Water area (Subsidence Overlay)

Water level areas are areas of which the water level is managed by a water authority. Water levels have to be kept high enough such that subsidence is minimized but low enough such that agriculture can flourish. When subsidence occurs, the subsidence model supports the mechanism of indexation in which water levels are automatically lowered to keep the ground water levels at a similar level. The subsidence terrain keys can all be overridden by overlapping Water level Areas.

Icon	Key	Unit	Range	Description	Default value
	WATER_LEVEL	m + datum		The datum height of the water level in the Water Area.	n/a
	CLAY_THICKNESS	m		The thickness of the clay layer on the peat, for the calculation of the oxidation component of subsidence.	0.2
	PEAT_FRACTION			The fraction of the soil composed of peat, for the calculation of the compaction component of subsidence.	0.4
	TOPLAYER_THICKNESS	m		The thickness of the layer covering the peat, for the calculation of the compaction component of subsidence.	1.2
	SUBSIDENCE	boolean		Whether or not subsidence should be calculated for a terrain or in a given area. Subsidence is calculated when the value is not equal to 0.	false
	INDEXATION	m		When Indexation is non zero, the water level is automatically adjusted each simulation year, depending on the calculated subsidence. Indexation may range from 0 (0%) to 1 (100%).	10.7
	WATER_LEVEL_OUTPUT	m + datum		The new datum height of the water level in the Water Area as a result of indexation in response to subsidence.	n/a

Notes

• In the subsidence models, water levels of water areas only influence the ground water level indirectly. Automatic adjustments of water levels, by indexation, do not always lower the ground water level in the same amount.

See also

• Indexation formula

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Subsidence Module

Subsidence Overlay

Tutorials

Overview

Theory

Benchmarks

Group

Subsidence features

Model

Overview • Calculation • Theory

Water area

Water level • Water level output • Indexation

Ground water level

Hi ground water level • Low ground water level

Subsidence area

Peat fraction • Clay thickness • Toplayer thickness • Subsidence

Terrain

Peat fraction • Clay thickness • Toplayer thickness • Subsidence

Drainage

Drainage

Related

Model attributes • Rasters • Result type •  Subsidence Model