Abstract: A method for reducing water leakage through sandbag dikes is disclosed, wherein a bentonite or other clay mud slurry is applied to the sandbags. The mud slurry may further include a water loss reducing chemical and/or a water blocking material. The mud slurry may be applied to the river side of the sandbags and may be covered with a plastic sheeting before the river level reaches the sandbags. The mud slurry, and any included chemicals and/or water blocking materials(s), form a coating on both woven plastic fabric and cloth sandbags as well as sandbags of non-porous plastic for reducing water flow through and between the sandbags. The plastic sheeting also makes it feasible to repair the dikes after the sandbags have become submerged by the rising water. That is, hoses can be inserted between the sandbags and the plastic sheeting for injecting the mud slurry at points having excessive leakage.