0.8. Environmental context:
Coastal Geology
The site is at a depth of 45m on a flat bottom in open waters, 5 to 6 nautical miles out from the Nässja and Kampudden peninsula west of the town of Vadstena, and ca 1 nautical mile east of the island of Jungfrun in the same lake.
This part of the lake has been denominated as the sediment area of Lake Vättern
(Håkansson and Ahl 1976, p 12 f). The bottom is covered by sand, gravel and clay and is flat and even, with low sand banks with a diffuse horizontal configuration that has been sounded. The site is supposedly inside an area with postglacial to sub aquatic-slope deposits (sand to clay), as well as with silt sediments that have an organic content. For a description and discussion of the character of the lake’s bottom and the sedimentation process in Lake Vättern
(see Norrman 1964, p 113 f and 195 f). For the recent sedimentary, deposits and sediment chemistry (see Håkansson and Ahl 1976). For a description of the topography and sediment distribution on the bottom (also see Norrman, J.O., and Königsson, L-K., 1972).
John, O. Norrman, 1964. Lake Vättern. Investigations on shore and bottom morphology. Medd. från Uppsala Universitets Geografiska Inst., Ser. A, Nr 194 John, O. Norrman, and Königsson, L-K. 1972. The sediment distribution in Lake Vättern and some analyses of cores from its southern basin. Publ. From the Dept of Quaternary Geology, Univ. of Uppsala No 66
Håkansson, L., & Ahl, T., 1976. Vättern – recenta sediment och sedimentkemi.
Lake Vättern – Recent Sedimentary Deposits and Sediment Chemistry. Statens Naturvårdsverk 1976. SNV PM 740 NLU Rapport 88
Climate
Cold temperate climate on the border to warm temperate climate (acc. to the Köppel standards). Relatively little rain (less than 500 mm a year / arithmetic median value). Relatively mild autumns and winters and late springs – due to the influence of the temperature of the Vättern lake water.
Source: Meteorologist Hans Alexandersson, the Swedish State Institute of Meteorology and Hydrology (SMHI).
Flora and Fauna
Does not apply here as the site is in an open water area.
Human impact
The site seems acc. to the damage on the ship to have been subject to disturbance due to trawler fishing and skin diving.
During the latter part of the 1990s an extensive amount of diving by scuba divers took place on the site of the E. Nordevall. Diving tours were arranged to the site by commercial diving companies and others, and marketed in diving journals and on the web.
One can record that this diving has caused disturbance and damage to the hull and its fittings. The number of disturbances seems to have diminished, although possibly not ended completely, since a diving ban was established on the site in 1999. There is nevertheless still a risk that such damage might occur due to the fact that the site is far out in Lake Vättern and therefore difficult to supervise.
(See 2.4 Risk assessment below)
Sedang diterjemahkan, harap tunggu..
