An emergency dike is a temporary flood defence raised or installed when high water threatens, in order to prevent flooding or serious water damage. Unlike a permanent dike it is not meant to stay: it goes up before the water arrives and is cleared away afterwards.
When is one used?
- During river flooding, when the water level approaches the crest of an existing embankment
- When a dike shows signs of weakness during a flood, such as seepage or slumping
- During works on an existing defence, to protect the area behind it in the meantime
- For local flooding, for example around a pumping station or a low-lying industrial estate
Types
| Type | Characteristic |
|---|---|
| Sandbags | Traditional, labour-intensive, suited to low heights and awkward junctions |
| Big bags | Large units that a crane can place quickly |
| Demountable barrier | Steel or aluminium stop logs slotted into permanent guides in a wall or embankment |
| Water-filled barrier | Tubes filled with water that build up their own restraining weight |
| Earth bank | A dam of clay or sand placed with earthmoving plant |
Points to watch
- Build it in time — an emergency dike must be finished before the water arrives; during a flood the access route along the dike is often already unusable
- The ground matters — a temporary barrier only holds water if the ground beneath it is also tight; seepage can come up underneath
- Junctions — the weak point is almost always the connection to existing structures or at a service penetration
- Permission — works in or near a watercourse or flood defence are regulated; private individuals cannot simply throw up their own bank
Where it fits
Water authorities use emergency dikes alongside dike patrols, extra pumping capacity and water level management. They remain an emergency measure: structural safety comes from the permanent flood defences, which are assessed and reinforced against statutory standards.
Related terms
- Dike
- Dike patrol
- Seepage
- Flood defence
- Embankment
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