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| ==What is the rainfall overlay==
| | [[File:Rainfall-Overlay.jpg|thumb|right|200px|Rainfall overlay]] |
| | The Rainfall Overlay is a variant of the [[Water Overlay]], which in turn is a [[Grid overlay|grid overlay]]. Water overlays are connected to the [[Water Module]], a complex hydrological calculation module within the {{software}}. |
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| | The Rainfall overlay specializes in displaying the hazard and impact of (heavy) rainfall over the project area. Based on the elevation model, terrain roughness and representations of the sewer and water systems, several result types can be generated by the accompanying Water Module. |
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| | A [[Rainfall_Overlay_tutorial|Rainfall Overlay Tutorial]] is available to get you started with this overlay. |
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| ==Calculation principles==
| | In order to get more familiar with the different components of the Rainfall Overlay check out Quadrant 2 of the [[Testbed_water_module|Water Module Testbed]]. This Testbed is available to you as a project in the {{software}}. |
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| The basic principle of the calculations is that all water is stored in a grid of containers, representing possible water storage for the data of a given location. The size and location of the containers is based on the size of the [[grid overlay|grid]], and the type of container. Water can flow from some containers to other containers. In the [[#Containers|Containers]] section, more information can be found regarding each type of container. | | ==Rainfall overlay results== |
| | The Rainfall Overlay is a Water Overlay that is connected to the Water Module. This Water Module performs two dimensional grid based water simulations for a large set of input data and parameters, configured mostly through a related [[Water Overlay Wizard]]. When a simulation finishes, the module stores the result in the Rainfall overlay based on the selected result type. Only one result type can be stored per Rainfall overlay. |
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| Most containers are part of a water level area. A water level area is an area which is treated as an area with a single water level set for the surface water. In principle, water never flows between water level areas.
| | The Water Module however, is not restricted to generating only one type of result. Instead it can produce multiple unique result types for one single simulation. |
| | Fortunately it is possible to add additional result type overlays which relate to a particular Rainfall overlay. These are known as [[Result Child Overlay]]s. Again, each child overlay only stores one particular result type. |
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| Water level areas can be connected using weirs. Weirs are structures which allow water to be transferred between bodies of water. In the model, they allow the water level areas to be connected. When the surface water exceeds the height of the weir, water flows from one water level area to the other.
| | Apart from multiple result types, the Rainfall overlay can also store result data of multiple, intermediate simulation results, instead of just a single end result. These intermediate simulation results are known as [[timeframes (Water Overlay)|timeframes]]. |
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| ===Containers===
| | For the full list of result types, see [[Result type (Water Overlay)#List of Result Types|List of Result Types]]. |
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| Here there should be an overview of all the calculations steps within a water level area (peilgebied). BOB: Flowchart?
| | For other results, which are not overlay results, but still related to the simulation for a particular Rainfall overlay, see [[Results (Water Overlay)|Rainfall overlay results]]. |
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| ====Rainfall==== | | ==Module== |
| | A Rainfall Overlay can be configured by opening the Rainfall Overlay Wizard. More in-depth information can be found under each of the categories below. |
| | {{Water Module buttons}} |
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| Water is created in the form of rainfall. The amount of water created per calculation step is based on the amount of calculation steps for the simulation, the duration of the rain, and the amount of rains which falls during that time. Water is created for each [[grid overlay|grid cell]]. Water is never "stored" as rainfall. Directly after being created by rainfall, water can be placed in one of the follow containers:
| | ==References== |
| | # [[Water Module Theory#Formulas|Water model formulas]] |
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| {| class="wikitable" | | {{WaterOverlay output nav}} |
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| | {{Overlay nav}} |
| ! style="width: 250px;"| Can flow to container
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| ! Condition
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| | Sewer
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| | If there is a SEWER [[area]] present, which is defined by the presence of a non-zero SEWER_STORAGE attribute, and there is a building present with the SEWERED attribute ("Connected to Sewer") set to 1, and the sewer container is not yet full, the water is moved directly into the sewer.
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| | Building storage
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| | If there is a building present with the WATER_STORAGE_M attribute ("Water Storage (m3/m2) )") set to a value greater than 0, and the building container is not yet full, the water is moved directly into the building container.
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| | Surface water
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| | If there is surface water present (i.e. a terrain with the WATER attribute set to 1), the water is moved into the surface water container.
