Coupled 1D–Quasi2D Flood Inundation Model with Unstructured Grids
When an Asset Becomes a Curse. Isostatic uplift and 17th century military planning – old causes...
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Isostatic uplift and 17 th century military planning – causes for the flooding of a historic Swedish town EAA Glasgow 2015 – Session LV 4 Claes Pettersson, archaeologist Jönköpings County Museum Sweden [email protected] Fredric Jonsson, Fire Protection Engineer Fire and Rescue Services, Jönköping Municipality Sweden [email protected]
Transcript of When an Asset Becomes a Curse. Isostatic uplift and 17th century military planning – old causes...
Isostatic uplift and 17th century military planning – causes for the f looding of a historic Swedish town
EAA Glasgow 2015 – Session LV 4
Claes Pettersson,
archaeologistJönköpings County [email protected]
Fredric Jonsson,
Fire Protection EngineerFire and Rescue Services, Jönköping [email protected]
…or rather an inland fjord?
Jönköping – pop. 123 000Founded in the 13th century / relocated in 1613Situated on the southern end of Lake Vättern
Length = 135 km / Width = 31 kmMax depth = 120 mVolume = 77,6 billion m3 water
Motala ström –the sole outlet
The New Jönköping – a 17th century State of the Art Design
A strategically important border fortressPlanned according to Simon Stevins’ principlesWater and wetland being its first line of defence
The town in 1690
Draft from 1619
Landfill made by private owners 1640 – 1800
Sand – landfill funded by the Crown in the 1610s
Where to build:
“The Morass”- a peat bog…
Where to build:
On timber caissons and landfill…
An estimated 20 000 wagon loads of landfill was needed before any of the houses in the new town could be built…
Casemates in the Carolus bastion; Jönköping Castle, built in the 1610s Stone cellar built in 1618, issued with a number of floor levels due to rising ground water
The ground water level in the central part of historic Jönköping (the 17th century town) has risen with an estimated 40 cm due to the isostatic uplift. Thus drowning previously dry floor levels and other remains.
Jönköpings railway station during an ice-storm in 1928
A street in the 17th century town during the flood of 1920
In the 400 years that has passed since the fortress town was built numerous floods and severe storms have caused severe damage in Jönköping
No margins – a northerner hits town in the 1940s
Todays’ situation: Areas in the historic town that will be flooded if the water table rises with between 0,5 and 1 meter
The average water level in Lake Vättern:
+ 88.52 meters above the sea level with a normal span of variation from + 87.92 to + 88.95 as seen on a yearly basis. (Source: SMHI)
But during heavy rainfall rapidly rising water levels in streams and lakes south of the historic town centre might spill over into the build up areas.
2013 – 63 mm in 30 minutes flooded the Ryhov hospital area…
Jönköping valley today – after landfill A thousand years from nowFive hundred years ago
The isostatic uplift will slowly drown the historic city centre - Lake Vättern moves southwards
Measures to slow down the consequences:• Levees protecting the core area• Increased water-flow in the outlet, Motala Ström• New built-up areas planned in safe levels
(Source: SGU)
Living very close to water – something essential?
Jönköping in 2030 – with a new district south of the lakes
The Vision:
• 150 000 inhabitants in 2030
• A new district south of the lakes
• …partly built on former wetland
• High speed railway
+ 90,3 meters above sea level = the lowest safe level for new housing
Hydropower and fisheries share a long tradition in the Motala StrömRiver
Drainage area for Lake Vättern
Water level in Jönköping 1900 to 2006
Difference in water level between Motalaand Jönköping 1900 to 2006
A more rapid isostatic uplift in the northern end of Lake Vättern results in a water level rising with 1,1 to 1,7 mm yearly in Jönköping
A bronze age cairn in Huskvarnabay:
• Diameter 20 meter• Height 2 meter• Today 5 meters below the surface
The Huskvarna Bay offers a quite unique submerged inlandlandscape. A lagoon at the river mouth, an oak forest, a peatbog. Plus a number of man made features like cairns, polesand timber constructions. Finds include two swords and atorque from the bronze age, deposited in the bog.
Mårup Church in Denmark – soon to fall off the edge Rosenlundsbankarna – erosion and a changing coastline caused by isostatic uplift
Although far less spectacular than the rapidly retreating coastline in Danish Western Jutland, the erosion in the south Vättern basin continues with at least 20 – 30 meter in a century.
Close to the Rosenlund Heights the Sanna parish church disappeared in the 16th century.
Old place-names indicates that there might have been Pre-Christian cemeteries too, using the magnificent setting.
Kristianstad – built on a small island among lakes and marshes. A late 17th century map
Two medieval towns discontinued, being replaced by Kristianstad
The same conflict – The Kalmar War of 1611 – 1613
The same causes – Old towns devastated
The same solutions – Fortress towns in Dutch fashion
…and the same problems – re-occurring floods!
Kristianstad on the brink of disaster in 2002…
By rowboat in the city centre in 1928(+ 2.23 m above sea level)
Makeshift levee in the city centre 2002 (+ 2.15 m above sea level)
With a changing climate historic Kristianstad is even worse off than Jönköping, being situated between + 4 meter above and – 2.41 meter below sea level…
Normal water levels Worst case scenario today – with a rise of 2 meters + failing levees
New levees -safeguarding the city against seasonal floods
… but will that be sufficient in times of a changing climate?
Strategic considerations makes lousy town planning… Plans for the future
The paradox – fortress towns once protected by water …became civil towns threatened by that same fluid
Jönköping in the 21st century:
• A historic city centre• Plagued by re-occurring floods since its foundation• Isostatic uplift makes things worse …and unstoppable• Experiences from the past – a help in the present• Archaeological data combined with written sources becomes
an asset in todays planning!
