Recent channel planform evolution of a braided-wandering river using multitemporal data and GIS (case study of the Belá River, Slovak Carpathians)

The paper aims to the identification of the recent channel planform evolution of the braided-wandering Belá River using multitemporal data analyses of channel parameters in GIS (river active zone width, channel number, island number and mid-channel bar number) within consecutive 100-m-long channel segments (227 in total) for seven time horizons (1949, 1961, 1973, 1986, 1992, 2003 and 2009). The main types of planform (single, braided and wandering) of 227 channel segments were shown in the spatiotemporal matrix. Prevailing occurrence of a channel planform types in an individual CHS within seven time spans more than 4 times served as minimum for the discrimination of the trend of planform evolution during last sixty years. Seven evolutionary trends (B – braided, W – wandering, S – single thread, S-W – single-wandering, W-S – wandering-single, B-W – braided-wandering, W-B – wandering-braided) of planform were identified. The averages of confinement ratio were used to specify their longitudinal diversity. The largest proportion of the braided planform was identified in 1949. The stabilization of in-channel landforms and channel narrowing between years 1973 and 1992 reflect the prevailing of wandering channel planform. Situation has been changed in 2003 where the number of channel segments with braided channel planform increased. The last evolutionary period (2009) is specific by mid-channel bar stabilization and its transformation into islands as well as by significantly decrease in braided channel planform at the expense of the transitional – wandering one