Basic water model use case (Water Overlay)

Water Module

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Overview

Theory

Benchmarks

For all effective uses of any variant of the water overlay, you must first set up a basic water model. This water model includes both your hydrological system, as well as the parameters used to perform any calculations. The behavior of any water, whether it's pre-existing, expected inflow, or due to natural event or calamity, is affected by the presence of features which can capture or steer water in other directions. The more real-world hydrological features and hydrological constructions are loaded in, the more accurately the water flow can be simulated.

Requirements

Before getting started, there are a few requirements which must be met first.

Determine what overlay you need

The first step is to determine which variant of the Water Overlay best suits your needs. This depends largely on what primary calculation you wish to perform.

Create your project

The Water Overlay will be able to calculate most accurately if your project has been created with the following criteria in mind:

• Your project has been loaded in with a high-resolution DEM. This can be configured during the new project wizard.
• Your project is large enough to account for edge effects.

Prepare your data

The next step is preparing your data. Note that data can be skipped if you do not have this data, or the data is not applicable for your project.

The following data should be prepared as GeoJSONS. Click on any topic for more information.

Data	Description	Alternative/default
Water areas	Water areas set the water level of all open water in the area they envelop.	In the configuration wizard, it is possible to generate a single water area for the entire project area.
Weirs	Weirs allow for water to flow between bodies of water, with the amount of water increasing as the water level increases.	There are no default weirs in a project.
Culverts	Culverts allow for water to flow between bodies of water, with a maximum amount dictated by the size of the culvert.	For projects in the Netherlands some culverts may be loaded in as part of the project creation process.
Pumps	Pumps move water from locations with a lower water level to locations with a higher water level.	There are no default pumps in a project.
Inlets and outlets	Inlets are points where water can be added to the water system. Outlets are points where water can leave the water system.	There are no default inlets or outlets in a project.
Sewer areas	Sewer areas form controlled storage for water which ends up on constructions landing on sewer areas.	In the configuration wizard, it is possible to generate sewer areas based on the neighborhoods in the project area.
Sewer overflows	Sewer overflows are a way for water to flow out of the sewer, and back onto the surface water system.	There are no default sewer overflows in a project, even when sewers are loaded in or generated.

Note that it is preferable to use the Tygron Platform's naming convention for attributes (such as CULVERT_HEIGHT) when preparing GeoJSON files, to prevent multiple structures or features from having the same keys and conflicting with each other in the Water Overlay's setup.

The following data should be prepared as GeoTiffs. Click on any topic for more information.

Data	Description	Alternative/default
Groundwater	Only relevant for groundwater overlays. Will set the height of the saturated zone's water in the underground.	The groundwater overlay will assume the entire ground is saturated. Other overlays will not use the underground water model.

Verify your data

Missing attributes

When your datasets have been created, take a moment to check how many features in your data have either missing attributes or placeholder values for attributes. Make sure that for each data type, you are aware of how the Tygron Platform will react when data is missing, or set to an unrealistic (or realistic) placeholder value.

Construction shapes

Make sure that all constructions which should be line-shaped are actually line-shaped. Constructions such as weirs are commonly stored as points, while the Tygron Platform requires them to be lines, so that it can be determined exactly where the water flows to and from.

Consequences of construction shapes

Also make sure that when a line-shaped construction exists in a waterway, the water which is ment to flow via the construction has no alternative way of flowing past the construction. In practice, this often means blocking the waterway in which the construction lies, in the location of the construction, such that flowing through the construction is the only way water can flow past the obstruction. Consider the following options:

• You can manually create an obstruction in the DEM by adjusting the elevation model
• You can draw a breach in the waterway with a BREACH_HEIGHT set to the height of the surrounding land.

Construction placement in waterways

Make sure all hydrological constructions are placed such that their relevant centers are well in the waterways they apply to. If the endpoint of a culvert or other line-base construction is on the edge or slope of a waterway, exact topography may case the construction to be less well connected to the actual water, requiring water to rise to a higher level before it is affected by the construction. In general, topology matters more than exact topography, so moving construction endpoints should not cause considerable deviations from realism.

Overlapping constructions of the same type

If there are multiple constructions in the same location, such as parallel culverts, make sure their endpoints do not overlap/end up in the same cell. If such culverts exist, consider the following options:

• Move the culverts, so that their endpoints are no longer in the same cell
• Merge the culverts, by creating a single one with appropriate attributes to mimic the combined function of the two separate culverts.

Overlapping constructions of different types

If there are multiple constructions in the same location, such as a culvert with a weir directly on the end, they should be adjusted as well to prevent multiple endpoints ending up in the same cell. In these situations, consider the following options:

• Move the constructions, such that water first passes through the first construction into an intermediate water basin, and then flows on through the other construction.
• Merge the constructions, such that only as single construction exists but which constricts/facilitates the waterflow mimicking/approximating the combined effect of the two separate constructions.

Pre-existing constructions

If you have prepared your own dataset of hydrological structures, make sure to delete any pre-existing structures of the same type before loading in your dataset. You can perform this action in the wizard.

Steps

How to create a basic water model:

1. Add the overlay, as described here: How-to add and remove an overlay.
2. Open the overlay's wizard, and perform each step if possible. When in doubt on what to configure exactly, a step can be skipped.

Notes

The rainfall and groundwater variants of the Water Overlay already form basic water models when they are added to a project without further configuration.

Additional tips for preparation and use

There are a number of additional points of attention when creating a project with the intent of using this overlay:

• When creating a new project in the new project wizard, consider using the AHN3 dataset rather than the default AHN2. Where coverage is available, the AHN3 dataset will be more accurate. Where coverage is not available, the default AHN2 should be used.
• Additionally, when creating a new project, consider whether you want to use the IMWA dataset for hydrological constructions. Although this dataset is not complete, some information about constructions which serve as culverts other relevant objects can be loaded in from this datasource. If more complete or accurate data is available to be loaded in into the project after it is created, it may be desirable to disregard this source so that hydrological constructions are not doubly included.
• Water flow can often be dictated by small features in an area, such as small openings between buildings, and thin levees. To have these small features included properly in the calculations, the grid cell size will need to be set to an appropriate size. The default setting offered by the Tygron Platform will often need to be adjusted to allow for smaller features to be recognized without having their presence averaged out with their surroundings.
• The water overlay performs a complete simulation, which is a series of complex calculations across multiple layers. Depending on the configuration of the overlay, the calculation time can range from seconds to hours. If the overlay is to be used in a setting where response times need to be short, it may be preferable to configure the overlay for greater speed rather than excessive precision.

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Water Module

Water Module

Tutorials

Overview

Theory

Benchmarks

Group

Use cases

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How to import a GeoTIFF of waterway depths

How to add Subsidence

Flooding

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Visualize levee breach from water body outside project area use case

Flood wave use case

Drought

Drought excessive drain use case

Drought excessive evaporation use case

Water quality

How to trace water through project area

Stationary analyses

Calculate stable water level use case