Water Overlay: Difference between revisions

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{{learned|what the Water Overlays are|how to configure the Water Overlays}}
A Water Overlay is a [[Grid Overlay|grid overlay]] for which results are calculated by the [[Water Module]]. The [[Water_Module_Basics|Basic theory of the Water Module]] in the {{software}} is an implementation of a 2D grid based shallow water model based on the 2D Saint Venant equations. The module is further enhanced with infiltration, evaporation, groundwater flow and hydraulic structures. Depending on the use case, the simulated period can be set to few seconds and up to a few months. The [[Water_Module_Theory|theory]] section describes in detail how calculations are performed.
__NOTOC__
To perform the calculations, the project area is divided into a [[Grid overlay|grid of cells]]. Each cell has a specific quantity of water and specific hydrological parameters based on the data in the project. The total time which should be simulated is divided into discrete [[Timestep formula (Water Overlay)|timesteps]]. Per timestep, each cell communicates with its adjacent cells to exchange water, based on its water level, surface height, current flow direction and other factors. Accuracy and reliability is obtained by dividing the project area and simulation time into sufficiently small cells and steps, at the cost of more computation time.


==What are the Water Overlays==
The final results of the calculation can be inspected, as well as intermediate snapshots of the hydrological situation during the simulation, known as [[Timeframes (Water Overlay)|timeframes]].
With the Water Overlays the following overlays are meant:
* [[Rainfall_(Overlay)|Rainfall Overlay]]
* [[Flooding_(Overlay)|Flooding Overlay]]
* [[Groundwater_(Overlay)|Groundwater Overlay]]


Each of these overlays have some common configuration steps which will be described on this page.
==Variants==
 
A Water Module will be initialized by adding one of the following Overlays to a project. Each variant has a number of parameters tuned to best fit specific use-cases. This means that each of these overlays is based on the same theory and calculation method, however they are customized to conveniently provide insight in different aspects of the Water Module.  
==Result types==
Each Water Overlay is a [[grid overlay]] showing results on the surface (flooding), sub-surface (groundwater), open water and sewer system. The following results are produced:
{| class="wikitable"
{| class="wikitable"
! Result type
|[[File:Overlay_rainfall.png]]
! Unit
|[[Rainfall_(Overlay)|Rainfall Overlay]]
! Description
|provides insight into the water stress and impact caused by (excessive) rainfall
|-
|BASE_GROUNDWATER_DISTANCE
|m (below surface)
|Initial groundwater level relative to the surface level (NL: ontwateringsdiepte).
|-
|BASE_TYPES
|nominal value
|Division of gridcells in water, land or sewer areas that are connected to the sewer.
|-f
|EVAPORATED
|m (mm)¹
|Total evaporation over the simulation period
|-
|IMPACTED_BUILDINGS
|nominal value
|Constructions impacted by flood: the value from the function value indicator is assigned to a building if the water depth at a grid-cell surrounding the building exceeds the overlay attribute value IMPACT_FLOOD_TRESHOLD_M
|-
|-
|SEWER_LAST_VALUE
|[[File:Overlay_flooding.png]]
|m (mm)¹
|[[Flooding_(Overlay)|Flooding Overlay]]
|The amount of water in the sewer storage at the end of simulation
|provides insight into water stress and impact caused by breaches in levees or other sources causing excessive water inflow
|-
|-
|SEWER_MAX_VALUE
||[[File:Overlay_groundwater.png]]
|m (mm)¹
|[[Groundwater_(Overlay)|Groundwater Overlay]]
|Maximum amount of water in the sewer storage during the simulation
|provides insight into long-term processes of water flow both on the surface and underground
|-
|SURFACE_DURATION
|s (min)¹
|The amount of time the water depth in a cell exceeds the value set in the overlay attribute value SHOW_DURATION_FLOOD_LEVEL_M
|-
|SURFACE_FLOW
|m3/m2
|Total volume of water passed a grid-cell, scaled by the cell surface (grid cell-size^2)
|-
|SURFACE_LAST_VALUE
|m (min)¹
|Water depth at the end of simulation
|-
|SURFACE_MAX_VALUE
|m (min)¹
|Maximum water depth during the simulation
|-
|UNDERGROUND_FLOW
|m³/m²
|Totall infiltration amount from the surface to groundwater
|-
|UNDERGROUND_LAST_VALUE
|m (mm)
|The amount by which the groundwater table has risen above the initial groundwater level at the end of simulation
|-
|UNDERGROUND_MAX_VALUE
|m (mm)
|The maximum amount by which the groundwater table has risen above the initial groundwater during the simulation
|-
|WATER_STRESS
|m (mm)
|The Maximum water depth during the simulation. At water cells only a water depth is shown if the depth exceeds the overlay attribute value ALLOWED_WATER_INCREASE_M
 
