Breach (Water Overlay): Difference between revisions

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==Features==
==Features==
* The breach can grow over time, based on its initial width, critical speed and inner and outer water level, for more details see [[Breach_growth_formula_(Water_Overlay)|Breach growth formula]].  
* 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)|Breach growth formula]].  


* Instead of using an input area you can also define a fictitious external area, this can repersent 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]].
* Instead of using an input area you can also define a fictitious external area, this can repersent 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]].

Revision as of 12:07, 2 September 2022

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

Overview

A breach area can be defined via the 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 (or external area) into the breach area just behind the levee and vise versa.

Below a simple schematic of the breach elements.

Top Down

Breach-side.png

Side View

Breach-top.png

Features

  • Instead of using an input area you can also define a fictitious external area, this can repersent a larger water body outside the project area, e.g. the entire sea. The external area also has it's own Surface level, Water level and Area.
  • If a 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, called "active", that water will flow in from the input area. The radius of the circle defining the intersection will expand as water flows.
  • Water flowing through or across a breach will flow in the direction defined by the 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 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 attribute 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.
  • The BREACH_HEIGHT attribute can also have multiple values over time, this allows you this simulate the breach vertical growth.

Notes

  • The elevation map covered by the entire breach area is adjusted to at least the minimum height defined by its 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 and outer water levels are visualized per timeframe on the breach object in the 3D map, these can be very useful to see how the breach is progressing.