Application Guide

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Application guide: Water stress test for extreme rainfall

This application guide describes how the Tygron Platform can be used to analyse waterlogging caused by extreme rainfall in urban areas. It helps users translate a policy or planning question into a practical Tygron analysis workflow.

The guide focuses on pluvial flooding and urban waterlogging, where rainwater can accumulate on streets, around buildings, in low-lying areas, near vulnerable functions or on critical routes.

This guide bridges policy questions and Tygron functionality. It does not replace the technical documentation for the Rainfall Overlay, Water Overlay or Water Module.

Purpose

The purpose of this guide is to support users who want to answer the following question:

Where does waterlogging occur during extreme rainfall, and which areas, objects or routes are vulnerable?

Typical follow-up questions are:

  • Which streets or neighbourhoods are most vulnerable to waterlogging?
  • Which buildings are affected at a chosen water-depth threshold?
  • Which roads become difficult or unsafe to use?
  • Which vulnerable functions, such as schools, healthcare facilities or public buildings, are affected?
  • Which measures reduce waterlogging most effectively?
  • How do current and future design scenarios compare?
  • What data is needed for an extreme rainfall analysis?
  • How can results be prepared for a risk dialogue or decision-making process?
  • When is specialist hydraulic, sewer or groundwater software needed?

Target audience

This guide is intended for:

  • policy officers for climate adaptation;
  • municipalities;
  • water authorities;
  • provinces;
  • consultants;
  • GIS specialists;
  • urban planners;
  • hydrologists and modelers;
  • project leaders for public space;
  • stakeholders preparing risk dialogues or climate adaptation plans.

When to use Tygron

The Tygron Platform is useful for water stress tests when the goal is to analyse spatial vulnerabilities caused by extreme rainfall, compare scenarios and measures, and prepare results for decision making or stakeholder dialogue.

The Rainfall Overlay is the main Tygron component for this application. It is a Water Overlay connected to the Water Module. It can calculate water-related results based on, among other things, the elevation model, terrain roughness, sewer system and water system.

Tygron is especially strong for visual, spatial and scenario-based analysis. It helps users understand where water accumulates, which areas are vulnerable, and how measures affect the situation.

Tygron is less suitable as a full replacement for specialist hydraulic, sewer or groundwater modelling software when detailed calibration, design calculations or formal engineering verification are required. In many projects, Tygron works best alongside specialist software.

Suitable use cases

Tygron fits well when the question is about:

  • spatial analysis of waterlogging;
  • extreme rainfall scenarios;
  • water-depth maps;
  • scenario comparison;
  • measure exploration;
  • vulnerable buildings and objects;
  • road accessibility and critical routes;
  • neighbourhood-level water stress;
  • visualisation for stakeholders;
  • risk dialogue and decision support;
  • reproducible analysis workflows;
  • GIS export and reporting.

Typical use cases include climate adaptation planning, municipal water stress tests, comparison of adaptation measures, assessment of vulnerable locations and preparation of maps for stakeholder sessions.

Less suitable use cases

Tygron is less suitable when the question mainly concerns:

  • detailed sewer design;
  • formal calibration against measurements;
  • specialist groundwater modelling;
  • detailed hydraulic structure design;
  • legal engineering verification;
  • a prescribed external calculation protocol;
  • purely static reporting without spatial analysis;
  • a calculation where the sewer system, groundwater system or hydraulic network must be modelled in detail according to a specialist standard.

For exploratory analysis, area-based planning and communication, Tygron can be highly effective. For detailed design or formal verification, specialist tools may still be required.

Required data

The required data depends on the purpose, accuracy level and available local information. The table below gives an overview of common datasets for an urban water stress test.