|}
|}
<!--==Input Data and Settings==
The calculations performed by the Water Overlay are influenced by many kinds of geographical information present in the project area. For any given location, [[terrain]], [[construction]]s and other features can influence either the initial state of the simulation or how water flows in a given area.


&sup1; the units between () are as displayed in the 3D client. If exported to GTiff the SI-convention is used: meters (m) and seconds (s).
Furthermore, the Water Overlay features a number of overall settings which can be configured for the hydrological calculations and its results. These settings do not have a geographical or temporal element to them, and are fixed values relevant for the simulation as a whole.
 
==General Tab==
[[File:General_tab.JPG|250px|right|The geberal tab of the Water Overlays.]]
The General Tab can be found at the panel on the right side, when selecting a Water Overlay. In this tab several settings can be adjusted.
 
===1. Calculation Preference===
Here you can manipulate the computation time step by choosing between the option SPEED, AVERAGE and ACCURACY. The computational timesteps will be set according to the Courant criterion:
 
Δt  = Δx /u<sub>max</sub>
 
where:
* Δt = computational timestep
* Δx = grid cell size
* u<sub>max</sub> = max velocity, assumed 2.5 (SPEED), 5 (AVERAGE) and 10 (ACCURACY) m&sub3;/s respectively


===2. Grid cell size===
;[[Hydrologic_features_(Water_Overlay)|Hydrological features]]
The {{software}} computes flow equations over a rectangular cartesian grid, the grid cell size can be set by cliking on Change Grid.
:The water system can be enhanced with a number of hydrological features, which can be loaded in as [[area]]s. These hydrological features form special properties or modifications on the hydrological system. See [[Hydrologic_features_(Water_Overlay)|Hydological features]] for a list of supported features.
Note: if you choose a smaller grid cell size, both the amount of time steps (see Calculation Preference) and amount of computational cells increase.
;[[Hydraulic structures (Water Overlay)|Hydraulic structures]]
:See [[Hydraulic structures (Water Overlay)|Hydraulic structures]] for the list of supported structures.
===3. Refresh Grid===
;[[Additional_hydrological_attributes_of_buildings_(Water Overlay)|Hydrological attributes of buildings]]
By Refreshing the grid, the Overlay is recalculated. This may take some time, depending on the grid cell size, the size of your project and the calcualtion preference.
:Besides the [[building]]s which directly influence the hydrologic model as a [[Hydraulic structures (Water Overlay)|hydraulic structure]], each building may also have attributes which can contribute to the hydrological model in some way. These attributes are stored and used on a grid cell level. This is different from the hydraulic structure attributes, which are stored and used on an object level. For a full list, see [[Additional_hydrological_attributes_of_buildings_(Water Overlay)|Additional hydrological attributes of buildings]].
;[[Terrain_attributes_(Water_Overlay)| Hydrological attributes of terrain]]
:[[Terrain]]s in a project have a number of hydrological attributes which can influence the flow of water in a project. Because there is always both surface and underground terrain defined for the entirety of the project area, all cells are affected by all attributes of terrains, unless a building is present with overwriting values. For a full list, see [[Terrain_attributes_(Water_Overlay)| Terrain attributes for the water overlay]].
;[[Model_attributes_(Water_Overlay)|Model settings]]
:For a full list, see: [[Model_attributes_(Water_Overlay)|Water Model attributes]]


