Morfologiske og sedimentologiske spor av en paleokanal. Effekten av en enkelt flomhendelse i Ottaelva

Abstract

The main purpose of this master`s thesis is to look for geomorphologic and sedimentary traces of a palaeo channel in Bismo, to examine a previous avulsion. After a remote sensing of the area, a topographical trace was found and assessed important for the case study. Seven cross sections were measured in this hollow topographical trace and four cross sections in the active river channel for comparison, and soil samples were collected from the stratigraphic sequence in six profiles. Geomorphologic traces as flood plain, river banks and bars were observed, and the sediment in those areas showed fluvial deposits associated to processes before and after the avulsion. The topographical trace is hence interpreted as an ancient river channel, which signifies that an avulsion in fact has occurred in the Otta River. The characteristics of the present river channel can interpret to occurred during flood, thus the avulsion probably happened during Storofsen which had a significant impact on the landscape.