Man's impact on the transformation of channel patterns (the Skawa River, southern Poland)

Abstract

The research objective was to answer the question, how and why have the patterns of the channels of the lower course of the Skawa River changed over the past 200 years? This problem is important in the context of contemporary waterway construction plans in Poland. Overall, this study shows the effects of natural restoration in the event of the destruction of bank protections. The Skawa River is a mountain tributary of the Vistula River (southern Poland). In the first step, the channels were classified in the period from the 19th to the 21st centuries. In the second step, it was checked how channelization, water damming, gravel mining, embankment construction, changes in the forest area and channel incision, determined the change of the channel patterns. There were four periods in the functioning of the Skawa riverbed. In the first period (before 1901), the reaches of a natural riverbed were sinuous, braiding, or anabranching. In the second period (1901–1943), the riverbed was completely channelized. In the third period (1943–2003), the riverbed had artificial, braiding, and sinuous reaches. In the fourth period (after 2003), the riverbed had high energy anabranching and sinuous reaches. This study shows that man led to the transformation of the Skawa River channel due to the building of the network of navigable canals and rivers. This study shows how various factors can determine changes in the channel pattern, and that the destruction of bank protections enables natural restoration and forming the braided or anabranching channel pattern.

Influence of 200 Years of Water Resource Management on a Typical Central European River 

“…Witkowski evaluated sinuosity, the braiding and anastomosing index as well as the average number of mid-channel forms and the average distance of the outer banks of the river channel [94]. Although indicators and proceeding slightly differ from the present study, findings are very comparable.…”

“…For the Skawa River which is a mountain tributary of the Vistula River, five digitalized maps from the mid-19 th century until 2016 were evaluated to explain the human impact on the river [94]. As the Rur River in its upper reach, the Skawa River is a gravel embossed river [94].…”

“…Although indicators and proceeding slightly differ from the present study, findings are very comparable. In the early 20 th century agriculture and settlements in the floodplain of the Skawa River led to the construction of embankments [94]. Between 1864 and 1911 islands reduced and the bed narrowed, meaning that anastomosis structures decreased [94].…”

“…In the early 20 th century agriculture and settlements in the floodplain of the Skawa River led to the construction of embankments [94]. Between 1864 and 1911 islands reduced and the bed narrowed, meaning that anastomosis structures decreased [94]. On the Rur River a drop in islands also correlates with increasing settlements and agriculture in the floodplains (cf.…”

“…In the mid-20 th century, the riverbed of the Skawa River was completely channelized [94]. Since the 21 st century more anabranching structures occurred and sinuosity increases again after removal of riverbank protections on the Skawa River [94]. The channel width is increasing again since the late 1970s.…”