Rainfall Overlay tutorial

This article may contain references or images in the style of the old Tygron Platform.

Getting Started

1. Contact Tygron Support to request the Kockengen Tutorial project
2. Open the Tygron Platform, logon with your user name and password and open the project Kockengen Tutorial
3. Download and unpack the content of this zip-file on your desktop: [1]

Open the Tygron Platform and start the project Kockengen Tutorial. The project will appear:

Adding a Rainfall Overlay

Follow these steps below to add a Rainfall Overlay:

1. Hover over the button Overlays, in the current situation tab and select Add Rainfall. The rainfall overlay is added to the Overlays in the left-side-panel. And in the overlay bar on the right side of the map:
2. Select the Rainfall overlay in the left side panel and take a moment to familiarize yourself with the tabs in the right panel: General, Keys, Legend and Attributes
   • General contains the most common information necessary to interpret the rainfall overlay.
   • In Keys you can relate settings for the Rainfall overlay to attribute information stored in the 3D world.
   • Legend allows you to customize your legend
   • Attributes contains the general settings of the Rainfall overlay.
3. Click on the Configuration Wizard button. With the Rainfall Wizard, you can configure your water system, this includes:
   • The setup of the weather boundary condition
   • Definition of the water system, including water level areas (peilgebieden) and sewer districts
   • Setting of hydrological parameters

The Rainfall Wizard

With the Rainfall Overlay Wizard you can configure your water system, including surface water and sewer districts. In this part of the tutorial you need to have prepared the following GeoJSON-files:

• waterlevelareas.geojson
• sewerdistricts.geojson
• weirs.geojson
• overflows.geojson

Some tips for using vector data files for the Water_Overlay:

• All files need to have a coordinate reference system (CRS) defined, for the Tygron Platform to place the data on the correct location.
• Hydraulic structures (weirs, culverts, pumps and overflows) should be imported as polygons, but translated in the Tygron Platform to either work as point- or line based structures. Read here more about this difference.

Step 1: defining the weather

Press Next to proceed to the Weather panel, here the user can define rainfall and evaporation input. Select the Option 'Linear' for rainfall over time. Change all numbers according to this picture:

By this setting you have defined a rainfall event:

• Uniform rainfall in 120 minutes
• With a total rainfall amount of 50mm
• With a dry period after rainfall of 120 minutes, so a total simulation time of 4 hours
• Reference evapotranspiration will be assumed on 1.5mm/day

Step 2: setup of the water system

Press next to proceed to the introduction screen: Setup Water System. Here you can define your water system using the prepared GeoJSONS.

Step 2.1: adding water level areas

Press next to the screen for importing water areas. A water level area is an area with a spatially uniform water level varying in time. Variation is caused by rainfall + evaporation on the surface water, inflow from sewer areas, inflow from the surface and groundwater inflow.

There are several options to define your water system:

• Do Nothing: the surface water system effectively has infinite storage
• Import Water Areas: allows you to import a set of water level areas
• Generate Water Areas: allows you to define 1 water level area for your project area
• Select existing water level areas based on attribute: allows you to connect already imported water level data by using an existing attribute of this dataset

Select Import Water Level Areas and press Import Water Level Areas. The Geo Data Wizard will open. We will import waterlevelareas.geojson. Use the following attributes in the GeoJSON file as attributes for the Rainfall Overlay:

• WATERLEVEL: the initial Water Level in the water level area (m + datum)
• NAME: the name of the water level area

Steps in the Geo Data Wizard:

1. Select Import a GeoJSON file and press Next. Press Select File and locate the waterlevelareas.geojson. Press Open and press Next.
2. An overview of your areas is generated; see right-side pictures. Press Next
3. In the next step you can filter features based on an existing attribute. We skip this step (because we do not want the filter our dataset) by pressing Next
4. We assign names to the water level areas using the NAME attribute from the geojson; ; see right-side pictures. Press Next
5. We select all attributes, importing all attribute data from the geojson, and press Next. Note that only numerical attributes can be imported to the Tygron Platform.
6. We assign the WATERLEVEL attribute of the GeoJSON to the WATER_LEVEL key of the overlay; see right-side pictures
7. At Finalize we press Finish to upload the areas to the server

After importing your water level areas you can review all parameters by opening the selection menu. Take some time to review the attribute values. What is the meaning?

