Edge effects (Water Overlay): Difference between revisions

From Tygron Support wiki
Jump to navigation Jump to search
← Older edit
Frank@tygron.nl (talk | contribs)
Tygron, Tygron_admin, Bureaucrats, Interface administrators, Administrators
46,429 edits
No edit summary
No edit summary
 
(17 intermediate revisions by 5 users not shown)
Line 1: Line 1:
{{stub}}
When the Water Module calculates the flow of water, it can "freely" flow across the entirety of the map, until it reaches the edge of the project area. Water cannot flow in or out of the project edge. It behaves as an impenetrable barrier and causes water to bounce back. Edge effects include both the lack of external water flow and the behavior of water bouncing off the boundary.


{{Water Module buttons}}
All hydrological models require some forethought on the existence of edge effects when performing hydrological calculations and analyses. Depending on your use-case, you can consider doing any or all of the following to account for edge effects.


When the Water Module calculates the flow of water, it can "freely" flow across the entirety of the map, until it reaches the edge of the project area. Water cannot flow out of the project area at the edge, nor can any water flow in from outside the project area. The edge behaves as an impenetrable barrier which water cannot pass, and in fact can bounce back from. Both the lack of natural water flow from the cells beyond the edge, as well as the behavior of water hitting the edge and being forced to flow back are known as edge effects.
Note that there is no clear-cut single method for perfectly resolving these limitations. For every situation and use-case you will need to make your own judgement call as to which solution is most appropriate.
 
All hydrological models require some forethought on the existance of edge effects when performing hydrological calculations and analyses. Depending on your use-case, you can consider doing any or all of the following to account for edge effects.
 
Note that there is no clear-cut single method for perfectly resolving these artifacts. For every situation and use-case you will need to make your own judgement call as to which solution is most appropriate.


===Larger project area===
===Larger project area===
By creating a larger project area, the water which flows out of your area of interest does not immediately reflect back in. Instead, it has the room to flow further, continuing onwards to the edge. Additionally, when dealing with water sources such as rain, water from just outside the area of interest can flow in naturally as well, creating a more truthful representation of the amount and movement of the water in your model.
By creating a larger project area, the water which flows out of your area of interest does not immediately reflect back in. Instead, it has the room to flow further, continuing onward to the edge. Additionally, when dealing with water sources such as rain, water from just outside the area of interest can flow in naturally as well, creating a more accurate representation of the amount and movement of water in your model.


The degree to which this lessens the edge effect depends on the increase in size and the impulse of the water.
The degree to which this lessens the edge effect depends on the increase in size and the impulse of the water.


===Boundary conditions===
===Boundary conditions===
By adding boundary conditions, in the form of [[inlets]], [[breach]]es, or even just very deep [[terrain|water terrain]], it's possible to define in greater detail what happens with water flowing into (and potentially out of) the edge. The boundary conditions would allow water which reaches the edge to be removed from the hydrological model, preventing water from flowing back into your area of interest. At the same time, it's possible to define specific points as inlets which add water to the model, also allowing for water to flow into a project area. This can be relevant when modelling a steadily flowing river.
[[Inlet (Water Overlay)|Inlet, outlets]] and [[Breach (Water Overlay)|Breaches]] can be used to add or remove water at the boundary when it reaches a particular level. This can be relevant when modelling a steadily flowing river.
Deep [[Terrain water (Water Overlay)|waterways]] or [[Elevation model (Water Overlay)|ditches]] allow you to store water that reaches the project's boundary, keeping it inside the project.


The degree to which this lessens the edge effects depends on the amount of boundary conditions added to the project, their capacities relative to the amount of water they are to process, and their exact placement.
The degree to which this lessens the edge effects depends on the amount of boundary conditions added to the project, their capacities relative to the amount of water they are to process, and their placement.
 
===Limit Areas===
[[Limit area (Water Overlay)|Limit Area]]s can be added to a Water Overlay to control which part of the project area is simulated. Parts that are not simulated act as a boundary.


===Accept artifacts===
===Accept artifacts===
It's not necessarily so that all edge effects are an issue in all use-cases or all calculations. The results of some calculations may already be so inaccurate (for example, because the dataset used to configure the model is very crude), or the level of detail required may not be so high, that the effect of the edge does not have a significant impact on the accuracy of the results. In these cases, it is important to be aware of the presence of such an artifact.
Edge effects may not be an issue for all use cases or calculations. Edge effects may be negligible if the required detail is low or if existing dataset inaccuracies already outweigh them. In these cases, it is important to be aware of the presence of such an artifact.
 
{{Article end
|seealso=*[[Border model (Water Overlay)]]
*[[Limit area (Water Overlay)]]
|howtos=*[[How to investigate odd behavior near model edges]]
*[[How to correct your Water Overlay data]]
}}
 
{{WaterOverlay formula nav}}

Latest revision as of 13:05, 14 July 2026

When the Water Module calculates the flow of water, it can "freely" flow across the entirety of the map, until it reaches the edge of the project area. Water cannot flow in or out of the project edge. It behaves as an impenetrable barrier and causes water to bounce back. Edge effects include both the lack of external water flow and the behavior of water bouncing off the boundary.

All hydrological models require some forethought on the existence of edge effects when performing hydrological calculations and analyses. Depending on your use-case, you can consider doing any or all of the following to account for edge effects.

Note that there is no clear-cut single method for perfectly resolving these limitations. For every situation and use-case you will need to make your own judgement call as to which solution is most appropriate.

Larger project area

By creating a larger project area, the water which flows out of your area of interest does not immediately reflect back in. Instead, it has the room to flow further, continuing onward to the edge. Additionally, when dealing with water sources such as rain, water from just outside the area of interest can flow in naturally as well, creating a more accurate representation of the amount and movement of water in your model.

The degree to which this lessens the edge effect depends on the increase in size and the impulse of the water.

Boundary conditions

Inlet, outlets and Breaches can be used to add or remove water at the boundary when it reaches a particular level. This can be relevant when modelling a steadily flowing river. Deep waterways or ditches allow you to store water that reaches the project's boundary, keeping it inside the project.

The degree to which this lessens the edge effects depends on the amount of boundary conditions added to the project, their capacities relative to the amount of water they are to process, and their placement.

Limit Areas

Limit Areas can be added to a Water Overlay to control which part of the project area is simulated. Parts that are not simulated act as a boundary.

Accept artifacts

Edge effects may not be an issue for all use cases or calculations. Edge effects may be negligible if the required detail is low or if existing dataset inaccuracies already outweigh them. In these cases, it is important to be aware of the presence of such an artifact.

How-to's

See also

Water Module
Water Module
Tutorials
Overview
Theory
Benchmarks
Models
Surface • Ground • Rain • Evapotranspiration • Infiltration • Elevation • Breach • Sewer • Storage • Tracer flow • Border • Order
Model formulas
Timestep • Season • Surface water level • Groundwater level
Flow formulas
Surface flow • Surface infiltration • Ground flow • Ground infiltration • Surface evaporation • Ground evaporation • Ground bottom flow
Hydraulic structure formulas
Culvert • Weir • Breach growth • Breach flow • Pump • Sewer Overflow • Inlet • Drainage
Related
Building attributes • Hydrological features • Hydraulic structures •  Terrain attributes • Model attributes • Prequels • Results • Simulation data
Retrieved from "https://support.tygron.com/w/index.php?title=Edge_effects_(Water_Overlay)&oldid=91555"