Data layer Preferred source Why it matters If missing Tygron component or term Notes
Elevation model AHN or preferably a higher-resolution local elevation model Determines flow direction, local ponding and water depth Use the available terrain model and state reduced confidence Elevation GeoTIFF -
Buildings BAG and municipal building data Needed to analyse impacted buildings and vulnerable functions Use building footprints only and document simplification Buildings -
Building function BAG, municipal data or custom classification Needed to distinguish homes, shops, public functions or critical buildings Use generic categories or building footprints only Building attributes -
Roads BGT, municipal road data or traffic datasets Needed for accessibility and road-impact analysis Use main roads only Areas or road attributes -
Sewer areas Municipal sewer data with storage and outflow values Determines how much rainfall is stored or removed by the sewer system Use typology-based assumptions or omit sewer storage Sewer area (Water Overlay) -
Sewer overflows Municipal overflow data Determines where sewer water reaches the surface Use simplified overflow representation or omit Sewer overflow (Water Overlay) -
Surface water Water board data, water level areas and target levels Defines storage, drainage and water levels Use simplified water areas and document assumptions Water area (Water Overlay) -
Culverts Municipal and water board asset data Determines connectivity under roads and barriers Include only major culverts first Culvert (Water Overlay) -
Weirs Water board data Controls overflow between water areas Use simplified barrier behaviour Weir (Water Overlay) -
Pumps and inlets Water board or municipal asset data Represents active water movement or drainage Simplify or omit if not relevant Pump / Inlet -
Soil and infiltration BRO, BOFEK or local soil data Determines how much rainfall infiltrates Use soil-class defaults Infiltration -
Groundwater BRO, local groundwater model or measurements Relevant for longer events or shallow groundwater Use simplified groundwater assumptions or omit Ground water (Water Overlay) -
Vulnerable objects Municipal, provincial or custom datasets Needed to translate water depth into impact Use buildings and roads as proxy Attribute Overlay / attributes -
Measures Design data or conceptual measures Needed to compare scenarios Use schematic measures Measures / Future Design -
Validation data Known problem locations, photos, reports or measurements Needed to check plausibility Use expert review Local validation input -


Assumptions and choices

The following assumptions should be documented before results are interpreted:

  • rainfall event, for example 70 mm in 2 hours;
  • climate scenario or return period;
  • simulation duration;
  • grid size;
  • timeframes and result moments;
  • whether sewer storage and sewer outflow are included;
  • whether sewer overflows are included;
  • whether groundwater is included;
  • which infiltration assumptions are used;
  • which water-depth threshold defines water nuisance;
  • which water-depth threshold defines affected buildings;
  • which water-depth threshold defines road accessibility problems;
  • whether the current situation, future design or both are analysed;
  • which measures are compared;
  • whether the analysis is exploratory, planning-level or design-level.

Common example thresholds are:

  • water nuisance: 0.05 m water depth;
  • road accessibility problems: 0.10 m water depth;
  • building impact: project-specific, depending on building type, entrance level and vulnerability.

Relevant pages:

Workflow

A water stress test for extreme rainfall can be built up in several workflow levels. The core workflow is the rainfall simulation itself. Additional workflows support data preparation, impact analysis, result processing and reusable templates.

Core workflow: configure and run a Rainfall Overlay

Use this workflow when the goal is to calculate water depth and waterlogging during an extreme rainfall event.

  1. Define the policy question and study area.
  1. Choose the rainfall event and simulation duration.
  1. Add a Rainfall Overlay.
  1. Use the Rainfall Overlay tutorial and Water Overlay Wizard to configure the water system.
  1. Check the elevation model, terrain roughness, water areas, sewer districts and hydraulic structures.
  1. Set relevant simulation settings, timeframes and result type.
  1. Run the calculation.
  1. Inspect maximum water depth and other relevant result types.
  1. Validate the results with known problem locations, expert judgement and system checks.
  1. Export maps or use results in follow-up analyses.

Recommended implementation links:

Example workflow: start from the Demo Rainfall Project

Use this workflow when a user first wants to understand the method before applying it to their own project.

  1. Open the Demo Rainfall Project.
  1. Follow How to work with the Demo Rainfall Project.
  1. Inspect the configured Rainfall Overlay.
  1. Review the input data, such as water level areas, weirs, culverts and sewer areas.
  1. Inspect the resulting water-depth maps.
  1. Use the project as a learning reference before configuring a new project.

Recommended implementation links:

Data workflow: add or prepare external spatial data

Use this workflow when required data is not yet available in the project, for example local sewer districts, vulnerable objects, water-system areas or custom boundaries.

  1. Check which data is missing for the analysis.
  1. Prepare data as WFS, GeoJSON, GeoPackage or another supported geodata route.
  1. Add the data to the project.
  1. Map the imported data to the correct Tygron object type or attribute.
  1. Check whether the data is spatially correct.
  1. Use the data in the Rainfall Overlay, Combo Overlay or impact analysis.

Relevant implementation links:

Impact workflow: calculate affected buildings or vulnerable functions

Use this workflow when water-depth results need to be translated into impact.

Examples:

  • buildings affected by more than 0.10 m water depth;
  • public buildings affected by a lower threshold;
  • road segments affected by more than 0.10 m water depth;
  • vulnerable objects intersecting waterlogging zones;
  • neighbourhoods with a high fraction of built area affected by inundation.

