Flood control areas (FCAs)
A flood control area is an area adjacent to the river that is surrounded by a ring levee. This area serves as a water buffer zone in extreme weather conditions.
We work with two types of flood control areas:
- Flood control areas with mainly a safety function: flood control areas (FCAs)
- Flood control areas with a safety and a conservation function: flood control areas with reduced tides (FCA-RTs)
How does an FCA work?
In a well-defined area, we build a high, sturdy ring levee inland, along the river. The existing river levee is then lowered and reinforced. The water can then flow over this overflow levee in the event of high water levels on the river. The ring levee protects the residential areas beyond it from flooding.
This creates a flood control area, which can store large amounts of water, along the river. The river’s water level is then reduced, which in turn relieves the pressure on the levees. The tidal wave loses a great deal of its force, and the risk of flooding or of a levee breach declines.
As soon as the water level in the river is sufficiently reduced, the water in the flood control area drains away through discharge sluices.
Generally speaking, a flood control area only occasionally fills with water. The rest of the time the area can have another function. Farmers can let their livestock graze in some flood control areas, while valuable nature can develop in others.
This animation shows how an FCA works:
How does an FCA-RT work?
In a flood control area with reduced tides, we combine safety with conservation. We do this by installing special sluices in the flood control area. Every day, the high intake sluice allows a little bit of water flow into and out of the area – in time with the rhythm of ebb and flow. After some time, this process results in the creation of tidal nature with mudflats and marshes.
When flooding occurs, the water runs over the overflow levee. The ring levee protects the residential areas, roads and other infrastructure situated beyond it from flooding. Once the storm has died down, the low discharge sluice allows the water to drain away again.
This animation shows how an FCA-RT works: