Subsidence Overlay overview: Difference between revisions

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[[File:Subsidence-Overlay.jpg|thumb|200px|right|The subsidence overlay]]
The [[Subsidence Overlay]] calculates subsidence by calculating oxidation and compaction in an iterative process to simulate the progression over a configurable number of years.
[[File:Groundwater-Overlay.jpg|thumb|200px|right|The ground water overlay]]
The Subsidence Overlay is an [[Grid overlay|overlay]] that shows which places in the [[3D world]] are subject to subsidence due to oxidation and/or compaction of peat. The [[subsidence calulation|calculations]] can give result about the subsidence, and the effects it has on groundwater levels. To add a subsidence overlay go to Geo Data -> Overlays -> Add Subsidence.


The Subsidence Overlay can be used to calculate the amount of subsidence which takes place on peat soil, specifically due to peat oxidation and compaction. The calculations are specific for peat soil. Separate formulas for other soil types have not yet been implemented. Although it's possible to use the overlay to give an impression of subsidence resulting from other factors, the results will be less accurate. This means that results have a greater margin of error for different use-cases.
===Calculation model steps===
To calculate subsidence, the parameters are initialized based on data available in the [[Project]].
{{gallery
| mode=traditional
| width=250px
| subsidence_step1.png  | The groundwater situation is determined based on an initial groundwater input, and changes to surface water policy.
| subsidence_step2.png  | Terrain properties are determined through present [[Terrain Type]]s, and otherwise based on defaults.
}}
Next, a number of steps are repeated to simulate the yearly subsidence, and to update the intermediately changing parameters for the calculation accordingly. These steps are repeated n times, where n is the amount of [[Years (Subsidence Overlay)|years]] configured.
{{gallery
| width=250px
| mode=traditional
| subsidence_step8.png  | A calculation cycle is repeated for each year the simulation is set to compute.
| subsidence_step3.png  | 3: Oxidation is dependent on configured [[Parameter a recalculation formula (Subsidence Overlay)|climate model]], [[High ground water level prequel (Subsidence Overlay)|high-]] and [[Low ground water level prequel (Subsidence Overlay)|low ground water levels]], [[Peat fraction (Subsidence Overlay)|peat fraction]] and [[Clay thickness prequel (Subsidence Overlay)|clay thickness]].
| subsidence_step4.png  | 4: Compaction is dependent on added soil, settling into itself and pre-existing terrain.
}}<br>
{{gallery
| width=250px
| mode=traditional
| subsidence_step5.png  | 5: Subsidence is computed per cell, based on oxidation and compaction.
| subsidence_step6.png  | 6: Water levels are [[indexation (Subsidence Overlay)|indexed]] (if configured as such), meaning they are adjusted to compensate for subsidence so their height relative to the surface remains the same, or less depending on the indexation percentage.
| subsidence_step7.png  | 7: Ground water levels are recalculated based on the adjusted water levels and the lowered surface.
}}
{{clear}}


It is possible to add multiple subsidence overlays to a project. By varying their configuration slightly, it is possible to calculate multiple scenario's or time-frames simultaneously.
===Overlay Results===


{{Template:Subsidence Module buttons}}
The overlay offers the following result types:
 
{{result types|suppresscategory=true|allowselflinks=true|
  {{:Subsidence result type (Subsidence Overlay)}}
  {{:Oxidation result type (Subsidence Overlay)}}
  {{:Settlement result type (Subsidence Overlay)}}
  {{:Hi ground water result type (Subsidence Overlay)}}
  {{:Low ground water result type (Subsidence Overlay)}}
}}
 
===Legend===
The legend of the subsidence overlays is automatically calculated, based on the amount of years being calculated by the overlay. The colors will remain constant based on average subsidence per year. I.e. if the amount of years is doubled, the values in the legend, corresponding to specific colors, are doubled as well. Because the legend displays total amounts of subsidence rather than averages, the displayed range of amounts changes when the amount of calculation years changes.
 
The legend of the groundwater overlays is constant, and will display a color from blue through yellow to red to indicate how wet the soil is. The closer the groundwater is to the surface of the land, the bluer the overlay. In contrast to the subsidence legends, the range of values for groundwater do not change.
 
<gallery heights=62px mode="packed">
Image:Subsidence30-legend.jpg|Subsidence legend for 30 years
Image:Subsidence60-legend.jpg|Subsidence legend for 60 years
Image:GLG-legend.jpg|Groundwater legend
</gallery>
 
==Output==
The output of all result types of the overlay is in meters. The results can be [[Grid overlay#Export as GeoTIFF|exported as GeoTIFF]].
===Timeframes===
The amount of timeframes generated for the subsidence overlay are determined by [[Years (Subsidence Overlay)]] divided by [[Years per timeframe (Subsidence Overlay)]]
 
===Subsidence output===
The output of the [[grid overlay|grid]] of each subsidence result type is the subsidence in meters. Depending on the exact result type used, the output is the amount of subsidence as the result of one specific calculation, or the sum of all the calculations of subsidence.
 
