Anastomosing rivers were historically common around the world before agricultural and industrial development in river valleys. Presently, one preserved example of this type of river in Europe is the Upper Narew River in Poland. The uniqueness of the river determined embracing the 35 km-long section of its length and adjacent valley by formal protection as Narew National Park (NNP) and a Natura 2000 site. At present, the NNP Authorities are implementing a hands-off strategy focusing on maintenance of the processes. To assess the efficiency of such a policy, the current hydromorphological conditions of anastomosing river reach in NNP and the historical changes of the river planform at reach scale were recognized. The hierarchical framework tool (HF) was used for this purpose. Although current processes seem to prefer anastomoses maintenance, an analysis of historical river changes showed an accelerating pace of channel extinction. The anastomosing planform of the Narew was created through natural processes, but it has been maintained through a long history of human use and modification of the river system. The hands-off approach to direct channel management will most likely result in the further loss of anabranches, and hence the hands-on protection strategy seems to be a reasonable solution for protecting the NNP.