# 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. | |

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 underground water flow is simulated during the calculation. If this is deactivated, surface infiltration, 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 (1) or everywhere (0). | |

MAX_WATER_DEPTH_M | m | ||

MIN_SLOPE | ratio | The minimum slope required to account for the effect of gravity on the speed of the water. If the slope of the terrain is less than the minimum slope, the effect of gravity on the speed of the water is assumed to be 0. The ratio is the height over distance. | |

QUAD_CELL | boolean | This attribute name is reserved for future functionality. Currently, this marks an experimental feature which is currently under development and may result in unexpected behavior when activated. | |

SEWER_OVERFLOW_THRESHOLD | fraction | 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. The total simulation time is divided by this value, and at each interval of that period of time a snapshot of the results so far is made. Note that the first timeframe does not contain the starting conditions of the simulation, but the state of the simulation after the first period of time has passed. | |

WALL_ANGLE | degrees | The minimal angle for a slope to be considered a wall. Cells that have a wall behavior will slow down and reflect the water's movement considerably. The x- and y-direction are handled separately. |