Nepal, Oct. 17 -- At a hydropower plant in Rasuwa on the morning of August 26, the warning siren blared, and a worker named Dawa ran. She later told colleagues from the United Nations Population Fund (UNFPA) that her friends were swept away while she ran, and that people climbed over one another trying to reach higher ground. High above the Lhende River, on the other side of the border, a section of glacier and bedrock about 600 metres wide had broken away at roughly 5,200 metres. Nepal issued an alert 38 minutes after the collapse. For many people downstream, that was too late.

In obstetric emergencies, too, time is the decisive variable. UNFPA estimated that the affected included some 5,030 pregnant women and that approximately 250 cou...