Sandbags are sacks, typically made from burlap or cotton duck, which are filled with sand or heavy earth. Particularly durable ones for long term applications are made from polypropylene or other plastics. Although sandbags are most closely associated with flood control, they actually have a number of applications, from environmental remediation to home building. Because they are cheap, easy to handle, and sturdy, they can be used in a wide variety of situations, and by people from varying economic classes.
The easily stackable nature of sandbags makes them ideal for flood prevention, and in areas which are prone to flooding, many people keep them on hand. They can be stacked like bricks, and the earth or sand that fills them will settle, creating a solid, strong wall. Sandbags intended for use in flood control are usually made from plastic bags, or they may be painted with waterproof solutions to make them more permanent.
Additionally, sandbags can be used for erosion control. Roadway cuttings, for example, are often lined with sandbags to prevent the materials behind them from collapsing in a rock or mudslide. These are often made from burlap, and they may be designed to sprout grasses and other groundcovers, creating a solid wall of plant material to further check erosion. Since they can be filled with essentially anything, they can be packed with nutrient rich earth and seeds. Sandbags designed for use in environmental remediation are often used this way, as self-contained planters.
The military also has uses for sandbags, which can be utilized to create fortifications. Structures are often sandbagged so that windows do not break, and they are also used on the battlefield to create protected areas. A sandbag wall can absorb heavy impacts such as those caused by vehicle collisions and munitions attacks.
People who experiment with alternative home building techniques also use sandbags, in this case to make extremely sturdy, solid, well-insulated rammed earth homes. They can be used to create walls, and stacked strategically to make vaulted windows and doors. Earth or plaster can be smeared on top of the sandbags for an aesthetically pleasing and weather tight wall. These homes are versatile, very cheap to build, and beneficial for the environment, since they can be made with recycled bags and materials found on site.
Ballast is another use for sandbags. Cars, boats, and other crafts that may require weight to balance a load can use them. Once the ballast is no longer needed, the sandbags can be delivered to someone else who may be able to make use of them.