# Compaction formula (Subsidence Overlay)

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The amount of subsidence due to compaction is calculated by the following formula:

where

- is the calculated subsidence due to compaction.
- is the peat fraction of the respective grid cell c.
- is the top layer thickness of the respective grid cell c.
- The terrain height increase as a result of the actions taken during a session, such as the creation of levees.
- is the number of days in a year times the current year being calculated.
- is the first regression constant (0.015853041) for the effect of the peat fraction and time in days.
- is the first regression constant (0.006617643) for the top layer thickness and time in days.
- is a regression constant (0.200468677) for the change in surface height, for example caused by added materials.
- is the second regression constant (0.02348519) for the effect of the peat fraction.
- is the second regression constant (-0.010061616) for the top layer thickness.

This formula is based on provided expert data in the form of a reference table, indicating the amount of subsidence based on the parameters used in the formula above. The formula's results conform to the reference table to within an average of a tenth of the margin of error of the original table.