Possible role of stream piracy in evolution of drainage network in Pasmo Połonin: the Roztoki Stream valley (Bieszczady Wysokie, Polish Carpathians)

Stream piracy is proposed to explain unusual relief of two neighbouring valleys in the Bieszczady Mountains, SE Poland. The Muczny Stream for more than 2 km of its headwater course is an underfit stream and the upstream continuation of its former valley is traceable in the present-day Roztoki Stream. The Roztoki Stream broke through its former right bank along a zone of a large tectonic fault, where disintegrated and displaced rocks provided routes for water escape by sapping toward the San valley. The barrier was weakened and destroyed by groundwater sapping, mass wasting on its distal side and headward erosion at the outflows of the escaped water. The gradient of the stream increased, resulting in incision of bedrock in the stream’s lower course and in construction of an alluvial fan whose size is exceptional for the area. Headward erosion created a deeply incised channel, outstanding in narrowness and depth among the other stream channels in the area. Incision of this channel, in turn, provoked capture of a nearby eastward stream that had been flowing straight to the San in a broad gentle valley. Headward erosion after the capture led to incision of a deep and narrow channel in the bottom of this old gentle valley.

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Opracowanie rekordu ze środków MNiSW, umowa Nr 461252 w ramach programu "Społeczna odpowiedzialność nauki" - moduł: Popularyzacja nauki i promocja sportu (2021).