Thousands of lives have been saved in Namibia, after both livestock and people were evacuated in time to avoid rising flood waters in the Caprivi Strip thanks to an informal inter-country early warning system (details here). The area is susceptible to (annual) flooding of the Zambezi. Local authorities have their own, informal early warning system that involves people phoning or emailing each other with the latest water level information.
The system is considered one of the most efficient in the region. There are probably complicated and sophisticated systems that could be used to do this, but this informal system seems to be working really well. A great reminder that sometimes people, and relationships, are as useful as complicated, sophisticated technology.