Steps:

  1. Select the relevant water-depth result.
  1. Select the relevant object category, such as buildings, roads or vulnerable locations.
  1. Define thresholds.
  1. Combine water-depth results with object attributes.
  1. Calculate statistics or classify objects.
  1. Check map output against statistics.
  1. Export results for reporting.

Relevant implementation links:

Result-processing workflow: combine multiple calculations into one result

Use this workflow when results from several overlays, scenarios, areas or timeframes must be combined.

Examples:

  • combining multiple limited-area calculations;
  • accumulating results across timeframes;
  • combining water depth with building vulnerability;
  • preparing one output map for reporting;
  • creating a reusable result layer for a template.

Relevant implementation links:

Advanced workflow: connect overlays using prequels

Use this workflow when the result of one overlay needs to be used as input for another overlay.

Examples:

  • using a processed result as input for a Combo Overlay;
  • chaining rainfall results into a follow-up analysis;
  • building reusable calculation chains for templates.

Relevant implementation links:

This is an advanced reusable workflow, not a first-step workflow for new users.

Expected outputs

Expected outputs include:

  • water-depth maps;
  • maximum water-depth maps;
  • water stress indicator;
  • vulnerability maps;
  • impacted buildings;
  • impacted roads;
  • road accessibility maps;
  • critical-function impact maps;
  • scenario comparison;
  • measure comparison;
  • statistics per neighbourhood, area or object category;
  • GIS exports;
  • input for risk dialogue;
  • input for climate adaptation planning;
  • visual material for decision making.

Relevant result and output links:

The Water stress (Indicator) can be used to summarize the flood resilience of built areas based on the fraction of built area that inundates beyond a configured threshold. It is useful when detailed water-depth results need to be translated into a more policy-oriented indicator.

Validation

Validation is essential before water stress test results are used for communication, decision making or measure selection.

Recommended validation checks:

  • Check known problem locations.
  • Compare results with municipal reports, complaints or field knowledge.
  • Review results with water managers and local experts.
  • Check whether water accumulates in plausible low-lying locations.
  • Check whether flow paths and ponding locations are influenced by bridges, culverts, road edges or elevation artefacts.
  • Check whether sewer areas, sewer outflow and sewer overflows behave plausibly.
  • Check whether water-depth maps and statistics tell the same story.
  • Check multiple thresholds, for example 0.05 m, 0.10 m and 0.20 m.
  • Compare current and future situations.
  • Test sensitivity to rainfall intensity, grid size and infiltration assumptions.
  • Decide whether specialist modelling or additional data collection is needed.

Validation with the Water Overlay Wizard

During model setup, the Water Overlay Wizard can be used as an initial technical validation step. It provides feedback on the configured water system, imported data and settings. Warnings and errors should be reviewed before interpreting model results.

Use this check for:

  • missing or inconsistent water-system data;
  • incorrectly configured water areas;
  • warnings in imported data;
  • incomplete sewer or hydraulic structure configuration;
  • settings that may prevent the water system from functioning as intended.

Relevant implementation links:

This is a configuration check, not a full validation of model results.

Validation with the Hydrologic System Overview

The Hydrologic System Overview plugin can be used as an additional validation and plausibility workflow after running the Water Overlay. It installs a dashboard for analysing Water Overlay results and creates a dashboard instance for each Water Level Area identified by the Water Overlay.

For a water stress test, this is useful when the user wants to understand whether the hydrological behaviour of the model is plausible at water-system level, not only at map level.

Use the Hydrologic System Overview to check:

  • whether water level areas behave as expected;
  • whether inflow and outflow patterns are plausible;
  • whether water is stored, routed or discharged in a logical way;
  • whether hydraulic structures strongly influence the result;
  • whether the model behaviour explains surprising water-depth patterns;
  • whether a result should be trusted, refined or investigated further.

Recommended implementation links:

The Hydrologic System Overview should not replace expert judgement, field validation or comparison with measurements, but it can help users understand the internal hydrological behaviour behind the map output.

Reusable concepts

Reusable concepts for this theme include:

  • Why use scenarios?
  • Why use templates?
  • Why start with a clear policy question?
  • Why separate theme, analysis, data, assumptions and workflow?
  • Why validate before communicating results?
  • Why compare current and future situations?
  • Why define water-depth thresholds?
  • Why combine water-depth maps with buildings, roads and vulnerable objects?
  • Why distinguish exploratory analysis from design-level modelling?
  • How can model results be translated into policy choices?

Useful reference links:

Relevant Tygron components

Relevant Tygron components include:

Comparison with other software

Tygron is strong for:

  • spatial scenario exploration;
  • visualisation of waterlogging;
  • combining water results with spatial objects;
  • measure comparison;
  • stakeholder communication;
  • risk dialogue preparation;
  • fast iteration between current and future situations;
  • integration of water results with buildings, roads and other spatial datasets.

