Sandbags

The advantages are that the bags and sand are inexpensive. When empty, the bags are compact and lightweight for easy storage and transportation. They can be brought to a site empty and filled with local sand or soil. They can also become contaminated by sewage in flood waters making them difficult to deal with after flood waters recede. In a military context, improvised up-armouring of tanks or armoured personnel carriers with sandbags is not effective against cannons (though it may offer protection against some small arms).