Summary:

Within their catchment basins, brooks and rivers form a structure under which the water flow and morphological processes impact each other. A structure of the flowing water is characterized by such variables as type of substratum, cross-section of the rook channel, longitudinal profile, and horizontal arrangement. Each change in the water flow and intensity of rubble transportation causes the morphology of the brook bed to change, and the direct causes are erosion and deposition processes. The objective of the survey studies presented in this mono-graph was to identify regularities controlling the processes of lateral and deep erosion, transportation, and sedimentation processes in two Carpathian brooks: Słomka and Kasinka. The survey studies were performed in a period from 2004 to 2006.
The Słomka brook is a 25.2 km long, left-bank tributary of the Dunajec river and drains an area of 69.90 km2. The Kasinka brook is a right-bank tributary of the Raba river, and it pours into this river at km 92 +750, below the Mszanka brook mouth. The studies comprised both the straight sections of the brook channels and the strongly eroded section along the concave bank (the Kasinka brook). Within the gauging sections, comprehensive measurements were performed in order to identify lateral erosion processes (at a horizontal level) and deep and deposition processes (vertically). All the measurements were taken twice a year; thus, two annual series of measurements were available. The processes observed were documented in the form of surveying plans, diagrams, and photographs. The measurement included:
- a geodetic survey of transversal cross-sections and longitudinal profiles;
- the determination of granulometric composition of the brook bed material.
The survey studies focused, first of all, on assessing the retreat of eroded banks and the transformation of bars and brook bed within the selected sites. Ad-ditionally, a method with the use of pins was applied to support the geodetic sur-veys. 50 cm long pins having a 1 cm diameter were driven in the uncovered part of the bank, starting from the water level and upwards, every 0.50 cm. Along with the increase in the size of the bank's undercut section, the length of the uncovered pin increased; this length was measured and the pin was again driven into the scarp so as to make it level with the scarp surface.
The measurement results were applied to compute the brook power, shear-ing stresses in the channel, and the intensity of rubble transportation. The compu-tations were performed using a Bagnold's equation. The results obtained showed that the progress of erosion processes was similar in the two brooks studied. The banks of the brook channels surveyed are composed of non-cohesive deposits (gravels, sands) and are clearly susceptible to lateral erosion. The maximum lon-gitudinal gradient of the Słomka brook was i = 1.7%, and of the Kasinka brook: i = 1.01%. The mean speed of lateral migration of meanders in the Słomka brook ranged between ve = 0.6 m/annum and ve = 1.7 m/annum. As for the Kasinka brook, those values were in the range from ve = 0.1 m/annum to ve = 1.0 m/annum. The erosion material eroded from the outer banks of the meanders was only par-tially deposited on the opposite side (closer to the inner bank). The rate of lateral migration of those forms (meander-bars) does not equal the rate of the migration of the brook channel. Volumetrically, the erosion and deposition processes have not balanced.
In the two brooks, it was found that the transportation of the bed materials in the brook channels took place at an overflow smaller than Q50%. The computed brook power and the forecast transportation of dragged rubble makes it possible to assess the scale of this phenomenon. The ability of flow to destroy the channel and banks of the brook results from the large brook power surplus that greatly exceeds the critical brook power connected with the beginning of the flow movement. For example: during the raised water culmination in the Słomka brook, the multiple was as high as 32.
Channel erosion is a process to accompany the rubble transportation. In the case of the brooks studied, typically, this process was found in the sections along the meanders. It caused the bed sediments to be eroded directly near the outer bank. In the places, where the deep erosion process was found, overdeepings were formed and shaped as elongated erosion channels, their depth being even as much as 1.30 m (the Kasinka brook).
The granulometric composition of the bed rubble in the two brooks is highly differentiated. This material consists of diverse grains and is poorly sorted, in the majority, it consists of gravel and stony fractions. It was found that the composition of the rubble grains, determined using a liquid nitrogen freezing method, could be used as a stability indicator of the brook channel bed, since it is possible to determine the pavement layer in the brook channel bed. Where there is no stability, the bed material is totally mixed.