Step 2.2: initial groundwater level

In step 2.2, you can specify ground water levels. Since this tutorial is about Rainfall, we choose the default option ('Do Nothing')

; see right-side picture.

Step 2.3: adding sewer areas

Sewer districts are represented by areas which have one storage value [m], uniform in space. Sewer storage will vary in time by sewer inflow from connected buildings (buildings, roads, etc), pumped outflow to a WWTP (in the Tygron Platform this is to an external area outside of the project) and sewer overflow to surface water. In the wizard there are several options for defining the sewer system:

• Do nothing: no sewer areas are defined, this means that there is no sewerage in the project
• Import sewers: import sewer data
• Generate sewers: let the Tygron Platform generate sewer areas, based on adjustable parameters
• Select existing sewers based on attribute: if you have already sewer areas imported, you can connect them by choosing a common attribute of the already imported data

Press import sewers and import the file sewerareas.geojson via the Geo data wizard. Assign the following attributes:

• NAME: name of the sewer district
• POC: pump capacity assigned to the sewer district [m3/s]
• STORAGE: storage of the sewer district. [mm]
  

Follow the steps in the Geo Wizard according to the steps described in the water level areas section:

• At step 5, multiply the attribute value for STORAGE in the GeoJSON (mm) by 0,001 (conversion to m); see right-side pictures.
• At step 6, assign the the STORAGE attribute to the SEWER_STORAGE key and the POC attribute to the SEWER_PUMP_SPEED key

Take some time to review the attribute values in the imported area Kockengen. What is the meaning?

Step 2.4: adding inundation areas

Inundation areas are used to represent inundated of flooded areas in advance of the model's simulation. The following options are available:

• Do Nothing: there is no inundation area
• Import Water Areas: allows you to import inundation area(s)
• Generate Water Areas: allows you to define 1 inundation area for your project area
• Select existing water level areas based on attribute: allows you to connect already imported inundation data by using an existing attribute of this dataset

In this Tutorial, choose the default option (Do Nothing).

Step 2.5: adding hydraulic structures

In the Rainfall wizard it is possible to import the following hydraulic structures:

• Weirs
• Culverts
• Pumps
• Inlets
• Sewer overflows

2.5.1 Adding Weirs

You can upload weirs.geojson by selecting Import Weirs in the Weirs screen and pressing Import Weirs. We will import weirs.geojson, using the following attributes:

• NAME: the name of the weir
• WEIR_HEIGHT: the crest height [m + datum]; to be assigned to the WEIR_HEIGHT key
• WEIR_WIDTH: the width of the crest [m]; to be assigned to the WEIR_WIDTH key
• WEIR_COEFF: tthe flow coefficient related to the shape of the weir; to be assigned to the WEIR_COEFFICIENT key

In the Geo Wizard follow the steps:

1. Select Import a GeoJSON file and press Next. Press Select File and locate the wiers.geojson. Press Open and press Next.
2. An overview of your areas is generated as below. Press Next
3. In the next step you can filter features based on attribute filtering. We skip this step by pressing Next
4. We assign names to the water level areas using the NAME attribute from the geojson and press Next
5. We select all attributes, importing all attribute data from the geojson, and press Next
6. We assign the WEIR_HEIGHT attribute of the GeoJSON to the WEIR_HEIGHT key of the overlay, the WEIR_WIDTH attribute of the GeoJSON to the WEIR_WIDTH key of the rainfall overlay and the WEIR_COEFF attribute of the GeoJSON to the WEIR_COEFFICIENT attribute of the rainfall overlay.
   File:Kockengen figure11.PNG
7. At Finalize we press Finish to upload the areas to the server

Take some time to review the attribute values. What is the meaning?

2.5.2 Adding Culverts & 2.5.3 Adding Pumps & 2.5.4 Adding Inlets

Similar to the import procedure of Weirs, you can add pumps, culverts and inlets. In this Tutorial, choose the default (Do Nothing).

