in lowland river valleys due to the availability of water and light. Uncontrolled growth of this plant results in a lower capacity of floodplain areas. Vegetation can narrow the active width of water flow, as well as change water flow velocities at hydrometric verticals falling within the floodplain and the main channel. This paper analyses the impact of long-term growth of willow shrubs on flow resistance coefficient values. Both an increase in the average diameter and the density characterised by the average distance between branches have a significant impact on reducing the flow. The adopted research variants were based on data on the growth rate of the most popular species and forms of willow found in the floodplains of the Warta River above the Jeziorsko reservoir. Two research scenarios were analysed, including data from 12 years, on the development of floodplain vegetation. The first scenario included only the change in diameter (vegetation grew on a cultivation plot), whereas the density remained constant. The second scenario investigated the inverse model—vegetation growing in an uncontrolled manner. The analysis of the tests proved the impact of various bush development scenarios on flow conditions. The results, referred to in the available research papers, indicated the importance of the dynamics of shrub development to the local flow conditions. It was stated that reduction in the flow, depending on the analysed scenario, could reach 45% for scenarios in which the only considered factor was the increase in diameter (at a constant density), and up to 70% in the case of increase in the density of vegetation. Thorough knowledge of this phenomenon may help manage and maintain natural river valleys.