Shore Displacement at the Hållnäs Peninsula, Uppland, Central Sweden, Calculated From the Evidence of Old Maps

ABSTRACT

During the latter half of the 18th century quite a large number of Swedish maps was constructed. The question, whether this map material can be used for a study of shoredis-placement is illuminated by a case study from the Hållnäs peninsula in northern Uppland. It was found that, in this case, the old shoreline was not very well mapped. However, a careful analysis of the altitude of areas that were mapped as rocks or skerries on the old maps might provide valuable information about the maximum shore displacement since the map was constructed. Also, levelling of areas that were mapped as sounds or narrow channels on the old maps but are now dry land might provide valuable information about the minimum shore displacement since the map was constructed. An examination of the lowest maximum values and the highest minimum values leaves, in this case, a very small gap which leads to the assumption of a shore displacement in the area of 1.50 m during the last 230 years. This value is well in accordance with observations from the old water mark at Lövgrundet, and extrapolated values from tide-gauge observations.