It is generally known, that the area of Finland is steadily increasing. The reason is a phenomenon known as post-glacial rebound. During the last ice age the Earth’s crust was depressed 500 metres due to Fennoscandian ice sheets weight.
After the ice melted, the crust started to rise again and the rise is still perceptible today. In Finland, the Land uplift is most apparent in the Mid-Western area (about 10 mm per year) while the slowest is on the Southeast of Finland (3 mm per year).
Since the urban and city planning is one of the FCG:s core services, our objective was to look at what kind of impact this phenomenon will have on the Finnish cities. We tried to use the GIS methods to visualize the shoreline change among two selected cities, Oulu and Rauma, and study, how it will affect the coastal areas.
How is the shoreline length going to change? And what about the total area of available land?
Shoreline Change among Oulu and Rauma
For the reference years we decided to look further enough into the future and picked up the sequence of years up to 2100. Based on the several resources (Geological Survey of Finland & National Land Survey of Finland, 2017) it was deducted that the land rises about 8.5 mm per year in the Oulu region, whereas in around the city of Rauma around 6.5 mm per year.
As the source spatial data, we used the open source national digital elevation data model and the bathymetrical data (National Land Survey of Finland, 2015). We then developed an algorithm using the ESRI’s ArcGIS and got following results.
In the year 2015 the shoreline at the Oulu study area was 148 km long. According to the study, by the year 2100 it will be most probably shortened by more than an half to 62 km.
In the Rauma study area the uplift is not that fast, but the change in length of shoreline is also noticeable. In 2015 the length of shoreline was 370 km and by the year 2100 it will shorten approximately to 220 km, respectively 237 km in the year 2050.
At this point it is necessary to note, that the availability of precise bathymetrical data for the study area was limited and it might bias the results. We might in the future observe creation of new small islands which will probably result in not that significant loss in shoreline length. But in the end, the shoreline length might not be the most interesting value.
Change in Area of Available Land
This phenomenon is also associated with the change in total area of available land, which is actually more interesting value if we consider the city planning. As we all know, city planning is about the area and available land.
While at the studied part of Oulu the total area was 298 km2 in 2015, by the year 2050 it will grow up to 307 km2 and by the year 2100 up to 311 km2.
In Rauma, the total area of available land will be significantly rising as well. Whereas in 2015 the area of study area was 134 km2, we can expect it to be 151 km2 by the year 2100.
Within 85 years, the city of Oulu will gain at the study area more than 10 km2 of land and the city of Rauma around 17 km2. We need to point out, that we are speaking about appreciated shore areas, which are highly valued with sometimes double the prices in comparison to the not much further inner-land situated real estates.
If we really simplify the complexity of real estate economics, we can hypothetically estimate the value of the raw land increase is 30 million euros in Oulu and 51 million euros in Rauma. Aren’t these obvious reasons, why we should discuss the need for long term strategical shore planning, especially among the west-coast situated cities?
The city shore areas should be probably more pragmatically reserved for the city expansion, e.g. on one side for the construction of shore residential areas, on the other side for the promotion of the city green infrastructure. We might also need to evaluate, if we need adequate legal policies to address the ownership of such areas and if we should more carefully bind this value for the future generations.
Or will the glaciers strike back and we anyway loose this potential due to Climate change related rise of the sea levels predicted by the IPCC?
The study was concluded by Denisa Kujovská, Bachelor’s degree programme student at the Czech University of Life Sciences Prague (CULS), during her Erasmus+ traineeship at FCG in the summer 2017.
Jan Tvrdy, Senior Advisor, Urban and Strategic Planning