Sudden storms called "guerrilla downpours" have been hitting with increasing frequency over the past five decades and are now considered a growing disaster threat.

As municipalities struggle to deal with the increase in floods, companies are proposing new technology based on what they say is their only useful lead in predicting flood risk — manhole covers.

Attaching communication chips to their backs turns manhole covers into real-time monitoring devices that can show the water levels in sewers, and hence the places most likely to flood when heavy rain strikes.