King Tides: Using an app to measure rising sea levels Because of rising sea levels, in just 30 years an estimated 150 million people will be at risk because they live on land that will be below the high tide line. Fighting tides can seem hopeless, but citizens in Norfolk, Va., has come together with a unique effort to protect their community, by monitoring the highest, or "king tides," that threaten their homes. Brook Silva-Braga reports.