Assessing the potential benefits of soil water measurements in urban drainage modelling (2024-2027)

Climate change, combined with ongoing urbanization and the traditional approach of using 'grey infrastructure' for stormwater management, poses major challenges and limits the possibilities for climate adaptation of cities and communities. Nature-based solutions (NBS) are an increasingly popular option that has the potential to offer significant benefits not only for water management but also for improving the living environment in cities.

For good stormwater system design, computer models are often used to predict how the system will perform under different weather and climate conditions. As NBS is relatively new, traditional computer models have only recently begun to include them, and this means that much is unclear about how to model processes that are important in NBS, such as infiltration of water into the ground and what happens to the water in the ground over time.

This leads to errors or greater uncertainty in any modelling results. This can lead to systems that are oversized (unnecessary expensive and taking up unnecessary space) or undersized, leading to higher flood risks and damage to people, property and infrastructure.

At the same time, NBS also offers new opportunities to measure soil moisture. This information can contribute to more reliable models, but it is not yet clear how this can best be done and what exactly the benefits might be.

One advantage of soil moisture measurements is that they are relatively easy to install and maintain, especially compared to measurements of flow in e.g. stormwater pipes. If it is possible to replace flow measurements with soil moisture measurements, it creates better opportunities for measuring and monitoring stormwater systems.

In this project, field measurement campaigns will therefore be combined with modelling approaches to investigate:

• Where to measure soil moisture
• How soil moisture can be adequately modelled
• How soil moisture data can be used in the calibration of stormwater models
• Whether soil moisture measurements can be used as a substitute for flow measurements

The project, which is funded by Formas, will also test whether data from flow measurements can be replaced by a combination of rainfall and soil moisture data in combination with machine learning methods.