I've always had a fondness for North Dakota, my mom's home state. Right now Fargo, the capital, is experiencing major flooding. Like the floods for the last 100 years the tool of choice to prevent the river from rising are sandbags.
Recently Slate had a good article on why we still use sandbags. First, they are cheap. Second, they are easy to use. This a good combo for response to floods. Not surprisingly, Midwestern spirit had led to 100s or perhaps 1000s of volunteers to help fill sandbags. So there is usually is an abundance of cheap/free labor in response to the flood, but few volunteers have experience or expertise.
So a technology that is labor intensive is likely to be used, so that's why will likely see sandbags for years to come.