The [[hover panel]] will display the following information:
* The amount of subsidence taking place over the configured amount of years.
* The current surface water level, and to what level it will have changed after the subsidence has taken place.
* The [[subsidence calculation#Indexation|indexation]] policy currently configured for this water area.
 
===Groundwater level output===
The output of the [[grid overlay|grid]] of each groundwater result type is the final distance from the groundwater level to the surface of the land in meters.
 
The [[hover panel]] will display the following information:
* The level to which the groundwater will have changed, after the subsidence has taken place.
 
===Final water level===
The overlay can also write the final [[Water level output (Subsidence Overlay)|surface water level]] to the [[Water area (Subsidence Overlay)|water area]].
 
{{SubsidenceOverlay_nav}}

Latest revision as of 14:19, 23 February 2023

The Subsidence Overlay calculates subsidence by calculating oxidation and compaction in an iterative process to simulate the progression over a configurable number of years.

Calculation model steps

To calculate subsidence, the parameters are initialized based on data available in the Project.

  • The groundwater situation is determined based on an initial groundwater input, and changes to surface water policy.

  • Terrain properties are determined through present Terrain Types, and otherwise based on defaults.

Next, a number of steps are repeated to simulate the yearly subsidence, and to update the intermediately changing parameters for the calculation accordingly. These steps are repeated n times, where n is the amount of years configured.


  • 5: Subsidence is computed per cell, based on oxidation and compaction.

  • 6: Water levels are indexed (if configured as such), meaning they are adjusted to compensate for subsidence so their height relative to the surface remains the same, or less depending on the indexation percentage.

  • 7: Ground water levels are recalculated based on the adjusted water levels and the lowered surface.

Overlay Results

The overlay offers the following result types:

Icon Result type Unit Mode Description
Overlay icon subsidence subsidence.png SUBSIDENCE m Total The amount that the ground has lowered as a result of subsidence, both oxidation and compaction.
Overlay icon subsidence oxidation.png OXIDATION m Total The amount that the ground has lowered as a result of peat oxidation.
Overlay icon subsidence settlement.png SETTLEMENT m Total The amount that the ground has lowered as a result of compaction.
Overlay icon subsidence hi ground water.png HI_GROUND_WATER m Total The distance between the ground surface and the highest ground water level.
Overlay icon subsidence low ground water.png LOW_GROUND_WATER m Total The distance between the ground surface and the lowest ground water level.

Legend

The legend of the subsidence overlays is automatically calculated, based on the amount of years being calculated by the overlay. The colors will remain constant based on average subsidence per year. I.e. if the amount of years is doubled, the values in the legend, corresponding to specific colors, are doubled as well. Because the legend displays total amounts of subsidence rather than averages, the displayed range of amounts changes when the amount of calculation years changes.

The legend of the groundwater overlays is constant, and will display a color from blue through yellow to red to indicate how wet the soil is. The closer the groundwater is to the surface of the land, the bluer the overlay. In contrast to the subsidence legends, the range of values for groundwater do not change.

  • Subsidence legend for 30 years

  • Subsidence legend for 60 years

  • Groundwater legend

Output

The output of all result types of the overlay is in meters. The results can be exported as GeoTIFF.

Timeframes

The amount of timeframes generated for the subsidence overlay are determined by Years (Subsidence Overlay) divided by Years per timeframe (Subsidence Overlay)

Subsidence output

The output of the grid of each subsidence result type is the subsidence in meters. Depending on the exact result type used, the output is the amount of subsidence as the result of one specific calculation, or the sum of all the calculations of subsidence.

The hover panel will display the following information:

  • The amount of subsidence taking place over the configured amount of years.
  • The current surface water level, and to what level it will have changed after the subsidence has taken place.
  • The indexation policy currently configured for this water area.

Groundwater level output

The output of the grid of each groundwater result type is the final distance from the groundwater level to the surface of the land in meters.

The hover panel will display the following information:

  • The level to which the groundwater will have changed, after the subsidence has taken place.

Final water level

The overlay can also write the final surface water level to the water area.

Subsidence Module
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Subsidence wiki2.png
Subsidence Overlay
Benchmarks button.png
Getting started button.png
Tutorials
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Overview button.png
Overview
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Theory button.png
Theory
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Benchmarks
Group
Model
Overview • Calculation • Theory
Formulas
Parameter a recalculation • Ground water depth • Oxidation • Compaction • Subsidence • Indexation
Related
Features • Model attributes • Rasters • Result type


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