The Eidefoss electricity company, Vågå local council and Glommen & Laagen Landowners association set up a flood-water depth marker alongside the picnic site by road 15 west of Lalm in 1989. Here, the water level of the Ottaelva river can be studied during flood periods. The highest ever flood height was in 1789 when the terrible flood occurred on the 20th of July after much rain and high temperatures. The flood damage was the worst in the history of the area. Water and avalanches of mud pushed houses and farms into the river, and the valley landscape was greatly changed. Lake Mjøsa was filled with houses, trees and other vegetation and the water was like porridge. When the rain stopped on the 24th of July, 68 people and 900 animals had lost their lives. 1082 houses were destroyed as well as comprehensive destruction of nature.