If you are looking for flood control look at aqua dam products. Easy to full just use water easy to drain let water out and roll up, sandbags once wet are a nightmare to clean up.
The use of 3/4 crushed gravel in sand bags are amazing ballistic protection expecially near choke points.
There is another style of continous sand bag called and earth bag, these can be used to build housing that is cheap, well insulated, sound proof, ballistic protected, minimal skills required.
If you have heavy equipment you can use them to fill bags fast. Using mini totes 3x3x5 feet cubes of woven 0lplatic that feed, concrete, ect come in as portable re enforcements. BeSt part about these is when done you lift up and move to sand/gravel storage and there is a spout you undo and bag empties and you can roll up for next emergancy. They are easy to patch either sew or glue (glue you need to do from inside)