Roman Soja

Vegetation-controlled modern anastomosing system of the upper Narew River (NE Poland) and its sediments

Abstract The anastomosing system of the upper Narew River consists of a network of interconnected channels. The channels are relatively deep (width/depth ratio 2–10), straight to sinuous, and they lack natural levees. They are characterised by a low water slope and very low stream power. The river is distinctly bedload-dominated and the transport of suspended clastic fines is minimal. Channel deposits consist almost exclusively of medium- to coarse-grained sand. Laterally extensive interchannel areas are flat and covered with peat-forming vegetation. These stable wetlands are flooded for many weeks during high water stages. Except for the channels, the valley fill consists of peat layer reaching 4 m in thickness. The rate of vertical aggradation of the peat deposit is estimated at 1–1.5 mm/year. The radiocarbon dating indicates that the peat layer is predominantly late Holocene in age. The impact of vegetation on the system is overwhelming. Vegetation produces an erosion-resistant peat layer, stabilizes channel banks and slows down the water flow. Vegetation also stimulates aggradation of bedload material on the channel bottom, and contributes to avulsion by blocking the channels. The channel network owes its origin to repeated though infrequent avulsion. Avulsion in the studied system is a small-scale, gradational and slow process. New channels evolve very slowly because of unfavourable hydrologic conditions and the presence of a resistant peat substratum. A new channel eventually intercepts only a part of the flow, while the old channel is still active, though to a limited extent. Although newly formed channels might subsequently be abandoned, long-lasting ones predominate within the system.

Community perception of the Klimkówka Reservoir in Poland

This article presents the results of a survey on how people perceive the Klimkówka storage reservoir located on the Ropa River in the Polish Carpathians. The analysis focused on establishing the role of various factors which impact the assessment of the reservoir by the local community. Community perception of the reservoir was analyzed in relation to several aspects linked to the reservoir itself, e.g. the risk of dam failure, feeling of safety, pros and cons, and how accustomed people were to the reservoir. A crucial issue was to identify how the real threat of a flood, experienced by people living below the dam, affected the way people perceived the reservoir. As a result of the analysis, a hierarchy of factors which determine peoples assessment of large hydraulic structures was established. The results can be applied to determine specific measures aimed at limiting negative community perception of water infrastructure.