Sandbag Dike Construction
Floodfighters can use hand-filled sandbags either to increase the height of an existing earthen dike, or create a temporary flood protection structure on natural ground.
A sandbag dike first requires the builder to dig a "bonding trench" by removing a strip of soil from the middle of the foundation material. Then a key is formed by simply placing sandbags one deep and two wide in the trench.
A sandbag dike should be three times wider than it is high. For example, if the dike needs to be one metre high, the base should be at least three metres in width.
Sandbags are only half filled with clay, silt or sandy soil. The bottom layer of bags should run parallel to the current. The second layer of bags then goes crosswise on top of the first. The direction of each successive layer alternates, each one 90 degrees to the other. Each row is set back by the width of one-half bag on both sides of the structure.
| Bags Required for 30 Metres of Dike |
| Height |
Number of Bags |
| 1/3 metre |
600 |
| 2/3 metre |
2000 |
| 1 metre |
3400 |
It is not necessary to tie the sack openings. Bags placed parallel to the current, however, should have the open end facing upstream. This prevents soil from washing away. The unfilled portion of the sack is placed lengthwise towards the bottom of the sack, with the next course of bags on top. This is know as "lapping".
Workers must firmly tamp all sandbags in place.
Experienced dike builders always keep extra sandbags at the site to strengthen any weak or damaged spots.
Contact Us: E-Mail: Water.Stewardship@gov.bc.ca
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