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| | Surface container
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| | If there is no building connected to an empty sewer, no building with water storage, and no water terrain, the water is placed in a surface container.
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| |}
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| ====Surface containers====
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| Water in a surface container is resting on the surface of the world. Each [[grid overlay|grid cell]] has its own surface container.
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| The storage capacity of surface containers is effectively infinite.
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| For some calculations, the height of this container is relevant. The height is defined as the [[Terrain height|terrain height]], plus the height of the water in the container.
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| During a calculation step, the water can move to one of the following containers:
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| {| class="wikitable" | |
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| ! style="width: 250px;"| Can flow to container
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| ! Condition
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| | Underground container
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| | If the underground container is not filled to maximum capacity, an amount of water is transferred from the surface container to the underground container, based on the formula for vertical infiltration described below.
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| ''Note: after calculating vertical infiltration, the flow calculations continue, both for the surface containers and the underground containers.''
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| | Surface water or surface container
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| | Water may flow into the surface water container or into other underground containers, based on the flow-by-height principle and the Manning formula (for surface runoff) described below.
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| |}
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| ====Underground containers====
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| Water in underground containers is water which has infiltrated into the ground, and is now resting on, (or is part of) the ground water. Each [[grid overlay|grid cell]] has its own underground container.
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| The storage capacity of underground containers is based on the WATER_STORAGE_PERCENTAGE of the terrain in that location, the ground water level and the height of the surface.
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| For some calculations, the height of this container is relevant. The height is defined as the ground water level height, plus the height due to the amount of water in the container. This also takes into account the WATER_STORAGE_PERCENTAGE. They lower this percentage, the faster the container's height increases.
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| During the calculation step, water can move to the following containers.
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| {| class="wikitable"
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| ! style="width: 250px;"| Can flow to container
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| ! Condition
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| | Surface water or underground container
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| | Water may flow into the surface water container or into other underground containers, based on the flow-by-height principle and the formula for horizontal infiltration described below.
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| |}
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| ====Surface water====
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| Water in surface water containers is water which has been stored on existing bodies of water. These bodies are often intended to house some amount of water in them in cases of rainfall. There is a single surface water container for the entire water level area.
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| The storage capacity of surface water containers is effectively infinite.
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| For some calculations, the height of this container is relevant. The height is defined as the ground water level height, plus the height due to the amount of water in the container. This also takes into account the WATER_STORAGE_PERCENTAGE. The lower this percentage, the faster the container's height increases.
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| During the calculation step, water can move to the following containers.
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| {| class="wikitable" | |
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| ! style="width: 250px;"| Can flow to container
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| ! Condition
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| | Surface container
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| | Water may flow into surface containers, based on the flow-by-height principle and the Manning formula (for surface runoff) described below.
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| |}
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| ====Sewer====
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| Water in the sewer system is stored in underground pipes or other water systems. The sewer is defined using [[area]]s, and each area forms its own sewer, and thus its own container. There can be multiple sewers in the same level area, and sewers may extend beyond level areas.
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| The storage capacity of the sewers is based on the SEWER_STORAGE attribute of the area in that location.
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| Water may disappear from the model entirely by being pumped out of the sewer. This happens at a speed defined by the SEWER_PUMP_SPEED attribute of the area.
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| Water in the sewer does not move into other containers.
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| ====Building storage====
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| Water in building storage is stored on roofs and in gutters. In principle, all [[construction]]s can also store water, but may have a capacity of 0, rendering their containers inaccessible.
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| The storage capacity of buildings is based on their WATER_STORAGE_M attribute ("Water Storage (m3/m2) )").
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| Water never leaves building storage. It does not disappear from the model, nor does it move to a different container.
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| ===Between level areas===
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| ====Weirs====
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| A weir is a structure which connects two level areas. It exists in the Engine as a [[construction]]. It is a structure which can modelled as a small wall between the bodies of water, in this case the surface water containers of the relevant level areas. A weir has a height, defined by the attribute WEIR_HEIGHT_M. When the calculated height of the surface water container of either level area exceeds the height of the weir, water will be moved from the level area with the higher water level to the level area with the lower water level. The speed at which water is transferred is defined by the attribute WEIR_SPEED. This speed is constant, and does not vary with the amount of water in excess of the weir's height.
