View source for Uitgangspunten falen keringen template

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This page describes the assumptions that are used as input for the [[Falen_keringen_template|falen keringen template and manual]]. 

===Introduction===
The [[Falen_keringen_template|manual]] describes the steps that need to be taken to quickly and in an efficient manner create a new {{software}} project with a flooding scenario. The following settings/presence of data influences the accuracy and outcome of the calculation (in order of importance):
* The size of the breach
* The upstream (?)water level of the breach
* Capacity of water body upstream(?) breach (how quickly does the water level lower as a result of the breach?)
* Grid size
* Culverts in (the to be) inundated area
* Initial water level in (the to be) inundated area
Below the assumptions about these settings are explained in more detail.

====Breach size====
A [[Breach_(Water_Overlay)|breach]] is a modification to the [[Terrain_height_(Water_Overlay)|terrain height]], with an optional in- or outflow of water for the hydrological model. With breach size, the placement of the active breach area in the 3D model is meant. This breach area can be imported or manually drawn. In the [[Falen_keringen_template|falen keringen manual]], the breach area is drawn in he 3D world.

====Breach water level area====
In the {{software}} there are two methods of determining the amount of water that will flow through the breach: with an [[Breach_input_area_(Water_Overlay)|internal area]] or an [[External_area_(Water_Overlay)|external area]]. For this [[Falen_keringen_template|falen keringen template]], the external area is used, since it is easier to determine in the [[Water_Overlay_Wizard|wizard]] the parameters for the external area and it is not necessary to import water depth data of the main system to calculate a correct capacity of the water body. On the other hand, by using an external area, it is not possible to see the water in the main system lower to a different water level.

====Breach capacity====

====Grid size====
The [[Grid_Overlay#Grid_size|grid cell size]] influences the accuracy and the calculation time of the project. Since is assumed that projects are rather larger (magnitude: .. x .. km or larger), the grid cell size is set to 2 x 2m. Also, the [[Calculation_preference_formula_(Water_Overlay)|calculation preference]] is set to ''normal''.
(Note: outcome of tests should be added.)

====Culverts====
By default in the {{software}} in the Netherlands and where available, culverts are imported from the [[Project_Sources|IMWA]] dataset. Due to the unknown [[Culvert_diameter_(Water_Overlay)|culvert diameter]] of these hydrological constructions, the default diameter of 1m is used. Through tests, this default diameter proved to show differences in Flooding results, therefore in the [[Falen_keringen_template|manual]], culverts with their known [[Culvert_diameter_(Water_Overlay)|diameter]] need to be imported. Other hydrological constructions such as [[Weir_(Water_Overlay)|weirs]] and [[Pump_(Water_Overlay)|pumps]] proved to be insignificant for this use case.

====Water level====