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projectRainlevelr is an effective, successful measure against excess water thanks to close collaboration between Delfland (water authority), horticultural companies, and others .
This information was sourced from "Rainlevelr – A public-private partnership against flooding in a horticultural area" by Observatory of Public Sector Innovation (OECD), https://oecd-opsi.org/innovations/rainlevelr-a-public-private-partnership-against-flooding-in-a-horticultural-area/. Licensed under Creative Commons Attribution-ShareAlike 3.0 IGO (CC BY-SA 3.0 IGO).
Rainlevelr is an effective, successful measure against excess water thanks to close collaboration between Delfland (water authority), horticultural companies, and others . With the intensification of rainfall due to climate change, the risk of flooding is increasing. The greenhouse area - nearly 4,000 hectares in Delfland - cannot adequately buffer rainwater. By utilizing the water basins of horticultural companies, additional storage capacity is created, currently capable of storing approximately 40,000-80,000 m3 of water.
Traditionally, Delfland is an area with extensive horticulture. Because built areas, such as the greenhouses, have less capacity to absorb water compared to undeveloped land, heavy rainfall poses a problem here. There's insufficient space to collect rainwater, increasing the risk of flooding. Particularly in wet periods when the soil becomes saturated and rainwater catchments fill up, each rainfall leads to much more runoff: the water level rises faster and higher than in comparable rainfall during drier periods.
By utilizing the water basins of horticultural companies and equipping them with an automatic discharge valve, an additional course of action is created. Initially, this principle was only applied to new water basins, but now it's also being implemented in existing ones. Delfland covers the installation costs, after which the company takes ownership. By voluntarily creating space in their water basin before heavy rainfall, horticultural companies contribute to limiting excess water. Delfland informs the participants about the expected precipitation and specifies the necessary extra storage capacity. The functioning is explained in the attached animation.
The idea for this innovation arose after several instances of flooding, where many horticultural companies suffered crop losses. The uniqueness of this innovation lies in addressing technical, legal, social, and organizational aspects collectively. This has fostered substantial mutual trust and established joint ownership.
Through Rainlevelr, the available buffer capacity in the water basins of horticultural companies can be increased during predicted rainfall. It's a measure benefiting everyone: horticultural companies reduce the risk of crop damage, the surrounding environment keeps their feet dry, and Delfland avoids purchasing expensive land for natural water storage. Additionally, this helps sustain the horticultural area.
The uniqueness of this innovation lies in the collaboration among various stakeholders involved in the use of water buffers where different interests come into play—ensuring sufficient available irrigation water for the horticultural companies, while minimizing the risks of flooding for the surrounding areas. By integrating technical, legal, social, organizational aspects and involving all relevant stakeholders in the chain, this approach fostered substantial mutual trust and built joint ownership, which is one of the reasons why all participating parties speak proudly of this collaboration.
Rainlevelr has significantly grown from 25 companies at the beginning of 2020 to 75 companies by the end of 2023, reaching a total area of 400 hectares, which represents 10% of the horticultural area in Delfland. Rainlevelr is designed in a way that allows for easy adoption outside Delfland by other organizations.
While Rainlevelr is fully operational, there are several innovative steps on the horizon, including:
Rainlevelr is a collaboration between the municipality, the horticulture sector, Glastuinbouw Nederland, and Delfland. The project was made possible in part by a subsidy from Sponge2020 (Interreg 2 Seas). The relevant partners in this regard are not limited to: horticultural companies, horticulture advisory firms, water basin installation companies, suppliers of horticultural automation, and various departments within Delfland.
Rainlevelr prevents damage as a result of flooding. It not only avoids material damage for horticultural companies losing crops but also for residents whose gardens, basements, or homes get flooded. An additional advantage for horticultural companies is that there's no/less need to allocate horticulture area for constructing natural water buffers. This gives regional governments more control and insight into the discharge of excess rainwater from horticultural companies into the water system.
The results are diverse:
The greatest challenge lies in the unpredictability of the weather. Particularly, summer thunderstorms are difficult to forecast. If a storm doesn't occur or is less severe than anticipated, resulting in the water basin not being filled, a horticultural company loses valuable irrigation water. That risk needs to be minimized. Additionally, if a storm occurs and Rainlevelr isn't deployed, this affects Rainlevelr's reputation. This risk also needs to be mitigated. If the participants release more water, the correlation with the water system and its management becomes more critical. If everyone discharges water simultaneously without coordination, there's a risk that this discharge may cause flooding if it cannot be pumped away adequately.
Conditions for success include:
Currently, Rainlevelr is limited to the management area of Delfland. However, the system is designed in such a way (including digitally) that upscaling or replicating it to other (horticultural) areas (within the Netherlands or globally) is easily achievable. The principle can also be applied to other climate-adaptive measures in densely populated areas, such as distribution centers, parking lots, and businesses where rainwater is stored and utilized.
Budget: Not disclosed
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