# 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.

Icon | 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 threshold 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 | nominal value | Whether and how water in the underground is simulated during the calculation. | |

GROUND_WATERTABLE_WITH_SURFACE | boolean | Whether the ground watertable result type should also include the surface water level, when the groundwater levels are close to the surface. | |

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 | nominal value | Whether and how calculations in the simulation should be limited to specific locations of the 3D world. | |

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. | |

MINIMAL_CULVERT_DIAMETER_M | m | The minimal culvert diameter in meters. | |

OBJECT_CORRECTION | boolean | Objects (culverts, pumps, weirs) can sometimes overlap each other and then one or more objects become inactive. When this happens the rasterizer automatically moves the inactive object(s) start/end point(s) by a maximum of one cell so the object(s) become active. | |

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. | |

SHORELINE | 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. This will result in a lower water level then is expected from the water level area value. To correct this, a "shoreline" is added at neighbouring cells. At the start of the simulation, these shoreline cells will also be filled with water up to the nearby water level to prevent the initial flush. By default this option is turned on, but can be turned off by changing the attribute to 0. | |

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. |