Lerfall ved Ness i Harran.

Abstract

A very big landslip, the biggest one in our country during the period here dealt with occurred on the beach of the Namsen river. It happened a few hundred m upstreams from the bridge Ness. There were no witnesses to the slip, but at the surrounding farms the roar was to be heard, and at the two Ness farms was felt a shaking of the ground supposed to be an earthquake. At daylight the inhabitants observed that a large area of the hills by the river had disappeard. During the following day the river steep was broken over a distance of 220 m, and behind the previous beach a new slope rose to a hight of 43 m above the stream level. The total slipping area amounted to 260 000 sq. m., most of which slid into the river. The profile of the fresh wall showed 2 m of sand and gravel on top of thinner alternating layers of clay and sand. The layers of fine grained sand were no more than 1-2 mm thick, only one of them attaining a thickness of 10 cm. The clay deposit of the deeper layers were weak, but by no means liquid. In accordance with the relatively dry masses the slope of the slided area got an inclination of 1:25, as against relatively wet clay masses where the inclination seldom exceeds 1:100. Probably the landslip started as a falling down of the river steep.