Breach (Water Overlay): Difference between revisions

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A Breach area can be used to simulate a breach in a levee or dam.
A Breach area can be used to simulate a breach in a levee or dam.
==Overview==
A Breach area can be defined via the [[Breach_height_(Water_Overlay)|BREACH_HEIGHT]] attribute. It can have an input area or external area with a water body outside of the hydrological model. Water can flow through the breach form the input into the Breach area just behind the levee and vise versa.
The breach is simulated as a generic [[Breach_flow_formula_(Water_Overlay)|weir]] with breach characteristics that models the energy loss, the weir input/output is dynamically mapped onto the 2D grid cells. Using the [[Breach_growth_formula_(Water_Overlay)|Verheij–van der Knaap]] method the breach can also grow over time from phase one deepening to phase two widening. Below a simple schematic of the different breach elements.
Side View
[[File:breach-side6.png|left]]
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Top View
[[File:breach-top5.png|left]]
{{clear}}
==Features==
* The breach can grow over time, based on its initial [[Breach_width_(Water_Overlay)|width]], [[Breach_speed_(Water_Overlay)|critical speed]] and inner and outer water level, for more details see [[Breach_growth_formula_(Water_Overlay)|Verheij–van der Knaap growth formula]].
* With larger breaches the water level inside the breach area can become turbulent. Therefor the inner water level (used for breach growth) is measured at a distance defined in [[Breach_measurement_distance_m_(Water_Overlay)|BREACH_MEASUREMENT_DISTANCE_M]] behind the breach area when an [[Breach_angle_(Water_Overlay)|BREACH_ANGLE]] is provided.
* Instead of using an input area you can also define a fictitious external area, this can represent a larger water body outside the project area, e.g. the entire sea. The external area also has it's own [[External_surface_level_(Water_Overlay)|Surface level]], [[External_water_level_(Water_Overlay)|Water level]] and [[External_area_(Water_Overlay)|Area]].
* If a [[Breach_width_(Water_Overlay)|BREACH_WIDTH]] attribute is defined, the breach's polygon is intersected with a circle emanating from the center-point of the polygon. It is only in that intersection, called "active", that water will flow in from the input area. The radius of the circle defining the intersection will expand as the breach grows over time.
* Water flowing through the breach will flow in the direction defined by the [[Breach_angle_(Water_Overlay)|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. When no [[Breach_angle_(Water_Overlay)|BREACH_ANGLE]] is defined, water can flow in any direction. Adding this attribute with also convert the breach advection speed (m/s) into the 2D cell of the breach area. It is recommended to always use this attribute for optimal flow.
* If no [[Breach_speed_(Water_Overlay)|BREACH_SPEED]] attribute is defined, the active breach will never grow.
* If no width is defined, the width is assumed to be very large, using the full Breach area polygon.
* The [[Breach_height_(Water_Overlay)|BREACH_HEIGHT]] attribute can also have multiple values over time, this allows you this simulate the breach vertical growth.
==Notes==
* The elevation model covered by the entire breach area is lowered to at least the minimum height defined by its [[Breach_height_(Water_Overlay)|BREACH_HEIGHT]] attribute. This is to prevent the terrain height from interfering with the flow.
* When using breach growth the inner water level is computed from the average value in the active breach area. For optimal flow simulation it is therefor recommended to place the breach area just behind the levee on a flat space.
* Water on a breach area is automatically spread across the entire active breach area equally.
* The inner/outer water levels and breach width are visualized per timeframe on the breach object in the 3D map, these can be very useful to see how the breach is progressing.
* The [[Base_types_result_type_(Water_Overlay)|Base Types Result]] child overlay can be used to see which part of entire the breach area is considered "active". Breach growth can be seen when checking multiple timeframes.
* You can also optionally change the default breach weir coefficient to model energy loss by adding a [[Weir_coefficient_(Water_Overlay)|WEIR_COEFFICIENT]] attribute to the Breach area.
* When the water level of in the input area drops over time the flow can also reverse, flowing back into the e.g. the river/sea.


==Attributes==
==Attributes==
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{{Overlay keys|suppresscategory=true|
{{:breach height (Water Overlay)}}
{{:breach height (Water Overlay)}}

Revision as of 13:24, 12 January 2023

A Breach area can be used to simulate a breach in a levee or dam.

Attributes

Icon Key Unit Range Description Default value
Waterwizard icon breach height.png BREACH_HEIGHT m + datum The new terrain height at the location of the breach. n/a
Waterwizard icon breach width.png BREACH_WIDTH m The initial width of the breach. 10000
Waterwizard icon breach angle.png BREACH_ANGLE geo angle (0-360°) -1.7976931348623157E308 to 1.7976931348623157E308 The angle at which water flows out through the breach. n/a
Waterwizard icon breach coefficient.png BREACH_COEFFICIENT coefficient The flow coefficient related to the shape of the breach. 1.37
Waterwizard icon breach speed.png BREACH_SPEED m/s The critical speed factor in the breach width grow-formula (e.g. 0.2 for sand and 0.5 for clay). n/a
Waterwizard icon breach input area.png BREACH_INPUT_AREA ID of an Area The Area item representing the influx area for the breach. none
Waterwizard icon external surface level.png EXTERNAL_SURFACE_LEVEL m + datum The height of the bottom of the external water body behind the breach. The lowest level the external water level can lower to. 0
Waterwizard icon external water level.png EXTERNAL_WATER_LEVEL m + datum The water level of the external water body behind the breach. The initial level the water level is set to. 0
Waterwizard icon external area.png 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 (or into it), and the smaller the effect of the inflow or outflow of water on the external water level. When provided with a second value, this key will also define a bottom area for the external water body, transforming its cross-section from a rectangle to a trapezoid. n/a

Overlay attributes

Icon Attribute Unit Range Description Default value
Waterwizard icon breach measurement distance m.png BREACH_MEASUREMENT_DISTANCE_M m Distance from the breach area to the automatically placed measurement point for the downstream water level of the breach, in the direction of the breach. 100

How-to's

Videos

Modeling breach growth

See also

Water Module
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Introduction button.png
Water Module
Benchmarks button.png
Getting started button.png
Tutorials
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Overview button.png
Overview
Benchmarks button.png
Theory button.png
Theory
Benchmarks button.png
Benchmarks button.png
Benchmarks
Group
Water area
Water level • Water relative
Sewer area
Sewer storage • Sewer pump speed
Inundation area
Inundation level
Aquifer
Aquifer kd • Aquifer datum
Breach
Breach height • Breach width • Breach angle • Breach coefficient • Breach speed • Breach input area • Breach level area • External surface level • External water level • External area
Rain area
Rain m
Limitation area
Limit area
Output
Object flow output • Object height output • Object datum output a • Object datum output b • Object width output
Related
Building attributes • Hydraulic structures •  Terrain attributes • Model attributes • Results • Simulation data
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