Flood protection by an inflatable rubber dam: Balgstuw Ramspol
The IJssel delta was vulnerable to flooding. In the event of high water in the Ketelmeer and the rivers of the IJssel delta, combined with a storm from the north-west, there was a danger that water would flood over the dikes into the hinterland. An inflatable flexible membrane dam or 'rubber dam', the Balgstuw Ramspol, protects the hinterland of the IJssel delta against flooding.
(Trees on the bank of a lake. A dam across water. Clouds drifting past. Some cows standing in a field. A dike next to a river. A viaduct and the dam from the air. On-screen title: Ramspol Inflatable Dam. Voice-over:)
OMINOUS MUSIC
VOICE-OVER: In the Netherlands water poses an ever-present threat. The IJssel delta was vulnerable to flooding. In the event of high water in the Ketelmeer and the rivers of the IJssel delta, combined with a north-western storm, the hinterland suffered a risk of being flooded.
HARRY STEFESS: Various alternatives are always considered when looking for a solution for somewhere like this and this inflatable rubber dam was the one eventually opted for. A bellow system is inexpensive. Inexpensive to maintain and inexpensive to install and, when empty and deflated, it cannot be seen.
(A bellow is inflated.)
VOICE-OVER: Rubber dams look like the magnified version of the inner tube of a bicycle. Here a total of three inflatable, flexible membranes are positioned next to each other, with a combined length of 240 metres. They consist of a very heavy rubber membrane.
When inflated the membrane rises up no less than ten metres in height. High enough to withstand any heavy storm. On average inflation is required once a year. The membrane reaches its full seize within an hour and provides total protection against the rising water.
(An animation of the inflated bellow.)
STEFESS: If the water level in the Ketelmeer rises above fifty centimetres, the system is activated. A small amount of air is blown into the bellow, then valves are opened, allowing water to flow in. The water continues to flow in until the water level inside the bellow is the same as the water level outside. After which, extra air is pumped in so that the bellow then acts as a dam.
(An animation of the bellow holding the water back. The inflatable dam at Ramspol from the air.)
LIVELY MUSIC
VOICE-OVER: This large rubber dam is unique in the world. When not in operation, the membrane is barely visible and blends into the landscape. And yet, should the need arise, it is always at the ready to protect the population of Overijssel from the water.
(Holland's coat of arms against a pale blue background. On-screen text: This was a production of the Dutch Government.)