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Climate Detectives Projects 2023-2024

Project title: How can we protect our school from floods?

College Hagelstein   Sint-Katelijne-Waver   Belgium

Research question

How we can protect our school from flooding and what is the water permeability on our school grounds?

Summary of the project

A few years ago, in July 2021, there was a huge flood in our country, specifically in Wallonia located in the south of Belgium. In 2023, the Westhoek, a region in the west of Belgium, also experienced flooding. These recent exceptional events may be related to climate change. Global warming is likely to increase size and frequency of heavy precipitation events, which in turn may increase the size, frequency and severity of floodings.
Given the increased flood risk, we wanted to investigate how to protect our school from flooding. Our full research questions are: “How we can protect our school from flooding and what is the water permeability on our school grounds?”.
To answer the first question, we analysed data from a weather station near our school, in Sint-Katelijne-Waver, located in the centre of Belgium. We analysed data from 2008 until 2023. For each year in the month of March, we calculated the average daily precipitation, the maximum daily precipitation and the number of dry days withouth rainfall.
For the second research question, we selected five different sites on the school grounds. On each of these sites, we used a bottomless bucket, put into the ground and filled it with water. Then, we registered the time it took for water to be absorbed by the soil to obtain water permeability. At each site we measured twice.

Main results and Conclusions

How we can protect our school from flooding and what is the water permeability on our school grounds?

This year, we experienced an exceptionally wet winter and a lot of rain during the period of the field experiment. As a result, the soil was already saturated, so we could not define the soil permeability. Another reason why the soil here saturates so quickly is because there is a thick layer of clay starting from one meter below the ground. Due to this clay layer, water cannot penetrate, so the water is no longer absorbed by the soil. This will cause floods.
We used precipitation data from the weather station in Sint-Katelijne-Waver to define the daily maximums, the daily averages and the number of dry days in the month of March 2008-2023. The results are shown in the enclosed graphs. Among these various data, there was no clear correlation present. However, what is clear is that starting from 2019, the maximums clearly begin to rise, and this is also the case with the average. This is peculiar when compared with the number of days without rainfall, which starts to decrease from 2019. From this, we can infer that the duration of rainfall is shorter, but the intensity of rainfall is increasing. When you combine this with the clay layer present under our school, it is clear that during a short period of high-intensity rainfall, the soil will be saturated very quickly. This rapid saturation will cause puddles en increase the risk of flooding.

What’s Next? Actions to make a difference and help lessen the problem

We found a possible solution to solve the problem namely: a ‘wadi’ its a Dutch abbreviation for: water drainage and infiltration. A wadi is filled with gravel/ sand and will store and filter rainwater and finally drains it in the underground. No more puddles in the school ground since excess water will be drained to the wadi. When there is a rainstorm there will be a lot of water and exactly that is the function of a wadi: holding piles of water. An extra bonus that comes with the wadi is that, thanks to the wadi there will be a rise in biodiversity because more organisms will find a place to live. A wadi is going to attract animals such as birds, frogs, small mammals.
In our school its best to place 2 wadi’s. One on the playground were the biggest problem is and one in the forest because the soil is there always verry wet. Thats way there will be less puddles on the playground and it will become possible to walk through the woods again.
An other solution to solve the flooding problem is to remove the clay layer in the soil with another type of soil that allows water to pass through better. The advantage of this solution is that water is more easily absorbed by soil. As a result, the groundwater level also goes up. This is good when there is a prolonged drought in the summer. There are many farmers in our school area. These farmers could then use our collected groundwater to water their crops.

Projects are created by the teams and they take the full responsibility of the shared data.
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