Model attributes (Water Overlay)

The water overlay's model calculations depend on a number of calculation-wide parameters. These parameters are available as attributes of the water overlay and can be modified as such.

Attribute	Unit	Description
ALLOWED_WATER_INCREASE_M	m	The amount by which the water level on a water terrain must increase before it is considered stressed by water. This is used to compute the WATER_STRESS result type.
CULVERT_DEM_THRESHOLD_M	m	The maximum distance a culvert's height can be below the terrain, for the terrain height to be adjusted to the height of the culvert.
DESIGN_FLOOD_ELEVATION_M	m	Constructions in the 3D world are assumed to have at most this height compared to the surface of the terrain. Greater values can create a more accurate model but will impact performance.
GRAVITY	m/s²	Used constant for gravitational acceleration.
GROUND_BOTTOM_DISTANCE_M	m	Assumed distance under the terrain surface where the soil becomes impenetrable for water. The groundwater level cannot go below this depth, relative to the surface. The maximum amount of water that can be stored underground is equal to this attribute multiplied by the local terrain's WATER_STORAGE_PERCENTAGE.
GROUND_WATER	boolean	Whether water in the underground is simulated during the calculation. If this is deactivated, surface and underground infiltration, and underground evaporation do not occur. Water flowing in- and out of the sewer are still simulated when sewers are present.
IMPACT_FLOOD_THRESHOLD_M	m	The amount of water a construction must experience before it is considered impacted by water. Water must reach this height either on one of the cells the construction is on, or on one of the cells adjacent to it. This is used to compute the IMPACTED BUILDINGS result type.
LIMIT_RAIN	boolean	Whether rainfall locations should be limited to water level areas, or rainfall will fall in the entire project area.
MAX_WATER_BOTTOM_M	m + datum	The maximum height for the bottoms of water terrains. Any water terrain with a bottom at a higher datum height has its bottom lowered to this value.
MAX_WATER_DEPTH_M	m	The maximum depth of water on a cell that is able to move horizontally. This parameter can be set to influence the wave part in the Saint-Venant equations.
OBJECT_CORRECTION	boolean	Objects (culverts, pumps, weirs) sometimes overlap each other and then one object becomes inactive. When this happens the rasterizer automatically moves the object start/end point by a maximum of one cell so both object are connected.
OBJECT_CORRECTION	boolean	When a Waterway polygon is not correctly positioned in relation to the DEM this can result in filling up the nearby land with water at the start of the simulation. Although this is not much it will result in a lower water level then is to be expected from the water area value. To correct this we have added a "shoreline" at neighbouring cells. These shoreline cell will also be filled with water from the start, thus preventing the flush.
SEWER_OVERFLOW_THRESHOLD	fraction (m/m)	How much of a sewer's storage must be filled with water before the sewer's overflows are allowed to overflow water.
SHOW_DURATION_FLOOD_LEVEL_M	m	The amount of water which must be present in a specific location before the duration of surface water can be recorded. This is used to compute the SURFACE_DURATION result type.
SURFACE_WATER_EVAPORATION_FACTOR	factor	The factor by which the weather's evaporation factor is multiplied to compute the amount of evaporation which takes place on the surface.
TIMEFRAMES	integer	The number of intermediate results recorded during the calculation. Each timeframe becomes a snapshot of data which can be viewed and analysed.