Channel typology based on stability criteria. Case study: Ialomita and Buzau watersheds (Romania)

摘要

In the context of Water Framework Directive, we intend to develop a hydromorphological typology oriented toward the stability of river channels. Based on recent topographic profiles and on the maps drawn in the late 1970s, several parameters of the bankfull stage are computed: the ratio between the maximum depth and the height of the lower bank, the ratio between the channel width and its mean depth, the river competence, and the specific stream power. This methodology is applied for 32 cross profiles in the perimeter of the gauging stations lying within the Ialomita and Buzau watersheds. In the case of our study area, three types of channels are distinguished, each showing a different stability under the present conditions: unstable channels susceptible to evolve laterally and vertically; unstable channels susceptible to evolve sideways; and moderately unstable channels. Each of these types includes sub-types differentiated by river competence and sub-sub-types described by channel pattern and characterized by specific stream power. The study confirms the idea that the sinuous channels of the Carpathian streams and the braided channels specific to the Sub-Carpathians and piedmont plains are susceptible to evolve rapidly, whereas the meandering channels belonging to the lowlands of the Romanian Plain have a slower evolution. Beyond this overall picture, the typology leaves room for identifying some particularities due especially to human interventions. Therefore, in perspective, the analysis of hydromorphological features needs to rely also on historical studies.