Soil subsidence - Dewatering depth 1.0 meters
Description
Soil subsidence in South Holland has a very strong connection with water management. As a result, it is not possible to make realistic predictions of subsidence over longer periods of time. Instead, the soil subsidence sensitivity has been mapped. For this, it was calculated how much peat oxidation and riveting would theoretically occur over a period of 100 years, at a fixed dewatering depth of 1 m and maintaining the current rising height in the first water-bearing package. Three classes were then made of the calculation results: 'not relevant', 'relevant' and 'special focus area'. The classes reflect variations in the structure of the subsurface. Where sand predominates, subsidence is irrelevant. In clay and peatlands
Soil subsidence does play an important role. Clay areas and areas with a relatively thin peat layer fall into the 'relevant' class. The 'special focus area' comprises the ten percent of the provincial land area with the highest subsidence sensitivity. This mainly concerns areas with a thick peat layer. The map for soil subsidence sensitivity shows that a large part of the peat meadow areas requires special attention from the theme of soil subsidence in design and water management. This is especially true for those areas where the peat occurs directly at ground level and is not covered by clay (including parts of Midden-Delfland, Alblasserwaard, Krimpenerwaard, the area between Gouda and Boskoop and around the Nieuwkoopse Plassen). In the polders around Zoetermeer, the peat has disappeared due to dyeing and soil subsidence is less relevant. Also along the Oude Rijn, on the islands of South Holland and in a wide zone along the North Sea coast, with the exception of the strata between the beach walls, subsidence is not relevant. Three scenarios of subsidence at a fixed dewatering depth of 0.5, 1.0 or 1.5 m are shown below. The soil subsidence sensitivity map was distilled from the scenario with a fixed dewatering depth of 1.0 m. The three scenarios provide insight into the dependence on subsidence for water management. For example, it can be seen that at a dewatering depth of 1.5 m, the area with a subsidence of more than 10 mm/year is more than twice as large as at a dewatering depth of 0.5 m. When zooming in on a specific area or question, it should always be checked whether further information is available.
Resources
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https://geodata.zuid-holland.nl/geoserver/bodem/wfs?service=WFS&version=2.0.0&request=GetCapabilities, https://geodata.zuid-holland.nl/geoserver/bodem/wms?service=WMS&version=1.3.0&request=GetCapabilities |