Breach (Water Overlay): Difference between revisions

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A breach is a modification to the [[terrain height]], with an optional in- or outflow of water for the hydrological model. This can be used to represent calamitous situations, such as a breach in a levee. Breaches can also be used to easily simulate a terrain height increase, effectively creating a levee.
A Breach area can be used to simulate a breach in a levee or dam. It is identified via the [[Breach_height_(Water_Overlay)|BREACH_HEIGHT]] attribute. Water flowing through the breach originates from a body of water. This body of water can be defined as an input area in the project or a conceptual external water body existing outside the project area. Water can flow through the breach from the input water body to the defined Breach area, and vice versa.  


A breach can either be defined solely as a terrain height modification using its {{inlink|BREACH_HEIGHT}} attribute, or as a connection to a water body outside of the hydrological model by adding attributes related to the external water body. If the breach is only defined as a terrain height change, only water that is already created or defined in some other way in the hydrological model can flow through and from it.
==Attributes==
{{Overlay keys|suppresscategory=true|
{{:breach height (Water Overlay)}}
{{:breach width (Water Overlay)}}
{{:breach angle (Water Overlay)}}
{{:breach coefficient (Water Overlay)}}
{{:breach speed (Water Overlay)}}
{{:breach input area (Water Overlay)}}
{{:breach level area (Water Overlay)}}
{{:external surface level (Water Overlay)}}
{{:external water level (Water Overlay)}}
{{:external area (Water Overlay)}}
}}


If the breach is given the attributes required for the external water body, water will automatically be created or removed uniformly on the breach, depending on the simulated water body "behind" the breach.
==Overlay attributes==
{{overlay attributes|suppresscategory=true|allowselflinks=true|
{{:breach measurement distance m (Water Overlay)}}
}}


The breach can grow over time, based on its initial width and the critical speed at which water may flow. If a {{inlink|BREACH_WIDTH}} is defined, the breach's polygon is intersected with a circle emanating from the centerpoint of the polygon. It is only in that intersection, dubbed the "active breach", that water will flow in from the simulated external water body.. The radius of the circle defining the intersection will expand when the water flowing in from the external water body exceeds the {{inlink|BREACH_SPEED}}. Water flowing in the hydrological model across the breach's surface without explicitly entering or leaving the hydrological model through the breach and its simulated water body does not "count" for the critical speed. All cells in the active breach are considered directly adjacent to the external water body.
{{article end
 
|notes=
The entire breach area is considered lowered to the height defined by its {{inlink|BREACH_HEIGHT}} attribute, even if the active breach does not extend across the entirety of the breach area.
* [[Breach (Water Overlay)|Breach]]es can only be configured for [[Flooding Overlay]]s.
 
|howtos=
Water flowing through or across a breach will flow in the direction defined by the {{inlink|BREACH_ANGLE}} attribute, regardless of whether the water flowed onto the breach from elsewhere in the water model, or from the simulated external water body. If no {{inlink|BREACH_ANGLE}} is defined, water can flow in any direction.
*[[How to add a breach with external area manually]]
 
*[[How to add a breach with input area manually]]
If no critical speed is defined, the active breach will never grow. If no width is defined, the width is assumed to be very large, creating an intersection exactly the size of the polygon.
*[[How to add a breach level area to a breach]]
 
*[[How to import a breach with input area]]
{| class="wikitable"
*[[How to set dynamic breach height]]
! Attribute
*[[How to visualize multiple sequential breaches (Water Overlay)]]
! Unit
*[[How to inspect breach output attributes of an overlay using the measurement tool]]
! Description
|seealso=
! Default (when attribute is not present)
* [[Breach model (Water Overlay)]]
|-
* [[Elevation model (Water Overlay)]]
|{{anchor|BREACH_HEIGHT|BREACH_HEIGHT}}
* [[Breach growth formula (Water Overlay)]]
|{{mdatum}}
* [[Breach flow formula (Water Overlay)]]
|The new [[terrain height]] at the location of the breach.
* [[Object width output (Water Overlay)]]
|n/a
}}
|-
{{WaterOverlay hydrological features nav}}
|{{anchor|BREACH_WIDTH|BREACH_WIDTH}}
|m
|The radius of the breach as drawn on the polygon defining the breach, emanating from the center point.
|10000
|-
|{{anchor|BREACH_ANGLE|BREACH_ANGLE}}
|{{geoangle}}
|The angle at which water can flow from the breach.
|n/a
|-
|{{anchor|BREACH_SPEED|BREACH_SPEED}}
|m/s
|The speed at which water should flow through the breach before the width begins to increase.
|n/a
|-
|{{anchor|EXTERNAL_SURFACE_LEVEL|EXTERNAL_SURFACE_LEVEL}}
|{{mdatum}}
|The height of the bottom of the external water body behind the breach. The lowest level the external water level can lower to.
|0
|-
|{{anchor|EXTERNAL_WATER_LEVEL|EXTERNAL_WATER_LEVEL}}
|{{mdatum}}
|The water level of the external water body behind the breach. The initial level the water level is set to.
|0
|-
|{{anchor|EXTERNAL_AREA|EXTERNAL_AREA}}
|m²
|The surface area of the external water body behind the breach. The larger the external water body, the more water can flow from it, and the smaller the effect of the inflow or outflow of water on the external water level.
|n/a
|}

Latest revision as of 15:22, 30 January 2024

A Breach area can be used to simulate a breach in a levee or dam. It is identified via the BREACH_HEIGHT attribute. Water flowing through the breach originates from a body of water. This body of water can be defined as an input area in the project or a conceptual external water body existing outside the project area. Water can flow through the breach from the input water body to the defined Breach area, and vice versa.

Attributes

Overlay attributes