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| ==Formulas==
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| ===Flow by height===
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| When a flow-by-height calculation is performed, the Engine takes into consideration for each container whether any adjacent containers have a height lower than or equal to the current container's height. All containers which meet this requirement are candidates for receiving water flow. The candidate container for which the flow would be greatest is the single container which actually receives water from the current container. All candidate containers, whether they receive water from the current container or not, can still receive water from other containers.
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| BOB: Diagram van hoogteberekening tussen 2 containers
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| ''To prevent issues with water "slushing" around in rare edge-cases, the direction of flow for surface containers on extremely flat land is "fixed" after the first few calculations. This means that some containers will only ever exchange water in 1 direction.''
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| ===Manning formula (surface runoff)===
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| ===Vertical infiltration===
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| ===Horizontal infiltration===
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| ==Data required==
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| The model can be refined with your own data. The following data can be prepared and uploaded in [[geojson]] format:
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| ===Water level areas===
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| For defining "level areas" with a set water level. This file is loaded in as [[area]]s.
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| {| class="wikitable" | |
| ! Attribute
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| ! Description
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| ! Example
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| ! Remark
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| | NAME
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| | The name of the water level area.
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| | PG 256
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| | This attribute is not loaded in as attribute, but can be used as name to identify the resulting area in the Engine later on.
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| |-
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| | WATER_LEVEL
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| | The height of the water, in meters, measured from Amsterdam Ordnance Datum (mNAP).
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| | 1.6
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| | For a water level area with infinite storage, this can be set to an extreme negative number (e.g. -9999). However, note that this would also place this area far below level areas with a proper height set.
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| |-
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| | OUTLET
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| | The amount of water which disappears from this level area in cubic meters per second (m3/s).
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| | 0.007
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| |}
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| If no water levels exist, a virtual water level area is assumed which covers the entire [[3D world]], with no OUTLET value and a WATER_LEVEL of -1000.
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| ===Sewers===
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| For defining "sewers" which allow for water storage. This file is loaded in as [[area]]s.
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| {| class="wikitable"
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| ! Attribute
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| ! Description
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| ! Example
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| ! Remark
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| | NAME
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| | The name of the sewer.
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| | Sewer North-East
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| | This attribute is not loaded in as attribute, but can be used as name to identify the resulting area in the Engine later on.
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| |-
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| | SEWER_PUMP_SPEED
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| | The speed at which water is pumped out of the sewer, in cubic meters per hour (m3/h).
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| | 1
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| | All areas which are not plots of this kind should either not have PERCEEL as an attribute, or should have it set to 0.
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| |-
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| | SEWER_STORAGE
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| | The amount of water which can be stored in this sewer, in meters (m).
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| | 0.007
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| | The total amount of storage for this sewer is the surface area of the polygon representing this sewer, times this attribute.
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| |}
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| If no sewers exist, the model has no water flowing into sewer containers for storage.
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| It's possible to generate sewers automatically, using the " Create Sewer Areas" function in the editor:
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| {{Editor ribbon|header=3D World|bar=Areas|dropdown=Create Sewer Areas}}
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| ===Weirs===
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| For defining connections between level areas. This file is loaded in as [[construction]]s.
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| {| class="wikitable"
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| ! Attribute
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| ! Description
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| ! Example
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| ! Remark
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| | NAME
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| | The name of the weir.
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| | PG 256
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| | This attribute is not loaded in as attribute, but can be used as name to identify the resulting contruction in the Engine later on.
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| |-
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| | WEIR_HEIGHT_M
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| | The height of the weir, in meters, measured from Amsterdam Ordnance Datum (mNAP).
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| | 1.8
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| | When using this model outside of the Netherlands, the height is in the same scale as the [[Terrain height]] of the project. When an extreme negative value is used, the construction acts like a culvert.
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| |-
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| | WEIR_SPEED
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| | The speed at which water is moved from one level area to the other, in cubic meters per second (m3/s).
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| | 0.007
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| | Once the water level exceeds the height of the weir, the water flows at this constant speed until the water level no longer exceeds the height of the weir.
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| |-
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| | WATEROUTLET
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| | The speed at which this construction also functions as a water outlet, in cubic meters per second (m3/s).
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| | 0.005
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| | This is in addition, and takes precedence, over the water pumped out at WEIR_SPEED.
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| |}
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| If no weirs exist, there are no connections between water level areas and water is not transferred between them.
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