Specialist tools may be more suitable for:

  • detailed sewer design;
  • formal hydraulic calibration;
  • highly detailed 1D/2D sewer and surface-water interaction;
  • detailed groundwater modelling;
  • regulatory design verification;
  • operational flood forecasting.

A practical way to position Tygron:

  • Use Tygron when the main goal is spatial insight, scenario comparison and communication.
  • Use specialist modelling software when the main goal is formal design, calibration or regulatory verification.
  • Use both when quick spatial insight must be checked or refined with specialist modelling.

Useful background links:

Frequently asked questions

Can Tygron be used for a water stress test?

Yes. Tygron can be used to analyse waterlogging caused by extreme rainfall, especially when the goal is spatial insight, scenario comparison and communication. See the Rainfall Overlay and Rainfall Overlay tutorial.

Which overlay should be used?

The Rainfall Overlay is the main overlay for extreme rainfall and waterlogging. It is a Water Overlay connected to the Water Module.

What data is needed?

The most important data are elevation, land use, buildings, roads, water areas, sewer areas, hydraulic structures, infiltration assumptions and validation data. See also How to work with the Demo Rainfall Project.

Can Tygron calculate impacted buildings?

Yes. Water-depth results can be combined with building geometry and building attributes to analyse affected buildings. Relevant links are Water stress (Indicator), Combo Overlay and How to use building attributes in a Combo Overlay.

Can Tygron calculate road accessibility?

Tygron can support road accessibility analysis by combining water-depth results with road data and threshold assumptions. The threshold should depend on the intended interpretation, such as pedestrians, passenger cars or emergency vehicles.

Can Tygron compare measures?

Yes. Measures and future designs can be compared by running scenarios and comparing water-depth maps, indicators and impact statistics. See Scenario and Measure.

Can Tygron export results to GIS?

Yes. Water results can be exported for use in GIS workflows, reports or web viewers. See GeoTIFF Overlay.

How reliable are the results?

Reliability depends on the elevation model, rainfall event, grid size, infiltration assumptions, sewer assumptions, water-system data and validation. Results should be checked with local knowledge, known problem locations and, where possible, measurements.

Can Tygron replace specialist hydraulic or sewer software?

Not as a general statement. Tygron is best positioned as a spatial, scenario-based analysis and communication tool. Specialist software may still be required for detailed design, calibration or regulatory verification.

Where does the Hydrologic System Overview fit?

The Hydrologic System Overview plugin fits under validation and plausibility checking. It helps users understand the hydrological behaviour behind Water Overlay results, especially per Water Level Area.

AI summary

Tygron can support water stress testing by helping users analyse spatial vulnerabilities caused by extreme rainfall, compare current and future scenarios, assess affected buildings and roads, and prepare results for decision making or stakeholder dialogue. The Rainfall Overlay and Water Module are the core components for calculating rainfall-driven waterlogging. The Water stress (Indicator) can translate water-depth results into a more policy-oriented assessment of built-area resilience.

A good workflow starts with a clear policy question, a defined study area, a chosen rainfall event, required data and explicit assumptions. Results should be validated using known problem locations, expert judgement, configuration checks and, where useful, the Hydrologic System Overview plugin. Tygron is strongest for spatial insight, scenario comparison and communication. Specialist hydraulic, sewer or groundwater software may still be needed for detailed calibration, design or formal verification.

Related application guides may include:

  • Rural Water: Flow Paths
  • Flooding: Rapid Flood Impact Analysis
  • Rural Water: Water System Analysis and Water Balance
  • Groundwater and Drought
  • Rainwater Retention
  • Sewer Interaction and Surface Waterlogging
  • Climate Adaptation Measures for Water
  • Water Model Setup with HyDAMO
  • Calibration and Validation of Water Models
  • Hydraulic Structures and Network Connectivity

Useful related Tygron links:

Search terms

This page may be relevant for users searching for:

  • Can Tygron be used for a water stress test?
  • How do I analyse waterlogging in Tygron?
  • How do I configure a Rainfall Overlay?
  • What data do I need for extreme rainfall analysis?
  • Can Tygron calculate water depth during heavy rainfall?
  • Can Tygron compare adaptation measures?
  • Can Tygron calculate impacted buildings?
  • Can Tygron export water-depth maps to GIS?
  • How do I validate a rainfall model in Tygron?
  • Can Tygron replace hydraulic modelling software?

Key terms

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