Formation and development of a 1st-order valley network in postglacial areas (the Dębnica catchment)

Abstract

This article describes the formation and development of the 1st-order valley network in the postglacial catchment of the Debnica River (NW Poland). Its valley network is an example of a system of polygenetic depressions, and its 1st-order sections are comprised of denudational hollows and valleys, dissections, and erosional-denudational valleys. In the article, both landforms with no permanent flow and those nourished by groundwater and included in the river runoff network are characterised. In the course of their development, dry valleys have continued to grow in width and length, while the gradient of their bottom has decreased due to slope wash processes. In groundwater outflow zones, in turn, the modelling of their slopes indicate re - treat as a result of seepage erosion and mass movements, which has led to the preservation of their convex parts and the development of a concave section at the foot, passing into the flat bottom of an alcove. In headwater alcoves, which mark the start of a valley or are inserted into older valley landforms, morphological contrasts are enhanced because of an increase in their width and depth, as well as changes in their cross-profile.