Subsidence calculation
Configuring overlays
The overlays part of the Subsidence collection of overlays all have a number of ways to configure them. Both values which serve as input for the overlays directly, as references to attributes of areas which provide input for the calculations.
Each overlay part of the Subsidence collection has a "Keys" tab in the right panel in the editor. Most keys are attributes of areas. When the overlay calculates, it will look per grid cell for the existence of these attributes.
| Attribute | Default | Description | Example | Remark |
|---|---|---|---|---|
| Water level | WATER_LEVEL | The surface water level, measured from Amsterdam Ordnance Datum (NAP). | -2.90 | When absent, "0" is assumed. |
| Output Level | WATER_LEVEL_OUTPUT | The attribute to write the final water level value to. | -3.20 | If the water level is indexed, subsidence will cause the water level to lower. By writing it into an attribute, the end value can be used. This option can be disabled by unchecking the related checkbox. |
| Ground Water Level | GLG | The Ground Water Level, measured from the surface of the terrain. | 0.5 | |
| Indexation | INDEXATION | The amount of indexation the water is subject to, from 0 (0%) to 1 (100%) | 1 | The surface water level is lowered each year by an amount equal to the subsidence times the indexation. From the perspective of the surface of the terrain, the water level in a location with 0% indexation will appear to increase as subsidence takes place. |
| Clay Thickness | CLAY_THICKNESS | The thickness of the clay layer on the peat, for the calculation of the oxidation component of subsidence. | 0.2 | When absent, the attribute DEFAULT_CLAY_THICKNESS of the overlay is used. |
| Toplayer Thickness | TOPLAYER_THICKNESS | The thickness of the layer covering the peat, for the calculation of the settlement component of subsidence. | 5 | When absent, the attribute DEFAULT_TOP_LAYER_THICKNESS of the overlay is used. |
| Peat Fraction | PEAT_FRACTION | The fraction of the soil composed of peat, for the calculation of the settlement component of subsidence. | 0.4 | When absent, the attribute DEFAULT_PEAT_FRACTION of the overlay is used. |
| Subsidence | SUBSIDENCE | Whether or not subsidence should be calculated in a given area. Subsidence is calculated when the value is greater than 0. | 1 | When absent, "1" is assumed (and thus subsidence is calculated). |
Besides these attributes, 2 more keys can be configured.
Years
The amount of years to simulate during the calculation, in 1-year steps. It's possible to set this value anywhere between 1 to 1000.
Ground Water Tiff
If the option to use a Ground Water Tiff is checked, a GeoTiff can be selected to use for the ground water levels. By default, a few GeoTiffs are available with open data concerning ground water levels.