2.5.5 Adding Overflows

You can upload the overflows.geojson by selecting Import Overflows in the Wizard. We will import overflows.geojson, using the following attributes:

• LEVEL: the crest level of the overflow; assign to the SEWER_OVERFLOW overlay key
• CAPACITY: the overflow capacity of the overflow; assign to the SEWER_OVERFLOW_SPEED overlay key

Follow the Geo Data Wizard similar to the procedure at importing weirs (see 2.5.1 Adding Weirs) and view the result. What do the values mean?

Step 3: setup of coefficients

In this step you can adjust default parameters related to the surface (e.g. roughness), sub-surface (e.g. conductivity) and infrastructure (e.g. is a type connected to a sewer or not). As we work with a 3D world containing a lot of data, the determination of model-coefficients can be complex. E.g.:

• A manning roughness coefficient can be related to the surface type (e.g. clay) if no infrastructure present. If infrastructure is present (e.g. a road), the value of the road will be used, and the value of the surface type will be ignored
• An infiltration parameter can be related to the surface (land cover), infrastructure or underground (sub-surface). The infiltration is calculated according to the surface infiltration formula and underground infiltration formula. You can inspect the values by going to the pages. We will leave everything to default by pressing next (4x)

Step 4: Interactions

Here you can choose to visualize your water system network in the rainfall overlay:

• Display Water System network: shows schematically the network of the water system
• Display Weirs with Panels: shows on the location of weirs a panel, allowing the user to overwrite structure settings
• Display Water level Areas with Panels: shows on all centroids of water level areas panels, allowing the user to overwrite initial water levels and outflow capacity

Step 5: Output Overlays

The Rainfall Overlay can produce one or more results. By default the Water Stress is chosen, which is the amount of water on the surface. For water terrains a maximum allowed increase model parameter is set. Below that depth no water stress will be perceived. Also, the number of Timeframes can be selected with the slider. The more timeframes, the more intermediate steps there are recorded and viewable for the user. Note that timeframes are not the same as timesteps.

Step 6: Input Overlays

The Rainfall Overlay uses several input parameters to compute output. These input overlays can be visualized in the Input Overlays section. Select the manning roughness value [m/s^1/3]

Press Finish to finalize the wizard

After completion of the wizard

The general tab in the right panel

The inactive copy of the Rainfall overlay is greyed out

After finishing the wizard, you need to Update the grid to recalculate the rainfall overlay. Every time you change a parameter in the model, whether that is in the wizard or in the editor itself, the overlay has to be recalculated by pressing Update Now. However, if the auto update is on, the overlay is automatically recalculated when changing a parameter in the wizard. When working in/with a large project, a small grid size, long simulation time etc., it can be desirable to turn the auto update off in order to not have to wait every time on the recalculation of the overlay, until you are done with editing and ready for the results. When dealing with very long calculations, take note of the peak hours, the option to cancel the calculation (if you notice that it will take a long time) and the option to delay the calculation.

When finished, please explore the following interesting features:

• In the General Tab you can show the Water Balance. Please explore
• Below there is a summary, the debug info, with among others the amount of computational timesteps.
• In the General Tab, you can specify the Calculation Preferences. The preference accuracy will respect a Courant number <1 until a maximum flow velocity of 10m/s, this flow velocity will be halved by specifying the preference average (max 5m/s) and again if specified speed (2.5m/s). Please try the different options, while keeping the grid size the same and evaluate the computation times. Can you explain their relation?
• In the General Tab you can press Change Grid to change the grid cell size. Can you see the difference, and see the impact on the computational timesteps?
• In the General Tab you can export the result as a GeoTiff. Please do so and visualize your result in a GIS, for example QGIS.
• In the General Tab, click on Save overlay result. Notice what happens: an inactive copy, which will not be recalculated, of the result type is created in the overlay left panel. This inactive copy can be used to store results, from for example a specific rain event, and compare it later with another result type of another rain event.
• In the General Tab, warnings may also appear.
• Create an overlay of the water level areas to provide more insight. Follow the (general) steps here for creating an overlay of the already imported water level areas.
• Open the Rainfall Wizard again. Select more and/or different result types and update the Rainfall overlay. Can you display and interpret the results?