A country known for dealing with inundations from the sea is home to the inventors of the SLAMDAM®, a rapidly deployable emergency barrier to minimize coastal and flash floods. SLAMDAM is easier than filling sandbags and requires much less effort and less time to deploy.
Having just written about potential flooding along California’s coastline because of the current El Niño, it would seem a good investment for the state, which just issued an emergency declaration, to stock up on SLAMDAMs for its coastal and flood-prone inland communities.
SLAMDAM doesn’t replace permanent flood-control structures. It is reusable, a rubber-made, water-filled levee that comes in 5-metre-long (16.4-foot) modules, stands 67 centimetres tall (2.2 feet) and can stop a 50 centimetre (1.64 feet) high flood. That doesn’t sound like much of a barrier, but in fact, it is sufficiently high to handle most coastal and inland floods.
Measuring Coastal Flood Norms
What is the height of typical coastal and inland floods? The U.S. National Weather Service uses these different categories in defining floods:
- Minor floods are up to 30 centimetres (approximately one foot) in height,
- Moderate flooding is up to 60 centimetres (approximately two feet),
- Major flooding is up to 120 centimetres (approximately four feet).
A typical 50-centimetre ocean rise, like a storm surge or high tide, never produces that flood height when inland. Usual flooding distributed over large areas translates to a few centimetres, flooding local roads, parking areas, coastal beaches and low-lying areas.
SLAMDAMs can handle minor to moderate flooding levels between 30 and 60 centimetres. California expects the high tides and storm surges accompanying the El Niño as it surges along the coast to produce rises within that range. Their deployment could protect beaches and coastal infrastructure, coastal roads, tidal marshes, lagoons and river mouths. Inland SLAMDAMs could be used to limit damage in flash flood-prone areas in the face of heavy rainfall events and atmospheric rivers that the El Niño will likely trigger. Deployment inland would minimize dangers from landslides and mud and debris flows that sandbagging typically cannot stop.
SLAMDAM Specifications
SLAMDAMs come in a box. Each 5-metre segment weighs 30 kilograms (66 pounds). They are easy to roll out and easy to store. They come with plumbing connections for hooking up to external water sources for filling. Once the barriers are filled, it is the water that gives SLAMDAMs the stability to become a barrier and keep things far drier than sandbagging.
SLAMDAMs come in several models: PROFIDAM, FIREDAM and AGRIDAM. All three can be rolled out on any type of surface from sand to shingle, roads, pasture, tidal flats, and more.
SLAMDAMs contain two tubes separated by an intermediate membrane. The tubes are easily filled with water to add weight. As floodwaters rise and press against them, the external pressure pushes one of the two tubes upward while the other rolls beneath. Together they create an equalized weight-bearing structure that makes for a formidable barrier.
SLAMDAMs are made using EPDM Rubber. This is a synthetic polymer that combines ethylene, propylene and Diene Monomer. The material retains elasticity in extreme temperatures ranging from -35∘C to +120∘C (−31∘F to 248∘F). It is insensitive to ultraviolet light and ozone. It is chemically resistant to acid rain, alkalis, salts, acids, and micro-organisms, and is vapour-proof. After a flood, SLAMDAMs can be rolled up and stored. The estimated service life is 40 years.
California should get out its order book. The Dutch have been plugging holes in dykes and creating barriers to North Sea floods. Their experience can teach California and flood-prone regions around the world a thing or two.