===4. Export Grid File===
==Troubleshoot, warnings and recommendations==
You can export the current result type as either a GeoTiff or ASCII file.
When the Water Overlay is used and calculations take place, there are some problems or points of attention the calculation can run into. Where possible, the Water Overlay will show appropriate warnings when running into any issues.
Also, it is possible to export the difference result type of the current and maquette situation.
See [[Warning_and_recommendations_(Water_Overlay)|Troubleshoot, warnings and recommendations]];
-->


===5. Save Overlay result===
==Results==
With this option you can create a duplicate inactive copy of the current overlay. This is noticeable in the Overlays panel on the left side of the screen. The duplicated overlay will have (inactive copy) behind the overlay name. This copy is not being recalculated when changing settings in the original duplicated overlay.
With a Water Overlay, a user can generate multiple [[Results_(Water_Overlay)|results]] for a single water simulation. For further information about these outcomes, see also [[Results_(Water_Overlay)|results]] and [[Result type (Water Overlay)|result types]].


===6. Show Water Balance===
==How-to's==
The Water Balance panel shows the in- and outflow of water in m3. The Water Balance panel is also visible when clicking on the Debug info (see below).
* [[How to add and remove an Overlay]]
The water balance is made up of the following components (dependent on what is in the project):
* [[How to manually configure a Water Overlay|Configure a Water Overlay]]
* Land surface: amount of water on the land surface after simulation (m3)
* [[How to edit an overlay legend|Edit an overlay legend]]
* Water surface: amount of water stored on water cells after simulation (m3)
* [[How to add Subsidence (Water Overlay)|Combine with Subsidence Overlay]]
* Building storage: amount of water stored in building storage (m3)
* [[Water Model Limits]] (some basic rules)
* Sewer storage: amount of water stored in sewers after simulation (m3)
* Underground storage: amount of water stored in the sub-soil after simulation (m3)
* Evaporated: amount of water evaporated after simulation (m3)
* Outlet: amount of water extracted from the model during the simulation via outlets of water areas or sewer pumps (m3).


===7. Warnings===
===Features and components===
When the grid cell size is too large in combination with the project size, a warning pops up. This means that calculated results are not accurate. The solution to this is to change the grid cell size to a smaller number.
* [[Hydrological features (Water Overlay)|Hydrological features]]
 
* [[Hydraulic structures (Water Overlay)|Hydraulic structures]]
===8. Debug Info===
* [[How to_manually_configure_a_Water_Overlay|Manual configuration Options]]
The debug info contains the following information:
* [[Simulation data (Water Overlay)|Simulation data]]
* Rain: the amount of rainfall (mm) in the duration of the rainfall event (hours)
* Total Simulation: the simulation period (hours)
* Cells: The dimensions of the simulation: the amount of computational cells and the amount of time steps (cycles)
* Water areas:
* Weir flow: the amount of water flown over weirs during simulation (m3)
* Sewer overflow: the amount of water flown over sewer overflows during simulation (m3)
* GPU time: the computation time on GPU (seconds)
* Volume: total volume of the in- and outflow of water in the model.
 
==Keys==
The tab Keys refers to the Overlay settings that are adjusted by following the configuration wizard in the General tab. It is therefore generally not needed to change the keys in this tab, as this can be done also in the configuration wizard. However, below an explanation of the Overlay Keys.
 
