Compaction formula (Subsidence Overlay)

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

Subsidence = (Peat fraction * PEAT_A + Top layer * TOP_LAYER_A) * log10(days)
+ Peat fraction * PEAT_B
+ Top Layer * TOP_LAYER_B
+ Height Increase * HEIGHT

• The peat fraction and thickness of the top layer are attributes in the project. The exact attributes which provide these can be configured as keys in the overlay.
• The height increase is a result of the actions taken during a session, such as the creation of levees.
• The days are equal to the number of days in a year, times the current year being calculated.
• PEAT_A (0.015853041) is a constant, for the effect of the peat fraction over time.
• PEAT_B (0.02348519) is a constant, for the base effect of the peat fraction.
• TOP_LAYER_A (0.006617643) is a constant, for the effect of the top layer thickness over time.
• TOP_LAYER_B (-0.010061616) is a constant, for the base effect of the top layer thickness.
• HEIGHT (0.200468677) is a constant, for the base effect of the height of added materials.

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.