I very much agree with the Grauniad

After the Flood is about how big global changes play out in microcosmic terms. The local councillor’s flummery when confronted (mostly by Molly – do not mess with a community linchpin who is distracting herself from grief) about the lack of sandbags, sirens and other resources that might have mitigated the dangers is emblematic of international inertia in the face of looming planetary catastrophe. The tragic failure of the old couple’s preparations shows the limits of what we as individuals – or even individual countries – can do. This message would be depressing enough to cause viewers to desert the show in droves, were it not folded into a good story playing out among even better characters, and made extra palatable by the rare and delightful sense that you are unexpectedly being served something much, much better than it needs to be.

After the Flood review – an unexpectedly riveting disaster drama | Television | The Guardian