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The river benches in the Ochotnica and Kamienica Valley (Gorce)

River beds often feature so-called river benches, which are horizontal surfaces forming stair-like shapes on both sides of the river bed. Along the rivers of the Outer Carpathians the location of respective bench levels is predominantly associated with recent tectonic movements. read more

It is worth noting that each river erodes, i.e. deepens its bed, to a specific level, referred to as the erosion base level. For rivers with estuaries flowing into seas or oceans, the erosion base level is, of course, the sea level. In turn, river tributaries erode to the level of the main river. The rate of bottom erosion depends primarily on the difference between the protrusion of the river bed over the erosion base level, and also on the gradient of the river bed and the amount of water. Based on this information and the observation of the levels of benches in the river bed, it is possible to evaluate the degree of elevation and the rate of erosion. In turn, comparing these values for various river beds provides information on differences in the elevation rate.

Walking through the valley of the Ochotnica River in Gorce, it is easy to notice flat spaces which constitute river benches. The oldest and the highest are as much as over 60 metres above the current river level. Scientific research carried out in the valley has made it possible to determine the bottom erosion rate (downcutting) of the river. Currently the rate for the Ochotnica and Kamienica rivers is around 1.22 mm per year. However, these two rivers have not always eroded at the same rate. Geological research points to the existence of an overthrust area for two minor units of the Magura nappe (the Krynicka and Bystrzycka nappes) and numerous faults connected with them. The changes in the erosion rate are probably associated with shifts along the faults (Olszak 2009). It is worth pointing out that benches also occur in the tributaries of the Ochotnica River (e.g. the Jamne and Jaszcze streams).

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