{| class="wikitable"
! Attribute
! Unit
! Description
|-
|Water Level
|m + datum
|initial water level, relative to datum, for all water cells in a water area
|-
|Outlet
|m3/s
|water abstraction for all water cells in a water area
|-
|Sewer Storage
|m         
|available storage in sewers at the start of simulation in a sewer area
|-
|Sewer Pump Speed
|m3/s
|sewer water abstraction for all cells in a sewer area
|}


Keys referring to structures (building attributes)
===Attributes===
{| class="wikitable"
* [[Model attributes (Water Overlay)|Water Module Attributes]]
! Attribute
* [[Hydrological attributes of buildings (Water Overlay)|Hydrological Attributes of Buildings]]
! Unit
* [[Hydrological attributes of terrains (Water Overlay)|Hydrological Attributes of Terrains]]
! Description
|-
|Weir Height
|m + datum
|weir crest level
|-
|Weir Width
|m
|the width of the crest of a weir
|-
|Weir Coefficient
|
|linear weir coefficient for accounting discharge & contraction losses
|-
|Culvert Speed
|m3/s
|the discharge capacity of a culvert
|-
|Pump Speed
|m3/s
|the capacity of a pump
|-
|Sewer Overflow Height
|m + datum
|the height of a crest of a sewer overflow
|-
|Sewer Overflow Speed
|m3/s
|the discharge capacity of a sewer overflow
|}


==Attributes==
{{WaterOverlay output nav}}
This tab shows the attributes of result types that can be adjusted. These attributes can also be adjusted in the configuration wizard in step 5 in the General tab. It is therefore generally not needed to change the attributes here. However, below an overview of the Overlay Attributes.
{{Overlay nav}}


{| class="wikitable"
[[Category:Water Module]][[Category:Overlays with result types]]
! Attribute
! Unit
! Description
|-
|ALLOWED_WATER_INCREASE_M
|m
|increment by which the water level on a water cell is allowed to increase before the depth is shown in the water stress result type
|-
|IMPACT FLOOD_THRESHOLD_M
|m
|maximum waterdepth around a building where after the building is assumed impacted
|-
|MIN_SLOPE
|
|slope whereunder the pressure slope is assumed 0
|-
|SEWER_OVERFLOW_THRESHOLD
|
|fraction of storage whereafter sewer overflows take place
|-
|SIMULATION_TIME_HOURS
|hours
|simulation time
|}

Latest revision as of 13:40, 17 January 2023

A Water Overlay is a grid overlay for which results are calculated by the Water Module. The Basic theory of the Water Module in the Tygron Platform is an implementation of a 2D grid based shallow water model based on the 2D Saint Venant equations. The module is further enhanced with infiltration, evaporation, groundwater flow and hydraulic structures. Depending on the use case, the simulated period can be set to few seconds and up to a few months. The theory section describes in detail how calculations are performed.

To perform the calculations, the project area is divided into a grid of cells. Each cell has a specific quantity of water and specific hydrological parameters based on the data in the project. The total time which should be simulated is divided into discrete timesteps. Per timestep, each cell communicates with its adjacent cells to exchange water, based on its water level, surface height, current flow direction and other factors. Accuracy and reliability is obtained by dividing the project area and simulation time into sufficiently small cells and steps, at the cost of more computation time.

The final results of the calculation can be inspected, as well as intermediate snapshots of the hydrological situation during the simulation, known as timeframes.

Variants

A Water Module will be initialized by adding one of the following Overlays to a project. Each variant has a number of parameters tuned to best fit specific use-cases. This means that each of these overlays is based on the same theory and calculation method, however they are customized to conveniently provide insight in different aspects of the Water Module.

Overlay rainfall.png Rainfall Overlay provides insight into the water stress and impact caused by (excessive) rainfall
Overlay flooding.png Flooding Overlay provides insight into water stress and impact caused by breaches in levees or other sources causing excessive water inflow
Overlay groundwater.png Groundwater Overlay provides insight into long-term processes of water flow both on the surface and underground

Results

With a Water Overlay, a user can generate multiple results for a single water simulation. For further information about these outcomes, see also results and result types.

How-to's

Features and components

Attributes

Water Module
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Water Module
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Overview
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Theory
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Benchmarks
Group
Output keys
Object flow output • Object height output • Object datum output a • Object datum output b • Object width output
Output other
Result type • Water balance • System visualization • Weather visualization • Debug info
Related
Building attributes • Hydraulic structures • Hydrological features •  Terrain attributes • Model attributes • Simulation data
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