The Great Flood vs Mega Flood

I just finished watching Perfect Disaster: Mega Flood on the Discovery Channel which lays out the problems and results of a flood due to storm surge hitting London. In the Docudrama the people in charge are portrayed as overconfident and almost bumbling as the water heads for London and the city floods before people are evacuated. In it's self this would just be pretty common for a docudrama except that before that i watched Paris 2010 the great flood. In both cases the cities do flood but the thing is that the leaders in Paris are portrayed as being prepared and ready for the disaster. Sure, things happen in Paris that they didn't predict but overall they're choice to react early and be honest with the public do result in people escaping and the city escaping serious damage. In London the story shows the over confident leaders being afraid to order an evacuation in case there is no need to evacuate. The 2 stories illustrate the problem in all disasters where there is a long lead time. Do you order the evacuation early and be hailed as a hero when there's 2 meters of water in the city, or do you order the evacuation and be called a scardy cat when the "flood" is nothing more than a trickle. Paris's choice to evacuate shows the correct decision but what if the flood hadn't happened and people spent a week in shelters for nothing??? In the end it's always the right choice to overreact and give the public an honest assessment that a flood/disaster is possible and that they should be prepared. While it's disruptive to send people out of harms way when in the end nothing happens it will eventually blow over. Nothing gets news coverage like bodies floating in the water.